Large-Scale Traveling Ionospheric Disturbances: Origin and Propagation

Abstract:

Large-scale traveling ionospheric disturbances (LSTIDs) are considered as an ionospheric signature of the magnetosphere-ionosphere-thermosphere coupling processes during space weather events. The exact physical mechanisms of LSTIDs formation, including transformation of various types of energy within the magnetosphere-ionosphere-thermosphere system, and the trigger mechanisms of releasing the stored energy are still not clear. We investigate the origin, occurrence, and propagation LSTIDs over the European region during the 19–21 December 2015 geomagnetic storm. Analysis of the total electron content (TEC) perturbation component is supported by the ground-based GPS/GLONASS observations. The high spatial-temporal resolution mapping approach provides a very detailed specification of the ionospheric small- to large-scale disturbances associated with two major sources of the LSTIDs generation: the solar terminator passage during the quiet time and auroral activity caused by auroral particle precipitation and field-aligned currents (FACs) intensification during space weather events. For the first time, the joint analysis of the ionospheric plasma irregularities, FACs, and LSTIDs reveals that a zone with the intense FACs and ionospheric irregularities occurred at the same region that represent the most probable source of LSTIDs excitation. We found that an equatorward expansion of the strong ionospheric irregularities zone and an increase of the FACs magnitude led to a simultaneous intensification of the LSTIDs occurrence at high latitudes. We discuss main features of ionospheric response to severe space weather events in domain of plasma irregularities and LSTIDs generation and propagation.