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This paper is concerned with the occurrence at high latitudes of a large number of geophysical phenomena, including geomagnetic agitation and bay disturbances, aurorae, and various irregular distributions of ionospheric electrons. It shows that these may all be related in a simple way to a single causal agency, namely, a certain convection system in the outer portion of the earth's magnetosphere. The source of this convection is taken to be a viscous-like interaction between the magnetosphere and an assumed solar wind, though other sources of an equivalent nature may also be available. The model is capable of accounting for many aspects of the phenomena concerned, including the morphology of auroral forms and the occurrence of 'spiral' patterns in the loci of maximum intensities of several features. It also bears directly on the steady state of the magnetosphere, and in particular on the production of trapped particles in the outer Van Allen belt. In short, it provides a new basis on which a full understanding of these several phenomena may in time be built.

I NTRODUCT~ONDuring the past few years, significant progress has been made in the area of cosmic ray acceleration with the recognition of the fact that energy can be transferred-by means of an efficient first-order Fermi mechanism4irectly to cosmic rays from supersonic motions of the background medium via shock waves.'-8 This idea is not entirely new, but it had previously been applied mainly in the context of the interplanetary medium, where there is clear evidence for shock acceleration in energetic storm particle events, corotating interaction regions, magnetospheric bow shocks, and (possibly) in the acceleration of solar flare particles.Several extensive reviews of this subject are now available.'-" The reader is referred to these for complete literature surveys and for more detailed analyses of basic processes than can be given here. We will instead concentrate largely on aspects of the subject that were less fully treated in earlier reviews.The properties of cosmic rays most relevant to the acceleration problem are the following.1. Their composition is rather normal (taking into account the effects of their passage through -5 g cm-' of interstellar matter). However, there is a depletion of alpha particles and, especially, protons relative to medium and heavy nuclei when compared with standard solar system abundances, and the electron flux is only about 1% of the proton flux. In general, the composition of galactic cosmic rays is very similar to that of the energetic particles produced in association with large solar flares.2. The primary ions have approximately the same power law spectra in the range 1010-1015 eV per nucleon (spectral index p 1 2.65), corresponding possibly to a "source" spectrum having p = 2.2. Secondary particles have a somewhat softer common spectrum, p = 3.3. The cosmic ray pressure, pE, is about the same as the magnetic field pressure, ( B2/87r), and the pressure of the interstellar gas, p ; namely, about lo-'' dyn cni ' .Since beryllium isotope measurements indicate a residence timescale of -10' years for cosmic rays in the galaxy, it is concluded that the cosmic ray source power is -3 x lo4' erg s-'.Shock waves provide an interesting acceleration mechanism for cosmic rays because they make it possible to explain the observed power law spectra, and the supersonic fluid motions prevalent in the interstellar medium can easily account for the power required. Possible energy sources for the supersonic motions are supernovae remnants (-lo4* ergs-'), O/B stellar winds (-lo4' erg s-'), and large expanding H I1 regions (-5 x erg s -' ) ; in fact, these sources should, perhaps, not be 297