Subjects: Astronomy submitted time 2023-10-07 Cooperative journals: 《天文学报》
Abstract： Fireball monitoring network is the main equipment for monitoring impact from small-size near-Earth objects (NEOs) and determining meteorite fall locations. In this paper, a monitoring system using a multi-station distributed all-sky video camera network is proposed and a regional prototype system has been constructed in Jiangsu and surrounding areas. The main processes of fireball monitoring were implemented, including network control, video capturing, data processing, trajectory determination, and orbit calculation. After running for 1\;yr, the results show that the limiting apparent magnitude $-1.0$ for meteors in the video and the absolute magnitude exhaustive detection regime can reach around $-2.5$. The flux of fireballs is found to be $2.68\!\times\! 10^{-7}$\;km$^{-2}$\,$\cdot $\,h$^{-1}$. The percentages of streams and sporadic meteors are 46\% and 54\%, respectively, and the fraction of cometary orbits equals 72.9\%, while for asteroidal-type it is 27.1\%. The statistical results are close to those of the international meteor monitoring networks, which verified the monitoring capability of the network system in practical operation.
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： As well known, more than 99\% of the observable matter in the universe is plasma and the plasma astrophysics studies various physical processes and phenomena occurring in cosmic plasmas, from small-scale collective interaction processes and energy transforming mechanisms in particle kinetics to the state of large-scale structure of cosmic objects and their eruptive phenomena. The present paper reviews the important role of the plasma astrophysics in the development of the modern astronomy as well as the formation of the modern plasma cosmology based on the history of the cosmic evolution, the formation of large-scale structures, and eruptive phenomena of cosmic objects. In addition, the unique function of satellite in situ exploring researches in space plasmas to act as the natural laboratory for the plasma astrophysics is further elaborated.
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