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Investigation of the homogeneity of the energy conversion processes atdipolarization fronts observed by MMSΑ
  • Soboh Al Qeeq,
  • Olivier LE CONTEL
Soboh Al Qeeq
Laboratoire de Physique des Plasmas (LPP - UMR 7648)

Corresponding Author:[email protected]

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CNRS Délégation Ile-de-France Sud,University of Paris,University of Paris,Sorbonne Université Campus Pierre et Marie Curie
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In the present work, we consider four dipolarization front (DF) events detected byMMS spacecraft in the Earth’s magnetotail during a substorm on 23rd of July 2017between 16:05 and 17:19 UT. From their ion scale properties, we show that thesefour DF events embedded in fast Earthward plasma flows have classical signatureswith increases of Bz, velocity and temperature and a decrease of density across theDF. We compute and compare current densities obtained from magnetic and particlemeasurements and analyse the Ohm’s law. We investigate the energy conversionprocesses in the spacecraft frame via J.E calculations averaged over the 4 spacecraft(s/c). We found both positive (loading) and negative (generator) values +0.023nW/m3 at DF crossing, -0.043 nW/m3 after DF respectively. In ion and electronframes, the energy conversion given by (J.(E+vexB)) or (J.(E+vixB)) values indicatesthat 4 s/c average values are mostly negative whereas individual s/c values can bepositive or negative. It suggests that the energy conversion is not homogeneous atthe scale of the tetrahedron (electron scale). Finally we discuss the origin of the nonhomogeneity of the energy conversion process by computing the standard deviation(SD) of E and J (obtained from particle measurement) normalized by their error bars.Larger SD for E than for J suggest that the non homogeneity comes from the electricfield fluctuations at the electron scale.