Geoff Reeves and Colleagues Publish Study on Red Aurora in the Magnetosphere

Geoff Reeves, a senior scientist at Los Alamos National Laboratory and the New Mexico Consortium, has recently published a paper titled, Multi-Event Analysis of Plasma and Field Variations in Source of Stable Auroral Red (SAR) Arcs in Inner Magnetosphere During Non-Storm-Time Substorms, in the Journal of Geophysical Research: Space Physics.

The stable auroral red (SAR) arc is an aurora that often occurs during the recovery phase of magnetic storms and substorms. SAR arcs have been studied for a many years now, since their discovery in the 1950s. This arc is red in color due to excited oxygen atoms at latitudes slightly lower than the auroral oval.

In this study, the scientists report on three SAR arc events. They examine the events using ground-based all‐sky cameras and inner magnetospheric satellites (Arase and Radiation Belt Storm Probes). For the first time, they measured the three possible activation mechanisms to a SAR arc event. They did this by using the data for full‐energy‐range plasma and electromagnetic wave data obtained by the satellites.

The results of this study show that although Coulomb collisions are the most plausible mechanism for generating SAR arcs, SAR arcs are not caused by Coulomb collisions alone. Sometimes electromagnetic or electrostatic waves are observed with SAR arcs. Last, SAR arcs occur during non-storm time substorms as well as during storm times, and this should be examined more.

The observations made in this research project require further study. Future research should look at not only the formation of SAR arcs, but also at the magnetosphere-thermosphere-ionosphere coupling process during non-storm-time and storm-time substorms.

Read the entire article at:

Inaba, Y., K. Shiokawa, S. i. Oyama, Y. Otsuka, M. Connors, I. Schofield, Y. Miyoshi, S. Imajo, A. Shinbori, A. Y. Gololobov, Y. Kazama, S. Y. Wang, S. W. Y. Tam, T. F. Chang, B. J. Wang, K. Asamura, S. Yokota, S. Kasahara, K. Keika, T. Hori, A. Matsuoka, Y. Kasahara, A. Kumamoto, S. Matsuda, Y. Kasaba, F. Tsuchiya, M. Shoji, M. Kitahara, S. Nakamura, I. Shinohara, H. E. Spence, G. D. Reeves, R. J. Macdowall, C. W. Smith, J. R. Wygant, and J. W. Bonnell (2021), Multi-Event Analysis of Plasma and Field Variations in Source of Stable Auroral Red (SAR) Arcs in Inner Magnetosphere During Non-Storm-Time Substorms, Journal of Geophysical Research: Space Physics, 126, 4, doi:10.1029/2020ja029081.

Find the article online at: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JA029081

Above image taken from Figure 10 in the paper. The red dashed curves show the trajectory of the footprint of the Arase satellite. The red stars indicate the positions of the footprint of Arase when the image was taken. The horizontal and vertical axes correspond to the geographic longitude and latitude. The black dot at the center indicates the location of the ground based all-sky camera.

Article by Carrie Talus, NMC