Middle-Latitude Ionospheric Irregularities and Ring Current Expansion during Geomagnetic Storms

Abstract:

This presentation will show distinguished pictures of middle-latitude ionospheric irregularities and its relationship with ring current enhancement and expansion during geomagnetic storms. Nominally ionospheric irregularities can occur at low latitudes after sunset during certain seasons. Under disturbed space weather perturbations, spatial and temporal variations of the plasma convection and dynamics of auroral arcs can drive development of ionospheric irregularities in the polar region. Such irregularities can cause scintillation and degradation of L-band GNSS radio signals and affect satellite navigation systems. To study the irregularities, snapshot Global Maps of Ionospheric Irregularities and Scintillation (GMIIS) have been generated at the Jet Propulsion Laboratory using GPS data collected from global GNSS networks. Analysis of GMIIS shows that the irregularities can expand down to sub-auroral and middle latitudes (well below 50 degree dip latitude) during certain storms. The affected middle-latitude region can be a major part of the U.S. continent during some events. Such events are distinguishably different from the well-established global picture in which ionospheric irregularities and scintillation are predominately occur at low and high latitudes. It is also discovered that all major events examined so far are associated with significant ring current enhancement before the recovery phase of the storms. The relationship between the irregularity and ring current activities indicates that the ring current expansion into the plasmasphere is likely responsible for the middle-latitude irregularity phenomenon. Under this condition the plasma convection driven by the magnetospheric processes penetrates into middle latitudes, and its variations can cause ionospheric irregularities as seen in GPS data. This presentation will show major events of middle-latitude irregularities and its relationship with the ring current. The responsible mechanisms will be discussed. The presentation will add the middle-latitude ionospheric irregularities and scintillation into the global picture of ionospheric irregularity and scintillation distribution.