Are short‐time variations of the solar S‐component emission identical with microwave bursts?

Abstract

AbstractExtended time series (time resolution about 2–3 min) of spatially resolved observations (≫ 17 arcsec) in one dimension of solar S‐component sources obtained at the Siberian Solar Radio Telescope (SSRT) at 5.2 cm wavelength allow the detection of evolutional features of the growth and decay of active regions in the solar corona. Characteristic slow flux variations with timescales of about 1–2 hours occurring during the decay phase of the radio emission in the low corona above plages and sunspots are compared with recently detected step‐like flux increases on timescales of about 10–20 min followed by quasi‐constant periods appearing in the initial phase of the development of active regions. Superimposed on this basic behaviour, also fluctuations at shorter timescales (or even periodic oscillations) have been observed.As it is well known from emission‐model calculations, the variations of the S‐component radiation can be due to variations of the magnetic field and/or changes of the energy of the radiating particles, which is basically the same emission mechanism as for microwave bursts. Since the “S‐component” is originally defined by its long timescale behaviour derived from whole‐Sun flux density measurements, the presently detected small‐timescale features in S‐component sources require either a revised definition of S‐component emission or must be considered as “burst‐like”.