Solar research at Metsähovi Radio Observatory

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At Metsähovi Radio Observatory we measure radiation from the Sun at several radio frequency bands on a daily basis. The frequencies in use are 50-850 MHz, 11.2 GHz and 37 GHz. We have a radio telescope with a diameter of 1.8 meters dedicated only for solar observations, which includes two separate instruments (Figure 1).

Figure 1. A radio telescope dedicated for solar observations at Metsähovi Radio Observatory. Solar observations are done at 11.2 GHz. The log periodic antennas attached at the sides of the dish measure the radiation from the Sun at 50-850 MHz with two different polarizations (vertical and horizontal).

The 1.8-metre radio telescope measures the total radiation intensity of the Sun at 11.2 GHz. The latest observations are displayed in the figure below.

Figure 2. The latest observations at 11.2 GHz. The spike at 09:00 or 10:00 UT is due to a daily calibration.

Figure 3. Uncalibrated 11.2 GHz data. Updated every 15 minutes.

The instrument is specially suited for investigating solar radio burst features. The two Callisto antennas attached to the dish measure broad band solar radio bursts at meter and decimeter ranges (50-850 MHz). The latest Callisto observations can be found here: http://soleil.i4ds.ch/solarradio/callistoQuicklooks/ , MRO = Metsähovi. Metsähovi belongs to the international e-Callisto network, which aims at observing solar radio bursts at a broad frequency range at several locations around the world simultaneously.

In addition, we strive to produce at least one solar radio map every day with the 14-metre radio telescope (see Figure 3) at 37 GHz [http://www.metsahovi.fi/solar-gallery]. During the summer time (April-September) the 14 meter radio telecope is used more extensively for solar observations. Then, we can, for example, follow a single radio brightening for several hours. In Figure 4 you can see an example of a tracking observation.

Figure 3. 13.7-metre radio telescope at Metsähovi.

A summary of Metsähovi's daily solar observations can be found here: http://www.metsahovi.fi/~kallunki/Solar_event/

Solar research

During the summer time, due to the Northern location of Metsähovi, we are able to do even 14-hour continuous solar observations. This ability is remarkable and brings a peculiar twist to our observations. The long time series measured at Metsähovi (since 1978) enable studying long term alterations (so-called cyclicity studies) in the Sun, for example, by investigating solar radio brightenings. Long measurements observed during a single day can be used for studying short term changes (so-called oscillations studies) in different structures (for example, radio brightenings and polar region brightenings). In addition, the versatile radio burst data is analyzed for single bursts and for statistical reasons.