Conductivity Modulation of Magnetosphere-Ionosphere Coupling

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Virginia Tech


Earth's ionosphere is a region of the upper atmosphere that consists of an energetic and electromagnetically reactive plasma. This region plays an important role in over-the-horizon and satellite radio communications, satellite orbits, and can electrically couple into human infrastructure like pipelines and power cables. Activity in the ionosphere is tightly coupled to the near-Earth space plasma region called the magnetosphere. This region is formed by interactions between the energetic particle outflow from the sun called the Solar Wind and Earth's magnetic field. Models of the coupling between these regions typically take a "sun to mud" perspective, as mass and energy from the sun are transferred into the magneto- sphere and ultimately into the upper atmosphere. However, the ionosphere also receives energy directly from ultra-violet radiation from the solar surface. This radiation is the nominal source of ionization in the upper atmosphere, but certain celestial events alter the magnitude of radiation that reaches the upper atmosphere. In the case of a solar eclipse, the moon directly shields a large portion of the Earth from solar radiation. This decreases both the temperature and ionization rate of the upper atmosphere, which in turn decreases the conductivity. A solar flare on the other hand increases the available ionizing energy, and consequently increases the conductivity of the ionosphere. Because the ionosphere is electrically coupled to the magnetosphere, changes in conductivity must necessarily affect the way that coupling occurs. In Chapters 1 and 3, we introduce some of the instrumen- tation used in observing magnetosphere-ionosphere coupling dynamics, as well as some of the difficulties associated with remote instrument operations in the high-latitude regions of Earth. Chapter 4 presents a case study of an Antarctic total solar eclipse, in which magnetic waves are observed from both northern and southern polar regions. The body of work in Chapter 5 suggests that large spatial scale variations in ionospheric conductivity related to solar eclipses are associated with geomagnetic substorms. All together, the research herein highlights the importance of considering ionospheric conductivity as a controlling parameter for magnetosphere-ionosphere coupling.



Magnetosphere, Ionosphere, Eclipse