Date of Award

9-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Daniel J. Emmons, PhD

Abstract

Using Non-Linear Force Free Field (NLFFF) extrapolation, 3D magnetic fields were modeled from the 12-minute cadence Helioseismic and Magnetic Imager (HMI) photospheric vector magnetograms, spanning a time period of one hour before through one hour after the start of 18 X-class flares and 12 M-class flares. Several magnetic field parameters were calculated from the modeled fields directly – as well as from the power spectrum of surface maps generated by summing the fields along the vertical axis – for two different regions: areas with photospheric Bz ≥ 300 G (Active Region – AR) and areas above the photosphere with the non-potential field strength greater than 3 standard deviations above the mean non-potential field strength of the AR field and either the twist number ≥ 1 turn or the shear angle ≥ 80° (Non-Potential Region – NPR). Superposed epoch plots of the magnetic field parameters were analyzed to investigate the evolution of the coronal field during the solar flare events and discern consistent trends across all solar flare events in the dataset, as well as across subsets of flare events categorized by their magnetic and sunspot classifications. The relationship between different flare properties and the magnetic field parameters was quantitatively described by the Spearman ranking correlation coefficient. The parameters that showed the most consistent and discernable trends amongst the flare events, particularly for the hour leading up to the eruption, were the total unsigned flux, free magnetic energy, total unsigned magnetic twist, and total unsigned free magnetic twist. Strong to very strong correlations were found between the magnetic field parameters and the following flare properties: peak X-ray flux, duration, rise time, decay time, impulsiveness, and integrated flux. The findings of this study indicate that magnetic field parameters calculated from the modeled coronal magnetic field have greater predictive capability than what has been found from only using photospheric data.

AFIT Designator

AFIT-ENP-DS-23-S-008

Comments

An embargo was observed for posting this dissertation.
This work is marked Distribution A: Approved for public release, distribution unlimited.
PA case number 88ABW-2023-0750

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