Magnetic Reconnection on Dayside Crustal Magnetic Fields at Mars: MAVEN Observations

Y Harada; J. S Halekas; G. A DiBraccio; S Xu; J Espley; J. P Mcfadden; D. L Mitchell; C Mazelle; D. A Brain; T Hara; Y. J Ma; S Ruhunusiri; B. M Jakosky

doi:10.1002/2018GL077281

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Magnetic Reconnection on Dayside Crustal Magnetic Fields at Mars: MAVEN Observations

Journal article

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Magnetic Reconnection on Dayside Crustal Magnetic Fields at Mars: MAVEN Observations

Y Harada, J. S Halekas, G. A DiBraccio, S Xu, J Espley, J. P Mcfadden, D. L Mitchell, C Mazelle, D. A Brain, T Hara, …

Geophysical research letters, Vol.45(10), pp.4550-4558

05/28/2018

DOI: 10.1002/2018GL077281

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Abstract

The identification of magnetic reconnection on the dayside of Mars has been elusive owing to the lack of comprehensive plasma and field measurements. Here we present direct measurements of dayside in situ reconnection signatures by the comprehensive particles and fields package on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft over strong crustal magnetic fields in the southern hemisphere of Mars. During a crossing of a bifurcated current sheet consisting of northward and southward magnetic fields, MAVEN recorded (i) ionospheric photoelectrons trapped on closed magnetic field lines, (ii) Hall magnetic fields and a nonzero normal field with polarity consistent with a crossing northward of the X line, and (iii) northward Alfvénic ion jets. Dayside magnetic reconnection on crustal magnetic fields could control the global configuration and topology of the Martian magnetosphere and alter the ion escape pattern from the dayside ionosphere. Plain Language Summary Magnetic reconnection is a fundamental and universal process in space plasmas. The occurrence of magnetic reconnection on the dayside of Mars has been long speculated but never been definitively demonstrated by comprehensive evidence of “smoking gun.” This paper presents Mars Atmosphere and Volatile EvolutioN observations of ions, electrons, and magnetic fields that collectively demonstrate that magnetic reconnection can operate above strong crustal magnetic fields on the dayside of Mars. This process could explain the “twisted” tail of Mars recently discovered by Mars Atmosphere and Volatile EvolutioN and may play an important role in modifying the atmospheric escape from Mars. Key Points MAVEN provides the first comprehensive evidence for in situ magnetic reconnection signatures over crustal magnetic fields on the dayside of Mars Observed signatures include closed magnetic topology, Hall and normal magnetic fields, and ion jets within a bifurcated current sheet Dayside reconnection could control the global magnetospheric configuration and dayside ion escape pathways

crustal magnetic field

magnetic reconnection

Mars

MAVEN

Details

Title: Subtitle: Magnetic Reconnection on Dayside Crustal Magnetic Fields at Mars: MAVEN Observations
Creators: Y Harada - Kyoto University
J. S Halekas - University of Iowa
G. A DiBraccio - Goddard Space Flight Center
S Xu - University of California, Berkeley
J Espley - Goddard Space Flight Center
J. P Mcfadden - University of California, Berkeley
D. L Mitchell - University of California, Berkeley
C Mazelle - Université de Toulouse
D. A Brain - University of Colorado Boulder
T Hara - University of California, Berkeley
Y. J Ma - University of California, Los Angeles
S Ruhunusiri - University of Iowa
B. M Jakosky - University of Colorado Boulder
Resource Type: Journal article
Publication Details: Geophysical research letters, Vol.45(10), pp.4550-4558
DOI: 10.1002/2018GL077281
ISSN: 0094-8276
eISSN: 1944-8007
Number of pages: 9
Language: English
Date published: 05/28/2018
Academic Unit: Physics and Astronomy
Record Identifier: 9984199923502771

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