July 27, 2015 to August 21, 2015
Nordita, Stockholm
Europe/Stockholm timezone

Magnetic Reconnection in the Magnetotail: Onset Mechanisms and Structure of Exhaust Jets in 3D

Aug 11, 2015, 3:45 PM
FD5 (Nordita, Stockholm)


Nordita, Stockholm

Oral Workshop, August 10-14 Afternoon II


Dr Philip Pritchett (University of California, Los Angeles)


Magnetic reconnection is widely accepted as the driver of dynamics in the Earth’s magnetotail despite the difficulty in understanding how reconnection can be initiated in a current sheet with curved magnetic field lines associated with a small normal B_z component. In particular, reconnection is the favored mechanism for explaining the generation of bursty bulk flows and dipolarization fronts despite the lack of any obvious mechanism to produce the characteristic cross-tail width of 1-3 R_E for such fronts observed in the tail plasma sheet. The results of recent particle-in-cell simulations in 2D and 3D that bear on these issues will be discussed. 2D simulations show that an isolated B_z “hump” configuration does not produce tearing instabilities. At most, it can generate an ideal-like instability with a growth rate an order of magnitude smaller than previous estimates in an open system that leads to an earthward shift of the hump and an erosion of the tailward side. Such an unstable hump configuration is unlikely to be produced by external driving of a current sheet with no B_z accumulation. In 3D simulations the imposition of an effective anomalous resistivity localized in the cross-tail direction is used to study the structure of the exhaust jets produced by reconnection. Relatively narrow fronts (<10 d_i) expand in the ion-drift direction to reach widths of 15-20 d_i . Broader initial fronts (25-50 d_i) tend to form a 10-15 d_i width higher speed structure on the dawn side of the front. All of these fronts exhibit a tendency to filament into structures of order 1- 2 d_i in width, apparently due to the action of the ballooning/interchange instability. At longer times, these finger structures tend to aggregate into structures of order 5 d_i in width. The implications of these results will be discussed.

Primary author

Dr Philip Pritchett (University of California, Los Angeles)

Presentation materials