Join the disputation
The PhD defence and trial lecture will be 100% in-person. The room opens for participation just before the disputation starts, and closes for new participants approximately 15 minutes after the defence has begun.
Join the trial lecture - 6th of October 22nd at 10:15 (Aud. 209, Svein Rosselands Hus)
"Why can stellar superflares be so much more powerful than solar flares?"
Conferral summary
Denne avhandlingen undersøker mekanismene bak de sterke emisjonene i synlig lys som kan observeres i noen solutbrudd. Sascha benytter seg både av de nyeste simuleringene utviklet internt og observasjoner fra det svenske solteleskopet på øya La Palma. Resultatene gir oss en bedre forståelse av dette fenomenet, som har vært uoppklart i over et århundre.
Main research findings:
Solar flares are sudden brightenings of localized regions in the atmosphere of the Sun. They accelerate particles, like electrons and protons, and heat the solar plasma to several millions of degrees. The enormous amounts of radiation released in these events, combined with associated phenomena, have a major influence on space weather around our planet Earth, and it is therefore of vital importance for us to understand the mechanisms behind them.
This work investigates solar flares with emissions in the visible light (termed white-light flares, or WLFs for short). These emissions challenge the standard flare model used in solar physics. We use a combination of simulations and observations to determine the mechanisms behind these emissions. We also identify a simple way to deduce these mechanisms from observations.
Our results show intensity enhancements caused primarily by free electrons attaching to ionized hydrogen atoms, sending out light at visible wavelengths. These emissions come from the chromosphere, the layer above the visible solar surface. Some additional enhancements appear in the lower layers during the later stages of the flare evolution. With our simulations, we are able to account for the discrepancy in intensity between simulated and observed flares.
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