The PhD defence and trial lecture will be hybrid. Attendees can therefore participate either in-person or via Zoom. The link will be available the day before the disputation. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation. The Zoom links will be published no later than the day before the disputation.
Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants' -> 'Raise hand'.
Join the disputation
The meeting 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 - 3rd of September at 10:15 (Aud. 209, Svein Rosselands Hus)
"The magnetic connection of the Sun to the solar wind"
Conferral summary
Avhandlingen tar et dypdykk inn i solaratmosfærkoden, Bifrost, fra de indre mekanisme av modellen til simuleringene som er produsert. Ved å utvikle en ny metode for å identifisere bølger i realistisk simuleringer, diskuterer George hvordan energioverføring via bølger forbinder den nedre og øvre delen av solatmosfæren, og kan bidra til oppvarming av solatmosfæren og akselerasjonen av solvinden.
Main research findings:
Just like in the oceans and atmosphere on Earth, a vast range of waves exist in the plasma of the solar atmosphere. Understanding the transfer of energy via these magnetohydrodynamic (MHD) waves has important implications for our theory on the heating of the upper solar atmosphere (coronal heating) and the prediction of geomagnetic storms by monitoring the solar wind. Despite extensive theory and simulations, the detection of waves in realistic simulations still presents a large challenge, due to wave interaction, conversion, dissipation and numerical artefacts: it is like finding a needle in a haystack full of needle-like objects.
Through the development of a new method for detecting wave activity in simulations, I have demonstrated that different magnetic structures can inhibit and prohibit the propagation of waves, including the dominant oscillations at 3.5 mHz and 5 mHz, which have previously been detected as “global modes” in both observations and simulations. Specifically, we find that twisted magnetic features called swirls enable the transport of magnetoacoustic waves at 3.5 mHz waves to the upper atmosphere, whilst in the absence of swirls, plasma motions in the chromosphere enhance the wave activity at 5 mHz. These results lead to exciting prospects in the realm of quantifying the energy deposit to the upper atmosphere in different solar regimes.
