Speaker
Description
We present LOFAR observations of an M class flare, that was accompanied by intense type III radio bursts. Some isolated burst have a fundamental-harmonic structure, but for most bursts this is not visible due to a rapid succession of bursts. Spectroscopic imaging with LOFAR shows type III bursts as a compact source for a given observing frequency. The intensity varies with burst evolution, but the location remains largely fixed since it is determined by where in the solar corona the local plasma frequency matches the observing frequency. But from time to time the source changes its position, with dual structures during the transition. We interpret this as signatures of fundamental and harmonic emission, the latter originating from a higher location in the corona so that the local plasma frequency there matches half of the observing frequency. Fundamental-harmonic pairs, e.g. fundamental emission at 35 MHz and harmonic emission at 70 MHz, should originate from the same plasma volume. Differences in their positions and intensity variations are expected since radio wave transport effects in the corona, like scattering and refraction, should affect fundamental more than harmonic emission. Analyzing such differences therefore allows for quantifying these effects.
| What is your career stage? | Tenured scientist |
|---|---|
| Which telescopes do you use / are you affiliated with? | LOFAR |
