MMS Observations of Dipolarization Fronts

Thursday, 17 December 2015: 14:34
2018 (Moscone West)
Melvyn L Goldstein, NASA Goddard SFC, Greenbelt, MD, United States, Kyoung-Joo Hwang, NASA Goddard Space Flight Center, Greenbelt, MD, United States, David G Sibeck, NASA/GSFC, Greenbelt, MD, United States, Maha Ashour-Abdalla, University of California Los Angeles, Physics and Astronomy, Los Angeles, CA, United States, Rumi Nakamura, Austrian Academy of Sciences, Vienna, Austria, James L Burch, Southwest Research Institute San Antonio, San Antonio, TX, United States, Roy B Torbert, University of New Hampshire Main Campus, Durham, NH, United States, Thomas Earle Moore, NASA Goddard Space Flight Ctr, Greenbelt, MD, United States, Robert E Ergun, University of Colorado, Boulder, CO, United States, Craig J Pollock, NASA Goddard Space Flight Center, Heliophysics Sci. Div., Greenbelt, MD, United States, Barry Mauk, Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States and Stephen A Fuselier, Southwest Research Institute, San Antonio, TX, United States
We present MMS observations of dipolarization fronts. Dipolarization fronts commonly observed in Earth’s plasma sheet are characterized by intense gradients in the current sheet-normal component of the magnetic field and plasma/magnetic pressure across the front. These fronts are often embedded within fast earthward flows, i.e., bursty bulk flows. Analysis using data from all four spacecraft shows the presence of both typical and atypical dipolarization fronts. Typically dipolarization fronts propagate earthward and their normals point radially inward, however, we have identified dipolarization fronts propagating tailward with normals pointing significantly away from the radial direction. Atypical dipolarization fronts observed on 7 May 2015 and 21 July 2015 are preceded or accompanied by a rapid decrease in the Bx or By components of the magnetic field. These decreases indicate that the magnetotail is first thinning and then thickening. The resulting magnetic pile-up can cause the local Bz to increase rapidly, indicating propagation tailward, as observed. These new high time resolution field and plasma observations from MMS provide exciting new insights about the dynamical changes of magnetotail topology.