Ground observations of dayside small-scale dynamic features

Abstract

Two strategies for the use of ground magnetometer data in studies of small-scale features in the dayside high-latitude ionosphere are illuminated through a number of examples which, at the same time, demonstrate some of the recent progress within this area. An extensive network of magnetometer arrays are now established providing dense coverage of more than half of the high-latitude northern hemisphere. This fascilitates the adoption of a global perspective as demonstrated in two examples of high-latitude ionospheric travelling convection vortices. Results include detailed descriptions of the evolution of the events during their entire lifetime as they propagate through several local time sectors and/or magnetospheric regions and of their relations to the state and dynamics of the global ionospheric current and convection systems. Another important strategy is to combine different ionospheric data sets. Some results of this are demonstrated through three further examples. One concerns the identification of the ionospheric current system associated with events of poleward moving small-scale auroral structures. The second finds that the convection vortices in an event of a long continual series of vortices are closely related to the position and nature of the convection reversal boundary as identified in incoherent scatter radar data. The final example is a study which determine, in terms of particle precipitation data of low-altitude satellites, the magnetospheric source region of the field-aligned currents that drive impulsive travelling convection vortices and finds this to be inside the plasma sheet.