Date of Award
Doctor of Philosophy in Applied Physics - (Ph.D.)
Dale E. Gary
James A. Klimchuk
Radio diagnostics, in addition to their capabilities in exploring intense, impulsive bursts, also provide a high sensitivity to much weaker events, which may not show any substantial signature in other wavelengths.
The initial case study examines a complex event consisting of multiple radio sources/bursts associated with a fast coronal mass ejection (CME) and an M 2.1 class solar flare (SOL2015-09-20). ‘First-light’ data from the Owens Valley Radio Observatory–Long Wavelength Array is put in context with observations from Large Angle and Spectrometric Coronagraph onboard the Solar and Heliospheric Observatory, along with the WAVES radio spectrograph onboard WIND, the Expanded Owens Valley Solar Array, and the Air Force Radio Solar Telescope Network. One burst source exhibiting an outward motion is focused upon indicating movement associated with the core of the CME and is classified as type IVm burst. The source height, smoothness of the emission in frequency and time, along with a lower density in the region, indicate the likelihood of gyrosynchrotron as the underlying mechanism over plasma emission. Spectral fitting techniques are used to estimate the physical conditions during the outward movement of the source.
The second study investigates whether energy bursts from small breaks in stressed magnetic fields (nanoflares) can accelerate particles like full-sized flares, and if so, how efficiently? Since nanoflares may produce numerous ‘mildly energetic’ particles, at those energies, the emission in X-ray will be dominated by the thermal component. Type III radio bursts generated by propagating energetic electrons are best suited for the purpose. A model is created to simulate type III emission that may be produced by thousands of nanoflares occurring per second and the novel time–lag technique used to detect the motion of particles. The technique indeed detects the signature of type IIIs despite the numerous overlapping bursts and added noise that is expected in a radio instrument. Based on the findings of the model and associated testing, data from the Very Large Array, Low Frequency Array, and Long Wavelength Array are currently being looked at for signatures of such bursts in the corona. A similar test is performed on data from the FIELDS instrument onboard Parker Solar Probe to look for signatures of particle acceleration in the solar wind from small-scale reconnection events.
Chhabra, Sherry, "Radio diagnostics of particles and plasma in the solar corona" (2021). Dissertations. 1511.