| Autor: |
Luo, H.1,2 luohao06@gmail.com, Du, A. M.1,2, Ge, Y. S.1,2 ysge@mail.iggcas.ac.cn, Johnson, C. L.3,4, Mittelholz, A.5, Zhang, Y.1,2, Sun, S. Q.1, Zhao, L.1, Yu, Y.1,2, Tian, L.1,2, Li, S. Y.1,2, Xu, W. Y.1 |
| Předmět: |
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| Zdroj: |
Journal of Geophysical Research. Planets. Feb2022, Vol. 127 Issue 2, p1-15. 15p. |
| Abstrakt: |
Distinguishing different sources of magnetic field variations at InSight is important to understand dynamic processes in the Martian ionosphere as well as the coupling between the solar wind and the Martian induced magnetosphere. Recent studies based on magnetic field measurements from InSight have suggested that the daily and seasonal variations in the magnetic field at the Martian surface are at least partially the result of neutral wind‐driven ionospheric dynamo currents and their seasonal variations. However, the sources of the daily variations with different time scales need be further investigated. In this paper, magnetic field variations in a sol as well as during nearly a whole Martian year from InSight observations were decomposed into their natural orthogonal components. We found that the first eigenmode shows the previously identified early to midmorning peak, and varies with season. This corresponds to the solar quiet variations. The second and higher eigenmodes manifest the quasi‐Carrington and sub‐Carrington rotation periodicity represent disturbed components that may be stimulated by variations in the draped interplanetary magnetic field and/or the Martian ionospheric electron density. Different from their counterparts at the Earth, the amplitude of the first eigenmode is comparable with the sum of second to fifth ones, showing that the quiet and disturbed diurnal variations contribute similarly to the total diurnal variation. Decomposition of Martian surface magnetic field variations could provide monitoring of the Martian ionospheric current system as well as the solar wind conditions in the near‐Mars space, which will be greatly enhanced when combined with Zhurong Martian surface field measurements in the future. Plain Language Summary: The InSight flux magnetometer has made the first magnetic field measurements on the surface of Mars. The daily variations in the magnetic field have also been reported by previous studies. In this study, we investigate daily variations over nearly a whole Martian year by performing a natural orthogonal component analysis, which has been proven to be a valid method to decompose magnetic field signals into different parts. We conclude that the first part represents the quiet daily variations under lower solar wind dynamic pressure and magnetic field strength as measured by MAVEN satellite. The seasonal variations are also reflected in the first part. The disturbed variations with sol, time scales of one solar rotation and shorter, however, are reflected in the second‐fifth parts, which may indicate the stronger solar wind dynamic pressure and magnetic field strength and/or the Martian ionospheric electron density. Key Points: The daily magnetic fields at Martian surface from InSight are investigated by natural orthogonal component analysisThe first eigenmode is consistent with representing the contribution to those variations from averaged ionospheric dynamo currentThe disturbed variations with diurnal, quasi‐Carrington, and sub‐Carrington rotation time scales, are reflected in the higher eigenmodes [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
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