5:15 PM - 6:45 PM
[PEM13-P14] Relationship between energetic electron precipitation associated with omega band auroras and cosmic noise absorption measurements by spectral riometers
Keywords:pulsating aurora, omega band, cosmic noise absorption, spectral riometer
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 the appearance of PsA, a large-scale wavy auroral structure called the "omega band" is often identified. Recent studies have demonstrated that highly energetic electrons of radiation belt origin sometimes precipitate into the atmosphere during appearance of PsA. However, characteristics of electron precipitation during a storm-time omega band has not been investigated in detail due to a lack of good examples during large geomagnetic storms. To reveal this issue, we investigate the correlation between the auroral emission intensities and Cosmic Noise Absorption (CNA). We also investigate the relationship between the precipitation electron energy and CNA by quantitatively calculating CNA using an atmospheric model and measured electron densities. By these means, we aim to estimate the energy of the precipitating electrons from the auroral emission intensity using CNA as an intermediary object, and to visualize two-dimensionally the characteristics of the precipitation electrons at the onset of the omega band.
In this study, we investigated the spatiotemporal variations of CNA associated with omega band auroras that occurred during a geomagnetic storm by combining the observations of high-speed EMCCD all-sky cameras with a temporal resolution of 100 Hz, installed at four locations in Scandinavia (Tromsoe, Tjautjas, Sodankyla, and Kevo), and spectral riometers installed at five stations in the same region (Abisko, Kilpisjarvi, Sodankyla, Kevo, and Oulu). Specifically, we examined an event of omega bands during a Coronal Mass Ejection (CME) type large geomagnetic storm on March 23-24, 2023. By combining the optical data from the four EMCCD cameras, it was found that the torch structures of the omega bands drifted eastward quasi-periodically across the fields-of-view of the cameras. A comparison between the temporal variations in CNA and optical data indicated that the CNA significantly increased when the torch structures passed through the sensing areas of the riometers. Furthermore, by directly comparing the spatial structure of the omega bands and the CNA variations at the five locations, we found that the CNA increased not in a region of discrete aurora along the edge of the omega band, but in regions inside and outside of the torch structure that were filled with diffuse auroras. This suggests that harder electron precipitations, probably of radiation belt origin, occurs in the regions inside and outside the omega band structure where the morphology of aurora is more characterized by diffuse structures. The presentation will display the distribution of auroras across latitudes during magnetic storms, which will be visualized through wide-area imaging. Additionally, the presentation will highlight the CNA enhancement that occurs during the event. We will also show the results of correlation analysis between auroral emission intensity and CNA intensity, and the relationship between CNA derived from altitude profile of the electron density from the European Incoherent SCATer radar (EISCAT) observations and precipitation electron energy. We will discuss the relationship between the energy of precipitating electrons, altitude profile of ionization, and the spatial distribution of CNA.
In this study, we investigated the spatiotemporal variations of CNA associated with omega band auroras that occurred during a geomagnetic storm by combining the observations of high-speed EMCCD all-sky cameras with a temporal resolution of 100 Hz, installed at four locations in Scandinavia (Tromsoe, Tjautjas, Sodankyla, and Kevo), and spectral riometers installed at five stations in the same region (Abisko, Kilpisjarvi, Sodankyla, Kevo, and Oulu). Specifically, we examined an event of omega bands during a Coronal Mass Ejection (CME) type large geomagnetic storm on March 23-24, 2023. By combining the optical data from the four EMCCD cameras, it was found that the torch structures of the omega bands drifted eastward quasi-periodically across the fields-of-view of the cameras. A comparison between the temporal variations in CNA and optical data indicated that the CNA significantly increased when the torch structures passed through the sensing areas of the riometers. Furthermore, by directly comparing the spatial structure of the omega bands and the CNA variations at the five locations, we found that the CNA increased not in a region of discrete aurora along the edge of the omega band, but in regions inside and outside of the torch structure that were filled with diffuse auroras. This suggests that harder electron precipitations, probably of radiation belt origin, occurs in the regions inside and outside the omega band structure where the morphology of aurora is more characterized by diffuse structures. The presentation will display the distribution of auroras across latitudes during magnetic storms, which will be visualized through wide-area imaging. Additionally, the presentation will highlight the CNA enhancement that occurs during the event. We will also show the results of correlation analysis between auroral emission intensity and CNA intensity, and the relationship between CNA derived from altitude profile of the electron density from the European Incoherent SCATer radar (EISCAT) observations and precipitation electron energy. We will discuss the relationship between the energy of precipitating electrons, altitude profile of ionization, and the spatial distribution of CNA.