EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

A statistical study of dipolarization fronts observed by MMS

Soboh Alqeeq1, olivier Le Contel1, Patrick Canu1, Alessandro Retinò1, Hugo Breuillard1, Thomas Chust1, Alexandra Alexandrova1, Laurent Mirioni, Yuri Khotyaintsev2, Rumi Nakamura3, Frederick Wilder4, Hanying Wei5, David Fischer3, Daniel Gershman7, James Burch8, Roy Torbert6, Barbara Giles7, Stephen Fuselier8, Robert Ergun4, Per Arne Lindqvist9, and the MMS Team*
Soboh Alqeeq et al.
  • 1Laboratoire de Physique des Plasmas, CNRS/Ecole Polytechnique IP Paris/Sorbonne Université/Université Paris Saclay/Observatoire de Paris, Paris, France
  • 2Swedish Institute of Space Physics, Uppsala, Sweden
  • 3Space Research Institute, Austrian Academy of Sciences, Graz, Austria
  • 4Laboratory of Atmospheric and Space Physics, Colorado, USA
  • 5Institute of Geophysics and Planetary Physics, Los Angeles, USA
  • 6Space Science Center and Department of Physics, University of New Hampshire, Durham, USA
  • 7NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 8Southwest Research Institute, San Antonio, Texas, USA
  • 9Space and Plasma Group, Royal Institute of Technology, Stockholm, Sweden
  • *A full list of authors appears at the end of the abstract

In the present work, we consider 49 dipolarization fronts (DF) detected by the Magnetospheric Multiscale (MMS) mission on 2017, near the Earth’s magnetotail equator (Bx<5nT). Criteria for selecting DF using an AIDApy routine are based on difference of maximum and minimum values computed with a 306 s sliding window. They request a Bz increase, an ion velocity increase and a density decrease. This first automatic selection is then ajusted manually with the following criteria : Bz increase larger than 5 nT, ion velocity larger than 150 km/s, density decrease and both ion and electron temperature increases. All these events belong to the most common category (A) defined by Schmid et al., 2015 in term of density decrease and temperature increase at the DF. However, based on a superposed epoch analysis of DF basic properties (magnetic field, density, velocity, ...) we distinguish two subcategories of events depending on the shape of the DF. The first subcategory (55.1%) corresponds to a slow decrease of the magnetic field after the DF and is associated with smaller ion velocity and hotter plasma. The second subcategory (44.9%) has the same time scale for the rising and the falling of the magnetic field (a bump) associated with a decrease of ion and electron pressures and faster velocity as shown in Alqeeq et al. 2021. For both categories we found that ions are mostly decoupled from the magnetic field by the Hall fields. The electron pressure gradient term is also contributing to the ion decoupling and likely responsible for an electron decoupling at DF. We also analyzed the energy conversion process. For the first subcategory we found that the energy in the spacecraft frame is transferred from the electromagnetic field to the plasma (J·E>0) ahead or at the DF. For the second subcategory, we found the same behavior ahead or at the DF whereas it is the opposite (J·E<0) behind the front. In the fluid frame, we found that the energy is mostly transferred from the plasma to the electromagnetic field (J·E ′ <0) ahead or at the DF for both subcategories but energy dissipation (J·E ′ >0) only occurs behind the front for the second subcategory. The possible origin of these two subcategories is discussed.

MMS Team:

C.T Russell (5), R. J. Strangeway (5), D. L. Turner (10), I. J. Cohen (11)

How to cite: Alqeeq, S., Le Contel, O., Canu, P., Retinò, A., Breuillard, H., Chust, T., Alexandrova, A., Mirioni, L., Khotyaintsev, Y., Nakamura, R., Wilder, F., Wei, H., Fischer, D., Gershman, D., Burch, J., Torbert, R., Giles, B., Fuselier, S., Ergun, R., and Lindqvist, P. A. and the MMS Team: A statistical study of dipolarization fronts observed by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9532,, 2022.

Comments on the display material

to access the discussion