Coincidence of the Explosive Phase of Solar Flares with 10.7-cm. Solar Noise Bursts

The Importance of Synoptic Solar Radio Observations

“…Amidst the excitement of all these new phenomena, the value of simply tracking the level of the Sun's non-flaring radio flux was also recognized. Starting in 1947, Arthur Covington in Canada began monitoring the solar flux at 2.8 GHz (λ = 10.7 cm; e.g., Covington 1951), an effort that continues to this day (e.g., Tapping 2013) and has become a critical part of both tracking solar activity as well as understanding the impact of the Sun on the Earth's atmosphere. F10.7, as the measurement of the flux at the wavelength of 10.7 cm is known, is arguably the second-most widely used measure of solar activity after sunspot number, and tends to be favored in atmospheric modelling because it has a more direct physical connection to the sources of the short-wavelength solar emission that is absorbed in the terrestrial atmosphere (e.g., Tobiska 1991).…”

Some studies on solar microwave bursts in relation to the phases of the associated H?-flares and their spectral nature

“…Results obtained are: (i) about 76 % of the flare-associated bursts occur in the pre-maximum phase and the remaining 24 % occurs in the post-maximum phase irrespective of the flare classification, intensity-wise or area-wise; (ii) 'impulsive' and 'gradual rise and fall' bursts are relatively more important in the pre-maximum phase while 'post burst increase' bursts show comparatively higher occurrences in the post-maximum phase; (iii) peak flux and energy excess spectra of the concurrent microwave bursts in the pre-maximum phase of the flare are mostly of 'inverted U' and 'increasing with frequency' spectral types. Of these, 'impulsive' bursts are predominantly of the 'inverted U' and the 'grf' bursts are of the 'increasing with frequency' spectral type.Solar microwave bursts associated with He-flares are generally believed to occur in the flash phase (Ellison, 1949) or in the explosive phase (Covington and Harvey, 1961 ; Sakurai, 1966;Harvey, 1971) of the flare. However, it appears that the relative occurrences and the nature of these bm sts in relation to the different phases of the life time of the associated flares of different classes are not precisely known.…”

“…Solar microwave bursts associated with He-flares are generally believed to occur in the flash phase (Ellison, 1949) or in the explosive phase (Covington and Harvey, 1961 ; Sakurai, 1966;Harvey, 1971) of the flare. However, it appears that the relative occurrences and the nature of these bm sts in relation to the different phases of the life time of the associated flares of different classes are not precisely known.…”