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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 (D_LL) 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.

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=k_y<V_d> where k_y is the transverse wavelength and <V_d> 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.

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.

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.

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.

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.

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.

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.

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.

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^◦− 20^◦ using 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.

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 4^th 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.