Remarks on the slowly varying component of solar radio emission during the proton flare period of July 1966

The centre of activity which produced the proton event of 7 July 1966 was characterized by an unusual increase of the slowly varying (S) component of solar radio emission at short centimetre waves. One day before the proton event a monotonic spectrum was present indicating a rapid growth of electron density. However, such a monotonic increase of the spectrum of the S-component towards higher frequencies is not in every case a necessary condition for the occurrence of proton flares, as comparisons with the development of the S-component in August and September 1966 show.