Magnetic activity associated with radio noise storms

As it crossed the solar disk in May and June 1998, AR 8227 was tracked by T RACE, Yohkoh, SOHO, and many ground-based observatories. We have studied ho w the evolution of the magnetic field resulted in changes in activity in th e corona. In particular, we examine how the evolving field may have led to the acceleration of electrons which emit noise storms observed by the Nanca y Radio Heliograph between 30 May and 1 June 1998, in the absence of any fl are. The magnetic changes were related to moving magnetic features (MMFs) i n the vicinity of the leading spot and are related to the decay of this spo t. Within the limits of the instrumental capabilities, the location in time and space of the radio emissions followed the changes observed in the phot ospheric magnetograms. We have extrapolated the photospheric magnetic field with a linear force-free approximation and find that the active region mag netic field was very close to being potential. These computations show a co mplex magnetic topology associated to the MMFs. The observed photospheric e volution is expected to drive magnetic reconnection in such complex magneti c topology. We therefore propose that the MMFs are at the origin of the obs erved metric noise-storms.