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Structure of EUV Emission in Dipolar Active Regions of Solar Cycle 24

Presentation #105.09 in the session Ambient Solar Atmosphere Posters.

Published onSep 18, 2023
Structure of EUV Emission in Dipolar Active Regions of Solar Cycle 24

Heating of the solar corona is one of outstanding problems of solar physics, and analysis of coronal loops is often done in order to determine the properties of heating. Owing to large optical depth, discerning individual structures along the line of sight can be difficult, but assumptions are often made that a given coronal loop is a thin, coherent structure, representing a particular magnetic flux tube. A recent theory, however, proposes that some unknown amount of coronal loops are not coherent structures, but are rather line-of-sight artifacts of emission of large veil-like structures (‘wrinkles in the veil’). If true, this will necessitate different analytical approaches to determine properties of plasma from coronal loop observations. In our project, we attempt to infer spatial properties of the emitting volume above solar active regions. We argue that by studying the relationship between the total EUV flux, and the number of coronal loops this flux is structured into, it may be possible to discern whether the emission is structured into (a) individual bright flux tubes embedded in diffuse background, (b) large emitting structure with irregular boundaries, and (c) thin and extended veil-like structures. To this end, we have assembled a database of active regions of Solar Cycle 25 observed by SDO, which have particularly easy to analyze properties: they are isolated from other regions, approximately dipolar, do not exhibit eruptive activity, and are observed above the central meridian. We describe the database, which we would like to make open for other researchers, describe statistical properties of such active regions, and discuss the first results we got from studying this dataset.

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