Simulations of propagating electron beams along perturbed field lines. The open red circles show the frequencies probed by PSP/FIELDS. Credit: Clarkson, D.L., et al. 2026

Solar radio bursts are intrinsically linked to the motion of their emitting source through the coronal and heliospheric plasma. Electron transport is mostly confined to magnetic field lines. These electrons move at a substantial fraction of the speed of light and often generate radio emission via the plasma emission process.

The resulting radio bursts, such as type III bursts from electrons streaming along open field lines, are an excellent diagnostic of the environment through which they propagate.

Tracing the spine of a radio burst by its peak intensity provides the frequency drift rate. For an electron beam moving along a radial path, one would expect a drift rate that gradually decreases over time. Yet type III burst drift rates can vary on smaller frequency scales.…