Publication Date:
2016-05-08
Description:
We report ion velocity distribution functions (VDFs) observed by Magnetospheric Multiscale mission (MMS), and present evidence for demagnetized ion speiser motion during magnetopause reconnection. The demagnetization is observed in the vicinity of the X-line, as well as near the current sheet mid-plane about tens of ion skin depths (d i ) away from the X-line. Close to the X-line before the outflow is built up, the VDFs are elongated, and the elongated part of VDFs rotates from the out-of-plane current direction towards the outflow directions downstream from the X-line. Further downstream, demagnetized ions exhibit a characteristic half-ring structure in the VDFs, as a result of the mixture of ions that have experienced different amounts of cyclotron turning around the magnetic field normal to the current sheet. Signatures of acceleration by electric fields are more pronounced in the VDFs near the X line than downstream.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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