Subjects: Astronomy submitted time 2024-07-03 Cooperative journals: 《天文学进展》
Abstract： Ion cyclotron waves are widely present upstream from the Martian bow shock, with frequencies near the local proton cyclotron frequency in the spacecraft frame. The waves propagate quasi-parallel to the background magnetic field, and are associated with the Solar wind picking up newly-ionized hydrogen from the Martian exosphere. In this work, a typical ion cyclotron wave event was observed by MAVEN upstream from the Martian bow shock. The further MAV analysis results for this event show that the magnetic field perturbations are left-handed polarized and propagate quasi-parallel (the propagation angle θ = 12.37◦ ) to the background magnetic field. The relationship between the plasma perturbations and magnetic field perturbations is theoretically derived for slow magnetosonic, Alfv´en, and fast magnetosonic waves based on the magnetohydrodynamic theory. If we take the wave propagation angle θ = 12.37◦ estimated from the MVA analysis, the theoretically expected density perturbation and velocity perturbation along the background magnetic field are in serious disagreement with the MAVEN data. Through fitting the plasma density fluctuation, velocity fluctuation and magnetic field fluctuation, it is found that the ion cyclotron wave event can be explained by the superposition of oblique fast magnetosonic waves with a propagation angle of 63◦ relative to the background magnetic field and parallel propagating Alfv´en waves. The results are helpful to further understand the physical nature of the observed ion cyclotron wave-related perturbations upstream from the Martian bow shock and have guiding implications for the re-modeling and numerical simulation of the plasma physical processes therein.
Subjects: Astronomy submitted time 2023-12-15 Cooperative journals: 《天文学报》
Abstract： Alfv{\'e}n waves are ubiquitous in the solar wind and have important implications for the plasma heating and acceleration. The advances in Alfv{\'e}n wave research in the solar wind in recent years are summarized from the aspects of solar wind structures, solar wind turbulence, global models of the solar wind, plasma instabilities (the parametric decay instability and firehose instability), and the solar wind heating and acceleration. In view of the current research trend, the future research of Alfv{\'e}n waves is foreseen in three directions: the sub-Alfv{\'e}nic solar winds, global models of the solar wind and solar source regions.
Subjects: Astronomy submitted time 2023-07-14 Cooperative journals: 《天文学报》
Abstract： Ion cyclotron waves (ICWs) are one kind of plasma waves whose frequency is close to the ion cyclotron frequency. They exist widely in the upstream of Mars, and the frequency observed by satellites is generally near the proton cyclotron frequency. ICWs are byproducts in the production processes of pick-up ions. The occurrence of ICWs constitutes, in principle, an indirect signature of the presence of newborn planetary protons. ICWs upstream of Mars have received much attention since they were first reported in 1990. In this review, we summarize the research progress of ICWs in the upstream of Mars, including the observation of ICWs, the wave generation mechanism, their statistical properties and related future research trends.
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