Ionospheric control of the dawn‐dusk asymmetry of the Mars magnetotail current sheet. Issue 6 (28th June 2017)

• Record Type: Journal Article
• Authors: Liemohn, Michael W.; Xu, Shaosui; Dong, Chuanfei; Bougher, Stephen W.; Johnson, Blake C.; Ilie, Raluca; De Zeeuw, Darren L.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 6(2017)
• Page Start: 6397
• Page End: 6414
• Publication Date: 2017-06-28
• Subjects: Mars magnetotail -- Mars current sheet -- solar wind‐magnetosphere interaction -- magnetized ionosphere; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA023707
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: This study investigates the role of solar EUV intensity at controlling the location of the Mars magnetotail current sheet and the structure of the lobes. Four simulation results are examined from a multifluid magnetohydrodynamic model. The solar wind and interplanetary magnetic field (IMF) conditions are held constant, and the Mars crustal field sources are omitted from the simulation configuration. This isolates the influence of solar EUV. It is found that solar maximum conditions, regardless of season, result in a Venus‐like tail configuration with the current sheet shifted to the − Y (dawnside) direction. Solar minimum conditions result in a flipped tail configuration with the current sheet shifted to the + Y (duskside) direction. The lobes follow this pattern, with the current sheet shifting away from the larger lobe with the higher magnetic field magnitude. The physical process responsible for this solar EUV control of the magnetotail is the magnetization of the dayside ionosphere. During solar maximum, the ionosphere is relatively strong and the draped IMF field lines quickly slip past Mars. At solar minimum, the weaker ionosphere allows the draped IMF to move closer to the planet. These lower altitudes of the closest approach of the field line to Mars greatly hinder the day‐to‐night flow of magnetic flux. This results in a buildup of magnetic flux in the dawnside lobe as the S‐shaped topology on that side of the magnetosheath extends farther downtail. The study demonstrates that the Mars dayside ionosphere exerts significant control over the nightside induced magnetosphere of that planet. Plain Language Summary: Mars, which does not have a strong magnetic field, has an induced magnetic environment from the draping of the interplanetary magnetic field from the Sun. It folds around Mars, forming two "lobes" of magnetic field behind the planet with a current sheet of electrified gas (plasma) behind it. The current sheet is not directly behind the planet but rather shifted toward the dawn or dusk direction. It is shown here that one factor controlling the location of the current sheet is the dayside ionosphere. At solar maximum, the ionosphere is dense, the magnetic field slips easily by the planet, and the current sheet is shifted toward dawn. At solar minimum, the ionosphere is relatively weak, the magnetic field slippage is slowed down, and the current sheet shifts toward dusk. Key Points: There is a systematic Y (i.e., dawn‐dusk) asymmetry in the location of the Martian magnetotail current sheet in modified MSE coordinates The asymmetry is controlled by ionospheric conditions, shifting to the dawn (‐ Y ) during solar maximum and to the dusk during solar minimum The shift found in this study is not a function of crustal fields, which were omitted, or solar wind conditions, which were held constant