Bibliography

Evaluation of Plasma Properties From Chorus Waves Observed at the Generation Region

In this study we present an inversion method which provides thermal plasma population parameters from characteristics of chorus emissions only. Our ultimate goal is to apply this method to ground-based data in order to derive the lower-energy boundary condition for many radiation belt models. The first step is to test the chorus inversion method on in situ data of the Van Allen Probes in the generation region. The density and thermal velocity of energetic electrons (few kiloelectron volts to 100 keV) are derived from frequency sweep rate and starting frequencies of chorus emissions through analysis of wave data from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes. The nonlinear wave growth theory of Omura and Nunn (2011, https://doi.org/10.1029/2010JA016280) serves as the basis for our inversion method, assuming that the triggering wave is originated by the linear cyclotron instability. We present 16 consecutive rising-tone emissions recorded in the generation region between 11 and 12 UT on 14 November 2012. The results of the inversion are compared with density and thermal velocities (parallel and perpendicular) of energetic electrons derived from the unidirectional flux data of the Helium, Oxygen, Proton, and Electron instrument, showing a good agreement: The normalized root-mean-square deviation between the measured and predicted values are less than \~15\%. We found that the theoretical amplitudes are consistent with the measured ones. The relation between linear and nonlinear wave growth agrees with our basic assumption; namely, linear growth is a preceding process of nonlinear wave growth. We analyze electron distributions at the relativistic resonant energy ranges.

asz, Lilla; Omura, Yoshiharu; Lichtenberger, J\; Friedel, Reinhard;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2019

YEAR: 2019     DOI: 10.1029/2018JA026337

chorus inversion; Van Allen Probes; Wave-particle interaction

THEMIS observation of intermittent turbulence behind the quasi-parallel and quasi-perpendicular shocks

Turbulence is complex behavior that is ubiquitous in nature, but its mechanism is still not sufficiently clear. Therefore, the main aim of this paper is analysis of intermittent turbulence in magnetospheric and solar wind plasmas using a statistical approach based on experimental data acquired from space missions. The quintet spacecraft of Time History of Events and Macroscale Interactions during Substorms (THEMIS) allows us to investigate the details of turbulent plasma parameters behind the collisionless shocks. We investigate both the solar wind and magnetospheric data by using statistical probability distribution functions of Elsässer variables that can reveal the intermittent character of turbulence in space plasma. Our results suggest that turbulence behind the quasi-perpendicular shock is more intermittent with larger kurtosis than that behind the quasi-parallel shocks, which are immersed in a relatively quiet solar wind plasma, as confirmed by Wind measurements. It seems that behind the quasi-perpendicular shock the waves propagating outward from the Sun are larger than possibly damped waves propagating inward. In particular, we hope that this difference in characteristic behavior of the fluctuating space plasma parameters behind both types of shocks can help identify complex plasma structures in the future space missions. We also expect that the results obtained in this paper will be important for general models of turbulence.

Macek, W.; Wawrzaszek, A.; Sibeck, D.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 09/2015

YEAR: 2015     DOI: 10.1002/2015JA021656

intermittency; magnetosheath; shocks; Solar wind; Space plasma; turbulence