Multiscale Magnetotail Dipolarizations
Abstract
Magnetotail dipolarizations that release large amount of energy to power substorms, storms and smaller-scale processes, such as pseudobreakups, bursty bulk flows and dipolarization fronts, are inherently multiscale. They combine global reconfigurations of the magnetosphere with kinetic processes on the scales of ion and electron orbits, which are necessary to provide dissipation in collisionless plasmas making dipolarizations irreversible. At the same time, the free energy for magnetotail instabilities resulting in dipolarizations depends on the global structure of the tail, including equatorial distributions of currents and magnetic flux. In this study we to try to understand the mechanisms of multiscale dipolarizations and their contributions to energy conversion and dissipation in magnetospheric plasmas by combining global and local kinetic analyses. On the global scale, the MHD description of substorms is compared with the data-derived picture of their currents and magnetic field inferred from spacebourne magnetometer data to identify regions that require non-MHD description. They include X-lines, thin current sheets, with the thickness comparable to the thermal ion gyroradius and regions of the tailward gradient of the equatorial magnetic field. The parameters of non-MHD regions are then used to guide micro-scale kinetic analysis and simulations. On micro scales, dipolarizations are simulated using PIC codes and compared with observations tail destabilization regimes and their features, including the ion and electron energy conversion and dissipation. Complementing observations and simulations of the electron diffusion region, this study is focused on the energy conversion around dipolarization fronts and in thin current sheets, as well as on ion kinetics, which is closer to MHD scales.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSM42A..03S
- Keywords:
-
- 2730 Magnetosphere: inner;
- MAGNETOSPHERIC PHYSICSDE: 2736 Magnetosphere/ionosphere interactions;
- MAGNETOSPHERIC PHYSICSDE: 2740 Magnetospheric configuration and dynamics;
- MAGNETOSPHERIC PHYSICSDE: 2788 Magnetic storms and substorms;
- MAGNETOSPHERIC PHYSICS