Premium
Photometric and interferometric observations of the Sar arc event of March 5/6, 1981
Author(s) -
Watanabe T.,
Kim J. S.
Publication year - 1982
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl009i001p00064
Subject(s) - arc (geometry) , zenith , photometer , optics , geology , physics , geodesy , geometry , mathematics
An extraordinary stable auroral red (SAR) arc was observed on the night of March 5/6, 1981 (EST) at a field station near Albany (42.63° N; 73.98°W), New York with a multicolor meridian scanning photometer and a 15‐cm high‐resolution Fabry‐Perot interferometer. The arc was extraordinary in the sense that: (a) it was the most intense arc (∼2.2 kR) observed during the past twelve years at Albany, New York; (b) it was a multiple arc consisting of two SAR arcs (the major arc occurred between zenith angles of 40° (L = 2.7) and 54°S (L = 2.5) throughout the observation period, and the minor arc occurred in close proximity for a duration of only one hour; (c) a visible aurora was not sighted from Albany during the observation period. Thermospheric temperatures were derived from Doppler line profiles of the [OI] 6300Å emission, obtained within the arc and outside the arc at zenith angles of 70°S, 50°N, and 70°N. The temperatures within the arc were quite stable with respect to time, even during the period of very rapid and large decrease in the arc intensity, and they were approximately equal to those measured at 70°N. The temperatures at 70°S, which varied considerably in time, were different from those at 50°N or 70°N. The temperatures within the arc were generally higher than those at 50°N or 70°S. The observed enhancement of the temperatures within the arc is much greater than the value predicted by the two‐dimensional model calculations of the SAR arc.