Upper atmosphere during geomagnetic disturbances—I: Some regular features of low-latitute auroral emissions

Abstract

A search is made for correlation between the intensities of emissions of low-latitude auroras and different geomagnetic indices. It is found that lg I(6300) = βD st + G where I(6300) is the intensity of the oxygen emission at 6300 Å, and β abd G are empiric coefficients: the value β is a function of the geomagnetic latitude and varies within the limits of 2 × 10 −3–1.7 × 10 −2 for latitudes of 35–60 deg, while the value G represents the variations I(6300) as a function of solar activity, and from 1957 to 1959 varied within the limits of 1.9−0.9. The energy released in λ6300 during low-latitude auroras on the night side within the limits from −60 to + 60 deg of the geomagnetic latitude may hence be calculated. During the aurora on 11 February 1958 it was 5 × 10 23 ergs. The global value must be much greater since the λ6300 emission on the dayside and in high-latitude regions was not taken into account in the calculation. It exceeds the energy which is usually ascribed to geomagnetic storms. On 11 February 1958 D st reached −409 gammas. Such D st can be obtained as a result of uniform inflation of the magnetosphere by charged particles with the total energy of 1.7 × 10 23 ergs.