Göttingen 2025 – wissenschaftliches Programm
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EP: Fachverband Extraterrestrische Physik
EP 11: Sun and Heliosphere IV
EP 11.7: Vortrag
Donnerstag, 3. April 2025, 15:15–15:30, ZHG101
Evolution of fundamental and harmonic sources in LOFAR type III radio burst images — •Christian Vocks1, Mario Bisi2, Bartosz Dabrowski3, Diana Morosan4, Peter Gallagher5, Andrzej Krankowski3, Jasmina Magdalenic6, Gottfried Mann1, Christophe Marque6, Barbara Matyjasiak7, Hanna Rothkaehl7, and Pietro Zucca8 — 1Leibniz Institute for Astrophysics Potsdam (AIP), Germany — 2RAL Space, United Kingdom — 3University of Warmia and Mazury, Olsztyn, Poland — 4University of Turku, Finland — 5DIAS, Dublin, Ireland — 6Royal Observatory of Belgium, Brussels, Belgium — 7Polish Academy of Sciences, Warsaw, Poland — 8ASTRON, Dwingeloo, Netherlands
We present LOFAR observations of an M class flare with 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 frequency. The intensity varies with burst evolution, and transient dual-source structures appear. We interpret these as signatures of fundamental and harmonic emission, the latter from a higher location in the corona. 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.
Keywords: LOFAR; Solar corona; Solar flare; Radio bursts; Radio wave propagation