Evolution of Magnetic Field Twist and Tilt in Active Region NOAA 10930

TL;DR

This study tracks the evolution of magnetic twist and tilt in NOAA 10930, revealing how these parameters change before major flares, and highlights the relationship between magnetic helicity and flare activity.

Contribution

It provides detailed measurements of magnetic twist and tilt evolution in NOAA 10930 leading up to X-class flares, using multi-layer observational data.

Findings

Twist increases and tilt decreases before flares.

Total twist exceeds one winding prior to the flare.

Injected helicity is negative and exceeds 10^43 Mx^2 before flares.

Abstract

Magnetic twist of the active region has been measured over a decade using photospheric vector field data, chromospheric H_alpha data, and coronal loop data. The twist and tilt of the active regions have been measured at the photospheric level with the vector magnetic field measurements. The active region NOAA 10930 is a highly twisted emerging region. The same active region produced several flares and has been extensively observed by Hinode. In this paper, we will show the evolution of twist and tilt in this active region leading up to the two X-class flares. We find that the twist initially increases with time for a few days with a simultaneous decrease in the tilt until before the X3.4 class flare on December 13, 2006. The total twist acquired by the active region is larger than one complete winding before the X3.4 class flare and it decreases in later part of observations. The injected helicity into the corona is negative and it is in excess of 10^43 Mx^2 before the flares.