04 Aug 2023
 | 04 Aug 2023
Status: a revised version of this preprint is currently under review for the journal ANGEO.

Three-dimensional ionospheric conductivity associated with pulsating auroral patches: Reconstruction from ground-based optical observations

Mizuki Fukizawa, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, and Tero Raita

Abstract. Pulsating auroras (PsAs) appear over a wide area within the aurora oval from the midnight sector to the noon sector. In previous studies, observations by magnetometers onboard satellites have reported the presence of field-aligned currents (FACs) near the edges and interiors of pulsating aurora patches. PsAs are thus a key research target for understanding the magnetosphere–ionosphere coupling process. However, the three-dimensional (3-D) structure of the electric currents has yet to be clarified, since each satellite observation is limited to the single dimension along its orbit. This study’s aim was a reconstruction of the 3-D structure of ionospheric conductivity, which is necessary to elucidate the 3-D ionospheric current. Tomographic analysis was used to estimate the 3-D ionospheric conductivity for rapidly changing auroral phenomena such as PsAs. The reconstructed Hall conductivity reached its maximum value of 1.4 × 10–3 S m–1 at 94 km altitude, while the Pedersen conductivity reached its maximum value of 2.6 × 10–4 S m–1 at 116 km altitude. The Pedersen conductivity, which is driven by the motion of electrons, exhibited a secondary peak value of 9.9 × 10–5 S m–1 at 86 km altitude. The electron Pedersen conductivity maximum value in the D region was approximately 38 % of the ion Pedersen conductivity maximum value in the E region. The FAC, derived under the assumption of a uniform ionospheric electric field, was approximately 70 µA m–2 near the edge of the PsA patch. This FAC value was approximately 10 times that observed by satellites in previous studies. If the conductivity around the patch is underestimated or the assumption of a uniform field distribution is incorrect, the FAC could be overestimated. On the contrary, due to sharper boundary structures, the FAC could actually have had such a large FAC.

Mizuki Fukizawa et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on angeo-2023-24', Anonymous Referee #1, 09 Aug 2023
    • AC2: 'Reply on RC1', Mizuki Fukizawa, 15 Sep 2023
  • RC2: 'Comment on angeo-2023-24', Spencer Hatch, 23 Aug 2023
    • AC1: 'Reply on RC2', Mizuki Fukizawa, 14 Sep 2023

Mizuki Fukizawa et al.

Mizuki Fukizawa et al.


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Short summary
We use computed tomography to reconstruct the three-dimensional distributions of the Hall and Pedersen conductivities of pulsating auroras, a key research target for understanding the magnetosphere–ionosphere coupling process. It is suggested that the high-energy electron precipitation associated with pulsating auroras may have a greater impact on the closure of field-aligned currents in the ionosphere than has been previously reported.