Department of Climate and Space Sciences and Engineering in the College of Engineering at the University of Michigan

CLaSP Summer Seminar - San Lu

Date: July 11, 2018
Time: 3:30 pm - 4:30 pm
Location: CSRB Auditorium, room 2246

Our guest for this week's CLaSP Summer Seminar will be San Lu of the UCLA Department of Earth, Planetary and Space Sciences. Please join us! 

Title: "Kinetic simulations of dawn-dusk asymmetry in Earth’s magnetotail"

Abstract: In the past twenty years, spacecraft observations have revealed a duskside preponderance of Earth’s magnetotail dynamic features (such as magnetic reconnection, substorm onsets, dipolarization fronts, fast flows, energetic particle injections, and flux ropes). The reason for this ubiquitous magnetotail dawn-dusk asymmetry is presently unclear. Using three-dimensional global hybrid and particle-in-cell simulations, we investigate the origin of the asymmetry. The magnetotail current sheet is compressed by an external driving electric field down to a thickness on the order of ion kinetic scales. In the resultant thin current sheet (TCS), a significant portion of the ions becomes unmagnetized and decoupled from the magnetized electrons, giving rise to a Hall electric field Ez and an additional cross-tail current jy caused by the unmagnetized ions being unable to comove with the electrons in the Hall electric field. The Hall electric field transports via E×B drift magnetic flux and magnetized plasma dawnward, causing a reduction of the current sheet thickness and the normal magnetic field Bz on the duskside. This leads to an even stronger Hall effect (stronger Ez and jy) in the duskside TCS. Thus, due to the internal kinetic effects in the TCS, namely the Hall effect and the associated dawnward E×B drift, the magnetotail dawn-dusk asymmetry forms in a short time scale without any global, long-term effects. The duskside preference of reconnection and associated dynamic phenomena can thus be explained as a consequence of this TCS asymmetry.

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