9:00 AM - 10:30 AM
[PEM13-P12] Spatio-temporal structure of precipitating electrons during omega-band auroras
Keywords:Pulsating aurora, omega band, radiation belt
Auroras are classified into two broad categories: discrete auroras, which have a clear and distinct shape, and diffuse auroras, which have a vague and blurred shape. Most diffuse auroras show quasi-periodic brightness modulations, which are known as "Pulsating Aurora (PsA)". Along with appearance of PsA, a large-scale wavy auroral phenomena called the "omega band" are often identified. Recent studies have demonstrated that the high energy (sub-relativistic) electrons of radiation belt origin often precipitate during intervals of PsA and omega band aurora. To date, however, the spatial distribution of such radiation belt electron precipitations during omega band auroras has not yet been clarified in detail. One of the possible methods, for revealing the characteristics of high energy electron precipitation during PsA and omega band, is to visualize the two-dimensional spatial distribution of the radiation belt electron precipitation by combining optical data from ground-based all-sky cameras and the Cosmic Noise Absorption (CNA) measurements by riometers.
In this study, we investigate the relationship between the intensity of the omega band emission and the temporal variation of CNA by using data from EMCCD all-sky imagers and spectral riometers. Three events were selected and analyzed: March 1, 2021 02:00:00-03:00:00 UT, March 3, 2021 01:30:00-02:30:00 UT, and March 25, 2021 01:00:00-02:00:00 UT, when the omega bands were observed. As a result, it was found that the CNA intensity is larger in the western part of the omega bands where the emission intensity is stronger than other area of the omega band. This infers that the precipitation of radiation belt electrons is more prominent in the western part of the omega band. Analyses of solar wind parameters for the three events revealed that the event on March 1, when the CNA intensity was smallest, may have been affected by a coronal mass ejection (CME). The events on March 3 and 25, when the CNA intensity was larger than that of March 1, 2021, were found to have occurred in the recovery phase of magnetic storms caused by the Corotating Interaction Region (CIR). These observational results suggest that the amount of precipitation of radiation belt electrons varies depending on the solar wind structure, especially the time since the start of magnetic storms. In the presentation, we will demonstrate the difference between the emission intensity and CNA in one omega band structure and discuss the dependence of the characteristics of radiation belt electron precipitation on the solar wind structures.
In this study, we investigate the relationship between the intensity of the omega band emission and the temporal variation of CNA by using data from EMCCD all-sky imagers and spectral riometers. Three events were selected and analyzed: March 1, 2021 02:00:00-03:00:00 UT, March 3, 2021 01:30:00-02:30:00 UT, and March 25, 2021 01:00:00-02:00:00 UT, when the omega bands were observed. As a result, it was found that the CNA intensity is larger in the western part of the omega bands where the emission intensity is stronger than other area of the omega band. This infers that the precipitation of radiation belt electrons is more prominent in the western part of the omega band. Analyses of solar wind parameters for the three events revealed that the event on March 1, when the CNA intensity was smallest, may have been affected by a coronal mass ejection (CME). The events on March 3 and 25, when the CNA intensity was larger than that of March 1, 2021, were found to have occurred in the recovery phase of magnetic storms caused by the Corotating Interaction Region (CIR). These observational results suggest that the amount of precipitation of radiation belt electrons varies depending on the solar wind structure, especially the time since the start of magnetic storms. In the presentation, we will demonstrate the difference between the emission intensity and CNA in one omega band structure and discuss the dependence of the characteristics of radiation belt electron precipitation on the solar wind structures.