Subjects: Astronomy submitted time 2023-07-14 Cooperative journals: 《天文学报》
Abstract： Collisionless magnetic reconnection, which converts the magnetic energy into the kinetic energy of plasma particles via the heating or acceleration, has been believed widely to be able to explain various eruptive phenomena such as solar flares and geomagnetic storms. However, the microphysical mechanism of anomalous resistivity in the collisionless magnetic reconnection is still an unsolved fundamental problem. Among the many physical mechanisms of anomalous resistivity formation, chaos-induced resistivity based on the chaos of the charged particle orbits near the magnetic neutral point is not the most popular formation mechanism, but its microscopic physical picture is the clearest. This paper first briefly reviews the early research and physical model of the chaos-induced resistivity in collisionless magnetic reconnection region, introduces the recent research progress of the chaos-induced resistivity, and expounds the future research direction of the chaos-induced resistivity.
Subjects: Astronomy submitted time 2023-07-14 Cooperative journals: 《天文学报》
Abstract： Radio bursts are ubiquitous in the cosmic plasma. Solar radio emission mainly comes from the outer atmosphere of the sun. It is an induced radiation phenomenon generated by the interaction between energetic electrons and solar atmospheric plasma. Different dynamic spectra of solar radio bursts (SRBs) contain physical information of the plasma structure and state in the radiation source region. Therefore, the radiative mechanism of radio bursts has always been the object of research. There are two kinds of coherent radiation mechanisms related to solar radio bursts: one is the plasma radiation mechanism based on electron Langmuir frequency; the other is the electron cyclotron maser (ECM) radiation mechanism based on the electron cyclotron frequency. Although these two radiation mechanisms were proposed almost at the same time, based on the understanding of the coronal environment and the ECM mechanism at that time, the ECM radiation mechanism did encounter some difficulties in explaining SRBs. Until 1979, Wu $\&$ Lee introduced the relativistic effect and used the ECM radiation to explain the earth's Auroral Kilometric Radiation (AKR). Since then, the ECM emission has attracted wide attention. Considering some difficulties in applying the ECM emission mechanism to SRBs, we proposed a series of modified models in recent years. Firstly, the cutoff in the energy spectrum of the power-law electrons can effectively drive the ECM instability without relying on the anisotropic distribution of electron velocity. Secondly, considering the influence of Alfv\'{e}n wave perturbations which are prevalent in space and celestial plasmas, a self-consistent ECM emission mechanism excited by energetic electron beams is developed. On this basis, this paper summarizes the application of the ECM emission mechanism in traditional SRB phenomena from type I to V and microwave SRBs in recent years.
Subjects: Astronomy submitted time 2023-07-14 Cooperative journals: 《天文学报》
Abstract： Electromagnetic Ion Cyclotron (EMIC) waves in the solar wind have received much attention since they were discovered. EMIC waves are important in the plasma heating and acceleration in the solar wind because they can effectively transfer wave energy to ions via the cyclotron resonance. This paper summarizes the progress of EMIC waves observation and theoretical research in the solar wind, including a series of results obtained from EMIC waves observation in and out of magnetic clouds, Interplanetary Coronal Mass Ejections (ICMEs) sheath region, and the research progress for excitation mechanism of EMIC waves based on observations. Finally, the potential research of EMIC waves in the solar wind in the future is anticipated.
Subjects: Astronomy submitted time 2023-07-14 Cooperative journals: 《天文学报》
Abstract： Kinetic Alfv\'en waves (KAWs) are dispersive Alfv\'en waves with a perpendicular wavelength comparable to the ion gyroradius or the electron inertial length. Due to the scale of waves matching to the kinetic scale of particles, KAWs can play an important role in the heating and acceleration of particles in solar and space plasmas. Therefore, KAWs are often regarded as a candidate for the coronal heating. In this paper, the excitation and dissipation mechanisms of KAWs in the solar atmosphere are investigated systematically. Based on the coronal plasma environment, this paper introduces several excitation mechanisms of KAWs: anisotropic temperature instability, field-aligned current instability, electron beam instability, density inhomogeneity instability and resonant mode conversion. The dissipation mechanisms of KAWs in the solar atmosphere are introduced, and their effects on the plasma heating in the sunspot, coronal loop and coronal plume are also discussed. This review not only provides a reasonable theoretical basis for understanding the driving mechanism, dynamic evolution characteristics and wave-particle interaction of KAWs in the solar atmosphere, but also helps to reveal the microscopic physical mechanism of energy storage and release, as well as particle heating in the corona.
Subjects: Astronomy submitted time 2023-07-14 Cooperative journals: 《天文学报》
Abstract： The solar wind originates from the solar atmosphere. It undergoes heating when it propagates in the interplanetary space. It is unclear what heats the solar wind, a frontier problem in space physics. The solar wind is commonly in the state of turbulence, and the turbulence energy is believed to be an important source of the solar wind heating. However, two key questions remain, i.e., what is the specific medium heating the solar wind and what is the microscopic mechanism of the heating. This paper reviews the history of the studies on the solar wind heating problem, with the focus on domestic works about solar wind ion-scale turbulence and its heating. This paper also raises several questions to be solved and interesting topics on the solar wind heating in the future.
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