North-South Asymmetry of the Plasmaspheric Densities: Observations from the IMAGE Radio Plasma Imager
Abstract
The Radio Plasma Imager (RPI) on board the IMAGE satellite transmitted coded signals in space and measured the amplitude of the returned echo signals as functions of echo frequency, which is related to the plasma frequency at the remote reflection point, and echo delay time, which is related to the distance of the reflection point from the receiver. An algorithm developed at the Center for Atmospheric Research, University of Massachusetts Lowell, can derive the plasma density distribution in space that produces an echo trace and hence obtains the spatial distributions of the electron density. It has been shown that the discrete echo traces are produced by echoes that propagate along the magnetic field. This makes it possible to examine instantaneous plasma density distribution along a magnetic field line from one hemisphere to the other. While the density profiles are often symmetric to the equator, we have found several cases in which the plasma density profiles are strongly asymmetric with respect to the equator. There are multiple density profiles for consecutive RPI orbits during March, 2002 that show that day time densities are significantly higher in the southern hemisphere than in northern hemisphere, but night time profiles are almost perfectly symmetrical. This is in contradiction with earlier results suggesting that asymmetry is observed at solstices and symmetry at equinoxes. We investigated possible mechanisms that could cause such plasma density distribution, using RPI measurements and ionospheric electron densities as well as geomagnetic conditions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMSM11A1565O
- Keywords:
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- 2730 MAGNETOSPHERIC PHYSICS / Magnetosphere: inner;
- 2736 MAGNETOSPHERIC PHYSICS / Magnetosphere/ionosphere interactions;
- 2768 MAGNETOSPHERIC PHYSICS / Plasmasphere