Modeling UV and X-Ray Emission in a Post-CME Current Sheet
NAVAL RESEARCH LAB WASHINGTON DC SPACE SCIENCE DIV
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A post-CME current sheet CS is a common feature developed behind an erupting flux rope in CME models. Observationally, white light observations have recorded many occurrences of a thin ray appearing behind a CME eruption that closely resembles a post-CME CS in its spatial correspondence and morphology. UV and X-ray observations further strengthen this interpretation by the observations of high temperature emission at locations consistent with model predictions. The next question then becomes whether the properties inside a post-CME current sheet predicted by a model agree with observed properties. In this work, we assume that the post-CME CS is a consequence of Petschek-like reconnection and that the observed ray-like structure is bounded by a pair of slow mode shocks developed from the reconnection site. We perform time-dependent ionization calculations and model the UV line emission. We find that such a model is consistent with SOHOUVCS observations of the post-CME CS. The change of Fe XVIII emission in one event implies an inflow speed of 10 kms and a corresponding reconnection rate of MA 0.01. We calculate the expected X-ray emission for comparison with X-ray observations by HinodeXRT, as well as the ionic charge states as would be measured in-situ at 1 AU. We find that the predicted count rate for HinodeXRT agree with what was observed in a post- CME CS on April 9, 2008, and the predicted ionic charge states are consistent with high ionization states commonly measured in the interplanetary CMEs. The model results depend strongly on the physical parameters in the ambient corona namely the coronal magnetic field, the electron density and temperature during the CME event.
- Nuclear Physics and Elementary Particle Physics
- Environmental Health and Safety