Rapid ionospheric variations at high latitudes: Focusing on Greenland

The Helheim glacier, located in southeast Greenland, has more than ten campaign-type Global Positioning System (GPS) sites; data processing led to the observation of a very rapid change in the ionospheric delay. To identify the cause of these sporadic disturbances, we analyzed the slant total electron content (STEC), single-differenced STEC (SD-STEC) and scintillation proxy index called the delta phase rate (DPR). From this analysis, the abrupt change of those ionospheric indicators was attributed to the line-of-sight direction to the satellite and the temporal sequence of the event was found to be highly correlated with the geometry of the GPS sites. In addition, the disturbance based on the result of SD-STEC occurred mostly during the night, from 17 UTC through 7 UTC, and across a band spanning the east-west direction. Based on the DPR indices obtained from GPS stations distributed across all of Greenland, Iceland, and northeastern Canada, the rapid ionospheric variation was found to be correlated with the time of the day and the geomagnetic latitude of the station. The disturbance was larger at the relatively low geomagnetic latitudes at night but was more significant at higher latitudes in the daytime. These rapid ionospheric variations tended to appear in band shapes parallel to the geomagnetic field. These results allow us to attribute such disturbance observed at the Helheim glacier to aurora-related phenomena.