The solar wind plasma upstream of Mars observed by Tianwen-1: Comparison with Mars Express and MAVEN

Fan, Kai; Yan, Limei; Wei, Yong; Zhang, Aibing; Kong, Lingxue; Franz, Marianne; He, Fei; Chai, Lihui; Yuan, Chenfeng; Wang, Yuqi; Zhong, Jun; Rong, Zhaojin; Yao, Zhonghua; Pan, Yongxin; Cui, Jun; He, Jiansen; Li, Wenya; Tang, Binbin; Wang, Chi

doi:10.1007/s11430-021-9917-0

Cited by 12 publications

(3 citation statements)

References 35 publications

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“…Because Mars is 20°east of Earth, Mars and Earth are in very good magnetic connection (assuming a Parker field geometry) in this event. This conclusion is also supported by the recent works of Zhang et al (2022) and Fan et al (2022) in which the TW-1/MINPA data were available a few days before this event (between 2020 November 20 and 27). With this solar wind speed, the longitudinal angle between the flare and the magnetic footpoint of Earth is ∼157°, and it is ∼162°for TW-1.…”

Section: Overview Of the Sep Event On 2020 November 29supporting

confidence: 76%

First Report of a Solar Energetic Particle Event Observed by China’s Tianwen-1 Mission in Transit to Mars

Fu¹,

Ding²,

Zhang³

et al. 2022

ApJL

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Solar energetic particles (SEPs) associated with flares and/or coronal mass ejection (CME)-driven shocks can impose acute radiation hazards on space explorations. To measure energetic particles in near-Mars space, the Mars Energetic Particle Analyzer (MEPA) instrument on board China's Tianwen-1 (TW-1) mission was designed. Here, we report the first MEPA measurements of the widespread SEP event occurring on 2020 November 29 when TW-1 was in transit to Mars. This event occurred when TW-1 and Earth were magnetically well connected, known as the Hohmann–Parker effect, thus offering us a rare opportunity to understand the underlying particle acceleration and transport process. Measurements from TW-1 and near-Earth spacecraft show similar double-power-law spectra and a radial dependence of the SEP peak intensities. Moreover, the decay phases of the time–intensity profiles at different locations clearly show the reservoir effect. We conclude that the double-power-law spectrum is likely generated at the acceleration site and that a small but finite cross-field diffusion is crucial to understanding the formation of the SEP reservoir phenomenon. These results provide insight into particle acceleration and transport associated with CME-driven shocks, which may contribute to the improvement of relevant physical models.

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Section: Overview Of the Sep Event On 2020 November 29supporting

confidence: 76%

First Report of a Solar Energetic Particle Event Observed by China’s Tianwen-1 Mission in Transit to Mars

Fu¹,

Ding²,

Zhang³

et al. 2022

ApJL

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“…To validate the hypotheses above requires the simultaneous particle measurements. Unfortunately, the Mars Ion and Neutral Particle Analyzer (Kong & Zhang et al 2020;Fan et al 2022;Zhang & Kong et al 2022) on board Tianwen-1 was not working during this event. In future, more observational, theoretical, and numerical works are required to understand the planetary bow-shock dynamics (including wave generation and damping as well as particle heating and acceleration) modified by various solar wind disturbances.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Unusual Martian Foreshock Waves Triggered by a Solar Wind Stream Interaction Region

Wang

Zhang

et al. 2023

ApJL

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Planetary bow shocks noncollisionally dissipate the incident bulk flow energy of solar wind into some other forms. To what extent and how solar wind disturbances affect the energy dissipation processes at the bow shocks on different planets remain unclear. With the Chinese Tianwen-1 and American Mars Atmosphere and Volatile EvolutioN missions, we present the first observation of significant modifications by a solar wind stream interaction region to the Martian foreshock waves, which are an important energy dissipation product of the bow shock. After the stream interface hitting Mars, an unusual band of foreshock waves emerged, with a central frequency of ∼0.4 Hz and frequency width of ∼0.2 Hz. These waves exhibited highly distorted waveforms, with peak-to-peak amplitudes of 10–25 nT in contrast to a background magnetic field of 6–9 nT. They were approximately elliptically polarized with respect to the wavevector and propagated highly obliquely to the background magnetic field. These waves reported here differed greatly from the commonly known Martian foreshock “30 s waves” and “1 Hz waves,” but resembled, to some extent, the less frequently occurring terrestrial foreshock “3 s waves.” Our present findings may imply an unexpected energy dissipation pattern of the Martian bow shock to the disturbed solar wind, which needs further observational, theoretical, and numerical investigations.

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“…The journey of Tianwen-1 began with its launch on 23 July, 2020, followed by a seven-month cruise phase to Mars. During the cruise phase, MINPA operated for ap-proximately three months, demonstrating good in-flight performance [25][26][27]. After it successfully entered an orbit around Mars, MINPA commenced regular scientific data collection following an elliptical orbit of 243 km × 10,760 km from November 2021.…”

Section: In-flight Operation Of Tianwen-1 and Minpamentioning

confidence: 99%

Characterizing and Removing Ultra-Violet Contamination in Ion Observations on Board Tianwen-1

Wang,

Li,

et al. 2023

Atmosphere

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The Mars Ion and Neutral Particle Analyzer (MINPA) onboard Tianwen-1 aims to study the interaction between Mars and the solar wind via in situ ion measurement and energetic neutral atom imaging. Despite the efforts for Ultra-Violet suppression in MINPA design, 0.48% of ion observations from November 2021 to July 2022 were identified as UV-contaminated. The UV emissions primarily penetrate into the instrument through the ENA entrance. Statistically, the distribution of the UV contamination in phase space typically spans 3 to 4 azimuth sectors. The contamination is uniformly distributed across the polar dimension while, in the energy and mass dimensions, it is proportional to the time-of-flight duration. Comparisons between the in-flight performance and ground calibration suggest that azimuthal broadening and intensity variations of the contamination may result from differing responses across the azimuthal sectors. Based on the characteristics of the UV impact on MINPA ion observations, a removal algorithm is proposed to reduce contamination while preserving valid signals, which improves the data quality effectively and benefits the interpretation of MINPA’s ion measurements in the Martian space environment. The cause, effect, and distribution of the UV contamination obtained by this study may serve as a reference for other space ion observations.

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The solar wind plasma upstream of Mars observed by Tianwen-1: Comparison with Mars Express and MAVEN

Cited by 12 publications

References 35 publications

First Report of a Solar Energetic Particle Event Observed by China’s Tianwen-1 Mission in Transit to Mars

First Report of a Solar Energetic Particle Event Observed by China’s Tianwen-1 Mission in Transit to Mars

Unusual Martian Foreshock Waves Triggered by a Solar Wind Stream Interaction Region

Characterizing and Removing Ultra-Violet Contamination in Ion Observations on Board Tianwen-1

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