Modulation of radio emission, fast magnetoacoustic waves and magnetic field measurements in the solar corona with LOFAR by Kolotkov et al*21 Aug 2018, 09:21 UTC
Fast magnetoacoustic wave trains are a promising seismological probe of the corona, revealing the magnetic connectivity and providing the estimation of the absolute value of the coronal magnetic field. Low-frequency radio observations allow for the detection of fast wave trains in middle and upper corona, above the field-of-view of EUV imagers and spectrographs, via the modulation of the radio emission by the variations of the electron concentration.
We present the first identification of a quasi-periodic fast magnetoacoustic wave train propagating in the middle corona, in the fine structure of a metric type III radio burst (see Figure 1). Such a direct association of the observed quasi-periodic striation in the type III emission with a specific MHD wave is conducted for the first time is this work.
Figure 1. A schematic synopsis illustrating a qualitative scenario of the generation of quasi-periodic striation in a dynamic spectrum of the type III burst by a propagating fast magnetoacoustic wave train.
The analysed burst was observed with LOFAR (van Haarlem et al. 2013), see CESRA nugget by Kontar et al. for a detailed discussion of this event. The dynamic spectrum of the burst has a fine structure represented by slowly drifting quasi-periodic striae ...