A Comparison of Auroral Oval Proxies With the Boundaries of the Auroral Electrojets

• Published in: Space weather 2024-04, Vol.22 (4), p.n/a
• Main Authors: Walker, Simon James, Laundal, Karl Magnus, Reistad, Jone Peter, Ohma, Anders, Hatch, Spencer Mark, Chisham, Gareth, Decotte, Margot
• Format: Article
• Language: English
• Subjects: auroral electrojets; auroral electrojets boundary; auroral oval; auroral oval boundary; polar cap; spherical elementary currents
• ISSN: 1542-7390; 1542-7390
• DOI: 10.1029/2023SW003689

The boundaries of the auroral oval and auroral electrojets are an important source of information for understanding the coupling between the solar wind and the near‐earth plasma environment. Of these two types of boundaries the auroral electrojet boundaries have received comparatively little attention, and even less attention has been given to the connection between the two. Here we introduce a technique for estimating the electrojet boundaries, and other properties such as total current and peak current, from 1‐D latitudinal profiles of the eastward component of equivalent current sheet density. We apply this technique to a preexisting database of such currents along the 105° magnetic meridian, estimated using ground‐based magnetometers, producing a total of 11 years of 1‐min resolution electrojet boundaries during the period 2000–2020. Using statistics and conjunction events we compare our electrojet boundary data set with an existing electrojet boundary data set, based on Swarm satellite measurements, and auroral oval proxies based on particle precipitation and field‐aligned currents. This allows us to validate our data set and investigate the feasibility of an auroral oval proxy based on electrojet boundaries. Through this investigation we find the proton precipitation auroral oval is a closer match with the electrojet boundaries. However, the bimodal nature of the electrojet boundaries as we approach the noon and midnight discontinuities makes an average electrojet oval poorly defined. With this and the direct comparisons differing from the statistics, defining the proton auroral oval from electrojet boundaries across all local and universal times is challenging. Plain Language Summary The global location of the northern and southern lights (aurora) holds particular importance for understanding where energy from the solar wind and its coupling with the magnetosphere is deposited in the upper atmosphere. The brightness of these lights and related electrical currents also indirectly indicate the magnitude of the energy deposition. However, global imaging of aurora is limited by sunlight, with generally fewer observations during summer months. Furthermore, global observations are not possible from the ground, and space‐based global imaging has been missing for close to two decades. In this study we investigate alternative methods, with particular emphasis on a technique exploiting ground magnetometer data. Electrical currents have been robustly mapped fo