Apparent radio transients mapping the near-Earth plasma environment

Abstract

We report the discovery of bright, fast, radio flares lasting tens of seconds with the AARTFAAC high-cadence all-sky survey at 60 MHz. The vast majority of these coincide with known, bright radio sources that brighten by factors of up to 100 during such an event. We attribute them to magnification events induced by plasma near the Earth, most likely in the densest parts of the ionosphere. They can occur both in relative isolation, during otherwise quiescent ionospheric conditions, and in large clusters during more turbulent ionospheric conditions. We also find one event that has many properties in common with these events, but has a very well-determined dispersion delay as a function of frequency consistent with a very distant Galactic or extragalactic origin. If astrophysical, it represents extreme emission with a minimum brightness temperature of 10 28−34 K.

Detecting Dispersed Radio Transients in Real Time Using Convolutional Neural Networks

“…Using known equations, we can easily simulate dispersed astrophysical transients. The DM of non-astrophysical transients usually is close to 0 (i.e., no broadening of the pulse), making the DM possibly the most useful feature for separating signal from noise (Kuiack et al, 2020b). We build a dataset by injecting these simulated pulses into randomly sampled noise from the survey.…”