Advisor: Graham Kerr and Jiong Qiu
Solar flares release a tremendous amount of energy, a significant amount of which is transported to the lower solar atmosphere. Once this energy dissipates, plasma heating and ionisation in the chromosphere and transition region results in a broadband enhancement to the Sun's radiative output. At UV/optical/IR wavelengths this emission appears as dramatic ribbon-like structures that undergo apparent propagation as new field lines reconnect and release their energy. High-resolution, high-cadence observations in recent years have revealed that there is sub-structure within flare ribbons. Studying the properties of flare ribbons, and crucially, the sub-structure can reveal much about the energy transport and release processes that are difficult to probe directly. In this project we will tackle questions related to flare energetics: (1) does the energy flux density injected to flare ribbons vary strongly with flare magnitude (e.g. from B-X class flares)?; (2) does sub-structure within flare ribbons (e.g. brighter knots, or plasma properties identified from spectroscopic observations) seem to result from fine-scale differences in energy deposition or does the underlying pre-flare chromosphere have an impact?
We will begin with Question #1 by using SDO/AIA, IRIS, and Solar Orbiter/EUI images of flare ribbons in combination with hard X-ray observations from RHESSI or STIX. The total power delivered to the lower atmosphere can be inferred from X-ray observations. The crucial ingredient to infer the energy flux density delivered to the lower atmosphere is the area of the ribbons/footpoints. We will explore different ways to infer this property from the flare images (e.g. looking at newly brightened sources as functions of time). This will be performed on a large sample of flares of different magnitudes.
Then, if time allows, we will turn to Question #2, using the UV Footpoint Calorimeter method to identify spatially resolved energy flux densities input in a single flare ribbon, as well as inversions of pre-flare atmospheric structures, to determine how much each varies on small spatial scales.