The narrowband decimetric spikes belong to essentially the most fascinating photo voltaic radio bursts, as a result of they’re linked to the first flare course of. Their brightness temperature is as much as 1015 Ok. Within the radio spectrum, they happen in clouds of many narrowband bursts with a relative bandwidth of about 1-3 % and length lower than 100 ms (Benz, 1986). Many fashions of those spikes had been proposed, akin to these based mostly on the electron-cyclotron maser mechanism or based mostly on the plasma emission mechanism. Karlický et al. (1996) studied the frequency bandwidths of spikes by the Fourier technique. They discovered the power-law spectra with power-law indices near -5/3, the Kolmogorov turbulence index. Due to this fact, it was steered that the spikes are generated by suprathermal electrons within the magnetohydrodynamic turbulence.
Determine 1. Higher: Radio spectrum noticed at 13:41:30 – 13:42:30 UT in the course of the 2022 Might 10 flare. Backside: Its element at 13:42:00 – 13:42:03 UT. The white line marks an instance of the frequency drift of those spikes. The black horizontal strains within the each spectra present the frequency at which the durations had been analyzed.
Determine 2. SDO/AIA 171 A commentary of reconnecting threads (1 purple and a pair of blue) on the time of dm-spikes at 13:42:09 UT, see additionally the films in our paper.
Observations and outcomes
We studied the radio emission occurring as narrowband decimetric spikes noticed in the course of the 2022 Might 10 and 2022 August 26 flares. Utilizing the wavelet evaluation method we discovered that the spikes of their radio spectra had been distributed in teams that occurred quasi-periodically with the durations 5.1 s within the 2022 Might 10 flare and 9.1 s within the 2022 August 26 flare. An instance of those spikes noticed in the course of the 2022 Might 10 flare is proven in Determine 1, higher half.
In some components of the teams of spikes, subgroups of spikes distributed with the quasi-periods of 0.19 s (2022 Might 10 flare), and 0.17 s and 0.21 s (2022 August 26 flare) had been discovered. A few of these subgroups of spikes had optimistic frequency drift (930, 1100, and 1710 MHz s-1), whereas others had adverse drift (−1000 and −1330 MHz s-1), which was noticed for the primary time. An instance of subgroups with the quasi-period of 0.19 s noticed in the course of the 2022 Might 10 flare is proven in Determine 1 backside. There, the spikes drift from decrease to larger frequencies, as indicated by the white line.
The spikes at 13:42 UT on 2022 Might 10 occurred in the course of the precursor part of the X1.5-class X-ray flare as recorded by GOES-16. On the time of the spikes commentary, a pair of quick, mutually interacting loops had been recognized within the SDO/AIA EUV observations. One in all these loops was interpreted as a vivid thread belonging to the small erupting filament, whereas the opposite loop was an oppositely-oriented overlaying loop, see Determine 2.
Conclusions
We suggest that the talked about loops reconnected within the dynamic quasi-periodic regime with the interval 0.19 s, and that this reconnection is modulated by an oscillation of one of many interacting loops (the interval 5.1 s). We observe that comparable durations of spikes group (0.1–0.9 s) had been not too long ago additionally discovered by Huang et al. (2022).
The drift of teams of spikes had been noticed for the primary time. In settlement with Karlický et al. (1996), we suggest that the accelerated electrons from the reconnection course of are trapped within the reconnecting plasma outflows and transfer with them. Owing to this movement, the sources of spikes moved to larger or decrease plasma densities, and thus the drifting teams of spikes had been generated.
Throughout the 2022 August 26 flare comparable durations and drifts of teams of spikes had been discovered. Nevertheless, the magnetic construction of flare in SDO/AIA photos was fairly complicated, making it tough to uniquely recognized reconnecting constructions as within the 2022 Might 10 flare. Nonetheless, we discovered indications that the teams of spikes and their drifts had been generated by comparable processes as within the 2022 Might 10 flare.
Primarily based on the paper printed in Photo voltaic Physics 299: 113 (2024) by Marian Karlický, Jaroslav Dudík and Ján Rybák
References
Benz, A.O., 1986, Photo voltaic Phys. 104, 9
Huang, J., Tan, C., Chen, X. et al., 2022, Universe 8, 348
Karlický, M., Sobotka, M., Jičička, Ok., 1996, Photo voltaic Phys. 168, 375
