A research group at Xinjiang Astronomical Observatory (XAO) of the Chinese Academy of Sciences, together with their collaborators from the Lishui University and the Purple Mountain Observatory, carried out a preliminary study on the Electron Cyclotron Maser Emission (ECME) with a fully relativistic correction. The results showed that the fully ECME case has a greater advantage in exciting the ECM instability when non-thermal electron energy above 50 keV.
The results were published in The Astrophysical Journal.
Radio emission is critical for understanding the physical process of various outbursts because of carrying a wealth of information, and the ECME plays an important role as a coherent radiation mechanism in explaining radio emission phenomena from celestial bodies, such as the Earth and the Sun.
“Nowadays, most of studies on ECME are only consider the relativistic effects of resonance conditions, i.e., semi-relativistic corrections. However, when ECME is used to explain strong radio burst events that are produced by relativistic electrons, it is necessary to consider the effect of fully relativistic effects on the theory.” said Dr. SHEN Jinhua from XAO.
In the fully relativistic correction case, a power-law electron distribution with a low-energy cutoff is used to calculate the cyclotron maser instability. The researchers found that the fully correction has a large instability growth rate and a smaller peak frequency compared to the semi-relativistic case.
The researchers confirmed that the fully relativistic correct effects were important only in the energy above 50 keV, and the semi-relativistic ECM was still a good approximation for lower-energy case. In addition, for strong magnetic field environment, the X mode cutoff frequency can be lower than its peak frequency.
Moreover, the radio emission from pulsars, flare stars and Blazar jets usually has extremely high bright temperatures, which suggests cyclotron maser instability must be involved. Therefore, it is necessary to consider a fully relativistic correction for ECME, as well as being useful for understanding these high-energy radio emissions.
Contact: ZHANG Lijie; SHEN Jinhua
Xinjiang Astronomical Observatory, Chinese Academy of Sciences
Email: zhanglijie@xao.ac.cn shenjh@xao.ac.cn
