ALBERT

Beschreibung: Photometric and interferometric observations of three SAR arc events, occurring on October 4/5,1980, May 8/9,1981 and October 20/21,1981, were made at the field station near Albany (42.68°N; 73.82°W), New York. The maximum intensities of these arcs are 0.49,0.70, and 2.0 kR, respectively. The peak emission altitude of the intense arc observed on the night of October 20/21, 1981, determined by the triangulation method, was 505 ± 46 km at the earlier stage of observation. The temperatures measured within the arc on October 4/5, 1980 are in the range of 1138°K to 1475°K, with an average value of 1349°K; while for the arc of May 8/9, 1981 they ranged from 1508°K to 1840°K, with an average value of 1697°K. For the arc of October 20/21,1981, temperatures are in the range of 1379°K to 1557°K, with an average value of 1472°K. The temperature enhancement within the arc is approximately 200°K for the arc observed on October 20/21, 1981, and 100°K for both the arcs observed on October 4/5, 1980 and on May 8/9, 1981. Our previous measurements on the arc of March 5/6,1981 also show a temperature enhancement of more than 200°K within the arc (Watanabe and Kim, 1982). These temperature enhancements clearly exceeded those predicted by a 2-dimensional model calculation. The present results also show that the temperature enhancement within the arc is strongly correlated with the overall maximum intensity of the arc. When the maximum intensity of the arc reaches about 400 R, the temperatures within the arc are variable (see Okano and Kim, 1979), but the temperature enhancement within the arc becomes almost always detectable. However, when the overall maximum intensity of the arc reaches about 2 kR, the temperature within the arc is quite stable and the temperature enhancement within the arc is quite substantial. © 1984, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.