11:15 AM - 11:30 AM
[PEM10-09] CME Velocity Estimations from Solar Radio Bursts Observed in 2024-2025
Keywords:Solar flares, Solar radio observations, Coronal mass ejections, Solar activity
Solar activity has reached its maximum, and a total of 20 large-scale (X-class) solar flares occurred in May 2024. In particular, 12 large-scale solar flares occurred in the active region NOAA 13664, including the most intense flare of X8.7 in this solar cycle. The coronal mass ejections (CMEs) released by these solar flares caused the first major geomagnetic storm in 19 years, and Dellinger phenomena, ionospheric disturbances, and low-latitude auroras were observed in various parts of Japan. The National Institute of Information and Communications Technology (NICT) conducts steady-state observations of solar radio bursts with the Solar Radio Observation System at the Yamagawa Radio Observatory. It is known that Type II and Type III solar radio bursts are observed in association with CMEs and accelerated electron beams. By analyzing the spectrum of radio bursts observed in the frequency range of 70 MHz to 9 GHz, it is possible to derive near real-time CME velocities by assuming solar atmospheric density (Naoi et al. 2018 Fall Meeting of the Astronomical Society of Japan, M05a).
The system successfully observed more than 17 cases of solar radio bursts associated with numerous X- and M-class solar flares in May 2024. We detected 19 type-II and 69 type III bursts in May 2024, as well as 4 events in GHz range. These events were detected in real time by an automatic detection program and an automatic warning system. It seems that larger (X-class) flares tend to produce type-II bursts. We selected 7 major events for analysis and found that type-II bursts occurred 4~15 minutes after X-class flares, in association with fundamental and harmonics spectra. We investigated the dependence of the estimated velocities of CMEs from solar radio spectra on coronal density models. We found that the velocity fitted by 1-fold Saito model seems closest to the LASCO velocity, followed by 2-fold Saito model. Furthermore, we extended this analysis for other events observed in 2024-2025. In this talk, we will show observation data of solar radio bursts taken by the Yamagawa Radio Observatory in 2024-2025, and the analysis of CME velocity estimations.
The system successfully observed more than 17 cases of solar radio bursts associated with numerous X- and M-class solar flares in May 2024. We detected 19 type-II and 69 type III bursts in May 2024, as well as 4 events in GHz range. These events were detected in real time by an automatic detection program and an automatic warning system. It seems that larger (X-class) flares tend to produce type-II bursts. We selected 7 major events for analysis and found that type-II bursts occurred 4~15 minutes after X-class flares, in association with fundamental and harmonics spectra. We investigated the dependence of the estimated velocities of CMEs from solar radio spectra on coronal density models. We found that the velocity fitted by 1-fold Saito model seems closest to the LASCO velocity, followed by 2-fold Saito model. Furthermore, we extended this analysis for other events observed in 2024-2025. In this talk, we will show observation data of solar radio bursts taken by the Yamagawa Radio Observatory in 2024-2025, and the analysis of CME velocity estimations.