Tuesday 25 March 2014

Radio bright sun

On 20 March 2014, the Sun was particularly active. As it passed over the southern horizon, KAIRA detected strong radio emission. We had the station correlator running at the time and managed to capture this all-sky image sequence.

The video covers the period from approx. 10:05 until 10:15 UTC. Each frame is a 1-second integration, however it has been sped up to reduce the duration. The date/time (UTC) is shown in the filename at the top-left of the image sequence. The observing frequency is subband 300 (= approx. 58.6 MHz, with 195 kHz bandwidth).

The object near the centre of the image is Cas A and to its right is Cyg A. These are normally very bright radio sources. However, the sun (on the lower edge) easily outshines them... especially around 10:09 UTC (about 0:24 in the video). For the purposes of making this sequence, we really had to turn down the contrast to prevent complete saturation.

When the sun is radio-bright, strange artefacts can be seen in other parts of the image. These are the "sidelobe" responses of the telescope and are not real sources.

It says something about the strength of the solar radio bursts, when the sidelobe response can outshine even Cas A!

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