Laura Hayes (NASA): Solar Flares, Quasi-Periodic Pulsations and the Earth’s Ionosphere
Solar flares are the most powerful and energetic physical phenomena in our solar system, releasing radiation across the whole electromagnetic spectrum with total energies reaching on the order of 1025 J in a matter of minutes. On Earth, the conditions of the terrestrial ionosphere is significantly affected by solar flaring energy release. Enhanced X-ray and EUV emission drives a rapid increase of ionization on the entire dayside ionosphere resulting in substantial electron density increases in the lower ionosphere to extents large enough to effect the propagation of radio waves used in telecommunications. In this way we want to study solar flares to understand their driving mechanisms, emission spectra, and underlying physics to build towards a greater understanding of why, how, and when they occur. A key observational feature of the emission generated in solar flares is the presence of quasi-periodic pulsations (QPPs). The occurrence of such pulsations in flaring emission places additional constraints on the interpretation and processes that operate in solar flares, and hence a full description of the phenomena is required to build towards an integrated solar flare model. In this seminar I will present an overview of quasi-periodic pulsations that exists in solar flare emission, including their geophysical impacts on the Earth’s ionosphere, and discuss a recent statistical study of quasi-periodic pulsations observed in the X-ray emission from flares over the last solar cycle, placing the results in the context of proposed mechanisms.