Author ORCID Identifier
0000-0003-2802-850X
Document Type
Dissertation
Date of Award
5-31-2026
Degree Name
Doctor of Philosophy in Applied Physics - (Ph.D.)
Department
Physics
First Advisor
Bin Chen
Second Advisor
Dale E. Gary
Third Advisor
Gregory D. Fleishman
Fourth Advisor
Haimin Wang
Fifth Advisor
Xuejian Wu
Abstract
The broadband microwave imaging spectroscopy capability provided by the Expanded Owens Valley Solar Array (EOVSA) allows new diagnostics of high-energy processes in solar flares, providing spatially and temporally resolved spectra rich in information about the acceleration and transport of energetic electrons.
In this work, injections and transport of energy and particles into the solar corona during flares are studied. This is accomplished through the development and use of the PIP_Decomp Fitter, an automated fitting tool made by the author to fit injection and precipitation/decay parameters using the spatially resolved radio spectra obtained by EOVSA. These tools are used to study the particle injection and transport processes of multiple flares in the GHz frequency regime. The fits of these events are then further leveraged to gain insight into the trapping environment and energization processes in these flares.
Specifically, transport and trapping parameters for the motion of microwave-emitting, nonthermal electrons through multiple injections are fit to four solar flares in different active regions using EOVSA data and PIP_Decomp. The results provide new insights complementary to existing multi-wavelength flare and active region analyses that involve the use of radio data, such as gyrosynchrotron spectral fitting to determine source parameters, including nonthermal electron density and magnetic field, or joint X-ray—radio analyses of flare events, etc.
The investigation itself scales up in spatial complexity, beginning with fitting whole flares with combined transport models, and progressing to fitting one flare with spatially resolved transport parameters and localizing an injection event to a small portion of that flare.
Analyses of the spectra of PIP_Decomp transport parameters for these flares reveal a nuanced picture of the electron transport processes. The more complex flares of Chapter 6 are well modeled by multiple particle injections into a set of trapping loops, perhaps overlaid with an oscillation. Whereas the flares chosen for their relatively simple time profiles and clear exponential decay in Chapters 5 and 7 show peculiarly long decay times with a frequency dependence that cannot be explained by a simple collisional transport model, but requires diffusive transport processes.
Recommended Citation
O’Donnell, Brian Eugene, "Disentangling non-thermal electron injection and decay in solar flares using multi-wavelength radio observations" (2026). Dissertations. 1887.
https://digitalcommons.njit.edu/dissertations/1887
