Flashes, Flares, and Aftershocks: Uncovering Unique Solar Flare Signatures with the Dunn Solar Telescope
Solar flares are sudden releases of magnetic energy, driving adverse space weather that can disrupt radio communications, degrade GPS accuracy, and pose risks to satellites and astronauts. While multi-day forecasts exist, operational entities require actionable, minute-scale nowcasts for immediate mitigation. This talk presents a new, observationally-driven nowcasting approach to address this critical gap.
We introduce a real-time method using high-cadence observations of the chromosphere in the Ca II K line (393.4 nm) from the Dunn Solar Telescope. An efficient algorithm monitors intensity in active regions to detect the sharp, impulsive rise phase of a flare, a direct thermal response to initial particle beams. We compare the timing of these Ca II K peaks against the standard 1-8 Å soft X-ray (SXR) flux curves from NOAA’s GOES satellites, which define the official flare peak.
Our analysis of C- to M-class flares demonstrates a consistent, operationally significant result: the impulsive Ca II K peak typically precedes the GOES SXR peak by 20 to 30 minutes. This lead time provides a reliable warning signal, offering a crucial window for stakeholders to take protective action before the flare's most intense phase.
Additionally, we present a complementary analysis of an X-class event, revealing a distinct pattern of multiple, sequential secondary brightenings deep into the post-flare decay phase. These "aftershocks" suggest continued, smaller-scale energy release not captured by standard models. We will discuss representative examples and explore working hypotheses for their drivers.
This talk connects the development of a high-impact operational nowcast with new scientific questions about flare energy release. We will conclude by charting next steps for refining this method and its potential for adoption across a global network of ground-based solar observatories.
Dr. Juie Shetye is an Assistant Professor of Astronomy at New Mexico State University and the Science Lead/Director for the Dunn Solar Telescope at Sunspot Solar Observatory. Her research focuses on high-cadence observations of the solar chromosphere, including jets, swirls, and practical flare nowcasting, and she is a co-author on the Sunspot Solar Observatory Data Archive operations paper. Recent work includes first high-resolution observations of chromospheric swirls from the Dunn. She completed a master’s in Space Science at University College London and a PhD in Physics at Queen’s University Belfast.