Spectral Diagnostics of Active Prominences

TitleSpectral Diagnostics of Active Prominences
Publication TypeConference Paper
Year of Publication2007
AuthorsLabrosse, N., Gouttebroze P., and Vial J.-C.
EditorHeinzel, P., Dorotovič I., and Rutten R. J.
Conference NameThe Physics of Chromospheric Plasmas
Date PublishedMay

Active prominences exhibit plasma motions, resulting in difficulties with the interpretation of spectroscopic observations. These solar features being strongly influenced by the radiation coming from the solar disk, Doppler dimming or brightening effects may arise, depending on which lines are observed and on the velocity of the plasma. Interlocking between the different atomic energy levels and non local thermodynamic equilibrium lead to non-trivial spectral line profiles, and this calls for complex numerical modeling of the radiative transfer in order to understand the observations. We present such a tool, which solves the radiative transfer and statistical equilibrium for H, He I, He II, and Ca II in moving prominences where radial plasma motions are taking place. It is found that for isothermal, isobaric prominence models, the He II resonance lines are very sensitive to the Doppler effect and thus show a strong Doppler dimming. The Ca II lines Doppler effect for the prominence models considered here. We illustrate how the code makes it possible to retrieve the plasma thermodynamic parameters by comparing computed and observed line profiles of hydrogen and helium resonance lines in a quiescent prominence. This new non-LTE radiative transfer code including velocities allows us to better understand the formation of several lines of importance in prominences, and in conjunction with observations, infer the prominence plasma thermodynamic properties and full velocity vector.