Winds in the upper atmosphere deduced from the dynamo theory of geomagnetic disturbance

Abstract

Average features of geomagnetic disturbance are represented by atmospheric-electric current-systems. These cannot be uniquely inferred from the magnetic observations at ground level. Using the Balfour Stewart dynamo theory, these electric current-systems are then tentatively replaced by equivalent atmospheric windsystems, using order of magnitude calculations. It is found that these supposed wind-systems will differ in accordance with the degree of electric polarization of the atmosphere, and with the intensity of toroidal or solenoidal electric currents likely to be present, as a consequence of zonal winds. A simple monthly mean wind-system of geomagnetic disturbance shows good general agreement with a wind-system derived by Kellogg and Schilling from meteorology. A qualitative version of a possible wind-system for the main phase of a magnetic storm is derived and found to show some measure of agreement with diurnal features of atmospheric motions deduced from radio-star scintillations and auroral motions. The causes of such wind-systems, and the effective transverse conductivity of the atmosphere, are briefly but inconclusively discussed. It is shown that the flux of X-rays producing ionization of the E-region is apparently the same on days of magnetic storm as on days prior to the storm, and that the dynamo air-flow at the E-region yielding the quiet-day diurnal variation also appears inappreciably affected by the presence of a magnetic storm.