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Yunnan Observatory's small-scale asymmetric magnetic reconnection observation research progress
[ Instrument R & D of Instrumentation Network ] Researchers at the Sun Observation and Research Base of Fuxian Lake, Yunnan Astronomical Observatory, Chinese Academy of Sciences clearly observed that a small dark strip caused by asymmetric magnetic reconnection was cut off and exploded.
Magnetic reconnection, or magnetic field line reconnection, also known as magnetic field annihilation, is a very important rapid energy release process in astrophysics, and is also the conversion of magnetic energy into kinetic energy, thermal energy and radiant energy of particles the process of. It is generally believed that the energy release on the sun is caused by magnetic reconnection.
Magnetic reconnection, as the name implies, is a physical process in which two sets of magnetic lines of opposite directions are close to each other and reconnected to form a new magnetic line of force. Magnetic reconnection is a basic and very important physical process on the sun that quickly releases magnetic energy. Solar explosion events are almost all There is a certain relationship with magnetic reconnection, such as flares, dark stripe bursts, corona mass ejection, jets, etc., and small-scale magnetic reconnection may be closely related to corona heating. However, due to the limitation of the resolution of the observation equipment, there are very few observational studies on small-scale magnetic reconnection.
Xue Zhike et al. Mainly used the high-resolution data observed by the One-meter New Vacuum Solar Telescope (NVST) at the Yunnan Observatory ’s Fuxian Lake Solar Observation and Research Base, combined with the extreme ultraviolet (EUV) and vector magnetic field data of the Solar Dynamics Observatory (SDO) , Analyzed the complete process of small-scale asymmetric magnetic reconnection that occurred in the active area 12436 on October 23, 2015.
A vacuum solar telescope is a solar telescope in which all imaging optical elements are placed in a vacuum cylinder (with a pressure of less than 1 mm of mercury). The vacuum cylinder is used to eliminate the harmful effects of airflow inside the instrument on imaging. In addition, the hot air turbulence caused by the external structure (such as the dome) will also affect the imaging quality, so the dome (or other forms of movable roof) must be removed during observation, or the dome is not used, and an open-air telescope is used. structure.
They found that the dark bar and the magnetic ring moved in the same direction at the same time (different from the opposite movement in the classic magnetic reconnection), and then the magnetic reconnection occurred between them and formed a typical current piece. This magnetic reconnection is called For asymmetric magnetic reconnection, the plasma is finally injected into the newly formed magnetic ring in the form of a rotating jet.
A current sheet is a thin layer of current between two opposing magnetic fields, also known as a neutral sheet. The plasma flowing from both sides is magnetically merged here, which can heat and accelerate the plasma. The unstable process occurring in the current sheet also plays an important role in acceleration and heating. The main reason is that the ion acoustic instability produces ion acoustic turbulence, which makes the resistance abnormal and increases several orders of magnitude. The tear mode instability makes the current The sheet collapses into a series of separated current wires. Where the magnetic field between the current wires is zero, a strong induced electric field will be generated to accelerate the charged particles
In addition, from the H-alpha Doppler image, it was observed that during the entire magnetic reconnection process, the plasma in the magnetic reconnection region showed red-shift characteristics, which may be related to the magnetic topology.
Source: Encyclopedia, Yunnan Observatory