Space Weather Propagation in the Inner Heliosphere

Abstract

The inner region of our solar system is vast, spanning hundreds of millions of kilometers and is driven by dynamics ranging in time scales from less than seconds to more than centuries. Space weather originating at the Sun and impacting life at Earth propagates through this complicated region, known as the inner heliosphere, whose dynamics is driven by the Sun’s dynamic magnetic field. When space weather such as interplanetary coronal mass ejections (ICMEs) impact Earth, they can induce geomagnetic storms which cause the aurorae, cause damage to satellites, cause radio and GPS interference, and induce ground currents which can damage power grid infrastructure.

In order to accurately forecast space weather, we need to improve our ability to forecast space weather propagation through the inner heliosphere. To do so we need the ability to answer these two questions: “When observing space weather as far from the Sun as the Earth, how do we differentiate those features that are due to conditions near their origins at the Sun from those due to propagation effects as they traverse the inner heliosphere?” and “How do we then characterize those propagation effects to improve space weather predictions?”

To address these questions this dissertation investigates three aspects of space weather propagation through the inner heliosphere: 1) How well do heavy ion charge distributions now-cast ICMEs at 1 AU? 2) How do arrival time, velocity and intensity of solar energetic electrons compare to modeled magnetic connectivity using ADAPT-WSA vs the Parker spiral? 3) How often are counterstreaming (CSEs) and strahl suprathermal electrons (SSEs) observed during in situ observations of ICMEs and what are their characteristics when compared to suprathermal electrons in the solar wind?

In this thesis we analyze in situ observations of space weather to characterize features and quantify correlations which are due to interplanetary propagation effects versus those which are tied to properties near the Sun. We present this analysis and interpret the results in the context of space weather propagation to achieve significant progress in our understanding of the connection between the Sun and the near-Earth interplanetary environment. This will enable further study that can differentiate propagation effects from those of energization, acceleration and plasma conditions at the solar origins of these space weather events. Ultimately, this research will enhance our ability to forecast space weather propagation through the inner heliosphere.