A solar filament eruption causes a coronal mass ejection, which is a major cause of space weather. Understanding how filaments erupt is thus critical for forecasting space weather.
Both observations and simulations indicate that filament eruption is closely related to the emergence of magnetic fluxes. The eruption is thought to be caused by magnetic reconnection between a filament and an emerging flux. However, the specifics of such a reunion have rarely been revealed.
Recently, a research team led by Dr. Li Leping from the Chinese Academy of Sciences’ National Astronomical Observatories (NAOC) revealed the details of reconnection between a filament and its nearby emerging fields, which resulted in the filament’s reconfiguration and subsequent partial eruption.
On August 18, the study was published in The Astrophysical Journal.
On April 21, 2021, a filament was discovered over the polarity inversion lines in the active region NOAA 12816. Magnetic fields emerged and reconnected with the filament near the filament’s northwestern endpoints, forming a newly reconnected filament and loops.
A current sheet formed repeatedly at the interface of the filament and its neighbouring emerging fields. “We measured some parameters of the current sheets, such as the length, width, reconnection rate, temperature, emission measure, and electron number density, to understand the detailed reconnection,” said Dr. Li, the study’s first author.
Bright plasmoids formed in the current sheet and spread bidirectionally along it, as well as further along the newly reconnected filament and loops. “This result indicates the presence of plasmoid instabilities during the reconnection process,” said Max-Planck Institute for Solar System Research co-author Prof. Hardi Peter.
After that, the newly reconnected filament erupted, while the unreconnected filament remained stable. As a result, the filament only partially erupted. “These findings imply that the reconnection-favored orientation of emerging fields near the filament cannot result in the eruption of the entire filament,” Dr. Li said. “Also important for triggering the filament eruption are other parameters such as position, distance, strength, and area.”