Plasmapause deformations in the frame of the interchange instability mechanism

The mechanism of plasmapause formation based on interchange instability and a Kp-dependent magnetospheric electric field model, enables us to determine the position of the plasmapause as a function of Kp and local time. We illustrate here how this physical mechanism is able to account for the formation of shoulders like those observed by the Extreme Ultraviolet (EUV) imager onboard the IMAGE satellite. A wide variety of other structures observed by IMAGE like tails (also called plumes), and notches are also obtained with this mechanism for the formation of a "knee" in the high altitude cross-L distribution of the cold plasma density distribution. The position of the plasmapause given by this model can be simulated on the ESA-SSA web site. The program retrieves the geomagnetic activity level index Kp observed during the date given as input and 24 hours before. Then, it calculates the position of the plasmapause for the required time period, assuming the corotation and using the convection electric field model E5D and the associated magnetic field M2. The mechanism for the formation of the plasmapause is assumed to be the quasi-interchange instability. Finally, the position of the plasmapause is plotted in the geomagnetic equatorial plane as a function of radial distance and MLT with 30 minutes intervals.