Off-diagonal Ion Pressure Term Associated with Hall Fields in
Collisionless Magnetic Reconnection
- Kailai Wang,
- Lei Dai,
- Shan Wang,
- Yong Ren,
- Minghui Zhu,
- Chi Wang,
- Benoit Lavraud,
- Christopher Philippe Escoubet,
- James L Burch
Kailai Wang
National Space Science Center Chinese Academy of Sciences
Author ProfileYong Ren
State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences
Author ProfileMinghui Zhu
National Space Science Center, Chinese Academy of Sciences
Author ProfileChi Wang
National Space Science Center, Chinese Academy of Sciences
Author ProfileAbstract
Magnetic reconnection converts magnetic energy into particle energy,
with ion outflows being a prominent manifestation, particularly in
geospace. Hall fields are indicators of rapid energy conversion in
collisionless magnetic reconnection, yet the associated ion processes
and signatures are not fully understood. Here, we analyze in-situ data
and simulations to identify a distinct signature in the off-diagonal
component of the ion pressure tensor. This signature displays a bipolar
reversal that correlates with ion outflows across the reconnection
X-line. The bipolar signal arises from a distorted velocity distribution
during ion acceleration. Initially, Hall electric fields induce dawnward
ion motion, which is followed by enhanced ion acceleration due to
reconnection electric fields during cyclotron motion around the
reconnected magnetic field. This interaction distorts the velocity
distribution, producing the observed bipolar signals. The off-diagonal
component of the ion pressure tensor reflects increased ion acceleration
and energy conversion due to Hall electric fields.