SM22A-01
Spontaneous formation of magnetotail bursty bulk flows, dipolarization fronts, and corresponding changes of magnetic topology
Tuesday, 15 December 2015: 10:20
2018 (Moscone West)
Mikhail I. Sitnov, Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, Viacheslav G Merkin, Johns Hopkins University, Baltimore, MD, United States and Andrei Runov, University of California Los Angeles, Los Angeles, CA, United States
Abstract:
It is commonly assumed that magnetotail transients are caused by either changes of magnetic topology or buoyancy-driven ballooning/interchange processes. However, observations and 3D particle-in-cell simulations show that the primary process in the formation of dipolarization fronts, new X-lines, interchange fingers and flapping motions may be the spontaneous formation of bulk earthward plasma flows. It appears in tearing-unstable configurations with a tailward gradient of the normal magnetic field Bz. The earthward motion arising in these regions results in the formation of dipolarization fronts (DFs). While monopolar Bz variations in DFs can be explained by the MHD snowplow compression of plasma ahead of the front, the formation of new X-lines ahead of and behind the front occurs as a part of the kinetic process of the plasma bubble formation. This process enhances (initially mild) buoyancy of the magnetotail plasma sheet and thus instigates ballooning/interchange and flapping instabilities. We compare the properties of reconnection, buoyancy and flapping transients at the front, ahead and behind it as well as the corresponding energy conversion and plasma heating.
