Observation of a Solar Flare at 4.3-mm. Wave-length

Abstract

DURING a programme of solar observations at a wave-length of 4.3 mm., scans were made across the Sun on September 25, 26 and 27, 1957. The radio telescope used for these observations has a half-power beam-width of 6.7 minutes of arc. The antenna reflector is an aluminium paraboloid, 10 feet in diameter with a focal length of 35.8 inches. The receiver is mounted on the back of the antenna and is a Dicke-type radiometer consisting of a superheterodyne receiver preceded by a motor-driven attenuator wheel. This radio telescope has been described in a previous publication¹. The observations were made by pointing the antenna ahead of the Sun and locking it in position. The radiometer output was then recorded continuously as the Earth's rotation carried the Sun's image through the antenna beam. The scans were made across a large plage region located in the eastern part of the solar disk. The scans for each of the three days are shown in Fig. 1. The observed enhanced radiation from the plage region is clearly evident on all three scans. The scan on September 26 was made at the time of the maximum of an importance 3 solar flare occurring in the plage region. The enhancement recorded on September 26 is about twice the enhancement for the two scans made on the day before and the day after the flare. This indicates that the enhanced radiation is from the flare.