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

• Published in: Astrophysical journal. Letters Vol. 947; no. 2; p. L33
• Main Authors: Su, Zhenpeng, Wang, Yuming, Zhang, Tielong, Wu, Zhiyong, Cheng, Long, Zou, Zhuxuan, Shen, Chenglong, Guo, Jingnan, Xiao, Sudong, Wang, Guoqiang, Pan, Zonghao, Liu, Kai, Hao, Xinjun, Li, Yiren, Chen, Manming, Chi, Yutian, Xu, Mengjiao
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 01-04-2023; IOP Publishing
• Subjects: Charged particles; Corotating streams; Energy dissipation; Magnetic fields; Mars; Mars atmosphere; Planetary bow shocks; Planetary magnetic fields; Planets; Plasma physics; Solar energy; Solar wind; Solar wind disturbances; Solar-planetary interactions; Space plasmas; Space weather; Wave propagation; Waveforms
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/accb9f

Abstract
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.