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ST2.8

EDI
Inner-magnetosphere Interactions and Coupling

The Earth's inner magnetosphere contains different charged particle populations, such as the Van Allen radiation belts, ring current particles, and plasmaspheric particles. Their energy range varies from eV to several MeV, and the interplay among the charged particles provides feedback mechanisms that couple all those populations together. Ring current particles can generate various waves, for example, EMIC waves and chorus waves, which play important roles in the dynamic evolution of the radiation belts through wave-particle interactions. Ring current electrons can be accelerated to relativistic radiation belt electrons. The plasmaspheric medium can also affect these processes. In addition, precipitation of ring current and radiation belt particles will influence the ionosphere, while up-flows of ionospheric particles can affect dynamics in the inner magnetosphere. Understanding these coupling processes is crucial.

While the dynamics of outer planets’ magnetospheres are driven by a unique combination of internal coupling processes, these systems have several fascinating similarities which make comparative studies particularly interesting. We invite a broad range of theoretical, modeling, and observational studies focusing on the dynamics of the inner magnetosphere of the Earth and outer planets, including the coupling of the inner magnetosphere and ionosphere and coupling between the solar wind disturbances and various magnetospheric processes. Contributions from all relevant fields, including theoretical studies, numerical modeling, observations from satellite and ground-based missions are welcome. In particular, we encourage presentations using data from MMS, THEMIS, Van Allen Probes, Arase (ERG), Cluster, cube-sat missions, Juno, SuperDARN, magnetometer, optical imagers, IS-radars, and ground-based VLF measurements.

Co-organized by PS2
Convener: Dedong WangECSECS | Co-conveners: Chao YueECSECS, Hayley AllisonECSECS, Ondrej Santolik, Qiugang Zong
Presentations
| Mon, 23 May, 15:10–18:22 (CEST)
 
Room 1.85/86, Tue, 24 May, 08:30–09:54 (CEST)
 
Room 1.85/86

Mon, 23 May, 15:10–16:40

Chairpersons: Hayley Allison, Ondrej Santolik, Dedong Wang

15:10–15:16
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EGU22-7578
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ECS
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Highlight
Julia Himmelsbach et al.

Ring current particles affect the terrestrial magnetic field configuration, altering particle trajectories, as well as presenting a surface charging hazard for satellites. These particles can act as a seed population for the electron radiation belts and generate plasma waves. Accurately describing ring current dynamics is crucial to understand the near-Earth plasma environment. Here we report on our first results of the expansion of the Versatile Electron Radiation Belt (VERB) code to model ring current proton dynamics (proVERB). We perform sensitivity studies for the four dimensional grid, considering the grid resolution necessary to resolve proton dynamics. Analysing the banana shaped orbits for ring current protons shows that the azimuthal grid resolution is comparable to the electron grid, while the resolution in the radial grid has to be significantly enhanced. Loss mechanisms of charge exchange and Coulomb collisions, thought to be largely responsible for the decay of the ring current during the recovery phase of a storm, are included in proVERB. We present our first simulation results and compare them to observations from the Van Allen probes HOPE and MagEIS instruments. By retaining and omitting charge exchange and Coulomb collisions in our simulations, we study the role of these loss processes on the ring current evolution during active periods.

How to cite: Himmelsbach, J., Allison, H., Shprits, Y., Haas, B., Wutzig, M., and Wang, D.: Assessing the contribution of charge exchange and Coulomb collisions to ring current proton dynamics with the new 4-D Proton Versatile Electron RadiationBelt (proVERB) code, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7578, https://doi.org/10.5194/egusphere-egu22-7578, 2022.

15:16–15:26
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EGU22-633
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solicited
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Highlight
Yuri Y. Shprits and the Horizon 2020 PAGER team

This project aims to provide space weather predictions that will be initiated from observations on the Sun and to predict radiation in space and its effects on satellite infrastructure. Real-time predictions and a historical record of the dynamics of the cold plasma density and ring current allow for evaluation of surface charging, and predictions of the relativistic electron fluxes will allow for the evaluation of deep dielectric charging. The project aims to provide a 1-2 day probabilistic forecast of ring current and radiation belt environments, which will allow satellite operators to respond to predictions that present a significant threat. As a backbone of the project, we use the most advanced codes that currently exist and adapt existing codes to perform ensemble simulations and uncertainty quantifications. This project includes a number of innovative tools including data assimilation and uncertainty quantification, new models of near-Earth electromagnetic wave environment, ensemble predictions of solar wind parameters at L 1, and data-driven forecast of the geomangetic Kp index and plasma density. The developed codes may be used in the future for realistic modelling of extreme space weather events. The PAGER consortium is made up of leading academic and industry experts in space weather research, space physics, empirical data modelling, and space environment effects on spacecraft from Europe and the US.

How to cite: Shprits, Y. Y. and the Horizon 2020 PAGER team: Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-633, https://doi.org/10.5194/egusphere-egu22-633, 2022.

15:26–15:32
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EGU22-9530
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ECS
Marina García Peñaranda
The Earth’s ring current is a complex dynamic system that plays an important role in geomagnetic storms. This ring-shaped current environment changes its structure and intensity on different time scales as a result from the incoming solar wind. Particle populations display very different behaviors, making it extremely hard to develop physics-based forecasting models for the ring current environment.
 
Satellite data provides electron point measurements that can be used to study the different physical processes occurring in the Earth’s magnetospheric ring current. However, in order to fully understand the particle dynamics and injection processes in this region, high temporal and spatial data resolutions are required. We attempt to tackle this issue by using a combination of electron-flux observations from different satellite missions and instruments, in order to improve the global resolution of this dynamic environment.
 

In this work, we present a global reconstruction of the ring current population (energies from 1to a few 100 keV) using global multi-satellite data from Arase, POES, GOES, THEMIS and the Van Allen Probes (RBSP) missions. We achieved this by intercalibrating the satellite data for the year 2017.

Additionally, we present a comparison of the observed electron flux environment with a re-analysis of the ring current region obtained by using  the simplified version of the VERB-4D, which solves the convection equation and reduces the problem to a two-dimensional case by using parameterized lifetimes. For the reanalysis, we assimilate GOES and Van Allen Probes (RBSP A and RBSP B) data with a Stardard Kalman Filter.

How to cite: García Peñaranda, M.: Ring Current Reconstruction via Multi-Satellite Observations and Comparison with VERB-4D Reanalysis Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9530, https://doi.org/10.5194/egusphere-egu22-9530, 2022.

15:32–15:38
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EGU22-2106
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ECS
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Qi Zhu et al.

Via cyclotron resonant interactions, electromagnetic ion cyclotron (EMIC) waves play an important role in the loss of ring current protons. In this study, by calculating the proton bounce-averaged pitch angle diffusion coefficients using both the cold and hot plasma dispersion relations, we investigate the hot plasma effects on the EMIC wave-induced scattering loss of ring current protons. Our results show that, for H+ band (He+ band) EMIC waves, inclusion of hot protons results in significant decrease of pitch angle diffusion coefficients of ~ 10 - 60 keV (4 - 30 keV) protons, while the scattering efficiency of higher energy protons increases at low pitch angles and decreases at relatively high pitch angles. We also find that the cold plasma approximation seriously underestimates the loss timescales of protons at energies from a few keV to tens of keV but overestimate that of higher energy protons. The differences in proton loss timescales caused by hot plasmas are generally less than a factor of ~ 5 for H+ band but can exceed an order of magnitude for He+ band, showing a strong dependence on ,  and L-shell. This study confirms that hot plasma effects play a crucial role in the EMIC wave driven loss of ring current protons and should be included in future modeling of ring current dynamics.

How to cite: Zhu, Q., Cao, X., Ni, B., Gu, X., and Ma, X.: Hot Plasma Effects on the Pitch-Angle Scattering of Ring Current Protons by EMIC Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2106, https://doi.org/10.5194/egusphere-egu22-2106, 2022.

15:38–15:44
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EGU22-8485
Xingbin Tian et al.

Protons of tens of keV can be resonantly scattered by EMIC waves excited in the magnetosphere and further precipitate down to the upper atmosphere. In this study, we show a case event that shows direct linkage of the EMIC waves, proton precipitation, and ionospheric ionization using space-borne and ground-based measurements. On Oct 11, 2012, the POES observed that the precipitating flux of the proton much larger than that of the electrons in the night sector around magnetic latitude of 65°. Around the same time and location, ground-based magnetometer detected clear signature of EMIC waves, indicating the causal relation to the proton precipitation. We further simulate the impact of this tens of keV proton precipitation on the upper atmosphere, and found good agreement with PFISR observations of electron density and conductivity. On the other hand, the large ionization rate cannot be accounted for by the electron precipitation at that location. This study shows a clear evidence of the precipitating coupling processes within the magnetosphere-ionosphere system.

How to cite: Tian, X., Yu, Y., and Ma, L.: The EMIC wave-driven proton precipitation and related effects on the ionosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8485, https://doi.org/10.5194/egusphere-egu22-8485, 2022.

15:44–15:50
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EGU22-11822
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Highlight
Yoshizumi Miyoshi et al.

Whistler chorus waves cause energetic electron precipitations into the Earth’s atmosphere, and signatures of precipitations are observed as diffuse,
pulsating aurora, and microbursts of energetic electrons. In this talk, we present our model that propagating chorus waves cause wide energy electron precipitations and relativistic electron microbursts are a high-energy tail of the pulsating aurora electrons. The chorus waves can resonate with tens keV electrons near the magnetic equator, which causes the pulsating aurora emissions, while the chorus waves can resonate with sub-relativistic/relativistic electrons at the off-equator, which cause the microbursts of energetic electrons. Moreover, we discuss that relativistic electrons cause a significant ozone destruction at the middle atmosphere by conjugate observations of Arase, ground-based observations, SIC ion chemistry simulation.

How to cite: Miyoshi, Y., Saito, S., Hosokawa, K., Asamura, K., Oyama, S., Mitani, T., Sakanoi, T., Kero, A., Turunen, E., and Verronen, P.: Energetic electron precipitations by chorus waves and its impact on the middleatmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11822, https://doi.org/10.5194/egusphere-egu22-11822, 2022.

15:50–15:56
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EGU22-1097
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ECS
Ting Feng and Chen Zhou
15:56–16:02
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EGU22-7570
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ECS
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Highlight
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Bernhard Haas et al.

Low-energy ring current electrons of up to 50 keV represent a major threat to spacecrafts within the inner magnetosphere since they are one of the main causes of spacecraft surface charging. Furthermore, they can provide a seed population for relativistic radiation belt electrons during geomagnetic storms. In this work, we report the first results of coupling the Versatile Electron Radiation Belt (VERB) code with a fully MLT resolved physics-based plasmasphere model to investigate the loss mechanisms of low energy electrons. Our four dimensional ring current model used in this study includes radial diffusion, convection, and loss due to whistler-mode chorus and hiss waves. The physics-based model of the plasmasphere includes convection of cold plasma and refilling from the ionosphere.
We simulate two storm events from the Van Allen Probes' era and compare results of cold plasma density and electron flux against measurements from the twin Van Allen Probe satellites. Our plasmasphere model is not only capable of predicting the plasmapause location but also the formation of plasmaspheric plumes, where plume whistler mode waves propagate. Including the plume region, which usually has very restricted spatial coverage, allows us to examine the effect of plume whistler mode waves on the loss of ring current electrons during these two events. These plasma boundaries show significant dynamics during the main and recovery phase of storms and are crucial to correctly predict electron loss.
By using the extracted plasma boundaries to determine the spatial extent of different waves species, we find better agreement of electron flux results with measurements, especially during the main phase of storms. We also report on the first ring current simulation results including the loss introduced by spatially localised whistler-wave scattering in plasmaspheric plumes.

How to cite: Haas, B., Shprits, Y., Wutzig, M., Allison, H., and Wang, D.: The Effect of Plasmaspheric Plumes on the Loss of Ring Current Electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7570, https://doi.org/10.5194/egusphere-egu22-7570, 2022.

16:02–16:08
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EGU22-9063
Ondřej Santolík et al.

Our case study aims at contributing to the discussion on sources of plasmaspheric hiss, which is known for its interactions with the Earth radiation belts. We analyze multi-point measurements of electromagnetic field waves by the Wide Band Data instruments onboard the four Cluster spacecraft in order to find sources of hiss observed close to the geomagnetic equator in the dayside outer plasmasphere. We find hiss to be triggered from whistlers of different spectral properties. Whistlers with the lowest observed dispersion arrive to different spacecraft with time delays indicating their origin in the northern hemisphere. Positions of source lightning discharges are then found using the time coincidences with the Word Wide Lightning Location Network data from three active thunderstorm regions in Europe. We find that subionospheric propagation of lightning atmospherics is necessary to explain the observations. Geographic locations of their ionospheric exit points then determine spectral properties of resulting unducted whistlers and triggered hiss. By this well documented chain of events starting with a lightning discharge in the atmosphere we confirm that magnetospherically reflecting whistlers and hiss triggered from them are among possible sources of plasmaspheric hiss.

How to cite: Santolík, O., Kolmašová, I., Pickett, J. S., and Gurnett, D. A.: Coupling of lightning generated electromagnetic waves to the inner magnetosphere: a case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9063, https://doi.org/10.5194/egusphere-egu22-9063, 2022.

16:08–16:14
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EGU22-11316
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ECS
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Muhammad Shahid et al.

Energetic electron scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms of electrons losses in the inner magnetosphere. Such resonant scattering has been traditionally considered as a controlling process for the dynamics of relativistic electron fluxes in the Earth’s radiation belts. EMIC wave generation is mainly associated with the ring current ion population injected from the plasma sheet. These ions are drifting westward and generate the most intense EMIC waves on the dusk flank. In this work, we consider an alternative mechanism of EMIC wave generation due to local plasma compression by strong ultra-low-frequency (ULF) waves that modulate a quasi-periodical ion anisotropy responsible for EMIC excitation. Using THEMIS spacecraft observations of simultaneous EMIC waves and compressional ULF waves, we investigate the statistical properties of such quasi-periodic EMIC emission. We show spatial distributions of ULF-modulated EMIC waves, statistics of their amplitudes and typical frequencies. We also discuss the associated measurements of ULF-modulated hot ion populations responsible for EMIC wave generation.

How to cite: Shahid, M., Bashir, M. F., Artemyev, A., Zhang, X., Angelopoulos, V., and Murtaza, G.: Properties of quasi-periodical emission of electromagnetic ion cyclotron waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11316, https://doi.org/10.5194/egusphere-egu22-11316, 2022.

16:14–16:20
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EGU22-11179
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ECS
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Abdul Waheed et al.

Magnetopause perturbations by solar wind transients drive a wide variety of ultra-low-frequency (ULF) waves in the Earth’s magnetosphere. Compressional ULF waves modulate thermal and energetic electron fluxes, changing their flux anisotropy. Such modulation may move electron distributions beyond the threshold of instabilities and drive the generation of electron cyclotron harmonic (ECH) and whistler-mode waves. Given the importance of ECH and whistler-mode waves for electron scattering into the atmosphere, we statistically investigate the main characteristics of ULF-modulated ECH and whistler-mode waves. We find two main types of events: with the correlation of whistler-mode and ECH waves and with their anti-correlation. We present the spatial distribution of these two types of events and examine correlations of background plasma/magnetic field characteristics with properties of whistler and ECH waves modulated by ULF waves.

How to cite: Waheed, A., Bashir, M. F., Artemyev, A., and Zhang, X.: Whistler and electron cyclotron harmonic waves at the near-Earth dayside plasma sheet: statistics of modulation by ultra-low frequency waves , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11179, https://doi.org/10.5194/egusphere-egu22-11179, 2022.

16:20–16:26
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EGU22-11579
Yixin Hao et al.

In this study, we present in-situ measurement by Van Allen Probes showing that surface wave could oscillate the plasmapause and modulate hiss and electron cyclotron harmonic (ECH) waves. Plasmapause sur-face wave (PSW) in Ps6 band was observed during an intense substorm on 16 July 2017, accompanied with quasi-periodic emissions of hiss (positively correlated to plasma density) and ECH waves (anticorrelated to the density). Phase relation between magnetic field and velocity perturbations indicatesthat the PSW was an eigenmode between southern and northern ionosphere. Measurements from ground-based magnetometers suggest that such PSW propagates sunward at dusk flank and were excited around the expansion phase of an intense substorm. Addiational cases of PSWs are also presented to demonstrate that such waves are commonly observed near plasmapause and are likely to be related to substorm activities.

How to cite: Hao, Y., Zong, Q., Yue, C., Zhou, X., Zhang, H., Pu, Z., and Shprits, Y.: Plasmapause Surface Waves Triggered by Substorms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11579, https://doi.org/10.5194/egusphere-egu22-11579, 2022.

16:26–16:32
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EGU22-9045
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Haobo Fu et al.

The plasma properties in the inner magnetosphere play critical roles in plasma dynamics by changing magnetic field configurations and generating the ring current. Geomagnetic substorms, especially intense substorms can significantly influence inner magnetosphere. This study presents our preliminary statistical results of plasma properties and their substorm dependence at the equatorial plane based on the Van Allen Probe observations. We find that both H+ and O+ pressure increases significantly during substorms, and the pressure ratio of O+ to H+ also increases. The peak of H+ pressure is almost fixed around L=4, while that of O+ moves inward as the substorm intensifies. In addition, substorms can significantly change the ion energy distributions. They will increase the proportion of pressure provided by the lower energy components of H+ (E < ~100keV), especially in lower L-shells. At the same time, they decrease the contribution to the plasma pressure from lower energy components of O+, which shows almost no L-shell dependence. During quiet times, the perpendicular current density distributes roughly symmetrically, with negative value inside (L < ~4.5) and positive value outside. During substorms, the current density enhances and shows asymmetry with higher current density from the pre-dusk to the post-midnight. The parallel current density caused by the pressure gradient also increases with substorms. These field-aligned currents (FACs) enter the ionosphere at dusk and move upward at dawn, as region II FAC.

How to cite: Fu, H., Yue, C., Zong, Q., and Zhou, X.: Substorm influences on plasma properties distributions in the inner magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9045, https://doi.org/10.5194/egusphere-egu22-9045, 2022.

Mon, 23 May, 17:00–18:30

Chairpersons: Ondrej Santolik, Hayley Allison, Dedong Wang

17:00–17:06
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EGU22-9577
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ECS
Sigiava Aminalragia-Giamini et al.

The Earth’s outer radiation belt response to geospace disturbances is extremely variable spanning from a few hours to several months. In addition, the numerous physical mechanisms, which control this response, depend on the electron energy, the time-scale and the types of geospace disturbances. As a consequence, the various models that currently exist are either specialized, orbit-specific data-driven models, or sophisticated physics-based ones. In this paper we present a new approach for radiation belt modelling using Machine Learning methods driven solely by solar wind speed and pressure, Solar flux at 10.7 cm and the Russell-McPherron angle. We use Van Allen Probes data to train our model and show that it can successfully reproduce and predict the electron fluxes of the outer radiation belt in a broad energy (0.033–4.062 MeV) and L-shell (2.5–5.9) range and, moreover, it can capture the long-term modulation of the semi-annual variation. We also present validation studies of the model’s performance using data from other missions which are outside the spatio-temporal training regime such as the E>0.8 MeV electron flux measurements from GOES-15/EPEAD at geostationary orbit.

This work has received funding from the European Union’s Horizon 2020 research and innovation programme "SafeSpace" under grant agreement No 870437 and from the European Space Agency under the "European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System" activity under ESA Contract No 4000127282/19/NL/IB/gg.

How to cite: Aminalragia-Giamini, S., Katsavrias, C., Papadimitriou, C., Daglis, I., Sandberg, I., and Jiggens, P.: Radiation belt model including semi-annual variation and Solar driving (SENTINEL), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9577, https://doi.org/10.5194/egusphere-egu22-9577, 2022.

17:06–17:16
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EGU22-6518
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solicited
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Highlight
Ioannis A. Daglis and the SafeSpace Team

The European SafeSpace project has been implementing a synergistical approach to improve space weather forecasting capabilities from the current lead times of a few hours to 2-4 days. We have combined the solar wind acceleration model MULTI-VP with the heliospheric propagation models Helio1D and EUHFORIA to compute the evolution of the solar wind from the surface of the Sun to the Earth orbit. The forecasted solar wind conditions are then fed into the ONERA Geoffectiveness Neural Networks, to forecast the level of geomagnetic activity with the Kp index as the chosen proxy. The Kp index is used as the input parameter for the IASB plasmasphere model and for the Salammbô radiation belts code. The plasma density is used to estimate VLF wave amplitude and then VLF diffusion coefficients, while the predicted solar wind parameters are used to estimate the ULF diffusion coefficients. Plasmaspheric density and VLF/ULF diffusion coefficients are used by the Salammbô radiation belts code to deliver a detailed flux map of energetic electrons. Finally, particle radiation indicators will also be provided as a prototype space weather service of use to spacecraft operators and space industry. The performance of the prototype service will be evaluated in collaboration with space industry stakeholders. The work leading to this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace (Radiation Belt Environmental Indicators for the Safety of Space Assets) project.

How to cite: Daglis, I. A. and the SafeSpace Team: Advanced Prediction of the Outer Van Allen Belt Dynamics and a Prototype Service: the H2020 SafeSpace project , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6518, https://doi.org/10.5194/egusphere-egu22-6518, 2022.

17:16–17:22
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EGU22-6555
Ioannis A. Daglis et al.

Radial diffusion has been established as one of the most important mechanisms contributing to the acceleration and loss of relativistic electrons in the outer radiation belt. Over the past few years efforts have been devoted to identify empirical relationships of radial diffusion coefficients (DLL) for radiation belt simulations, yet several studies have suggested that the difference between the various models can be orders of magnitude different at high levels of geomagnetic activity, as the observed DLL have been shown to be highly event-specific. In the framework of the SafeSpace project we have used 12 years (2010 – 2020) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of calculated DLL. In this work we present the statistics on the evolution of DLL during the solar cycle 24 with respect to the various solar wind parameters, geomagnetic indices and universal coupling functions. Furthermore, we show the importance of the use of event-specific DLL through simulations of seed and relativistic electrons with the Salammbo code during the intense storm of St. Patricks 2015 and the high-speed stream driven storm of Christmas 2013. Finally, we present a new approach for a Machine Learning model driven solely by Solar wind parameters.

This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437.

How to cite: Daglis, I. A., Katsavrias, C., Aminalragia-Giamini, S., Nasi, A., Dahmen, N., Brunet, A., Bourdarie, S., and Papadimitriou, C.: Radial diffusion coefficients database in the framework of the SafeSpace project: A Machine Learning model and the application to radiation belt simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6555, https://doi.org/10.5194/egusphere-egu22-6555, 2022.

17:22–17:28
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EGU22-536
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Highlight
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Afroditi Nasi et al.

During July-October of 2019, a sequence of Corotating Interaction Regions (VSW ≥ 600 km/s) impacted the magnetosphere, for four consecutive solar rotations. Even though the series of CIRs resulted in relatively weak geomagnetic storms (SYM-Hmin ≈ -60 nT, Kpmax ≈ 5), the net effect of the outer radiation belt during each disturbance was different, depending on the electron energy. During the August-September CIR, intense substorm activity was recorded (SMLmin ≈ - 2000 nT), as well as significant enhancement of ultra-relativistic electrons.

We exploit coordinated and cross-calibrated particle measurements from the Van Allen Probes, Arase and Galileo 207, 215 satellites, to investigate the relative contribution of radial diffusion and gyro-resonant acceleration, using both electron fluxes and Phase Space Density (PSD) radial profiles, also compared with a 1D Fokker-Planck simulation.

Additionally, we use chorus wave amplitude and radial diffusion coefficient (DLL) estimations, from the SafeSpace DLL database, density measurements from the GFZ-Potsdam database, as well as solar wind and geomagnetic parameters, for a detailed investigation of these events.

This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace project.

How to cite: Nasi, A., Daglis, I. A., Katsavrias, C., Sandberg, I., Li, W., Allison, H., Miyoshi, Y., Imajo, S., Mitani, T., Hori, T., Shprits, Y., Kasahara, S., Yokota, S., Keika, K., Shinohara, I., Matsuoka, A., and Kasahara, Y.: Coordinated observations of relativistic electron enhancements following the arrival of consecutive Corotating Interaction Regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-536, https://doi.org/10.5194/egusphere-egu22-536, 2022.

17:28–17:34
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EGU22-13019
Robert Rankin et al.

It is demonstrated that the application of a height-integrated conductivity (HIC) boundary condition in theories of the ionospheric feedback instability is valid only for very thin (few km) conducting layers. In the presence of global convection, the strong variation of the ion mobility with altitude produces strongly sheared transverse ion flows within the E-layer.  These flows are not accounted for when the HIC boundary condition is applied, and when accounted for they cause a drastic reduction in growth rates of the IFI even for very large convection electric fields on the order of a few hundred mV/m. Thie reduction in IFI growth rates is verified through linear eigenmode analysis of the IFI similar to Watanabe & Maeyama (JGR, 45, 2018), except that (a) parallel electric fields in the ionosphere are accounted for, and (b) collision frequency profiles are determined from the IRI and MSIS models (Sydorenko and Rankin, GRL, 44, 2017).

The IFI in field line resonances (FLRs) and the ionospheric resonator (IAR) is studied for a collisional slab ionosphere of thickness 300 km. Constant density is assumed for FLRs, with the slab adjoining a collisionless plasma embedded in a constant magnetic field. Symmetry boundary conditions are applied at the equatorial magnetosphere. In the IAR study, the density varies with altitude and reflecting boundary conditions are used. Instability growth rates are computed numerically and compared with results for slabs of varying thickness (2 km to 300 km) and identical height-integrated conductivity. Growth rates for the most unstable mode are significantly reduced compared to the HIC case for layers as thin as 2 km, even in the long parallel wavelength limit.

The parallel electric field obtained from Faraday’s Law is strongly stabilizing for short transverse wavelength perturbations, especially for higher harmonics. A new unstable mode is found that does not require reflection of  waves within the IAR. It satisfies the resonance condition ω=ky<Vd> where ky is the transverse wavelength and <Vd> is the average ion drift velocity within the sptaially structured E-layer. The physical implication of this newly identified ionospheric instability is considered in the context of discrete auroral arcs and field line resonances.

How to cite: Rankin, R., Sydorenko, D., and Shen, W.: A new interpretation of the ionospheric feedback instability applied to feld line resonances and the ionospheric Alfven resonator, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13019, https://doi.org/10.5194/egusphere-egu22-13019, 2022.

17:34–17:40
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EGU22-8840
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Highlight
Muhammad Fraz Bashir et al.

Resonant scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms of relativistic electron losses in the inner magnetosphere. For the majority of observed waves, such scattering is well described by the quasi-linear diffusion theory. Low-altitude spacecraft measurements, however, often show that the energy range of precipitating electrons is wider than theoretical predictions based on the cold plasma dispersion of EMIC waves. We develop a hot plasma model based on the observed ion distribution functions and investigate the hot plasma effects on EMIC wave dispersion for a wide frequency range. The results obtained from the analytical hot plasma model agree very well with the numerical solution of the exact dispersion relation of EMIC waves for a wide range of plasma parameters. We also show the implementation of this model for diffusion rate evaluation. Combining near-equatorial spacecraft measurements and wave dispersion model, we show that hot ion effects tend to increase the minimum resonant energy for the frequency range around wave intensity maxima, but can decrease the minimum resonant energy for the higher-frequency part of wave spectra.

This study highlights the importance of hot plasma effects on the relativistic electron scattering and provides a hot plasma model applicable to a wide range of plasma parameters for realistic quasi-linear diffusion rate calculations.

How to cite: Bashir, M. F., Artemyev, A., Zhang, X., and Angelopoulos, V.: Relativistic electron scattering by electromagnetic ion cyclotron waves: the hot plasma Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8840, https://doi.org/10.5194/egusphere-egu22-8840, 2022.

17:40–17:46
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EGU22-4057
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ECS
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Highlight
Murong Qin et al.

In this study, we present simultaneous multi-point observations of whistler-mode chorus waves and global magnetospheric oscillations on a timescale of several to ~10s minutes (breathing mode magnetic field oscillations), associated with concurrent energetic electron precipitation observed through enhanced BARREL X-rays. Similar fluctuations on a timescale of several to ~10s minutes are observed in the X-ray measurements and the compressional component of global oscillations. The spatial scale of global oscillations spans from 4 to 12 h in MLT and from 5 to 11 in L shell. Such global oscillations, which have been suggested to play a potential role in precipitating energetic electrons by either wave scattering or loss cone modulation, show high correlation with the enhancement in X-rays. However, the correlation coefficient between whistler-mode waves and X-rays is low. Observations and model results show that the breathing-mode magnetic field oscillations could play a significant role in modulating the electron precipitation driven by whistler-mode waves even though the whistler-mode wave intensity is not fully modulated by global oscillations.

How to cite: Qin, M., Li, W., Ma, Q., Shen, X., and Shen, X.: Global magnetic field oscillations on the breathing-mode timescale and their effects on energetic electron precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4057, https://doi.org/10.5194/egusphere-egu22-4057, 2022.

17:46–17:52
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EGU22-6869
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ECS
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Highlight
Dong Lin et al.

Subauroral polarization streams (SAPS) typically refer to an enhanced westward plasma flow channel in the duskside subauroral ionosphere. SAPS overlap with the low-latitude part of downward Region-2 field-aligned currents (FACs). The relatively low subauroral conductance in this region requires a strong electric field for current closure, which drives the fast sunward plasma flow. Observations have shown dynamic variability of SAPS under various solar wind and interplanetary magnetic field (IMF) conditions, which are related to the variability of FACs and auroral precipitation, as well as their source regions in the ring current and plasmasheet. In this study, we use satellite observations and numerical simulations with the state-of-the-art Multiscale Atmosphere Geospace Environment (MAGE) model to investigate: 1) The role of diffuse electron precipitation in the formation of SAPS; 2) SAPS variability under IMF BY; and 3) Dawnside (as opposed to the more conventional duskside) SAPS as a unique feature of major geomagnetic storms. With data-model comparison, we will demonstrate that SAPS result from the different behaviors of ring current ions and plasma sheet electrons, and the corresponding self-consistent response of the ionosphere-thermosphere system via electrodynamic and particle coupling with the magnetosphere. We conclude that SAPS distribution and variability represent a fundamental feature of the geospace response to solar disturbances during storm time.

How to cite: Lin, D., Wang, W., Merkin, V., Wiltberger, M., Sorathia, K., Pham, K., Bao, S., Michael, A., Shi, X., Huang, C., Wu, Q., Zhang, Y., Oppenheim, M., Toffoletto, F., Lyon, J., Garretson, J., and Anderson, B.: Subauroral polarization streams (SAPS): Intrinsic response of geospace during storm time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6869, https://doi.org/10.5194/egusphere-egu22-6869, 2022.

17:52–17:58
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EGU22-1546
Dedong Wang et al.

Chorus waves can cause the loss of energetic electrons in the Earth's radiation belts and ring current via pitch-angle diffusion. To quantify the effect of chorus waves on energetic electrons, we calculated the bounce-averaged quasi-linear diffusion coefficients. In this study, using these diffusion coefficients, we parameterize the lifetime of the electrons with an energy range from 1 keV to 2 MeV. In each magnetic local time (MLT), we calculate the lifetime for each energy and L-shell using two different methods. By applying polynomial fits, we parameterize the electron lifetime as a function of L-shell and electron kinetic energy (Ek) in each MLT and geomagnetic activity (Kp). The parameterized electron lifetimes show a strong functional dependence on L-shell and electron energy. During storm time, the lifetimes for higher energy (> 100 keV) electrons range from hours to days in the heart of the radiation belts. In contrast, the lifetimes for electrons with lower energy (< 100 keV) range from minutes to hours. This parameterization of electron lifetime is convenient for inclusion in simulations in the inner magnetosphere. 

How to cite: Wang, D., Shprits, Y., and Haas, B.: Parameterized Lifetime of Energetic Electrons due to Interactions with Chorus Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1546, https://doi.org/10.5194/egusphere-egu22-1546, 2022.

17:58–18:04
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EGU22-8977
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Highlight
Ennio Sanchez et al.

Quantification of energetic electron precipitation caused by wave-particle interactions is fundamentally important to understand the cycle of particle energization and loss of the radiation belts. One important way to determine how well the wave-particle interaction models predict losses through pitch-angle scattering into the atmospheric loss cone is the direct comparison between the ionization altitude profiles expected in the atmosphere due to the precipitating fluxes and the ionization profiles actually measured with incoherent scatter radars. This paper reports such a comparison using a forward propagation of loss-cone electron fluxes, calculated with the electron pitch angle diffusion model applied to Van Allen Probes measurements, coupled with the Boulder Electron Radiation to Ionization (BERI) model, which propagates the fluxes into the atmosphere. The density profiles measured with the Poker Flat Incoherent Scatter Radar operating in modes especially designed to optimize measurements in the D-region, show multiple instances of quantitative agreement with predicted density profiles from precipitation of electrons caused by wave-particle interactions in the inner magnetosphere. There are two several-minute long intervals of close prediction-observation approximation in the 65-93 km altitude range. These results indicate that the whistler wave-electron interactions models are realistic and produce precipitation fluxes of electrons with energies between 10 keV to >100 keV that are consistent with observations.

How to cite: Sanchez, E., Ma, Q., Xu, W., Marshall, R., Bortnik, J., Reyes, P., Varney, R., and Kaeppler, S.: A Test of Energetic Particle Precipitation Models Using Simultaneous Incoherent Scatter Radar and Van Allen Probes Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8977, https://doi.org/10.5194/egusphere-egu22-8977, 2022.

18:04–18:10
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EGU22-8799
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ECS
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Highlight
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Leonid Olifer et al.

Properly characterizing fast relativistic electron losses in the terrestrial Van Allen belts remains a significant challenge for accurately simulating their dynamics. In particular, magnetopause shadowing losses can deplete the radiation belt within hours or even minutes but can have long-lasting impacts on the subsequent belt dynamics. By statistically analyzing seven years of data from the entire Van Allen Probes mission in the context of the last closed drift shell, here we show how these losses are much more organized and predictable than previously thought. Once magnetic storm electron dynamics are properly analyzed in terms of the location of the last closed drift shell, not only is the loss shown to be repeatable but its energy-dependent spatio-temporal evolution is also revealed to follow a very similar pattern from storm to storm. Employing an energy-dependent ULF wave radial diffusion model, we further show for the first time how the similar and repeatable fractional loss of the pre-storm electron population in each storm can be reproduced and explained. Empirical characterization of this loss may open a pathway toward improved radiation belt specification and forecast models. This is especially important since underestimates of loss can also create unrealistic sources in models, creating phantom electron radiation and leading to the prediction of an overly harsh radiation environment.

How to cite: Olifer, L., Mann, I., Ozeke, L., Claudepierre, S., Baker, D., and Spence, H.: On the Similarity and Repeatability of Fast Magnetopause Shadowing Loss, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8799, https://doi.org/10.5194/egusphere-egu22-8799, 2022.

18:10–18:16
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EGU22-6611
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ECS
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Highlight
Xiangning Chu et al.

We present a machine-learning-based model of relativistic electron fluxes >1.8 MeV using a neural network approach in the Earth's outer radiation belt. The Outer RadIation belt Electron Neural net model for Relativistic electrons (ORIENT-R) uses only solar wind conditions and geomagnetic indices as input. For the first time, we show that the state of the outer radiation belt can be determined using only solar wind conditions and geomagnetic indices, without any initial and boundary conditions. The most important features for determining outer radiation belt dynamics are found to be AL, solar wind flow speed and density, and SYM-H indices. ORIENT-R reproduces out-of-sample relativistic electron fluxes with a correlation coefficient of 0.95 and an uncertainty factor of ∼2. ORIENT-R reproduces radiation belt dynamics during an out-of-sample geomagnetic storm with good agreement to the observations. In addition, ORIENT-R was run for a completely out-of-sample period between March 2018 and October 2019 when the AL index ended and was replaced with the predicted AL index (lasp.colorado.edu/home/personnel/xinlin.li). It reproduces electron fluxes with a correlation coefficient of 0.92 and an out-of-sample uncertainty factor of ∼3. Furthermore, ORIENT-R captured the trend in the electron fluxes from low-earth-orbit (LEO) SAMPEX, which is a completely out-of-sample data set both temporally and spatially. In sum, the ORIENT-R model can reproduce transport, acceleration, decay, and dropouts of the outer radiation belt anywhere from short timescales (i.e., geomagnetic storms) and very long timescales (i.e., solar cycle) variations.

How to cite: Chu, X., Ma, D., Bortnik, J., Tobiska, W. K., Cruz, A., Bouwer, S. D., Zhao, H., Ma, Q., Zhang, K., Baker, D. N., Li, X., Spence, H., and Reeves, G. D.: A Neural Network-Based Model of the Relativistic Electrons Fluxes in the Outer Radiation Belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6611, https://doi.org/10.5194/egusphere-egu22-6611, 2022.

18:16–18:22
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EGU22-7732
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ECS
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Artem Smirnov et al.

Pitch angle distributions (PADs) of trapped particles play an important role in understanding the processes driving the dynamics of Earth’s radiation belts and ring current. The Van Allen Probes mission has provided electron observations of PADs with an unprecedented coverage in energy (from tens of keV to several MeV) and pitch angles during the mission’s lifespan. We approximate the equatorial electron PADs using the Fourier sine series expansion up to degree 5. The corresponding coefficients can be directly related to the main PAD shapes (pancake, butterfly, flat-top and cap), and the approximated PADs can be easily integrated and converted to omnidirectional flux. Using the entire Van Allen Probes MagEIS data set in 2012-2019, we analyze the response of the equatorial electron PAD shapes to 129 geomagnetic storms with minimum Dst< -50nT. At lower energies (<100 keV), the PADs are stable throughout geomagnetic storms and mainly exhibit a pancake shape. At higher energies, the storm-time PAD evolution depends on the magnetic local time (MLT). At dayside, the pancake distributions become steeper during the main phase and then recover to their original broader form during recovery phase, likely due to the inward radial diffusion. At nightside MLT, the butterfly distributions become more pronounced during the main phase due to the combination of drift-shell splitting and magnetopause shadowing. We present a simple polynomial regression model of PAD shapes driven by the solar wind dynamic pressure. The model allows reconstructions of the full equatorial PADs based on uni-directional measurements at low equatorial pitch angles (applicable to LEO satellite data), as well as from omnidirectional electron flux observations and significantly outperforms the standard sin(alpha) approximation.

How to cite: Smirnov, A., Shprits, Y., Allison, H., Aseev, N., Drozdov, A., Kollmann, P., Wang, D., and Saikin, A.: Equatorial electron pitch angle distributions in Earth's outer radiation belt: Storm-time evolution and empirical modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7732, https://doi.org/10.5194/egusphere-egu22-7732, 2022.

Tue, 24 May, 08:30–10:00

Chairpersons: Chao Yue, Hayley Allison, Ondrej Santolik

08:30–08:36
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EGU22-9039
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ECS
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Highlight
Sandeep Kumar et al.

Geomagnetic storms are the main component of space weather and are driven by coronal mass ejections (CMEs) or corotating interaction regions (CIRs). During the main phase of geomagnetic storms, the ring current enhances and a global decrease in the H component of the geomagnetic field is observed. The storm time distribution of ring current ions and electrons in the inner magnetosphere depend strongly on their transport in evolutions of electric and magnetic fields along with acceleration and loss. Recently, we showed that the electron pressure contributes to the depression of ground magnetic field during the storm time by comparing Ring current Atmosphere interactions Model with Self Consistent magnetic field (RAM-SCB) simulation, Arase in-situ plasma/particle data, and ground-based magnetometer data [Kumar et al., 2021]. In this study, we compare the contribution of electron pressure to the ring current during selected CIR and CME geomagnetic storms using ground observations and the self-consistent inner magnetosphere model: RAM-SCB. The previous results show that the ions are the major contributor (~ 90 %) to the total ring current and the electron contributes ~10 % to the ring current pressure in the post-midnight to dawn sector where electrons flux is higher compared to ions flux. As CIR and CME storms have different origins, we will discuss expected differences in the contribution of electron pressure to the ring current.

How to cite: Kumar, S., Miyoshi, Y., Jordanova, V. K., Engel, M., Asamura, K., Yokota, S., Kasahara, S., Kazama, Y., Wang, S.-Y., Mitani, T., Keika, K., Hori, T., Jun, C.-W., and Shinohara, I.: A comparative study on electron contribution to the ring current during CME and CIR driven geomagnetic storms using RAM-SCB simulations and Arase and ground magnetic data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9039, https://doi.org/10.5194/egusphere-egu22-9039, 2022.

08:36–08:42
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EGU22-9034
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ECS
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Yun Yan and Chao Yue

Electromagnetic ion cyclotron (EMIC) wave plays an important role in precipitating relativistic electrons. In this study, we analyze an EMIC wave event on 6 November 2015 that extended over 6 hours in local time and the amplitude of this EMIC wave is about 3nT. Solar wind dynamic pressure enhancement excites EMIC waves, and whistler mode chorus waves are observed at the same time. When the EMIC wave occurs, the flux of relativistic electrons with pitch angle around 90° increases and the flux of small-pitch-angle relativistic electrons decreases. We calculate the electron PSD, which proves that EMIC wave leads to relativistic electron precipitation. Our result indicates that the large-amplitude EMIC wave will lead to nonlinear wave-particle interaction, thus leading to relativistic electron precipitation. When the wave amplitude is larger, the nonlinear wave-particle interaction becomes stronger.

How to cite: Yan, Y. and Yue, C.: EMIC Waves Induced by the Enhancement of Solar Wind Dynamic Pressure and Subsequent Relativistic Electron Precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9034, https://doi.org/10.5194/egusphere-egu22-9034, 2022.

08:42–08:48
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EGU22-9648
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ECS
Yuxuan Li et al.

Interplanetary (IP) shocks in general have strong impact on particles and electromagnetic field. In this study, we have examined the dynamics of cross-energy ions and plasma waves observed by the Van Allen Probe B satellite which was located near the equator at the noon sector after the impact of an IP shock on 27 Feb, 2014. We found that the ULF waves and electromagnetic waves are induced and the differential fluxes of protons with different energies increased or decreased after the IP shock arrival. For low energy ions (10-100eV), the perpendicular flux increased intensively due to ExB drift and betatron acceleration. These adiabatic processes also accounted for the special behavior of 10~200 keV ions, which are due to the positive gradient in phase space density before the IP shock arrival. In addition, the short-lived ultra-low frequency waves triggered by the IP shock interacted with the ~100 keV protons and resulting in the stripes in pitch angle distribution. Meanwhile, the anisotropic ions of ~50-300 keV generate EMIC wave at higher L shell after the shock arrival. This study reveals that an IP shock event can cause comprehensive responses of different energy ions and drive several plasma waves at the same time.

How to cite: Li, Y., Yue, C., Zong, Q., and Zhou, X.: Simultaneous Cross-energy Ion Response and Wave Generation after An Interplanetary Shock: A Case Study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9648, https://doi.org/10.5194/egusphere-egu22-9648, 2022.

08:48–08:54
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EGU22-3288
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ECS
Jiawen Tang et al.

Auroral kilometric radiations (AKR) are existed by suprathermal (1-10keV) electrons, which are accelerated by parallel electric fields and pitch angle scattered by magnetic field gradients. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study of AKR distribution characteristic in the region of λ = 0°−40°and L = 3.0−9.0. Results (totally 32,043 samples) show that southern AKR on the nightside (12,853 samples) are positioned to the east relative to their northern conjugates (13,630 samples), the wave frequencies and amplitudes of AKR in the southern hemisphere are greater than those in the northern hemisphere. Further studies suggest that SYM-H indexes and interplanetary magnetic field (IMF) have different distributions in the northern and southern hemispheres. The probable reason is that different IMF conditions cause asymmetric Field-aligned currents between the northern and southern hemispheres, then yield the asymmetry of AKR and auroras. This study helps to provide more information on the magnetosphere-ionosphere-atmosphere coupling.

How to cite: Tang, J., Xiao, F., Liu, S., and Zhang, S.: Asymmetry of Auroral Kilometric Radiation in the Northern and Southern hemispheres, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3288, https://doi.org/10.5194/egusphere-egu22-3288, 2022.

08:54–09:00
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EGU22-2109
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ECS
Sina Sadeghzadeh et al.

A localized flux tube with reduced entropy (PV5/3, where P and V stand for the plasma pressure and flux tube volume, respectively) as compared to its neighbors is defined as a plasma-sheet bubble. Bubbles are susceptible to interchange instability. The interchange instability plays a key role in the transport of plasma from the magnetotail to the near-Earth region. A strong dawn-to-dusk electric field is formed inside the bubble which creates a shear flow. The E×B drift causes the bubble to grow earthward and the magnetic tension force drives it towards the equilibrium location where its total entropy matches the entropy of the surrounding area. According to the Vasyliunas equation, when the angle (α) between ∇V and ∇PV5/3 is either 0 (being parallel) or 180° (being antiparallel), the Birkeland current cannot be flown between the plasma sheet and the ionosphere. In this study, using the linear instability analysis we investigate the excitation and development of interchange modes in the low-beta plasma sheet (β<<1) when 0<α<180°. To this end, a boundary layer (with thickness δ) separating regions of higher and lower entropy is assumed in a small region of the ionosphere. The first-order electric potential (Φ) within this layer is numerically calculated based on time-sequence technique. The complete analytical solution for the temporal variation of Φ clearly shows that the unstable interchange modes with large wavelengths compared to the boundary layer (i.e., λ>>δ) can be generated.

How to cite: Sadeghzadeh, S., Yang, J., and Mousavi, A.: Interchange instability analysis based on magnetosphere-ionosphere coupling theory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2109, https://doi.org/10.5194/egusphere-egu22-2109, 2022.

09:00–09:06
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EGU22-1678
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ECS
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Zheng Huang et al.

The Van Allen Probe B satellite simultaneously observed electromagnetic ion cyclotron (EMIC) and fast magnetosonic (MS) waves in a magnetic dip on April 29, 2017. During the magnetic dip, we found the coexistence of flux enhancements of ring current protons (∼11.2–∼51.7 keV) and flux reductions of relativistic electrons (∼1 MeV), which are identified as typical signatures of a magnetic dip in the inner magnetosphere. Based on linear theoretical calculations and observational analysis, the observed ring current protons show an anisotropic temperature distribution and partial shell distribution for different energies during the magnetic dip to provide free energies for the generation of EMIC and MS waves, respectively. Our findings indicate that the complex unstable distribution in the velocity phase space of ring current protons during the magnetic dip can trigger the simultaneous generation of EMIC and MS waves in the inner magnetosphere.

How to cite: Huang, Z., Yuan, Z., Yu, X., Xue, Z., and Ouyang, Z.: Simultaneous Generation of EMIC and MS Waves During the Magnetic Dip in the Inner Magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1678, https://doi.org/10.5194/egusphere-egu22-1678, 2022.

09:06–09:12
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EGU22-1623
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ECS
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Dan Deng et al.

 In this letter, we report an electromagnetic ion cyclotron (EMIC) harmonic event observed by the Van Allen Probe B, whose generation is demonstrated to result from nonlinear wave-wave resonances through the bicoherence analysis. Hybrid simulation shows that the second to sixth harmonics could be excited in sequence after a pump EMIC wave is initially injected, which is in consistent with the observations of EMIC harmonic. It indicates the important role of the second harmonic in the generation of higher harmonics. Finally, the statistical distribution for the amplitude of EMIC second harmonic waves indicates that the energy transfer rate from the fundamental wave to the second harmonic is mainly less than 2%, which might be too low to result in third and other higher harmonics above the observational level. Our results will give some new insights into the excitation of EMIC harmonic waves in the inner magnetosphere.

How to cite: Deng, D., Yuan, Z., Huang, S., Xue, Z., Huang, Z., and Yu, X.: Electromagnetic Ion Cyclotron Harmonic Waves Generated via Nonlinear Wave-Wave couplings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1623, https://doi.org/10.5194/egusphere-egu22-1623, 2022.

09:12–09:18
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EGU22-1426
Zhengyang Zou et al.

Previous studies demonstrated that frequency harmonic structures of fast magnetosonic (MS) waves are usually excited by the hot proton instability. Here, we present an unusual event of MS waves with more than six harmonics wavebands (n = 1–6) in which their high harmonic bands are highly phase-coupled with their fundamental waveband. While calculations of the wave growth rates indicate that the local instability of the hot protons can excite the fundamental waveband (n = 1) as well as only a part of wave branches in the second and third wavebands (n = 2, 3), the bicoherence index adopted to analyze the phase coupling between different wavebands provides evidence that the wave–wave coupling between the low-frequency parts of MS waves can contribute to the generation of their higher harmonics (n > 1). Such wave–wave coupling processes have the potential to additionally redistribute the energy of MS waves and then broaden the frequency range of wave–particle interactions, which has important implications for a better understanding of the generation, distribution, and consequence of space plasma waves.

How to cite: Zou, Z., Gao, Z., Zuo, P., and Ni, B.: Evidence of wave–wave coupling between frequency harmonic bands of magnetosonic waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1426, https://doi.org/10.5194/egusphere-egu22-1426, 2022.

09:18–09:24
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EGU22-1081
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ECS
Haimeng Li

Using observations of Van Allen Probes, we present a statistical study of plasmaspheric plumes in the inner magnetosphere. Plasmaspheric plumes tend to occur during the recovery phase of geomagnetic storms. Furthermore, the results imply that the occurrence rate of observed plasmaspheric plume in the inner magnetosphere is larger during stronger geomagnetic activity. This statistical result is different from the observations of the Cluster satellite with much higher L-shells in most orbital period, which suggest that the plasmaspheric plume near the magnetopause tends to be observed during moderate geomagnetic activity (Lee et al., 2016). In the following, the dynamic evolutions of plasmaspheric plumes during a moderate geomagnetic storm in February 2013 and a strong geomagnetic storm in May 2013 are simulated through group test particle simulation. It is obvious that the plasmaspheric particles drift out on open convection paths due to sunward convection during both geomagnetic storms. It seems that the outer plasmaspheric particles exhaust sooner and the plasmasphere shrinks faster during strong geomagnetic storms. As a result, the longitudinal width of the plume is narrower and the plume is limited to lower L-shells during the recovery phase of strong geomagnetic storm. The simulated evolutions may provide a possible interpretation for the occurrence rates: Van Allen Probes tend to observe plumes during stronger geomagnetic storms, and the Cluster satellite with higher L-shells tends to observe plumes during moderate geomagnetic storms. 

How to cite: Li, H.: Statistical Study and Corresponding Evolution of Plasmaspheric Plumes under Different Levels of Geomagnetic Storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1081, https://doi.org/10.5194/egusphere-egu22-1081, 2022.

09:30–09:36
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EGU22-2136
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ECS
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Highlight
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Deyu Guo et al.

Bounce-resonant diffusion coefficients of radiation belt energetic electrons induced by extremely low-frequency (ELF) chorus waves are comprehensively evaluated using Van Allen Probes observations on 22 December 2014. ELF chorus waves can efficiently scatter 85° < eq < 89° electrons with bounce resonance pitch angle scattering rates above 10-4/s and energy scattering rates above 10-7/s. By comparing diffusion coefficients due to bounce resonance with those due to cyclotron and Landau resonances, we found that bounce resonance diffusion rates have slight energy dependence for >100 keV electrons while Landau-resonant scattering rates decrease significantly in the MeV energy range. These findings suggest that bounce resonances by ELF chorus waves have potentially significant contributions to the dynamics of energetic electrons and should be considered in the further modeling of Earth’s radiation belts.

How to cite: Guo, D., Xiang, Z., Ni, B., Cao, X., Fu, S., Zhou, R., Gu, X., Yi, J., Guo, Y., and Jiao, L.: Bounce Resonance Scattering of Radiation Belt Energetic Electrons by Extremely Low-Frequency Chorus Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2136, https://doi.org/10.5194/egusphere-egu22-2136, 2022.

09:36–09:42
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EGU22-1143
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ECS
Hui-Ting Feng et al.

Throat auroras frequently observed near local noon have been confirmed to correspond to magnetopause indentations, but the generation mechanisms for these indentations and the detailed properties of throat aurora are both not fully understood. Using all‐sky camera and magnetometer observations, we reported some new observational features of throat aurora as follows. (1) Throat auroras can occur under stable solar wind conditions and cause clear geomagnetic responses. (2) These geomagnetic responses can be simultaneously observed at conjugate geomagnetic meridian chains in the Northern and Southern Hemispheres. (3) The initial geomagnetic responses of throat aurora show concurrent onsets that were observed at all stations along the meridians. (4) Immediately after the concurrent onsets, poleward moving signatures and micropositive bays were observed in the X components at higher‐ and lower‐latitude stations, respectively. We argue that these observations provide evidence for throat aurora being generated by low‐latitude magnetopause reconnection. We suggest that the concurrent onsets reflect the instantaneous responses of the reconnection signal arriving at the ionosphere, the followed poleward moving signatures reflect the antisunward dragging of the footprint of newly opened field lines, and the micropositive bays may result from a pair of field‐aligned currents generated during the reconnection. This study may shed new light on the geomagnetic transients observed at cusp latitude near magnetic local noon.

How to cite: Feng, H.-T., Han, D., Chen, X., Liu, J., and Xu, Z.: Interhemispheric Conjugacy of Concurrent Onset and Poleward Traveling Geomagnetic Responses for Throat Aurora Observed Under Quiet Solar Wind Conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1143, https://doi.org/10.5194/egusphere-egu22-1143, 2022.

09:42–09:48
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EGU22-4043
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ECS
Ping Li et al.

Auroral kilometric radiation (AKR) is one of the strong radio emission phenomenons with kilometer wavelengths, and similar emissions have been detected on other magnetized planets of the solar system. AKR is generated by suprathermal electrons (1-10 keV) injected from the plasma sheet and has been observed at the lower latitude region of the radiation belts from the Van Allen Probes. Here, we analyze the seasonal characteristic of AKR in the region of L = 3-7 and λ = 0− 20using observations from 1 December 2012 to 31 November 2018. Statistical results (4,559 events in total) show that AKR emissions occur most frequently in autumn both in the northern and southern hemispheres. The correlation coefficient between the number of AKR events in each season and the Kp (the geomagnetic activity index) index of these events can reach 0.82. These results suggest that AKR emissions in the lower latitude regions depend on the geomagnetic activity.

How to cite: Li, P., Xiao, F., Liu, S., and Zhang, S.: Seasonal Characteristic of Auroral Kilometric Radiation in the Radiation Belts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4043, https://doi.org/10.5194/egusphere-egu22-4043, 2022.

09:48–09:54
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EGU22-6712
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ECS
Yang Qiwu et al.

Electron cyclotron harmonic (ECH) waves which mainly observed in the first harmonic band are believed to play a part in scattering diffuse aurora electrons in the Earth's magnetosphere. Here we report two enhanced ECH emission events with nominal wave magnitudes exceeding 1mV/m in higher bands ( up to the 4th harmonic bands) observed from Van Allen Probes mission during geomagnetic disturbance periods in the low density area. Based on actual measurements sampled by Van Allen Probes, we model the electron distribution using a superposition of bi-Maxwellian functions and then numerically evaluate the local growth rates and diffuse coefficients. These differences in frequency distribution for two events can be explained by differences in the loss cone feature of hot electron components. The scattering properties in the first four bands for two events are debated, these results suggest ECH waves in higher band can still cause efficient pitch angle scattering which are similar to ECH waves in the first band. This work broadens our understanding in the formation of diffuse aurora contributed by ECH waves.

How to cite: Qiwu, Y., Fuliang, X., Qinghua, Z., Si, L., Zhonglei, G., Yihua, H., Sai, Z., Zhoukun, D., and Jiawen, T.: Observations of Higher-band ECH waves and its impact on radiation belt energetic electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6712, https://doi.org/10.5194/egusphere-egu22-6712, 2022.