Abstract
The plasmapause marks the limit of the plasmasphere and is characterized by a sudden change in plasma density. This can influence the other regions of the magnetosphere, including due to different waves circulating inside and outside the plasmasphere. In the present work, we first compare the positions of the plasmapause measured by the NASA Van Allen Probes in 2015 with those of the Space Weather Integrated Forecasting Framework plasmasphere model (SPM). Using the Van Allen Probes and other satellite observations like PROBA-V, we investigate the links that can exist with the radiation belt boundaries. The inward motion of the outer radiation belt associated with sudden flux enhancements of energetic electrons can indeed be directly related to the plasmapause erosion during geomagnetic storms, suggesting possible links. Moreover, the position of the plasmapause projected in the ionosphere is compared with the ionospheric convection boundary. The equatorward motion of the plasmapause projected in the ionosphere is related to the equatorward edge motion of the auroral oval that goes to lower latitudes during storms due to the geomagnetic perturbation, like the low altitude plasmapause and the outer radiation belt. The links between these different regions are investigated during quiet periods, for which the plasmasphere is widely extended, as well as during geomagnetic storms for which plumes are generated, and then afterwards rotates with the plasmasphere. The magnetic local time dependence of these boundaries is especially studied on March 14, 2014 after a sudden northward turning of the interplanetary magnetic field (IMF) and for the geomagnetic storm of August 26, 2018, showing the importance of the magnetic field topology and of the convection electric field in the interactions between these different regions eventually leading to the coupling between magnetosphere and ionosphere.
Highlights
The plasmasphere is the extension of the ionosphere at low and mid-latitudes and is filled by low energy plasma (Lemaire and Gringauz, 1998; Darrouzet et al, 2009 for reviews)
We study the links between the Magnetic Local Time (MLT) distribution of the plasmapause, the ionospheric convection boundary, the radiation belts for different energies from 10 keV to 8 MeV, and the auroral oval during two specific events: March 14, 2014 corresponding to a quiet period with a sudden Northward turning of the interplanetary magnetic field (IMF), and August 26, 2018 corresponding to a geomagnetic storm
In Links Between the Plasmapause, Ionospheric Convection Boundary, Radiation Belts and Auroral Oval During the Storm Event of August 26, 2018, we show the evolution of these links during the geomagnetic storm of August 26, 2018, and show the strong decrease in latitude of all these boundaries during the main phase of the storm in the framework of the global magnetospheric dynamics and its effects on the ionosphere-atmosphere
Summary
The plasmasphere is the extension of the ionosphere at low and mid-latitudes and is filled by low energy plasma (Lemaire and Gringauz, 1998; Darrouzet et al, 2009 for reviews). They correspond to the average position of the plasmapause predicted by the theoretical model based on the mechanism of plasma interchange driven unstable by the enhancement of centrifugal effects and using McIlwain’s Kpdependent electric field model E5D and his M2 equatorial magnetic field model to calculate the magnetospheric convection velocity (Pierrard and Stegen, 2008). We find with the model a best linear relation (red line on bottom panel of Figure 1) corresponding to This relation based on averaged values can be used for long term comparisons, but the actual plasmapause positions given by the model are more precise since they take into account the historical evolution of Kp during the previous hours and the MLT sector of the plasmapause observation
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