Session NM10: Mini-Conference on Nonlinear Waves and Processes in Space Plasmas II

The Field-Particle Correlation Technique: A Nonlinear Method for Determining Particle Energization in Space Plasmas

Understanding the removal of energy from turbulent fluctuations in a
magnetized plasma and the consequent energization of the constituent
plasma particles is a major goal of heliophysics.  Under the weakly
collisional conditions typical of the solar wind plasma, kinetic
theory dictates that the energy of turbulent fluctuations of the
electromagnetic fields and plasma flows is removed collisionlessly
through inherently nonlinear interactions between the electromagnetic
fields and the individual motions of the charged particles that make
up the plasma.  We present the fundamentals of the recently developed
field-particle correlation technique, and show examples from nonlinear
kinetic numerical simulations of how it can be used with single-point
spacecraft measurements to distinguish and characterize different
collisionless particle energization mechanisms.   

Evidence for Electron Landau Damping in Space Plasma Turbulence

One of the unanswered questions in space plasma physics is how energy is dissipated at the small scale end of the turbulent cascade. To help address this, we apply a new field-particle correlation technique to measure the energy transfer to particles in magnetosheath turbulence. The technique separates the oscillatory and secular components and allows the secular energy transfer to be measured in velocity space. Here, we present results of the parallel transfer to electrons, which shows signatures consistent with Landau damping. This suggests electron Landau damping may play a significant role in turbulent dissipation and that the technique is a useful tool to understand the processes involved in turbulent dissipation.   

Plasma turbulence, nonlinear structures and cascades as seen in spacecraft and fusion-science data

We study nonlinear coupling of waves and the cascades near the outer Magnetospheric boundaries and compare the coupling with that in fusion devices. In [Budaev et al, JPP 81 (2015) 395810602] we demonstrated some universalities of turbulence in both space and fusion turbulent plasma. We conclude that the magnetopause resembles edge plasma in fusion devices. In both media, nonlinear bursts/structures lead to the intermittent anomalous transport. We discovered in space data (CLUSTER, INTERBALL-1, DOUBLE STAR, SPECTR-R, GEOTAIL) very weak but effective nonlinear bursts that govern, at first, the discrete 3-wave cascades at 0.3-10 mHz in the energetically dominant dynamic pressure. The 3-wave cascades (being smeared by the turbulent background plasma) transfer into the developed turbulence at the higher frequencies. We have detected those weak waves in the sunward Poynting flux component. We discuss the nature of these quasi-discrete waves, whether they are fast magnetosonic or fast Alfven nonlinear waves. Comparative analysis of space data with the fusion database is now a foundation for the program on plasma turbulence, nonlinear structures and cascades being studied in new plasma device PLM (plasma linear multi-cusps) recently constructed at NRU Moscow Power Engineering Institute   

The turbulent plasmasphere boundary layer

We explore multisatellite observations of enhanced plasma turbulence in the plasmasphere boundary layer during penetration of substorm-injected plasma jets into the plasmasphere.  injection events. A turbulent plasmaspheric boundary layer forms initially near the pre-substorm plasmapause due to interactions between the injected and plasmaspheric populations. A number of plasma instabilities develops during this highly dynamic process via interaction of the overlapping hot and cold plasma populations and excites lower hybrid/fast magnetosonic turbulence and broadband hiss-like VLF waves. The outcomes the excited turbulence for the subauroral geospace, such as collisionless heating and acceleration of plasma particles to suprathermal energies, which enhances the downward heat flux and concomitant heating of the ionospheric electrons, are discussed.   

Tearing-mode influence on two-dimensional magnetohydrodynamic turbulence

It has recently been proposed that magnetohydrodynamic (MHD) turbulence can be modified by the tearing mode in high Lundquist number flows. Simulations of strong MHD turbulence have demonstrated the creation of highly anisotropic, current-sheet-like structures at small scales within the inertial range. The recently proposed phenomenological picture contends that there exists some critical length scale at which the tearing mode within these structures can compete with the turbulent evolution of an eddy, and beyond which the turbulence within the end of the inertial range is modified, notably the energy spectra and alignment angle.

Our work numerically demonstrates that, in fact, the tearing mode can modify the turbulence within an anisotropic current sheet, changing the energy spectra. Using a highly-anisotropic two-dimensional simulation domain, one can access the high Lundquist numbers needed to produce this phenomenon.