Solar and stellar flares and their connection

Abstract

This thesis focuses on bridging the gap between solar and stellar physics through the study of flares. Solar flares are the most powerful explosions in the solar system and many stellar flares have been observed to be orders of magnitudes larger. However, is not yet known if these phenomena are formed through the same physical process. In this thesis we explore their common origins through a detailed case study of a solar flare and a robust statistical analysis of stellar flares with bespoke observations. Using data from the Swedish Solar Telescope, a detailed study of a solar flare associated with a filament eruption and jet was compared with advanced 3D MHD simulations. This amalgamation of observation and theory allows for a complete picture of the event including the pre-flare magnetic structure and the resulting kinematics of the jet post eruption. Overall, this study aims to characterise the physical environment capturing many evolutionary properties of the event providing a unique perspective on eruptive phenomena on the Sun. With regards to stellar flares, observational data from both K2 and TESS are used to conduct a statistical analysis on flares from both low mass and solar-type stars. As a result of this, no relationship between the rotational phase of stellar flares and starspots is present. This was unexpected as there is a well-established relationship between solar flares and sunspots. This result yields potential implications for how the magnetic field in fully convective low mass stars is generated. Possibly, this result implies the surface of these stars is more complex than the Sun. Furthermore, groups of rapidly fast rotating low mass and solar-type stars were discovered to exhibit very little flaring activity. This is unusual, as rotation is linked to a star’s dynamo mechanism and so faster rotating stars are expected to show higher levels of activity. This research has raised new questions surrounding the underpinning mechanisms driving stellar flares. In an effort to address this the solar 3D MHD simulation is scaled up to replicate flare energies seen in the observed stellar flares. This comparative analysis allows for the exploration of the flare mechanism and potential magnetic structure on these stars, which will be a subject of future research, in order to explain such high energy flares.

Date of Award	10 Jul 2020
Original language	English
Awarding Institution	Northumbria University
Supervisor	Gavin Ramsay (Supervisor), Gerry Doyle (Supervisor), Eamon Scullion (Supervisor) & James McLaughlin (Supervisor)