Multiscale Currents Observed by MMS in the Flow Braking Region
Nakamura, Rumi; Varsani, Ali; Genestreti, Kevin J.; Le Contel, Olivier; Nakamura, Takuma; Baumjohann, Wolfgang; Nagai, Tsugunobu; Artemyev, Anton; Birn, Joachim; Sergeev, Victor A.; Apatenkov, Sergey; Ergun, Robert E.; Fuselier, Stephen A.; Gershman, Daniel J.; Giles, Barbara J.; Khotyaintsev, Yuri V.; Lindqvist, Per‐arne; Magnes, Werner; Mauk, Barry; Petrukovich, Anatoli; Russell, Christopher T.; Stawarz, Julia; Strangeway, Robert J.; Anderson, Brian; Burch, James L.; Bromund, Ken R.; Cohen, Ian; Fischer, David; Jaynes, Allison; Kepko, Laurence; Le, Guan; Plaschke, Ferdinand; Reeves, Geoff; Singer, Howard J.; Slavin, James A.; Torbert, Roy B.; Turner, Drew L.
2018-02
Citation
Nakamura, Rumi; Varsani, Ali; Genestreti, Kevin J.; Le Contel, Olivier; Nakamura, Takuma; Baumjohann, Wolfgang; Nagai, Tsugunobu; Artemyev, Anton; Birn, Joachim; Sergeev, Victor A.; Apatenkov, Sergey; Ergun, Robert E.; Fuselier, Stephen A.; Gershman, Daniel J.; Giles, Barbara J.; Khotyaintsev, Yuri V.; Lindqvist, Per‐arne ; Magnes, Werner; Mauk, Barry; Petrukovich, Anatoli; Russell, Christopher T.; Stawarz, Julia; Strangeway, Robert J.; Anderson, Brian; Burch, James L.; Bromund, Ken R.; Cohen, Ian; Fischer, David; Jaynes, Allison; Kepko, Laurence; Le, Guan; Plaschke, Ferdinand; Reeves, Geoff; Singer, Howard J.; Slavin, James A.; Torbert, Roy B.; Turner, Drew L. (2018). "Multiscale Currents Observed by MMS in the Flow Braking Region." Journal of Geophysical Research: Space Physics 123(2): 1260-1278.
Abstract
We present characteristics of current layers in the offâ equatorial nearâ Earth plasma sheet boundary observed with high timeâ resolution measurements from the Magnetospheric Multiscale mission during an intense substorm associated with multiple dipolarizations. The four Magnetospheric Multiscale spacecraft, separated by distances of about 50Â km, were located in the southern hemisphere in the dusk portion of a substorm current wedge. They observed fast flow disturbances (up to about 500Â km/s), most intense in the dawnâ dusk direction. Fieldâ aligned currents were observed initially within the expanding plasma sheet, where the flow and field disturbances showed the distinct pattern expected in the braking region of localized flows. Subsequently, intense thin fieldâ aligned current layers were detected at the inner boundary of equatorward moving flux tubes together with Earthward streaming hot ions. Intense Hall current layers were found adjacent to the fieldâ aligned currents. In particular, we found a Hall current structure in the vicinity of the Earthward streaming ion jet that consisted of mixed ion components, that is, hot unmagnetized ions, cold EÂ Ã Â B drifting ions, and magnetized electrons. Our observations show that both the nearâ Earth plasma jet diversion and the thin Hall current layers formed around the reconnection jet boundary are the sites where diversion of the perpendicular currents take place that contribute to the observed fieldâ aligned current pattern as predicted by simulations of reconnection jets. Hence, multiscale structure of flow braking is preserved in the fieldâ aligned currents in the offâ equatorial plasma sheet and is also translated to ionosphere to become a part of the substorm fieldâ aligned current system.Key PointsMultiscale fieldâ aligned currents in the boundary of the expanding plasma sheet during plasma jet braking intervals are resolvedIntense Hall current layers are found at the inner boundary of the hot Earthward streaming ion jets and flow shear regionsBoth plasma jet diversion and Hall effects from reconnection region contribute to the structure of the substorm wedge currentsPublisher
Wiley Periodicals, Inc. European Space Agency
ISSN
2169-9380 2169-9402
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