分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yuming Wang
Tielong Zhang
Guoqiang Wang
Sudong Xiao
Zhuxuan Zou
Long Cheng
Zonghao Pan
Kai Liu
Xinjun Hao
Yiren Li
Manming Chen
Zhoubin Zhang
Wei Yan
Zhenpeng Su
Zhiyong Wu
Chenglong Shen
Yutian Chi
Mengjiao Xu
Jingnan Guo
Yang Du
摘要： Mars Orbiter MAGnetometer (MOMAG) is a scientifc instrument onboard the orbiter of China's first mission for Mars -- Tianwen-1. It started to routinely measure the magnetic field from the solar wind to magnetic pile-up region surrounding Mars since November 13, 2021. Here we present its in-flight performance and first science results based on the first one and a half months' data. By comparing with the magnetic field data in the solar wind from the Mars Atmosphere and Volatile EvolutioN (MAVEN), the magnetic field by MOMAG is at the same level in magnitude, and the same magnetic structures with the similar variations in three components could be found in MOMAG data. In the first one and a half months, we recognize 158 clear bow shock (BS) crossings from MOMAG data, whose locations statistically match well with the modeled average BS. We also identify 5 pairs of simultaneous BS crossings of the Tianwen-1's orbiter and MAVEN. These BS crossings confirm the global shape of modeled BS as well as the south-north asymmetry of the Martian BS. Two presented cases in this paper suggest that the BS is probably more dynamic at flank than near the nose. So far, MOMAG performs well, and provides accurate magnetic field vectors. MOMAG is continuously scanning the magnetic field surrounding Mars. These measurements complemented by observations from MAVEN will undoubtedly advance our understanding of the plasma environment of Mars.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yuming Wang
Tielong Zhang
Guoqiang Wang
Sudong Xiao
Zhuxuan Zou
Long Cheng
Zonghao Pan
Kai Liu
Xinjun Hao
Yiren Li
Manming Chen
Zhoubin Zhang
Wei Yan
Zhenpeng Su
Zhiyong Wu
Chenglong Shen
Yutian Chi
Mengjiao Xu
Jingnan Guo
Yang Du
摘要： Mars Orbiter MAGnetometer (MOMAG) is a scientifc instrument onboard the orbiter of China's first mission for Mars -- Tianwen-1. It started to routinely measure the magnetic field from the solar wind to magnetic pile-up region surrounding Mars since November 13, 2021. Here we present its in-flight performance and first science results based on the first one and a half months' data. By comparing with the magnetic field data in the solar wind from the Mars Atmosphere and Volatile EvolutioN (MAVEN), the magnetic field by MOMAG is at the same level in magnitude, and the same magnetic structures with the similar variations in three components could be found in MOMAG data. In the first one and a half months, we recognize 158 clear bow shock (BS) crossings from MOMAG data, whose locations statistically match well with the modeled average BS. We also identify 5 pairs of simultaneous BS crossings of the Tianwen-1's orbiter and MAVEN. These BS crossings confirm the global shape of modeled BS as well as the south-north asymmetry of the Martian BS. Two presented cases in this paper suggest that the BS is probably more dynamic at flank than near the nose. So far, MOMAG performs well, and provides accurate magnetic field vectors. MOMAG is continuously scanning the magnetic field surrounding Mars. These measurements complemented by observations from MAVEN will undoubtedly advance our understanding of the plasma environment of Mars.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The current work investigates the Venusian solar-wind-induced magnetosphere at a high spatial resolution using all Venus Express (VEX) magnetic observations through an unbiased statistical method. We first evaluate the predictability of the interplanetary magnetic field (IMF) during VEX's magnetospheric transits, and then map the induced field in a cylindrical coordinate system under different IMF conditions. Our high-resolution mapping enables resolving structures on various scales, ranging from the thin ionopause and the associated electric currents to the classical global-scale draped IMF. Our mapping also resolves two recently-reported structures, a low ionospheric magnetization over the terminator and a global "looping" structure in the near magnetotail, both of which are not depicted in the classical draping configuration. In contrast to the reported IMF-independent cylindrical magnetic field of both structures, our results illustrate their IMF dependence. In both structures, the cylindrical magnetic component is stronger in the hemisphere with an upward solar wind electric field ($E^{SW}$) than in the opposite hemisphere. Under downward $E^{SW}$, the "looping" structure even breaks, which is attributable to an additional draped magnetic field structure wrapping toward $-E^{SW}$. In addition, our results suggest that these two structures are spatially not overlapping with each other. The low ionospheric structure occurs in a very narrow region, at about 87--95$^\circ$ solar zenith angle and 190--210~km altitude, implying that future simulation to reproduce the structure entails at least a spatial resolution of about 10 km. We discuss this narrow structure in terms of a Cowling channel.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Zhuxuan Zou
Yuming Wang
Tielong Zhang
Guoqiang Wang
Sudong Xiao
Zonghao Pan
Zhoubin Zhang
Wei Yan
Yang Du
Yutian Chi
Long Cheng
Zhiyong Wu
Xinjun Hao
Yiren Li
Kai Liu
Manming Chen
Zhenpeng Su
Chenglong Shen
Mengjiao Xu
Jingnan Guo
摘要： Mars Orbiter Magnetometer (MOMAG) is one of seven science payloads onboard Tianwen-1's orbiter. Unlike most of the satellites, Tianwen-1's orbiter is not magnetically cleaned, and the boom where placed the magnetometer's sensors is not long enough. These pose many challenges to the magnetic field data processing. In this paper, we introduce the in-flight calibration process of the Tianwen-1/MOMAG. The magnetic interference from the spacecraft, including spacecraft generated dynamic field and slowly-changing offsets are cleaned in sequence. Then the calibrated magnetic field data are compared with the data from the Mars Atmosphere and Volatile EvolutioN (MAVEN). We find that some physical structures in the solar wind are consistent between the two data sets, and the distributions of the magnetic field strength in the solar wind are very similar. These results suggest that the in-flight calibration of the MOMAG is successful and the MOMAG provides reliable data for scientific research.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Zhuxuan Zou
Yuming Wang
Tielong Zhang
Guoqiang Wang
Sudong Xiao
Zonghao Pan
Zhoubin Zhang
Wei Yan
Yang Du
Yutian Chi
Long Cheng
Zhiyong Wu
Xinjun Hao
Yiren Li
Kai Liu
Manming Chen
Zhenpeng Su
Chenglong Shen
Mengjiao Xu
Jingnan Guo
摘要： Mars Orbiter Magnetometer (MOMAG) is one of seven science payloads onboard Tianwen-1's orbiter. Unlike most of the satellites, Tianwen-1's orbiter is not magnetically cleaned, and the boom where placed the magnetometer's sensors is not long enough. These pose many challenges to the magnetic field data processing. In this paper, we introduce the in-flight calibration process of the Tianwen-1/MOMAG. The magnetic interference from the spacecraft, including spacecraft generated dynamic field and slowly-changing offsets are cleaned in sequence. Then the calibrated magnetic field data are compared with the data from the Mars Atmosphere and Volatile EvolutioN (MAVEN). We find that some physical structures in the solar wind are consistent between the two data sets, and the distributions of the magnetic field strength in the solar wind are very similar. These results suggest that the in-flight calibration of the MOMAG is successful and the MOMAG provides reliable data for scientific research.
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