TY - JOUR
T1 - Effects of the IMF Direction on Atmospheric Escape From a Mars-like Planet Under Weak Intrinsic Magnetic Field Conditions
AU - Sakai, Shotaro
AU - Seki, Kanako
AU - Terada, Naoki
AU - Shinagawa, Hiroyuki
AU - Sakata, Ryoya
AU - Tanaka, Takashi
AU - Ebihara, Yusuke
N1 - Funding Information:
This work was supported by Grant‐in‐Aid for Scientific Research (A) 19H00707 and 20H00192, Fostering Joint International Research (B) 18KK0093, and Scientific Research on Innovative Areas 18H05439 from the JSPS. This work is related to MACH DRIVE Center supported by the NASA Heliophysics Program. The computer simulation was partly performed on the KDK computer system at the Research Institute for Sustainable Humanosphere (RISH), Kyoto University.
Funding Information:
This work was supported by Grant-in-Aid for Scientific Research (A) 19H00707 and 20H00192, Fostering Joint International Research (B) 18KK0093, and Scientific Research on Innovative Areas 18H05439 from the JSPS. This work is related to MACH DRIVE Center supported by the NASA Heliophysics Program. The computer simulation was partly performed on the KDK computer system at the Research Institute for Sustainable Humanosphere (RISH), Kyoto University.
Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2021/3
Y1 - 2021/3
N2 - Direction of the upstream interplanetary magnetic field (IMF) significantly changes the magnetospheric configuration, influencing the atmospheric escape mechanism. This paper investigates effects of IMF on the ion escape mechanism from a Mars-like planet that has a weak dipole magnetic field directing northward on the equatorial surface. The northward (parallel to the dipole at subsolar), southward (antiparallel), and Parker-spiral IMFs under present solar wind conditions are compared based on multispecies magnetohydrodynamics simulations. In the northward IMF case, molecular ions escape from the high-latitude lobe reconnection region, where ionospheric ions are transported upward along open field lines. Atomic oxygen ions originating either in the ionosphere or oxygen corona escape through a broader ring-shaped region. In the southward IMF case, the escape flux of heavy ions increases significantly and has peaks around the equatorial dawn and dusk flanks. The draped IMF can penetrate into the subsolar ionosphere by erosion, and the IMF becomes mass-loaded as it is transported through the dayside ionosphere. The mass-loaded draped IMF is carried to the tail, contributing to ion escape. The escape channels in the northward and southward IMF cases are different from those in the Parker-spiral IMF case. The escape rate is the lowest in the northward IMF case and comparable in the Parker-spiral and southward IMF cases. In the northward IMF case, a weak intrinsic dipole forms a magnetosphere configuration similar to that of Earth, quenching the escape rate, while the Parker-spiral and southward IMFs cause reconnection and erosion, promoting ion escape from the upper atmosphere.
AB - Direction of the upstream interplanetary magnetic field (IMF) significantly changes the magnetospheric configuration, influencing the atmospheric escape mechanism. This paper investigates effects of IMF on the ion escape mechanism from a Mars-like planet that has a weak dipole magnetic field directing northward on the equatorial surface. The northward (parallel to the dipole at subsolar), southward (antiparallel), and Parker-spiral IMFs under present solar wind conditions are compared based on multispecies magnetohydrodynamics simulations. In the northward IMF case, molecular ions escape from the high-latitude lobe reconnection region, where ionospheric ions are transported upward along open field lines. Atomic oxygen ions originating either in the ionosphere or oxygen corona escape through a broader ring-shaped region. In the southward IMF case, the escape flux of heavy ions increases significantly and has peaks around the equatorial dawn and dusk flanks. The draped IMF can penetrate into the subsolar ionosphere by erosion, and the IMF becomes mass-loaded as it is transported through the dayside ionosphere. The mass-loaded draped IMF is carried to the tail, contributing to ion escape. The escape channels in the northward and southward IMF cases are different from those in the Parker-spiral IMF case. The escape rate is the lowest in the northward IMF case and comparable in the Parker-spiral and southward IMF cases. In the northward IMF case, a weak intrinsic dipole forms a magnetosphere configuration similar to that of Earth, quenching the escape rate, while the Parker-spiral and southward IMFs cause reconnection and erosion, promoting ion escape from the upper atmosphere.
KW - IMF
KW - Mars
KW - atmospheric escape
KW - intrinsic magnetic field
KW - ion escape
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U2 - 10.1029/2020JA028485
DO - 10.1029/2020JA028485
M3 - Article
AN - SCOPUS:85103544363
VL - 126
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
SN - 2169-9380
IS - 3
M1 - e2020JA028485
ER -