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： Rapid increase of horizontal magnetic field ($B_h$) around the flaring polarity inversion line is the most prominent photospheric field change during flares. It is considered to be caused by the contraction of flare loops, the details behind which is still not fully understood. Here we investigate the $B_h$-increase in 35 major flares using HMI high-cadence vector magnetograms. We find that $B_h$-increase is always accompanied by the increase of field inclination. It usually initiates near the flare ribbons, showing step-like change in between the ribbons. In particular, its evolution in early flare phase shows close spatio-temporal correlation to flare ribbons. We further find that $B_h$-increase tends to have similar intensity in confined and eruptive flares, but larger spatial-extent in eruptive flares in a statistical sense. Its intensity and timescale have inverse and positive correlations to the initial ribbon separations, respectively. The results altogether are well consistent with a recent proposed scenario which suggests that the reconnection-driven contraction of flare loops enhances photospheric $B_h$ according to the ideal induction equation, providing statistical evidence to the reconnection-driven origin for $B_h$-increase for the first time.
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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