CAREER: Kinetic Phenomena Upstream from the Earth's Bow Shock and Their Geomagnetic Effects

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This project is focused on better understanding of the ways in which solar wind energy drives space weather disturbances near Earth. The Earth is protected from the direct impact of the solar wind by its magnetic field that extends out to high altitudes and causes the solar wind to be deflected around it. When the Earth?s magnetic field becomes connected to the Sun's magnetic field through a process called magnetic merging, some of the solar wind energy enters near-Earth space. The interaction between the solar wind and the Earth's magnetosphere accelerates plasma particles to energies high enough to threaten spacecraft electronics and astronaut health, and in addition, creates mega-ampere electric currents in the upper atmosphere that can disrupt power grids on the Earth's surface. To predict space weather and thus provide some warning to implement mediation strategies, it is important to understand the conditions in the solar wind that actually hit the magnetosphere. Complications arise because to get sufficient lead-time for the prediction to be of value, the solar wind must be measured upstream of the Earth. However, this undisturbed solar wind is not what eventually triggers the space storming. Instead the solar wind is modified as it forms a bow shock and a layer of shocked and heated plasma (called the magnetosheath) before arriving at the magnetosphere. As a result, it is important to be able to relate observations of the undisturbed solar wind far upstream of the Earth with the solar wind that actually arrives and then to the space storm that is produced. The results of this study will be used for graduate and undergraduate education purposes, and will be disseminated widely. Taking a longer-range perspective, a better understanding of the solar wind-magnetosphere interaction will likely result in improvements to space weather forecasting of value to society and will be relevant to the study of planetary and astrophysical plasma environments. Related space weather topics will be featured in public outreach activities in various venues. A partnership with the Public Information and Outreach Education Office at the Geophysical Institute will significantly increase the scope of the outreach activities beyond the proposing team alone.Observations indicate that a population of solar wind ions reflects from the bow shock, travels back toward the Sun and interacts non-linearly with the incoming solar wind producing a variety of transient features (i.e., hot flow anomalies, foreshock cavitons, and density holes) upstream of the bow shock. Though these transients have been observed for decades, the underlying physical mechanisms that produce them, how they modify the solar wind-magnetosphere interaction, and the types of signatures that result within near-Earth space are still not understood. Since the interaction of the solar wind with the magnetosphere produces the transients and the transients feed back to modify the solar wind-magnetosphere interaction, these features must be studies as a connected system in order to identify the underlying mechanisms. The present work will use observations to identify the various types of solar wind transients, and the conditions under which they are produced, and then use simulations to identify the underlying physical mechanisms. This holistic approach is expected to produce important advances.