MOTIONS OF THE AURORA AND RADIOAURORA AND THEIR RELATIONSHIPS TO IONOSPHERIC CURRENTS
Averaged observations of the longitudinal motions in aurorae and the motion of radio-aurora suggests that both kinds of motion occur in the same part of the ionosphere as, and are in approximately the opposite direction to, ionospheric currents responstble for magnetic disturbance. The motion of visible aurorae and radio-aurora is concluded to be caused by the motion of a source of excitation, for it is considered that only in rare circumstances can ionization be maintained in the lower E region without such a source. The electric fields from solar wind and ionospheric winds drive current in the ionospheric ionization produced. In general there is flow of current from the solar wind to the ionosphere. across the ionization in the ionosphere and back to the solar wind. Ionospheric inertia and therefore ionospheric winds play an important role in deciding motions in the magnetosphere. When bombardment of the lower ionosphere from the magnetosphere connects the magnetospheric potential system with that of ionospheric winds, a short circuit along the geomagnetic field followed by readjustment of magnetospheric potentials takes place. This sequence in turn changes the motion of magnetospheric bombarding sources. This short circuit gives rise to spikes on magnetograms Joule heating of the ionosphere during geomagnetic disturbance causes expansion of the ionosphere and therefore lift of the magnetosphere. The consequent lifting of lines of force of the geomagnetic field would contribute to the main phase of a magnetic storm. Likewise positive magnetic bays in H would be smaller in general than negative bays. It is suggested that three broad regions of the globe with distinctive characteristics exist: equatorwards of the auroral zone, owing to protection from the solar wind, gradients of pressure and hence currents in the outer magnetosphere connected to this region are small. Ionospheric currents are determined here principally by ionospheric winds. Considering a hori, zontally elongated filament of ionization (suggested by an auroral arc) the horizontal current parallel to the faces of it is very much greater than the current normal to its faces. In a second region in and near the auroral zone both electric fields from the magnetosphere and ionospheric wind combine to determine ionospheric current flow. Magnetospheric currents, driven by gradients of pressure in the magnetosphere, drive currents that are continued in the ionosphere along and across the geomagnetic field. In this region normal and parallel currents may be of similar order. Over the central polar caps a third region exists, in which the pressure gradient is simply that it is opposite the parallel current in direction. Over large areas of the globe this conclusion becomes that the auroral motion is approximately in the direction of motion of ionospheric electrons and of the same order of magnitude in speed. (auth)
- Research Organization:
- Dept. of External Affairs, Melbourne
- NSA Number:
- NSA-17-014502
- OSTI ID:
- 4749522
- Journal Information:
- Planetary Space Sci., Journal Name: Planetary Space Sci. Vol. Vol: 10
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
A HYDROMAGNETIC THEORY OF GEOMAGNETIC STORMS AND AURORAS
An auroral-zone electron precipitation event and its relationship to a magnetic bay