# Relationship between Magnetic Field Properties and an X-class Flare in Active Region NOAA 9077

## TL;DR

This study investigates how magnetic field properties in active region NOAA 9077 relate to an X-class solar flare, revealing changes in field line height, energy, and inclination that suggest energy release occurs mainly in closed magnetic structures.

## Contribution

The paper provides new insights into the magnetic field parameter changes associated with an X-class flare, emphasizing the role of closed magnetic field lines in energy release.

## Key findings

- Magnetic field lines became lower after the flare.
- Free magnetic energy peaked before the flare and decreased afterward.
- The ratio of closed to open field lines increased post-flare.

## Abstract

The magnetic field plays a key role in producing solar flares, so that the investigation on the relationship between the magnetic field properties and flares is significant. In this paper, based on the magnetic field extrapolated from the photospheric vector magnetograms of the active region NOAA 9077 obtained at Huairou Solar Observing Station, the magnetic field parameters including the height of field lines, force-free factor, free magnetic energy and inclination angle were studied with respect to an X-class flare in this region. We found that the magnetic field lines became lower and the ratio of number of closed field lines to those of open field lines increased after the flare. The force-free factor ($\alpha$) attained a large value before the flare and then decreased after the flare for the closed field lines, while the open field lines showed the opposite tendency. Free energy reach to maximum before flare, then decrease after flare. The magnetic inclination angles showed opposite change trends after the flare for closed and open field lines. Therefore, we may conclude that non-potential energy released by flare mostly contained in the closed magnetic field lines.