Evolution of Bz-dips and current systems around dipolarization fronts observed by MMS

Schmid, Daniel

Evolution of Bz-dips and current systems around dipolarization fronts observed by MMS

Thursday, 26 May 2016

Daniel Schmid¹, Rumi Nakamura², Ferdinand Plaschke¹, Martin Volwerk², Yasuhito Narita³, Wolfgang Baumjohann⁴, Werner Magnes⁴, David Fischer², Roy B Torbert⁵, Christopher T Russell⁶, Robert J Strangeway⁷, Hannes Karl Leinweber⁸, Kenneth R Bromund⁹, Brian J Anderson¹⁰, Guan Le⁹, Mark Chutter¹¹, James A Slavin¹², Larry Kepko⁹, Mark Moldwin¹² and Olivier Le Contel¹³, (1)IWF Institute for Space Research, Graz, Austria, (2)Austrian Academy of Sciences, Vienna, Austria, (3)Space Research Institute, Graz-St Peter, Austria, (4)Space Research Institute, Austrian Academy of Sciences, Graz, Austria, (5)University of New Hampshire Main Campus, Durham, NH, United States, (6)University of California Los Angeles, IGPP/EPSS, Los Angeles, CA, United States, (7)University of California Los Angeles, Los Angeles, CA, United States, (8)Institute of Geophysics and Planetary Physics Los Angeles, Los Angeles, CA, United States, (9)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (10)Johns Hopkins University, Baltimore, MD, United States, (11)University of New Hampshire, Durham, NH, United States, (12)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (13)Laboratoire de Physique des Plasmas (UMR7648), CNRS/Ecole Polytechnique/UPMC/Univ. Paris Sud/Obs. de Paris, Paris, France

Abstract:

Dipolarization fronts (DF) are a key ingredient of magnetic flux transport in the magnetotail. The defining feature of DFs is the asymmetric bipolar variation of the magnetic field Z-component perpendicular to the current sheet in the tail. The sharp increase in Bz is typically preceded by a decrease, a Bz-dip, which sometimes even turns negative.
We present a study on the temporal/spatial evolution of these Bz-dips and their associated current systems. We use MMS magnetotail observations during the commissioning phase when MMS has a "string-of-pearls" configuration at radial distances within 12 Re and inter-spacecraft distances of 100 km. This particular spacecraft constellation enables us to study the temporal/spatial evolution of DFs on a small scale. We characterize the DFs into two categories: earthward (Type A) and tailward (Type B) propagating DFs and examine the Bz and current change across the DF over time and/or space. The main aim of this study is to reveal common patterns of the evolution of DFs in order to better understand the magnetic flux transport in the magnetotail.