Proposal Outline
Although observation of "EIT" waves, so called following their discovery with SOHO/EIT by Thompson et aI., 1998, has been continuing for more than a decade, many issues still remain to be clarified - see Gallagher and Long, 2011 for a recent comprehensive review. The power of high resolution EUV spectroscopic observation with EIS for studies of wave phenomena has recently been demonstrated by the first detection of a coronal Moreton wave associated with an EIT wave (Harra et aI., 2011).
The observation to be undertaken in the present study would seek to determine the density change (if any) produced by the passage of an EIT wave following a CME. Although these waves have been observed in multiple passbands using imagers, any intensity increase could be produced by density or temperature increases or a combination of both. Using several different density diagnostics from EIS across a range of temperatures should allow this issue to be resolved. In addition by examining SWAP and AlA data, it will be possible to determine if the EIT wave forms the flank ofthe CME or is a separate feature.
Harra, L. K. et aI., 2011, Ap.J.L., 773:L4, 1.
Gallagher, P.T., Long, D.M., 2011, Space Sci. Rev., 158, 365.
Thompson, B. J. et aI., 1998, Geophys. Res. Lett., 25, 2465.
Target and Observation Plan
The observation would be on a ToO basis with the selection of a suitable flare-productive AR located on disk, but close to either limb. Operation as outlined below would take place over a 12-24 hour period in conjunction with Proba-2/SWAP. Since the wave observation would begin in response to the XRT flare trigger, the XRT would have the AR in its field-of-view. EIS would engage in a synoptic sit-and-stare study of the quiet Sun in a pre-selected position in the direction of disc centre - positioning to be determined by the proposers. This will allow a comparison of the density change arising from the passage of the EIT wave pulse. However following receipt of the XRT flare trigger signal, EIS would enter continuous sit-and-stare mode with 45s exposures for ~1 - 2hr. XRT would also begin taking higher cadence images for the same time period with the thin filters if possible, although this would be optional.
The SWAP observing plan calls for an offpoint to solar east or west depending on the location of the active region, with data reb inning and some manipulation of the observing cadence to produce high cadence, high intensity images which would allow coronal for an offpoint to solar east or west depending on the location of the active region, with data reb inning and some manipulation of the observing cadence to produce high cadence, high intensity images which would allow coronal features to be observed farther from the Sun. This operating mode has already been tested, and the intention would be to run this observing plan for ~24 hours when a suitable candidate AR has been identified. |
|