The slowly varying component of the solar radio radiation

 The slowly varying component of the solar radio radiation

The longer wavelengths from Sun that we receive on Earth originate in the corona where the characteristic temperature is high. The temperature relevant to the measured intensity of meter wavelengths is - 10° K. The intensity of this radiation undergoes slow variation, corresponding to the variations in the coronal structure. The measured radiation actually correspotids to a temperature of 10° K and a density nearly equel to three times the normal coronal density.

 The slowly varying component of the solar radio radiation thus fits with the concept that-it is thermal radiation trom regions of coronal condensations. The mechanism which gives risc to this radiation is free-free transition of clectrons in the hot coronal gas. The burst component of solar radio emission is sporadic, intense and nonthermal in character. This component is associated with the activity of the Sun. Different types of bursts have been recognized and the physics behind them is quite complex. As the name implies, bursts are manifested as the enhancement of. the radiosemission by onders of magnitude within periods as short as a few seconds.

 If the intensitaesof tursts are interpretedas of thermal origin, the corresponding equivalent blackbody temperatures would be of the order of 1012 K, which is absurd. The bursts are of different nature and they have been broadly classified into types 1, II, III. IV and V. Of these, all but the Type I bursts are correlated with flares.

 Type I bursts are not associated with flares or centres of activity. Type I bursts originate in noise storms that are produced high up in the corona usually above larger spots, their polarization showing no correlation with that o the spots. These bursts usually have lite-times of 0.1 to 0.2 seconds and during this period the wavelength of radiation remains fairly constant. The radiation.

 The theory of Gold and Hoyle thus predicts the release of the right amount of energy within the right amount of time as are observed in flares, through the meehanism of the magnetic field annihilation. The theory therefore implies the operation of a mechanism by which the twisted magnetic field which develops on the selar surface may become untwisted through flare discharge: Thistrunstormation irom twisted to untwisted field may have important bearing on the equilibriam configuration of the Sun. erg may be associated with such a twisted Soon after the production of radio frequency waves in the laboratory by Heinrich Hertz in 1888.

 Some scientists started thinking that the Sun might be a source of radie waves. Valuable work was one in this line by Wilsing. Scheiner, Nordmann, Jansky and others during the first few decades of this century and the end of the last century. But the actual detection of Sun.