Diagnostics of solar flare energetic particles: neglected hard X-ray processes and neutron astronomy in the inner heliosphere

Mallik, Procheta Chandra Vasu (2010) Diagnostics of solar flare energetic particles: neglected hard X-ray processes and neutron astronomy in the inner heliosphere. PhD thesis, University of Glasgow.

Abstract

For work on my thesis dissertation, we have been studying some energetic processes in solar flares. On our work on hard X-ray (HXR) emission from flares, we have shown that non-thermal recombination emission can compare with the
bremsstrahlung HXR flux for certain flare conditions. In this thesis, we show spectral features characteristic of non-thermal recombination HXR emission and suggest how it
plays a signicant role in the flare HXR continuum, something that has been ignored in the past. It is important to note that these results could demand a reconsideration of the numbers of accelerated electrons since recombination can be much more efficient in
producing HXR photons than bremsstrahlung. We go on to show that although nonthermal recombination is not likely to dominate the total HXR flux unless we consider
extreme parameter regimes, it can still form a signicant proportion of the HXR flux for typical flare conditions, thereby remaining important for both spectral inversion
and low energy electron cut-off diagnostic capabilities.

In related work on diagnosing particle acceleration in
flares, we also have an interest in studying solar neutrons. To this end, this thesis presents our work done with new-age neutron detectors developed by our colleagues at the University of New Hampshire. Using laboratory and simulated data from the detector to produce its response matrix, we then employ regularisation and deconvolution techniques to produce encouraging results for data inversion. As a corollary, we have been reconsidering the role of inverse Compton scattering (ICS) of photospheric photons. Gamma-ray observations clearly show the presence of 100 MeV electrons and positrons in the solar corona, by-products of GeV energy ions. We present results of ICS of solar flare photons taking proper account of radiation field geometry near the solar surface. If observed, such radiation would let us determine the number of secondary positrons produced in large flares, contributing to a full picture of ion acceleration and to predicting
neutron fluxes to be encountered by future inner heliosphere space missions.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Solar astronomy, Sun:flares, Sun:x-rays, gamma-rays, neutron astronomy, atomic processes, radiation mechanisms, acceleration of particles
• Subjects: Q Science > QB Astronomy; Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Brown, Prof. John C.
• Date of Award: 2010
• Depositing User: Mr. Procheta C V Mallik
• Unique ID: glathesis:2010-1510
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 25 Feb 2010
• Last Modified: 10 Dec 2012 13:41
• URI: https://theses.gla.ac.uk/id/eprint/1510