Arkadiy M. Uralov

The eruption of a large prominence and the resulting development of a coronal mass ejection (CME) were observed on June 12, 2023 by the Siberian Radioheliograph in microwaves up to heliocentric distances exceeding two solar radii, space-borne telescopes in the extreme ultraviolet, and coronagraphs in white light. The evolution of the CME structural components was traced and their kinematic characteristics were measured. The CME components underwent two successive acceleration pulses, comparable in magnitude and duration. According to the observations, the first acceleration pulse was caused by torus instability of the magnetic flux rope associated with the prominence. At this stage, its expansion was self-similar and consistent with the expansion of the CME frontal structure. The frontal structure was an expanding arcade that encompassed the pre-eruption prominence. The second acceleration pulse was associated with helical kink instability, which manifested itself in the deformation of the top of the erupting prominence, visible as a helical protrusion. The development of helical kink instability affected the motion of the CME frontal structure, but did not influence the motion of the main body of the CME core, shown up as the massive part of the erupting prominence beneath the helical protrusion. After the completion of the helical kink instability, the coordinated self-similar expansion of all CME components recovered. The fact that the helical kink instability occurred much later than the torus instability excludes its involvement in causing the latter, as has sometimes been assumed.

The eruption of a large prominence and the resulting development of a coronal mass ejection (CME) were observed on June 12, 2023 by the Siberian Radioheliograph in microwaves up to heliocentric distances exceeding two solar radii, space-borne telescopes in the extreme ultraviolet, and coronagraphs in white light. The evolution of the CME structural components was traced and their kinematic characteristics were measured. The CME components underwent two successive acceleration pulses, comparable in magnitude and duration. According to the observations, the first acceleration pulse was caused by torus instability of the magnetic flux rope associated with the prominence. At this stage, its expansion was self-similar and consistent with the expansion of the CME frontal structure. The frontal structure was an expanding arcade that encompassed the pre-eruption prominence. The second acceleration pulse was associated with helical kink instability, which manifested itself in the deformation of the top of the erupting prominence, visible as a helical protrusion. The development of helical kink instability affected the motion of the CME frontal structure, but did not influence the motion of the main body of the CME core, shown up as the massive part of the erupting prominence beneath the helical protrusion. After the completion of the helical kink instability, the coordinated self-similar expansion of all CME components recovered. The fact that the helical kink instability occurred much later than the torus instability excludes its involvement in causing the latter, as has sometimes been assumed.

Correlation curves of the multi-frequency Siberian Radioheliograph (SRH) provide a sensitive indication and demonstrative representation of monitoring the microwave life of the active Sun. We derive approximate relationships and briefly discuss the contribution of the quiet Sun, active regions, radio bursts, satellites, and atmospheric absorption to the radioheliograph’s correlation response. The estimates are obtained under the assumption that the activity centers and the quiet Sun are homogeneous disks of different sizes and brightness. The sensitivity of the correlation curves to weak sources of small angular sizes is due to their wide spatial spectrum. The wide spectrum means that each pair of antennas produces a noticeable interferometric response, so the total response is significant. The correlation curves allow us to estimate spatial sizes of the radio burst source at different frequencies, but do not allow us to calculate the shape of its radio spectrum. Variability in the atmospheric water content over time creates fluctuations of the received solar radio flux. The correlation response is much less susceptible to this factor.

Correlation curves of the multi-frequency Siberian Radioheliograph (SRH) provide a sensitive indication and demonstrative representation of monitoring the microwave life of the active Sun. We derive approximate relationships and briefly discuss the contribution of the quiet Sun, active regions, radio bursts, satellites, and atmospheric absorption to the radioheliograph’s correlation response. The estimates are obtained under the assumption that the activity centers and the quiet Sun are homogeneous disks of different sizes and brightness. The sensitivity of the correlation curves to weak sources of small angular sizes is due to their wide spatial spectrum. The wide spectrum means that each pair of antennas produces a noticeable interferometric response, so the total response is significant. The correlation curves allow us to estimate spatial sizes of the radio burst source at different frequencies, but do not allow us to calculate the shape of its radio spectrum. Variability in the atmospheric water content over time creates fluctuations of the received solar radio flux. The correlation response is much less susceptible to this factor.