Long-term helicity evolution in NOAA active region 8100

GREEN, L.M.; LÓPEZ FUENTES, M.C.; DÉMOULIN, P.; MANDRINI, C.H.; VAN DRIEL-GESZTELYI, L.

Vico Equence

Congreso; Second Solar Cycle and Space Weather Euroconference; 2001

ESA

Magnetic helicity is the topological parameter used to describe the structure in the magnetic field and has become increasingly important in coronal studies. Helicity is well preserved in the corona even under non-ideal MHD conditions (see Biskamp 1993), and the Sun can avoid endless accumulation of helicity by ejecting it via the launch of coronal mass ejections (eg. Rust 1994; Low 1996; Devore 2000). Computations are made for NOAA active region 8100 to determine the coronal helicity and helicity injected into the region by differential rotation. These values are then compared to the total amount of helicity lost via coronal mass ejections to test whether differential rotation can inject a significant amount of helicity into the corona. It is found that differential rotation cannot inject a significant amount of helicity to be a viable source for the coronal mass ejection activity. Instead, helicity is likely to be brought into the corona by the emergence of twisted and distorted flux tubes.