A Time-of-Arrival Technique to Estimate the Source of a Type III Solar Radio Burst

Type III solar radio bursts (SRBs) are the most common type of low-frequency emission caused by energized electrons coming from the Sun. They are frequently linked to solar flares that can lead to severe geomagnetic storms; consequently, one of the key objectives of NASA’s Sun Radio Interferometer Space Experiment (SunRISE) is to pinpoint the origin of SRBs. Here, we introduce a time-of-arrival method using data collected by the e-Callisto network and SunRISE Ground Radio Lab (GRL)’s dual-dipole antennas (DDA). 225 type III SRBs were manually identified for the year 2024 with spectrographs from the GRL network. A third of these events (75) were correlated with solar flares observed by GOES-18 or Solar Orbiter space missions. On August 5, 2024, seconds after 16:55 UTC, a type III SRB was observed at two DDA stations in the U.S. alongside 11 e-Callisto antennas worldwide. The SRB coincided with a flare reported by Solar Orbiter. The exact antenna positions and arrival times of the event were combined to estimate its possible origin in the solar atmosphere, then compared with the actual flare origin: the southwest quadrant of the Sun. This produced vectors pointing to all quadrants of the Sun. However, when only vectors with small average timing differences between observing stations are considered (< 1 second), most vectors point towards the Sun’s southwest quadrant (57.1%), in agreement with direct flare observation. Future direction will involve applying the time-of-arrival method to a catalog of solar flare-correlated type III SRBs to refine and validate the technique.