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Spacecraft measurements constraining the spatial extent of a magnetopause reconnection X line
Author(s) -
Walsh B. M.,
Komar C. M.,
PfauKempf Y.
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl073379
Subject(s) - magnetopause , magnetic reconnection , physics , spacecraft , geophysics , magnetohydrodynamics , interplanetary magnetic field , solar wind , field line , astrophysics , magnetic field , computational physics , astronomy , quantum mechanics
Multispacecraft measurements from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission are used to probe the spatial extent of an X line at the dayside magnetopause. A case study from 21 April 2014 is presented where two THEMIS spacecraft have a near‐simultaneous encounter with the equatorial dayside magnetopause separated by 3.9 Earth radii. Both spacecraft observe similar steady inflow conditions with southward interplanetary magnetic field and a high magnetic shear angle at the magnetopause (133°) boundary. One spacecraft observes clear fluid and kinetic signatures of active magnetic reconnection, while the other spacecraft does not observe reconnection. The predicted location of reconnection across the magnetopause is found using several theoretical models and a Block Adaptive Tree Solarwind Roe‐type Upwind Scheme (BATS‐R‐US) MHD simulation. Each model predicts a continuous X line passing close to the two spacecraft, suggesting both would observe reconnection, if active. Using the constraints of the multipoint measurements, the extent or length L of the reconnection is estimated to be 2.4≤ L < 5.2 h in local time or 6≤ L < 14 R E .