Geomagnetic Responses Associated With Throat Aurora

Throat aurora is a special discrete auroral form often observed at the ionospheric convection throat region near magnetic local noon. Some observational properties of throat aurora have been established, but the geomagnetic response is not yet explored. Using geomagnetic observations from a chain of stations in the Norwegian sector and auroral observations from an all-sky imager and the DMSP satellites, for the first time, we identify geomagnetic responses associated with the occurrence of throat aurora. These variations are well explained by combining the models of flux transfer events and throat aurora. The estimated increase in ionospheric equivalent current confirms the association of throat aurora with ground observations. The results provide further evidence for throat aurora being associated with magnetopause reconnection. Based on the observational features, a new association of geomagnetic variations with throat aurora may be defined to reflect their occurrence at high latitudes near local noon.