Solar Photospheric Magnetic Fields, Coronal Mass Ejections, and Type II Radio Bursts in Cycles 23 and 24

• Published in: Astronomy reports 2022-07, Vol.66 (7), p.579-594
• Main Author: Bilenko, I. A.
• Format: Article
• Language: English
• Subjects: Astronomy; Coronal mass ejection; Interplanetary magnetic field; Magnetic fields; Mathematical analysis; Observations and Techniques; Parameters; Photosphere; Photospheric magnetic fields; Physics; Physics and Astronomy; Plasma; Solar activity; Solar corona; Solar cycle; Solar magnetic field; Solar radio bursts
• ISSN: 1063-7729; 1562-6881
• DOI: 10.1134/S1063772922080017

We consider the events of type II radio bursts (RBII) in the decametric and hectometric ranges from 1 to 16 MHz and the dependence of the parameters of associated coronal mass ejections (CMEs) on the background characteristics of the plasma and interplanetary magnetic field (IMF) in the regions where each radio burst was detected in solar cycles 23 and 24. The IMF was calculated from the data of large-scale photospheric magnetic fields at RBII detection distances. The results indicate that the number of RBIIs and the mean values of the plasma and IMF parameters vary in the form of individual pulses in both cycles, and the nature of their variation differs in cycles 23 and 24. The differences in the plasma, IMF, and CME parameters could cause a decrease in the RBII number in cycle 24. Most RBIIs in cycles 23 and 24 and the main decrease in their number in cycle 24 are observed for bursts with Alfvén Mach numbers of 1–2.9. The largest number of RBIIs in cycle 23 corresponds to the IMF of 0–30 T, and in cycle 24 to 30–50 T. The main decrease in the RBII number in cycle 24 occurred due to events observed at IMF of 0–30 T. RBII-inducing CMEs are mostly detected during periods of maximum solar activity, and a significant part of them—61 (18.05%) in cycle 23 and 31 (17.22%) in cycle 24—have Alfvén Mach numbers less than unity. It is possible that a different, non-plasma mechanism of RBII generation is responsible for these events.