Watching the evolution of the aurora utilizing direct broadcast
As mentioned in Wednesday’s blog post, a significant geomagnetic storm continued to make impacts last night, with many across the central and northern portions of North America able to relatively easily spot the aurora borealis for the second night in a row. As anyone who has watched the aurora from the ground knows, it is a dynamic phenomenon with notable shifts in pattern and intensity over the course of minutes-to-hours. One unique way that we can examine the evolution of the aurora over the course of a night is to view a time series of VIIRS Day Night Band imagery from the JPSS constellation. While VIIRS imagery is often composited to provide wider geographic coverage, that technique has the downside of losing the short-term temporal aspect of the features in the image. Below is an 8 image sequence of VIIRS DNB imagery over the eastern and central United States covering from 6:06 – 9:47 UTC on November 13th, 2025. This features data from S-NPP (just back from an instrument anomaly), NOAA-20, and NOAA-21. This data was captured by SSEC’s direct broadcast antenna in Madison and processed with low-latency locally using CSPP SDR and Polar2Grid.
The large, bright white streaks over southern Canada indicate where the aurora was overhead at the time the satellite passed over. During times when the aurora was more dim, it takes on a more uniform east-west origination around 50 degrees North latitude, but when it is more bright and intense, the pattern of the aurora becomes more agitated and full of swirls. These short-lived periods of more intense aurora activity may be attributable to a phenomenon called geomagnetic substorms. The ESA has a nice explainer on the mechanisms behind substorm auroras here.
Alaska is well-known for its frequent aurora viewing opportunities, and last night’s storm was no exception. Thanks to direct broadcast VIIRS data collected by the Geographic Information Network of Alaska and processed at the University of Alaska Fairbanks, we can pick up from roughly the same time as the end of the loop above, providing coverage from 9:42 – 16:02 UTC. The intensity of the aurora over Alaska was generally fading through about 13:53 UTC, before becoming dramatically brighter during the 14:23 and 14:43 UTC overpasses over the northern half of the state.
