Global Dynamics of the Earth's Magnetosphere During Northward IMF Conditions in the Era of the Heliophysics System Observatory

Abstract

The dynamics of the Earth's magnetosphere is strongly influenced by the solar wind. Sudden changes in the solar wind such as dynamic pressure pulses or interplanetary shocks impacting the magnetosphere are ideal for the study of magnetohydrodynamics (MHD) wave energy transfer from the solar wind to the magnetosphere. In this thesis, I analyzed the magnetospheric global response to dynamic pressure pulses (DPPs) using the Heliophysics System Observatory (HSO) and ground magnetometers. During northward Interplanetary Magnetic Field (IMF) Bz conditions, the magnetosphere acts as a closed "cavity" and reacts to solar wind DPPs more simply than during southward IMF. I used solar wind data collected by Advanced Composition Explorer (ACE) and WIND together with magnetic field observations of Geotail, Cluster, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Magnetospheric Multiscale (MMS), Van Allen Probes, Geostationary Operational Environmental Satellite (GOES) missions, and ground magnetometer arrays to observe the magnetosphere (dayside, nightside, inner magnetosphere, magnetotail, magnetosheath, etc.) and ionosphere response simultaneously in several local time sectors and regions. I examine the global response of each event and identify systematic behavior of the magnetosphere due to DPPs' compression, such as MHD wave propagation, sudden impulses, and Ultra Low Frequency waves (ULF) in the Pc5 range. Our results confirm statistical studies with a more limited coverage that have been performed at different sectors and/or regions of the magnetosphere. I present observations of the different signatures generated in different regions that propagate through the magnetosphere. The signature of the tailward traveling DPP is observed to move at the same solar wind speed, and in superposition of other known magnetospheric perturbations. It is observed that the DPP also generates or increases the amplitude of Pc4-5 waves observed in the inner magnetosphere, while similar waves are observed on the ground. I also analyze the influence of the shock inclination relative to the dayside magnetosphere on the propagation of the preliminary impulse, whose travel-time from the dayside is important in magnetoseismology for the plasma density estimation on the magnetosphere. Finding that the arrival of the preliminary impulse at different latitudes depends on the relative angle between the shock and the dayside magnetosphere. The last study in this thesis consists of an analysis of the density profile of the magnetosphere using the preliminary reverse impulse observed by ground-based magnetometers and magnetic and electron density observation made by the HSO on the dayside magnetosphere.

This thesis addresses the challenges of the systematic use of the HSO to study different aspects of the global dynamics of the magnetosphere. In Chapter IV, this thesis presents the first and large sample and simultaneous spacecraft and ground observations in multiple regions and local time sectors and confirmed previous studies limited in space and time samples. In Chapter V this thesis also found that North-South inclination of shock has a measurable effect on arrival time of signals as a function of latitude similar to previous work that found importance of East-West/Local time effect. The implication is that ground-based observations can help determine in situ shock orientation methods. Chapter VI shows the first use of magnetoseismology using both in situ and ground-based observations to obtain an exact solution for the plasma mass density radial profile in the dayside magnetosphere.