Sunspot Group Analysis
: A Multi-Layer Thresholding Approach

  • Richard Grimes

Student thesis: Doctoral ThesisDoctor of Philosophy


Sunspots are tracers of the solar magnetic field and are closely linked to flaring activity on the Sun. In this report, a software package is presented which can be used to analyse the rotational and translational motions of sunspots in complex sunspot groups. The software uses a new technique called Multi-Layer Thresholding (MLT) to create a 3D representation of a sunspot group which allows the study of radial variation in rotational profiles, and the study of umbral sub-structure for any number of sunspots in a group. The first part of the report details the technical aspects of the newly developed technique and describes the refinement of parameters. In the second section, the program is applied to high-cadence data of a single sunspot exhibiting an X-class flare where the variation in angular velocity with umbral radius is considered. The study finds evidence for non-rigid rotation of the sunspot umbra, likely caused by a back-reaction from the flare. In the final section, the program is applied to long-timescale data of six active regions with varying amounts of flaring activity. The rotation profiles of several key umbrae in the regions are analysed for common features that could be used as a predictor for flaring. The evolution of these sunspot groups is also investigated in detail using MLT, which reveals that the accretion of pores into sunspot umbrae is a significant contributing factor to rotation
Date of Award2023
Original languageEnglish
Awarding Institution
  • Aberystwyth University
SupervisorManuel Grande (Supervisor) & Balazs Pinter (Supervisor)

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