The behaviour of the solar radio emission through cycles 22 to 24

Data: 
29/05/2019 - 14:00 - 15:00
Local: 
Auditório "Prof. Dr. Paulo Benevides Soares", Bloco G

The behaviour of the solar radio emission through cycles 22 to 24

 

Caius Lucius Selhorst

Universidade Cruzeiro do Sul

 

Along the last three solar cycles (22-24), an unexpected change has been observed in the solar behaviour. During this period the solar sunspot number (SSN) showed a great reduction. The daily SSN in cycle 22 reached values above 350, while in cycle 24 the SSN numbers reached about half this value. These changes reflected differently in the classical solar proxy at radio, the solar flux at 10.7 cm (F10.7). The good correlation between SSN and F10.7 are typically constant, disappeared after cycle 22, where F10.7 was observed to be higher than the usual levels given the SSN counts. A possible cause of this divergence could be the reduction of the mean magnetic field observed in the sunspots along the last cycles. In this work, we analysed the effects of the reduction of the solar magnetic field in the solar maps obtained at 17 GHz by the Nobeyama Radioheliograph (NoRH) since 1992. The analysis presented here includes the variation of the solar radius, polar brightening and the number of active regions (NAR). We find that the mean solar radius and the limb brightening presented a significante reduction. Moreover, we find that NAR minima are shorter than those of the SSN and F10.7. This shorter NAR minima could reflect the presence of active regions generated by faint magnetic fields or spotless regions, which were a considerable fraction of the counted active regions.