Identifying magnetohydrodynamic wave modes in the solar atmosphere

Abstract

Waves are ubiquitous in the solar atmosphere and have proved to be an important part of solar research. These plasma waves are used in coronal seismology to deduce properties of the solar atmosphere that are not directly observable. They are also thought to play a key role in heating the corona.

In a plasma with constant density and a uniform, homogenous magnetic field, there are three magnetohydrodynamic (MHD) wave modes: Alfvén, fast, and slow. Instead, if the magnetic field or density of the plasma is non-uniform, these wave modes are no longer distinct and have mixed properties, changing energy transport and dissipation properties. As such, a scheme to identify the MHD wave modes in the solar atmosphere is important to better understand the solar atmosphere, including for advancing coronal seismology and assessing how waves contribute to coronal heating.

In this thesis, I have investigated a wave mode identification (WMI) scheme to identify MHD wave modes in the solar atmosphere. In the first paper, we present a proof-of-concept for how this scheme can be used in synthetic observations to isolate properties of the Alfvén wave mode. In Paper II, we recreate the 2D wave experiments in Bogdan et al. (2003), and use their in-depth wave analysis to understand better the information we can deduce from the WMI scheme. We show that the WMI scheme is equivalent to the scheme used in the original article, with the added advantage of being naturally expandable to 3D. In Paper III, we expand the 2D experiments to 3D and analyse how the WMI scheme functions with different wave drivers and magnetic field strengths. We conclude that the scheme isolates the 3D MHD wave modes and that we can deduce several physical properties of the waves from the scheme, like location, period and steepening.

Date of Award	2 Dec 2025
Original language	English
Awarding Institution	University of St Andrews University of Oslo
Supervisor	Ineke De Moortel (Supervisor), Mats Carlsson (Supervisor), Thomas Howson (Supervisor) & Boris Vilhelm Gudiksen (Supervisor)