Importance of High Cadence Magnetometer Data for Investigating Geomagnetic Disturbances

Geomagnetic disturbances (GMDs) are rapid changes in the magnetic field of the Earth that may drive geomagnetically induced currents (GICs), known to cause damage to infrastructure such as power grids and pipelines. Globally, GIC measurements are often hard to obtain; therefore, GMDs are used as a proxy for GICs. GMDs have been previously shown to occur on different timescales which are related to different formation mechanisms such as magnetic storms, substorm activities and sudden commencements. 1 min cadence ground-magnetometer data has been available for decades and are the basis of many studies showing the frequency and intensity of GMDs. In recent years one-second cadence data have become available from a network of magnetometers through the SuperMAG portal. We take the 1-s data, averaged 10 s data, and compare the number of GMDs identified with the number found from the 1-minute data to test the GMDs related to the different timescales. We find that 1-s data consistently record higher amplitude GMDs as well as recording overall more GMDs, thus showing the importance of 1-s cadence data. This is most important for GMDs between 00 and 03 magnetic local time and at low geomagnetic latitudes (>50°) as these are the locations where difference between the number of GMD detections between the 1-s data and the 1-min data is the largest. However, the 1-s data have many artefacts due to unreliable data points in them leading a 10-s median being more reliable at correctly detecting GMDs.