Research Article

Fan-shaped aurora as seen from Japan during a great magnetic storm on February 11, 1958

¹ National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, 190-8518 Tokyo, Japan
² SOKENDAI, 10-3 Midori-cho, Tachikawa, 190-8518 Tokyo, Japan
³ Meteorological College, 7-4-81 Asahi-cho, Kashiwa, 277-0852 Chiba, Japan
⁴ National Institute of Japanese Literature, 10-3 Midori-cho, Tachikawa, 190-0014 Tokyo, Japan

^* Corresponding author: kataoka.ryuho@nipr.ac.jp

Received: 1 October 2018
Accepted: 19 March 2019

Abstract

During a great magnetic storm on Feb 11, 1958, a fan-shaped aurora was photographed at Memambetsu, Hokkaido, Japan – the first and oldest photograph record of auroras observed in Japan, accompanied by many hand-made drawings, thus, portraying a rare opportunity of coexistence between photograph images and hand-made drawings. In fact, the same portrayal reminds us of the great red aurora with fan-shaped white pillars observed during the 1872 and 1770 great magnetic storms. The hand-made sketches, photographs, and the spectral data revealed that the white pillars and red glow of the fan-shaped aurora were dominated by auroral green and red lines, respectively. From the analysis of newly digitized microfilm data and hand-made drawings, we found that the fan-shaped aurora appeared during the peak activity of magnetic storm and moved westward at 0.4 km/s at 400-km altitude at 38°–40° magnetic latitudes, which is consistent with the enhanced convection pattern in the middle latitude at storm time. Such a fan-shaped aurora can fundamentally characterize the middle-latitude evening-to-midnight auroras during great magnetic storms, which show the most destabilized transient appearance of the inner magnetosphere.