Signature of a magnetic reconnection event on the solar surface

Magnetic flux cancelation refers to the interaction of opposite polarity magnetic elements leading to magnetic flux removal from the solar surface. If the interacting elements are previously unconnected, their cancelation is treated as an observational signature of magnetic reconnection. Using high-resolution data obtained with the GREGOR telescope on Tenerife, we witnessed such a magnetic field reconnection event. The Integral Field Unit (IFU, built by Instituto de Astrofísica de Canarias, IAC) of the GREGOR Infrared Spectrograph (GRIS) recorded the Stokes profiles in the photospheric Si i 10827Å spectral line targeting the quiet-Sun at disk center.

Left: vertical magnetic field map — white represents magnetic field pointing towards the observer and black represents magnetic field pointing away from the observer; Right — Stokes V profiles for pixels denoted with asterisks. The vertical dotted line indicates the rest center wavelength. The values on the top right represents area asymmetry of negative and positive polarity Stokes V profiles. This first scientific output from the IFU instrument has made use of its rare capability to record 2D maps of the solar surface, simultaneously providing the full Stokes profiles.

Using Stokes Inversions we detected that the cancellation was preceded by a significant rise in line core intensity and temperature shortly before the magnetic features started to lose magnetic flux. We interpret this as the opposite polarity features undergoing reconnection above the photosphere. We also discovered that the border pixels neighboring the polarity inversion line of one of the polarities exhibited a systematic variation of area asymmetry in the Stokes V profiles. Analyzing Stokes profiles recorded from either side of the polarity inversion line could therefore potentially provide additional information on the reconnection process related to magnetic flux cancellation.

 

Reference: A. J. Kaithakkal, J. M. Borrero, C. E. Fischer, C. Dominguez-Tagle, and M. Collados, 2020, Astronomy & Astrophysics, 634, A131, https://doi.org/10.1051/0004-6361/201936941