Nonlinear Interaction of ULF Wave Packets, Formation of Non-Propagating EM-Plasma Structures and Plasma Energization (Invited)

Abstract:

The nonlinear interaction of ULF wave packets in strongly inhomogeneous plasma regions can produce non-propagating electromagnetic-plasma structures. The quasi-steady dynamical structures are often characterized by localized strong electrostatic electric fields, density cavities and enhanced magnetic and mechanical stresses. The free energy stored in locally enhanced magnetic and velocity fields can support the irreversible generation of electrostatic electric fields during a meaningful time interval. The generated electrostatic electric fields supported by the local dynamo can cause effective acceleration and energization of charged particles, deepening the low density cavity.

In auroral acceleration regions, transverse Alfvenic Double Layers (TA-DL) and charge holes (TA-CH) are such EM-plasma structures. These structures are responsible for auroral particle acceleration and the formation of quasi-static and Alfvenic discrete auroras. The TA-DL not only can accelerate electrons to high energy, but also may cause ion outflows, perpendicular ion heating and create proper conditions for generating Auroral Kilometric Radiation.

ULF waves play a crucial role in plasma energization and acceleration. By propagation and reflection, ULF waves provide a main energy supply for charged particle acceleration and energization. ULF waves also can redistribute the magnetic and kinetic stresses and generate a local stress concentration in regions of strong gradients in the plasma and fields. In such regions, the non-propagating EM-plasma structures are created by nonlinear interaction of ULF wave packets. These structures act as powerful high energy particle accelerators and important plasma EM wave radiators in cosmic plasmas.