STEREO-Wind Radio Positioning of an Unusually Slow Drifting Event

TL;DR

This study analyzes a long-duration, slow-drifting solar radio event observed by STEREO-B and Wind, using multi-instrument data and models to localize the source in high-density, slow solar wind regions.

Contribution

It provides a detailed analysis of a rare slow drifting radio event, combining radio direction finding, white-light observations, and modeling to localize the source region.

Findings

Radio source drift velocities are approximately 33-52 km/s.

The event is localized in regions of high density and slow solar wind.

The event lasted over 17 hours with a narrow frequency drift from 625 kHz to 425 kHz.

Abstract

On 13 March 2010 an unusually long duration event was observed by radio spectrographs onboard the STEREO-B and Wind spacecraft. The event started at about 13:00 UT and ended at approximately 06:00 UT on 14 March. The event presents itself as slow drifting, quasi-continuous emission in a very narrow frequency interval, with an apparent frequency drift from about 625 kHz to approximately 425 kHz. Using the Leblanc, Dulk, and Bougeret (1998) interplanetary density model we determined that the drift velocities of the radio source are $\approx$33km s$^{-1}$ and $\approx$52km s$^{-1}$ for 0.2 and 0.5 times the densities of Leblanc model, respectively with a normalization density of 7.2cm$^{-3}$ at 1AU and assuming harmonic emission. A joint analysis of the radio direction finding data, coronograph white-light observations and modeling revealed that the radio sources appear to be localized in regions of interaction with relatively high density and slow solar wind speed.