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Evidence for the core field polarity of magnetic flux ropes against the reconnection guide field
Author(s) -
Teh W.L.,
Abdullah M.,
Hasbi A. M.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020509
Subject(s) - magnetopause , magnetosheath , magnetic reconnection , physics , rope , flux (metallurgy) , magnetic field , field (mathematics) , polarity (international relations) , geophysics , magnetic flux , computational physics , astrophysics , solar wind , materials science , engineering , metallurgy , cell , mathematics , genetics , structural engineering , quantum mechanics , biology , pure mathematics
We present the observational evidence by Time History of Events and Macroscale Interactions during Substorms (THEMIS)‐D spacecraft to demonstrate that magnetic flux rope can have a core field polarity opposite to the guide field during asymmetric reconnection with a high magnetic shear across the magnetopause. In the presented event, a bipolar reconnection outflow was observed at the magnetopause, across which the magnetic shear was ~149° corresponding to a predicted guide field B G = −15.6 nT. The ratios for magnetic field strength and ion density between the magnetospheric and magnetosheath sides of the magnetopause were ~1.6 and ~0.15, respectively. During the event, the component of magnetic field along the M axis (the intermediate variance direction) remained negative and stable for most of the time, and its mean value agreed with the B G . Two magnetic flux ropes with a strong core field were identified, but one flux rope had a core field polarity against the guide field B G . Our finding differs from current theoretical simulations that the core field polarity of the flux ropes inherits from the guide field.