We present results from a multiscale spatiotemporal analysis of 3D Hall-MHD and hybrid kinetic numerical simulations of decaying plasma turbulence. By combining Fourier analysis and Fast Iterative Filtering, we compute the 3D k-ω power spectrum of the magnetic and velocity fluctuations at the time when turbulence has fully developed. We find that the magnetic fluctuations around and just below the ion characteristic scales mainly consist of strongly anisotropic perturbations, with temporal frequencies smaller than the ion-cyclotron frequency and with wave vectors almost perpendicular to the ambient magnetic field. Further analysis reveals that such perturbations cannot be described in terms of wave-like fluctuations, but rather consist of localized structures that are organized in a filamentary network of current sheets, which continuously form and disrupt as a consequence of magnetic reconnection, spontaneously induced by the interaction of turbulent structures. We discuss similarities and differences with respect to previous findings from 2D simulations, and we put our results in the context of spacecraft observations in the solar wind.

How to cite: Papini, E., Cicone, A., Piersanti, M., Franci, L., Verdini, A., Montagud-Camps, V., Hellinger, P., and Landi, S.: Characterization of space-time structures in 3D simulations of plasma turbulence with Fast Iterative Filtering., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7142, https://doi.org/10.5194/egusphere-egu22-7142, 2022.

First perihelion Parker Solar Probe magnetic field measurements (MAG and SCM merged data) allow to resolve the fluctuations on a wide range of scales: from MHD to ion plasma scales and smaller. We trace the cascade of the fluctuations and investigate the structures formed. Using the total energy of magnetic fluctuations in time and scales, we show that coherent structures cover all the observed scales. The filling factor of the structures is a few percents. We analyze the magnetic fluctuations at different frequency ranges. We observe the coexistence of events at MHD, ion and sub-ion scales in the form of sharp discontinuities and/or vortex-like events. The approach of selecting structures by total energy alone is not complete, as it can miss structures with change in magnetic field modulus. For completeness, we perform the same analysis on longitudinal magnetic fluctuations.

How to cite: Vinogradov, A., Alexandrova, O., Maksimovich, M., Artemyev, A., Mangeney, A., Vasiliev, A., Issautier, K., Moncuquet, M., and Petrukovich, A.: PSP observations of the solar wind coherent structures from MHD to sub-ion scales at 0.17 AU, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9796, https://doi.org/10.5194/egusphere-egu22-9796, 2022.

Fluctuations of magnetic field in space plasmas at sub-protonic scales have been supposed to be the result of a turbulence process involving different wave modes (EMHD, KAW, …). However, the observed spectral and scaling features seem to be non-universal. Furthermore, there is a wide evidence for the occurrence of a global scale invariance. Now, the complex nature of the fluctuations at these scales could be due to the interweaving of fluid and kinetic processes that might alter the usual scenario expected for the occurrence of strong turbulence. Here, using high-resolution data from the Parker’ Solar Probe mission we attempt an analysis of the scaling features of magnetic field fluctuations at sub-protonic scales using different approaches: i) the structure function analysis, ii) the singularity spectrum analysis and the rank-ordered multifractal analysis. The aim of these multiple approaches is to unveil the inherent complexity of fluctuation field at sub-protonic scale and to understand the controversial issues related to the occurrence of intermittency at these scales.

How to cite: Consolini, G., Benella, S., Alberti, T., and Stumpo, M.: On the scaling features of magnetic field fluctuations at sub-protonic scales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10948, https://doi.org/10.5194/egusphere-egu22-10948, 2022.

We investigate properties of solar-wind like plasma turbulence using direct numerical simulations. We analyze the transition from large (magnetohydrodynamic) scales to ion ones using two-dimensional hybrid (fluid electrons, kinetic ions) simulations of decaying turbulence. To quantify turbulence properties we apply spectral transfer and Karman-Howarth-Monin equations for extended compressible Hall MHD to the simulated results. The simulation results indicate that the transition from MHD to ion scales (the so called ion break) results from a combination of an onset of Hall physics and of an effective dissipation owing to the pressure-strain energy-exchange channel and resistivity. We discuss the simulation results in the context of the solar wind.

How to cite: Hellinger, P., Montagud-Camps, V., Franci, L., Matteini, L., Papini, E., Verdini, A., and Landi, S.: Ion-scale transition of plasma turbulence: Pressure-strain effect, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8357, https://doi.org/10.5194/egusphere-egu22-8357, 2022.

How to cite: David, V., Galtier, S., Sahraoui, F., and Hadid, L.: Energy transfer, discontinuities and heating in the inner solar wind measured with a weak and local formulation of the Politano-Pouquet law, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1155, https://doi.org/10.5194/egusphere-egu22-1155, 2022.

In recent years, the Kolmogorov's statistical formalism of exact law that describes incompressible hydrodynamic turbulence, has been extended to compressible magnetized fluid described by isothermal or polytropic closure. Such exact laws permit an evaluation of the energy cascade rate, assumed within this formalism to be equivalent to the dissipation rate. Its estimation in the solar wind can help to better understand particle heating in such collisionless media. But previous exact laws are insufficient in a system led by pressure anisotropy. We propose a general exact law of Hall-MHD turbulence based on models with a pressure tensor that allows us to study various known equations of state as particular limits, derive a new one corresponding to the CGL (i.e., gyrotropic pressure tensor), and correlate the cascade rate to instable plasma conditions. In the incompressible MHD limit we provide a generalization of the Politano & Pouquet law to pressure-anisotropic plasmas.

How to cite: Simon, P. and Sahraoui, F.: A link between turbulent cascade and gyrotropic pressure instabilities in compressible and magnetized fluids. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4524, https://doi.org/10.5194/egusphere-egu22-4524, 2022.

How to cite: Teissier, J.-M. and Müller, W.-C.: Inverse transfer of magnetic helicity in isothermal supersonic turbulence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11566, https://doi.org/10.5194/egusphere-egu22-11566, 2022.

Parker Solar Probe provides a unique opportunity to study anisotropic turbulence in the inner heliosphere. We summarize our recent investigations of solar wind turbulence observed by Parker Solar Probe during its first seven orbits ranging from 0.1 to 0.6 AU. First, we analyzed turbulence anisotropy based on the 2D + slab model and determined the power ratio between the 2D and slab components. We find that the fraction of the 2D component increases with radial distance. Second, we developed a method to identify small-scale magnetic flux ropes and Alfvenic structures based on the reduced magnetic helicity. Alfvenic structures are prevalent in both slow and fast solar wind in PSP's measurements, while the small flux ropes are quasi-2D structures and are relatively abundant near the heliospheric current sheet and slow solar wind. Finally, we analyzed intervals with solar wind velocity strictly parallel to the mean magnetic field. We find a Kolmogorov-like power spectrum with a power-law index of -5/3. Wave activities in both MHD and kinetic scales are also analyzed in these field-aligned intervals. Fast magnetosonic waves and ion-scale waves are identified.

How to cite: Zhao, L., Zank, G., Adhikari, L., Nakanotani, M., Telloni, D., Hu, Q., and He, J.: Turbulence anisotropy observed by Parker Solar Probe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10131, https://doi.org/10.5194/egusphere-egu22-10131, 2022.

The sheath regions driven by coronal mass ejections (CMEs) are large-scale heliospheric structures where magnetic field fluctuations are observed over various temporal scales. Their internal structure and nature of embedded  fluctuations are currently poorly understood. We report here the key characteristics of  magnetic field fluctuations in CME-driven sheaths, including their spectral index, intermittency, amplitude and compressibility. The results highlight the gradual formation of sheaths over several days as they propagate through interplanetary and the presence of intermittent coherent structures such as strong current sheets. The Jensen-Shannon permutation entropy and complexity analysis suggest that sheath fluctuations are stochastic, but have lower entropy and higher complexity than the preceding wind.  We also show the analysis results during the slow sheath at ~0.5 AU detected by Parker Solar Probe, highlighting that slow CMEs can have prominent sheaths with distinct fluctuation properties. 

How to cite: Kilpua, E., Good, S., Ala-Lahti, M., Osmane, A., Fontaine, D., Pal, S., Räsänen, J., Bale, S., Zhao, L., Hadid, L., Janvier, M., and Yordanova, E.: Magnetic field fluctuations in CME-driven sheath regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6199, https://doi.org/10.5194/egusphere-egu22-6199, 2022.

The solar wind is a continuous outflow of plasma from the Sun, which expands into the space between the planets in our solar system and forms the heliosphere. The solar wind is inherently turbulent and characterised by kinetic micro-instabilities on a range of scales.  Large-scale compressions (ubiquitous in solar-wind turbulence) create conditions for proton, alpha-particle and electron micro-instabilities, which transfer energy to small-scale fluctuations. These instabilities are driven by various sources of free energy (e.g. particle beams, differential flows, heat fluxes, temperature anisotropies) and make a significant contribution to the fluctuation spectrum at kinetic scales, where energy dissipation occurs. This presentation investigates the occurrence and the behaviour of kinetic instabilities in turbulent space plasmas with particular emphasis on the conditions necessary for instabilities to act.

We consider instabilities driven by proton temperature anisotropy in the turbulent solar wind by using statistical methods to analyse the Solar Orbiter data and characterise the turbulence at the relevant scales and amplitude. We compare theoretical calculations with the high-resolution data available from the Solar Orbiter MAG and SWA instruments. From this analysis we infer conditions that are necessary for instabilities to act in a turbulent plasma and demonstrate how these conditions relate to the assumptions that underpin theoretical analyses at kinetic scales. We will also introduce the next steps in this research, including the modelling and quantification of energy transfer processes at kinetic scales with particular reference to scaling law behaviours in the turbulent solar wind.   

How to cite: Opie, S., Verscharen, D., Chen, C., and Owen, C.: Can instabilities work in a turbulent plasma and if so, what conditions are needed for instabilities to act?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1298, https://doi.org/10.5194/egusphere-egu22-1298, 2022.

In the solar wind, whistler waves are thought to play an important role on the evolution of the electron velocity distribution function as a function of distance. In particular, oblique whistler waves may diffuse the Strahl electrons into the halo population. Using AC magnetic and electric field measured by the SCM (search coil magnetometer) and electric antenna of Solar Orbiter and Parker Solar Probe, we search for the presence of whistler waves at heliocentric distance between 0.17 and 1 AU. Spectral matrices computation and minimum variance analysis on continuous waveforms make it possible to identify whistler wave modes and to determine their direction of propagation with respect to the ambiant magnetic field (angle and direction : sunward or anti-sunward) . A statistical study of the inclination of these waves and of their parameters is presented and allows us to make assumptions about their roles. Single events are also presented in details

How to cite: Colomban, L., Kretzschmar, M., Krasnoselskikh, V., Maksimovic, M., Graham, D., Khotyainsev, Y., Berĉiĉ, L., Berthomier, M., and Froment, C.: What is the role of oblique whistler waves in shaping of the solar wind electron function between 0.17 and 1 AU ?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7265, https://doi.org/10.5194/egusphere-egu22-7265, 2022.

Magnetic holes are plasma structures that trap a large number of particles in a magnetic field that is weaker than its surroundings. The unprecedented high time-resolution in-situ observations by NASA's Magnetospheric Multi-Scale (MMS) mission enable us to study the particle dynamics in the Earth's magnetosheath plasma in great detail. For the first time, we reveal the local generation of whistler waves by the Landau-resonant instability of electron beams as a response to the large-scale evolution of a magnetic hole. As the magnetic hole converges, we find a pair of counter-streaming electron beams are formed near the hole's center as a consequence of the combined action of betatron cooling and Fermi acceleration. The beams trigger the generation of slightly oblique whistler waves near the hole center, which is supported by a remarkable agreement between observations and our ALPS model predictions. Our findings show that kinetic effects and wave-particle interactions are fundamental to the dynamics and the evolution of magnetic holes as an important type of coherent structures in collisionless plasmas.

How to cite: Jiang, W., Verscharen, D., Li, H., Wang, C., and Klein, K.: Local Emission of Whistler Waves by Landau Resonance As a Signature of a Converging Magnetic Hole, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12969, https://doi.org/10.5194/egusphere-egu22-12969, 2022.

Recent observational and theoretical work on solar wind turbulence and dissipation suggests that kinetic-scale fluctuations are both heating and isotropizing the solar wind during transit to 1 AU.  The nature of these fluctuations and associated heating processes are poorly understood. Whatever the dissipative process that links the fields and particles - Landau damping, cyclotron damping, stochastic heating, or energization through coherent structures - heating and acceleration of ions and electrons occurs because of electric field fluctuations. The dissipation due to the fluctuations depends intimately upon the temporal and spatial variations of those fluctuations in the plasma frame.  In order to derive that distribution in the plasma frame, one must also use magnetic field and density fluctuations, in addition to electric field fluctuations, as measured in the spacecraft frame (s/c) to help constrain the type of fluctuation and dissipation mechanisms that are at play.

We present here an analysis of electromagnetic fluctuations in the solar wind from MHD scales down to electron scales based on data from the Artemis spacecraft at 1 AU. We focus on a few time intervals of pristine solar wind, covering a reasonable range of solar wind properties (temperature ratios and anisotropies; plasma beta; and solar wind speed). We analyze magnetic, electric field, and density fluctuations from the 0.01 Hz (well in the inertial range) up to 1 kHz. We compute parameters such as the electric to magnetic field ratio, the magnetic compressibility, magnetic helicity, compressibility and other relevant quantities in order to diagnose the nature of the fluctuations at those scales between the ion and electron cyclotron frequencies, extracting information on the dominant modes composing the fluctuations. We also use the linear Vlasov-Maxwell solver, PLUME, to determine the various relevant modes of the plasma with parameters from the observed solar wind intervals. We discuss the results and the relevant modes as well as the major differences between our results in the solar wind and results in the magnetosheath.

How to cite: Salem, C., Bonnell, J., Huang, J., Chaston, C., Franci, L., Klein, K., and Verscharen, D.: Electric Field Turbulence in the Solar Wind from MHD down to Electron Scales: Artemis Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3967, https://doi.org/10.5194/egusphere-egu22-3967, 2022.

Quantifying the nature of turbulent fluctuations and the associated cascade of energy requires simultaneous measurements at multiple points spanning several characteristic length scales. Here, we present the HelioSwarm mission concept, which has been designed to reveal the three-dimensional, dynamic mechanisms controlling the physics of plasma turbulence. The HelioSwarm Observatory measures the plasma and magnetic fields with a novel configuration of spacecraft in the solar wind, magnetosheath, and magnetosphere. These simultaneous multi-point, multi-scale measurements span MHD, transition, and ion-scales, allowing us to address two overarching science goals: 1) Reveal the 3D spatial structure and dynamics of turbulence in a weakly collisional plasma and 2) Ascertain the mutual impact of turbulence near boundaries and large-scale structures. Addressing these goals is achieved using a first-ever "swarm" of nine spacecraft, consisting of a "hub" spacecraft and eight "node" spacecraft. The nine spacecraft co-orbit in a lunar resonant Earth orbit, with a 2-week period and an apogee/perigee of ~60/11 Earth radii. Flight dynamics design and on-board propulsion produce ideal inter-spacecraft separations ranging from fluid scales (1000's of km) to sub-ion kinetic scales (10's of km) in the necessary geometries to enable the application of a variety of established analysis techniques that distinguish between proposed models of turbulence. Each node possesses an identical instrument suite that consists of a Faraday cup, a fluxgate magnetometer, and a search coil magnetometer. The hub has the same instrument suite as the nodes, plus an ion electrostatic analyzer. With these measurements, the HelioSwarm Observatory promises an unprecedented view into the nature of space plasma turbulence.

How to cite: Klein, K. and Spence, H. and the The HelioSwarm Science Team: HelioSwarm: The Nature of Turbulence in Space Plasma, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12990, https://doi.org/10.5194/egusphere-egu22-12990, 2022.