Shasha Zou

Associate Professor

Department of Climate and Space Sciences and Engineering, College of Engineering, University of Michigan

Ongoing Research Areas

Formation processes of the ionospheric storm enhanced density and polar cap patches

The impact of solar wind disturbances on geospace is of particular importance during geomagnetic storms. During a geomagnetic storm, a ridge of electron density enhancement, called storm-enhanced density (SED), often occurs in the mid-latitude and subauroral region. These high-density structures can be transported into the polar cap and constitute a source for the enhanced F-region plasma observed in the polar region and the nightside aurora zone. The objective of this study is to investigate the relative importance of transport due to convection flows, local imbalance between production and loss due to uplifting, and enhanced local production due to precipitating energetic particles, in creating such prominent density structures using both observations and numerical modeling, i.e., the Global Ionosphere and Thermosphere Model (GITM).

Research areas for Professor Shasha Zou

Example of SED and SED plume. (From Zou et al. 2014, "On the generation/decay of the storm-enhanced density (SED) plumes: role of the convection flow and field-aligned ion flow")

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Ionospheric trough dynamics during Space Weather disturbances

The ionospheric electron density is a highly variable quantity and significantly affects the propagation of radio signals that pass through or are reflected by the ionosphere. Ionospheric troughs refer to regions of very low plasma density comparing with that of the surrounding regions. I am interested in studying the charateristics and formation mechanisms of ionospheric troughs during Space Weather disturbances.

Research areas for Professor Shasha Zou

Example of mid-latitude trough dynamics during substorms. (From Zou et al. 2011, "GPS TEC observations of dynamics of the mid-latitude trough during substorms")

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Dynamics of Subauroral Polarization Streams during geomagnetic disturbances and their effects on the coupled ionosphere-thermosphere system

The dynamics of Subauroral Polarization Streams (SAPS) is an outstanding magnetosphere-ionosphere coupling problem associated with the electrodynamics at the interface between the hot and cold particle populations in the inner magnetosphere. Although SAPS have been studied for over three decades, their generation/evolution during geomagnetic active times, in particular substorms, are still not well understood. In addition, wave-like oscillations embedded within SAPS have been reported. However, they are neither well characterized nor understood, and the geomagnetic disturbance conditions for these wave-like activities have not been established. Moreover, the effects of SAPS on the global ionosphere-thermosphere system have not been extensively studied. Ground-based observations, such as those from Super Dual Auroral Radar Network (SuperDARN) and all-sky imager arrays, and space-based measurements, such as those from the Time History of Events and Macro-scale Interactions during Substorms (THEMIS) and the Van Allen probes, as well as the Global Ionosphere Thermosphere Model (GITM) are used to carry out an integrated study of the dynamics of SAPS and their effects on the coupled IT system.

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Effects of solar wind dynamic pressure enhancements in the coupled magnetosphere-ionosphere-thermosphere (MIT) system

A sudden increase of solar wind dynamic pressure associated with an interplanetary shock or a discontinuity leads to a large-scale compression of the magnetosphere, and such a compression is referred to as sudden commencement (SC) based on the ground-based magnetometer observations. SC is usually used to describe a broad range of phenomena, including sudden storm commencement (SSC) and sudden impulse (SI), and emphasizes the compression effect associated with dynamic pressure enhancement regardless of whether or not a geomagnetic storm follows the compression. Depending on the polarities of the magnetic field perturbation and the fieldaligned currents (FACs), the response of the coupled system can be characterized into two phases, i.e., the preliminary impulse (PI) phase and the main impulse (MI) phase. I am interested in studying the effects of solar wind dynamic pressure in the coupled MIT system using various instruments and numerical models.

Research areas for Professor Shasha Zou

Example of ionosphere responses to solar wind dynamic pressure enhancement. (From Zou et al. 2017, "Effects of sudden commencement on the ionosphere: PFISR observations and global MHD simulation")

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