Space Weather, Extreme Ultraviolet Instruments and the Multithermal Corona

Abstract:

Observation of the solar corona from Earth orbit or from other locations such as L1 or L5 using suitably-chosen Extreme UltraViolet (EUV) wavelengths offers the possibility of addressing two major goals that will improve our ability to forecast and predict geoeffective space weather events: 1.) improve our understanding of the coronal conditions that control the opening and closing of the corona to the heliosphere and consequent solar wind streams, and 2.) improve our understanding of the physical processes that control the early evolution of CMEs and the formation of shocks from the solar surface out to beyond the nominal source surface. The time-varying solar corona is structured not only in space and in time but also in temperature. A method for efficiently observing multiple wavelengths, thereby recording emission lines formed at different temperatures, simultaneously is therefore desirable. These observations are especially necessary for CME detection, as the departing magnetized plasma shows markedly different structures at different temperatures and even the detectability of the event varies dramatically at different EUV wavelengths. EUV measurements can help to: i.) determine coronal structuring from its roots out to beyond 2.5 R_s; ii.) measure the changes in coronal connectivity; iii.) distinguish between and test solar wind models; iv.) establish the impact of pre-existing coronal structures on CME evolution; v.) confront theories of SEP acceleration and preconditioning; and vi.) establish the extent of energy release behind CMEs.