Author ORCID Identifier
0000-0002-2633-3562
Document Type
Dissertation
Date of Award
8-31-2025
Degree Name
Doctor of Philosophy in Applied Physics - (Ph.D.)
Department
Physics
First Advisor
Bin Chen
Second Advisor
Dale E. Gary
Third Advisor
Haimin Wang
Fourth Advisor
Jeongwoo Lee
Fifth Advisor
Jason T. L. Wang
Sixth Advisor
Neepa T. Maitra
Abstract
Impulsive solar energetic electron events (SEEs) are a common phenomenon originating from the Sun. They are characterized by rapid onset and brief duration, and are commonly associated with solar flares. Solar radio bursts, which offer a rich variety of diagnostic tools for solar activities, exhibits a close relationship with impulsive solar energetic electron events. Such diagnostics are particularly powerful when combined with multi-wavelength remote sensing and in situ observations. The dissertation focuses on combining state-of-the-art microwave imaging spectroscopy data obtained by the Expanded Owens Valley Solar Array (EOVSA) with other multi-messenger observations to investigate the origin of impulsive solar energetic electron events near the solar surface.
The first part of the dissertation is mainly focused on a case study on a type III radio burst event associated with an impulsive solar energetic electron event. The multi-instrument, multi-perspective observations of the interplanetary type III radio burst event shortly after the second perihelion of the Parker Solar Probe (PSP) are reported. This event is associated with a solar jet and an impulsive microwave burst event recorded by EOVSA. The good temporal correlation and magnetic connectivity suggest that the in situ energetic electrons observed by the PSP spacecraft originated from the magnetic reconnection region of the solar jet. PSP observed enhanced flux during the event with an antisunward, beam-like electron distribution across all energy channels. Furthermore, microwave imaging spectroscopy observations suggest that the escaping energetic electrons are injected into a large opening angle of about 90°, which is significantly broader than the apparent width of the jet spire.
In the second part of the dissertation, the analysis focuses on the timing and spectral characteristics of in situ energetic particles in association with their solar sources. One case study is on a relatively large solar energetic particle event associated with a GOES X1-class flare. I employ a velocity dispersion analysis method to derive the release time of the in situ energetic particles measured by multiple spacecraft and compare it to remote-sensing observations, including microwave gyrosynchrotron emission observed by EOVSA and bremsstrahlung emission observed by the Fermi spacecraft in hard X-rays. I found that the hard X-ray (HXR) light curve exhibit two impulsive periods, which is consistent with the in situ observations by PSP. The observation supports the two-phase particle acceleration scenario: the first, less energetic electron population was produced during the initial reconnection that triggers the flare eruption, and the second, more energetic electron population was accelerated in the region above the loop-top below a well-developed, large-scale reconnection current sheet induced by the eruption.
The third study investigates the origin of solar energetic electrons in association with recurrent solar jets. The primary science question I address is why only a small fraction of energetic electrons escape into interplanetary space compared to their microwave/X-ray-emitting counterparts near the solar surface. I focus on the study of a series of energetic electron events observed by Solar Orbiter during the mid-November 2022 period. One case study selected from these events is well covered by both EOVSA and Solar Orbiter/STIX, as well as three spacecraft offering in situ measurements from different heliocentric longitudes. Using microwave imaging spectroscopy and spatially resolved spectral analysis, I find that the number density of energetic electrons decreases rapidly by at least two orders of magnitude in the direction of open field lines away from the above-the-looptop region in the low corona. I attribute this significant drop in energetic electron density to local acceleration and effective trapping in the above-the-looptop region, resulting in only a small fraction of electrons entering interplanetary space as revealed by the multi-spacecraft in situ measurements.
This dissertation investigates the origin, acceleration, and transport of flare-associated SEE events. Radio imaging spectroscopy and spectra analysis from EOVSA play a crucial role in tracing the solar origin of these energetic electrons. By integrating microwave and HXR diagnostics with in situ observations from PSP, Solar Orbiter, and spacecraft positioned at 1 AU, the dissertation adopts a multi-messenger, multi-instrument approach to achieve a more comprehensive understanding of solar energetic electron events.
Recommended Citation
Wang, Meiqi, "Multi-messenger diagnostics of the origin and transport of solar energetic particles" (2025). Dissertations. 1858.
https://digitalcommons.njit.edu/dissertations/1858
