Open boundary particle‐in‐cell simulation of dipolarization front propagation

Abstract

[1] First results are presented from an ongoing open boundary 2½D particle-in-cell simulation study of dipolarization front (DF) propagation in Earth's magnetotail. At this stage, this study is focused on the compression, or pileup, region preceding the DF current sheet. We find that the earthward acceleration of the plasma in this region is in general agreement with a recent DF force balance model. A gyrophase bunched reflected ion population at the leading edge of the pileup region is reflected by a normal electric field in the pileup region itself, rather than through an interaction with the current sheet. We discuss plasma wave activity at the leading edge of the pileup region that may be driven by gradients, or by reflected ions, or both; the mode has not been identified. The waves oscillate near but above the ion cyclotron frequency with wavelength several ion inertial lengths. We show that the waves oscillate primarily in the perpendicular magnetic field components, do not propagate along the background magnetic field, are right handed elliptically (close to circularly) polarized, exist in a region of high electron and ion beta, and are stationary in the plasma frame moving earthward. We discuss the possibility that the waves are present in plasma sheet data, but have not, thus far, been discovered.

Electron dynamics surrounding the X line in asymmetric magnetic reconnection

“…where L = 0.5d i is the half thickness of the transition layer. This model was proposed by Pritchett [2008] and slightly modified by Klimas et al [2014]. The R = 1∕2 parameter gives a variation in magnetic field from −0.5B 0 to 1.5B 0 .…”

“…We used the following initial model, where L = 0.5 d i is the half thickness of the transition layer. This model was proposed by Pritchett [] and slightly modified by Klimas et al []. The R = 1/2 parameter gives a variation in magnetic field from −0.5 B 0 to 1.5 B 0 .…”

“…37 and slightly modified by Klimas et al26 . The R = 1/2 parameter gives a variation in magnetic field from −0.5B 0 to 1.5B 0 .…”

Contribution of ion reflection to the energy budgets of dipolarization fronts

“…Under the ideal magnetic frozen‐in approximation, there is no electric field in this frame of reference. Such an approximation neglects the Hall electric field in the DF normal direction [ Fu et al , ; Sun et al , ; Klimas et al , ], which according to Zhou et al [] only slightly changes the energy conversion picture of ion DF reflection. Therefore, the ion motion after its encounter with the DF can be treated as an elastic reflection.…”