Prof. LIN Jun from the Yunnan Observatories of Chinese Academy of Sciences, collaborating with Prof. CHEN Bin from the New Jersey Institute of Technology, conducted the radio observation of the magnetic field distribution and relativistic electron acceleration characteristics in the current sheet of solar flares.
The related research results were published in the journal Nature Astronomy on July 27, 2020.
Solar eruption is the most violent energy release process in the solar system, which is usually accompanied by solar flares and coronal mass ejections (CMEs). In the standard flare model, the large-scale current sheet of magnetic reconnection is considered as the core engine of driving the rapid release of the magnetic energy and the particle acceleration.
However, due to lack of observations on the magnetic field property and high-energy particles near the current sheet, the key question such as the location and the mechanism of energy release and particle acceleration in solar flares is still open.
Prof. CHEN Bin et al. analyzed the microwave radiation near the current sheet in an X-class flare event on September 10, 2017 by using the Expanded Owens Valley Solar Array (EOVSA) data and the numerical experiment based on the Lin-Forbes model developed by Prof. LIN Jun et al.
Lin-Forbes model is a theoretical solar eruption model for quantitative descriptions of the overall evolution in the magnetic field structure and its physical relation to magnetic reconnection during solar eruptive process. It is often used by researchers in the solar physics community to help interpret the observational phenomena, reveal the corresponding physical scenario and understand the physics behind it.
The research group found that the magnetic field in the current sheet shows a local maximum at the X-point of magnetic reconnection, and a local minimum in the region between the bottom of the current sheet and the top of the flare loop (also known as the magnetic bottle).
The microwave energy spectrum shows that the acceleration or accumulation of more than 99% relativistic electrons are likely to occur in the magnetic bottle region at the top of the flare loop, rather than near the reconnecting X-point.
These results not only provide direct observational evidence for solving the problem of particle acceleration in the solar eruptive process, but also confirm the Lin-Forbes model.
The finding is the fruit of good international academic collaboration.