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- Title
The Quasipersistent Feature of Highly Structured Field‐Aligned Currents in the Duskside Auroral Oval: Conjugate Observation Via Swarm Satellites and a Ground All‐Sky Imager.
- Authors
Yokoyama, Y.; Taguchi, S.; Iyemori, T.; Hosokawa, K.
- Abstract
During northward interplanetary magnetic field (IMF), irregular magnetic perturbations were observed in the duskside aurora oval via Swarm satellites instead of large‐scale Region 1/2 magnetic perturbations. By taking advantage of Swarm constellation measurements, and their conjugate observations with an all‐sky imager on the ground, the features of the irregular magnetic perturbations were examined. Detailed analysis of the data from Swarm A and Swarm C for two events demonstrated that the irregular magnetic perturbations are a result of highly structured quasistatic field‐aligned currents (FACs), not dynamic Alfvén waves. The typical latitudinal size of the upward FACs is 20–30 km. In each region of the upward FACs, 630‐nm aurora emissions are relatively strong, indicating that the energy flux of precipitating electrons having energies of a few hundred electron volts is high in each of the upward FAC regions. The enhanced mesoscale auroras continued to exist for at least approximately 30 min. These indicate that the mesoscale FAC structures also have quasipersistent features. The precipitating particle data from the Defense Meteorological Satellite Program satellite, which passed through the field of view of the all‐sky imager, indicate that the source of the precipitating particles is the duskside low‐latitude boundary layer (LLBL). We suggest that the highly structured quasipersistent FACs flow along the magnetic field lines connected to the duskside LLBL where cold dense ions exist. The highly structured FACs in the duskside aurora oval are the phenomena that are pertinent to the magnetosphere for a northward IMF condition, not a simple remnant of the typical Region 1. Key Points: Irregular magnetic perturbations occur in the dusk part of the auroral oval instead of Region 1/2 magnetic perturbationsThe irregular magnetic perturbations are a result of highly structured quasistatic field‐aligned currentsThe highly structured field‐aligned currents are the phenomena pertinent to the magnetosphere for a northward IMF condition
- Subjects
INTERPLANETARY magnetic fields; PERTURBATION theory; ELECTRON precipitation; FLUX (Energy); DATA analysis
- Publication
Journal of Geophysical Research. Space Physics, 2020, Vol 125, Issue 7, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2019JA027594