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Morphology of magnetic field in near‐Venus magnetotail: Venus express observations
Author(s) -
Rong Z. J.,
Barabash S.,
Futaana Y.,
Stenberg G.,
Zhang T. L.,
Wan W. X.,
Wei Y.,
Wang X.D.,
Chai L. H.,
Zhong J.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020461
Subject(s) - venus , plasma sheet , physics , current sheet , asymmetry , magnetic field , northern hemisphere , southern hemisphere , solar wind , geophysics , electric field , geology , magnetosphere , atmospheric sciences , astronomy , astrobiology , magnetohydrodynamics , quantum mechanics
Knowledge of the magnetic field morphology in the near‐Venus wake is essential to the studies of magnetotail dynamics and the planetary plasma escape. In this study we use the magnetic field measurements made by Venus Express during the period of April 2006 to December 2012 to investigate the global magnetic field morphology in the near‐Venus magnetotail (0–3 Venusian radii, R V , down tail) in the frame of solar wind electric field coordinates. The hemisphere with electric field pointing toward/away is indicated as ±E hemisphere. It has been reported that the cross‐tail field component has a hemispheric asymmetry in the Venusian magnetotail. We report here that this asymmetry should have been formed at the terminator and would transport tailward. In addition, we find that the draped magnetic field lines near both hemispheric flanks are directed equatorward in the region 0–1.5 R V down tail as it looks like “sinking” into Venus umbra. We estimate the thickness of the magnetotail current sheet and the current density at the sheet center. We find that the average half thickness of central current sheet near +E hemispheric flank (~460 km) is almost twice as thick as that near magnetic equatorial plane (~200 km), but the corresponding current densities at the sheet center are comparable (~6.0 nA/m 2 ). As a result, the larger cross‐tail field component found near the +E hemispheric flank suggests a stronger tailward j × B force, i.e., the more efficient tailward acceleration of plasma in this region, showing the agreement with previous observations of heavy ion outflow from Venus. In contrast, the average magnetic field structure near −E hemispheric flank is irregular, which suggests that dynamic activities, such as magnetic reconnection and magnetic field turbulence, preferentially appear there.