Long-Term Evolution Of Emissivity And Heating In A Solar Active Region

We study the evolution of the heating and emissivity of an active region from its birth throughout its decay during six solar rotations (July-Nov. 1996). We analyse multi-wavelength and multi-instrument data obtained from SOHO (EIT, SUMER, CDS, MDI), Yohkoh (SXT), GOES and 10.7cm radio data from DRAO, Canada. We take one ''snapshot'' per rotation at the time of the central meridian passage (CMP) of the AR, outside of time of flares, which appears to be representative enough to allow us to make some general conclusions about the long-term evolution. Deriving physical parameters like intensity (flux), temperature and emission measure of the entire AR vs. time, we formulate mathematically the change in radiation emitted by the decaying AR at several wavelengths. Combining the emissivity data with the evolution of magnetic flux density as the flux is being dispersed by small- and larger-scale convective motions, we make an attempt to understand the physics behind the emission and heating. We also analyse the effects of flaring on the heating of the AR, and study whether and how the flare properties evolve during the life of the active region.