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Initiator: ASTRON Netherlands Institute for Radio Astronomy

eu  SNN

This project was co-financed by the EU, the European Fund for Regional Development and the Northern Netherlands Provinces (SNN), and EZ/KOMPAS.

Scientific Rationale


Solar radio observations are an active research field of the Astrophysical Institute Potsdam (AIP) where they also have a long tradition. Since the foundation of the Observatory for Solar Radio Astronomy (OSRA) in Tremsdorf near Potsdam in 1955, the sun has here been monitored and studied for more than 4 decades. Therefore the solar radio group at the AIP has a strong interest to continue their research with the latest and best data available. It has therefore initiated the LOFAR's Key Science Project "Solar Physics and Space Weather with LOFAR" and coordinates all activities with respect to this subject in the European solar physics community (see management structure).

Figure 2. Image of the Radio Observatory in Tremsdorf.

Objectives of Key Science Project (KSP)

The KSP "Solar Physics and Space Weather with LOFAR" intends to use LOFAR for solar and Space Weather studies. The tasks include the definition of solar observing modes, the development of the necessary software and making the observations available to the scientific community.
In the solar corona, the radio waves are emitted near the local plasma frequency, which is defined by

fpe = 1/(2π) {Nee2/meε0}1/2

with the electron number density N_e, and/or its harmonics and/or its harmonics (Melrose, 1985). Due to the gravitationally stratified atmosphere of the Sun, the lower and higher frequencies are coming from the higher and lower corona as illustrated in Figure 3. The right image of Figure 3 shows the signature of an electron beam propagating along a closed magnetic field line through the corona. Therefore, radio spectroscopy can provide useful information about altitude of energetic processes in the solar atmosphere. LOFAR will offer radio maps of the Sun at different frequencies, i.e. at different height levels, allowing to study these processes in 3 dimensions. In summary, LOFAR will open a new window in solar radio astronomy.



Figure 3. At left, the height (red numbers) of the different frequency levels (black numbers) above the photosphere. The right image shows a dynamic radio spectrum of a solar burst recorded by the observatory of the AIP in Tremsdorf. Intense radio emission (red) is detected at falling and, subsequently, rising frequencies indicating the signature of an electron beam propagating upwards and downwards along closed magnetic field lines in the corona, respectively.

ASTRON initiated LOFAR as a new and innovative effort to force a breakthrough in sensitivity for astronomical observations at radio-frequencies below 250 MHz. 
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