On July 6, 2002 a special group of solar radio bursts was recorded during a collaborative campaign of solar radio observations performed by the Astrophysikalisches Institut Potsdam (AIP) (Potsdam, Germany), the Institut für Weltraumforschung (IWF) (Graz, Austria), and UTR (Kharkov, Ukrania). The dynamic radio spectra were simultaneously recorded by the radiospectralpolarimeter (40-100 MHz) of the AIP and the digital spectralpolarimeter (DSP-UTR2) (17-30 MHz) of the IWF at widely spaced observing sites. The aerial system of the UTR2 is the most sensitive in this frequency range worldwide.

The image presents a dynamic spectrum of type III bursts produced by the propagation of electron beams through the corona. That can be recognized as emission stripes drifting fast from higher to lower frequencies, i.e. a propagation away from the Sun. Additionally each individual type III burst consists of short, narrow-band bursts slowly drifting to lower frequencies. These fine spectral structures indicate a specific distribution of the plasma parameters along the electron beam propagation path and an unusual mechanism of radio emission.

The investigation of these fine structures allows us to make a diagnosis of the plasma parameters in the solar corona, such as the speed of the electron beams, plasma density, Alfvén speed etc.

(Credits: Solar Radio Astronomy Group, AIP, http://www.aip.de/groups/osra/)