Hard X-Ray Imaging of Solar Flares

verfasst von: Michele Piana, A. Gordon Emslie, Anna Maria Massone, Brian R. Dennis

Verlag: Springer International Publishing

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

The idea for this text emerged over several years as the authors participated in research projects related to analysis of data from NASA's RHESSI Small Explorer mission. The data produced over the operational lifetime of this mission inspired many investigations related to a specific science question: the when, where, and how of electron acceleration during solar flares in the stressed magnetic environment of the active Sun.
A vital key to unlocking this science problem is the ability to produce high-quality images of hard X-rays produced by bremsstrahlung radiation from electrons accelerated during a solar flare. The only practical way to do this within the technological and budgetary limitations of the RHESSI era was to opt for indirect modalities in which imaging information is encoded as a set of two-dimensional spatial Fourier components.
Radio astronomers had employed Fourier imaging for many years. However, differently than for radio astronomy, X-ray images produced by RHESSI had to be constructed from a very limited number of sparsely distributed and very noisy Fourier components. Further, Fourier imaging is hardly intuitive, and extensive validation of the methods was necessary to ensure that they produced images with sufficient accuracy and fidelity for scientific applications.
This book summarizes the results of this development of imaging techniques specifically designed for this form of data. It covers a set of published works that span over two decades, during which various imaging methods were introduced, validated, and applied to observations. Also considering that a new Fourier-based telescope, STIX, is now entering its nominal phase on-board the ESA Solar Orbiter, it became more and more apparent to the authors that it would be a good idea to put together a compendium of these imaging methods and their applications. Hence the book you are now reading.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Hard X-Ray Emission in Solar Flares

Abstract

In this chapter we provide an overview of the solar flare phenomenon with particular emphasis on aspects that can be best investigated through X-ray imaging. Studied for well over a century and a half, the observational manifestations of a solar flare are relatively well cataloged, and its essential nature—the explosive release of energy stored in current-carrying magnetic fields in the outer solar atmosphere—is generally accepted. However, the processes through which this stored energy is converted into the three energetically most important products—hot plasma, erupting material, and accelerated particles (both electrons and ions)—are still poorly understood. High-energy (“hard”) X-ray emission provides important information on the accelerated electrons, and the acquisition of imaging spectroscopy information on these hard X-rays is a key element in determining the spatial, temporal, and spectral properties of the electrons, and so to ultimately solving the puzzle of solar flare initiation and development.