Article

 

On the Sources of Cold and Dense Plasma in Plasmasphere Drainage Plumes Public Deposited

https://scholar.colorado.edu/concern/articles/hh63sw83p
Abstract
  • Previous observations have revealed that the ionospheric Storm Enhanced Density (SED) plumes are colocated with the cold, dense plumes observed at the dayside magnetopause. However, the origin of the cold, dense plume plasma is not well understood with multiple possible sources in the magnetosphere. Improving our understanding of these plasmaspheric plumes is crucial due to their impact on the dayside magnetic reconnection. We report that plumes were simultaneously observed in both the ionosphere and plasmasphere by TEC and geosynchronous spacecraft for the magnetic storms occurred in 2013 and 2015 on Mar 17. Moreover, in 2015, the plume was also observed by THEMIS spacecraft near the dayside magnetopause. Simulations using a physics-based model of the ionosphere and plasmasphere reproduced the observed plume colocation in the ionosphere and plasmasphere for both storms. Our results suggest that plasmaspheric plume was created by the enhanced convection transporting the plasma sunward that was peeled off from the outer plasmasphere, whereas the ionospheric plume plasma came from the density enhancement generated in the dayside subauroral ionosphere. These plumes were observed near the same closed field lines at the peak of the geomagnetic activity because the cold plasma motion in the ionosphere and plasmasphere is connected through the ExB drift motion. Furthermore, our results suggest that weaker storms transport more plasmaspheric materials toward the dayside/duskside magnetopause. However stronger storms may have a larger impact on the dayside reconnection because plasmaspheric plumes tend to be shifted to the noon MLT sector where dayside reconnections more likely to occur.

     

     

    Plain Language Summary

    The plasmasphere is the region of cold, relatively dense ionized gas (mostly protons and helium ions) that resides on the magnetic field lines close to the Earth. It is the upward extension of cold, dense Earth’s ionospheric plasma as the ionosphere had filled the persistently “closed” flux tubes of plasmasphere. Enhanced convection plasma flow during solar storms peels the cold, dense plasma away from the outer plasmasphere to form a plume of plasma that moves sunward. Recently, the plasmaspheric cold, dense plasma has been found near where the Earth’s magnetic field first contacts the solar wind, however, where the plasma originates from remains unclear. Understanding the plume plasma is very important because they could rearrange the magnetic topology by altering the rate of the magnetic reconnection, which determines how much solar wind energy gets into the Earth’s magnetosphere. Here we report that in two solar storms in 2013 and 2015, plumes were observed simultaneously in both ionosphere and plasmasphere. Our study suggests that the observed plumes in the plasmasphere and ionosphere were mainly created by different mechanisms, but were observed near the same magnetic field lines at the peak of the solar storms.

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  • 2020-02-07
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