| Presentation Title: | Cool and hot emission disambiguation in instrument passbands |
| Author(s): | P. Antolin, F. Auchère, E. Winch, E. Soubrié, R. Oliver |
Abstract:
Narrowband ultraviolet (UV) or extreme ultraviolet (EUV) imagers, despite being relatively narrow, typically include significant contribution from more than one ion, thus leading to uncertainty regarding the temperature of the observed plasma. This is particularly limiting for diagnostic purposes of very hot or cool plasmas, whose sole presence in the solar corona can be attributed to specific physical mechanisms such as magnetic reconnection or thermal instability. The ambiguity is particularly large when observing off-limb, where line-of-sight superposition is maximal and the diffuse, hot emission becomes comparable in intensity to that of clumpy, cool structures such as spicules, coronal rain and prominences. In this work we investigate 3 methods based on temperature and morphology that are able to distinguish the cool and hot emission, and apply them to the AIA 304, SJI 1330 and SJI 1440 passbands. The methods are based on the Differential Emission Measure (DEM), a linear decomposition of the AIA response functions (RFit) and the Blind Source Separation (BSS) technique. All three methods are found to produce satisfactory results in both quiescent and flaring conditions, decomposing each image into a pair, one with the hot diffuse corona and another with the cool material off-limb in sharp contrast with the background. For AIA 304 we compare our results with co-aligned IRIS data in the SJI 1400 and 2796 channels, and find the RFit method to best match the quantity and evolution of the cool material detected with IRIS. These methods are in principle applicable to any passband from any instrument suffering from similar cool and hot emission ambiguity as long as there is good coverage of the hot temperature range.