The ability of the cosmic‐ray neutron albedo mechanism to account for geomagnetically trapped electrons is investigated quantitatively. Injection as a function of energy, pitch angle, and altitude is computed from a reasonable neutron albedo model. Loss mechanisms (slowing down and pitch‐angle diffusion) based on Coulomb interactions with the residual atmosphere are considered to act both independently and simultaneously. It is found that slowing down is generally dominant. The resulting electron belt has the following features: (a) an intensity whose energy spectrum shows a peak at ∼200 kev; (b) an angular distribution that is approximately ‘isotropic’ up to the loss cone; and (c) an omnidirectional, integral intensity in the geomagnetic equatorial plane that is approximately constant vs. altitude. The absolute intensities depend directly on the atmospheric model used in the calculation; namely, rv−2.7, where atmospheric density is taken as ρ0r−v. These results agree only poorly with spectrometer observations which show an energy spectrum with a peak at a much lower energy. However, the quantitative agreement as to intensity is good at energies ≳400 kev. It is concluded that only a small fraction of the trapped electrons can be accounted for in terms of neutron albedo, essentially all trapped electrons >400 kev. An ‘auroral’ component of low‐energy electrons is also present. The energy of this low‐energy component probably derives from local acceleration, and ultimately from the sun. The effect of the Capetown magnetic anomaly is investigated and shown to produce a ‘slot’ of only 2 per cent in the equatorial plane in the vicinity of 2.7 earth radii.

Records for a three‐year period, from August 1, 1960, to July 16, 1963, have been examined for the occurrence of hydromagnetic emissions in California. It has been found that hm emissions are more likely to occur in the seven days after geomagnetic storms than during days in geomagnetically quiet periods.

Once introduced into captive orbits, protons and electrons should be strictly trapped in the earth's dipole magnetic field. However, various mechanisms exist which limit their lifetimes, such as collisions with atoms and ions in the earth's outer atmosphere, charge exchange, and scattering by hydromagnetic waves. This paper considers only the effect of the scattering of these particles by the ionized hydrogen and electron components of the outer atmosphere. However, the effect of scattering from neutral atoms can be qualitatively taken into account by using the radius of the atom in place of the Debye shielding length in the scattering formulas. The Fokker-Planck equation has been used to derive an expression for the change in the distribution function due to small-angle, single-particle Coulomb collisions. Upper lifetime limits, as determined by this mechanism, of both protons and electrons are derived as functions of their initial energies.

Recent experimental results are presented concerning the occurrence, structure, and frequency-latitude dependence of hydromagnetic emissions (regular oscillatory micropulsations in the frequency range 0.4-7 cps). Results are also presented fo.r the occurrence of no.ise bursts (irregular micropulsations in the same frequency range). Evidence is considered suggesting that both hm emissions and noise bursts are generated by related mechanisms. The experimental results are summarized as follows: (1) Occurrence. First, short hm emission bursts sometimes occur about I min after the sudden commencement of magnetic storms. Second, simultaneous occurrence with X-ray bursts and increased riometer absorption has been noted.(2) Structure. Hydromagnetic emissions tend to occur in distinct frequency bands. The bands are usually characterized by a fine structure consisting of a superposition of repetitive wave trains of a few minutes' duration and rapidly increasing frequency. (3) Frequency-latitude dependence. An inverse relationship has been found between the highest observed hm emission frequency and the geomagnetic latitude at which the signal is observed.In this paper we consider micropulsations of still shorter periods, that is, signals in the frequency range near I cps. More specifically, a band pass of 0.4-7 cps is employed. Most micropulsations: of the types of interest to us here occur in this general frequency range. However, the actual lower and upper limits of the pass band, 0.4 and 7 cps respectively, were determined by the design parameters of the detection equipment [Tepley, 1961b].The micropulsations are placed in two general categories. SignMs in one of the categories, referred to below as 'noise bursts,' are closely related to micropulsations of longer periods. Sig-nMs in the other category, which are the primary concern of this paper, are les. s clo.sely related to other types of geomagnetic fiuctuatio.ns. We refer to micropulsations in the latter cate-3317 3318 TEPLEY AND gory as 'hydromagnetic emis'sions,' since it has been demonstrated in separate studies that the properties of the signals are consistent with their generation either above or high in the ionosphere and their subsequent propagation downward through the ionosphere by hydromagnetic waves [Wentworth, 1961; Tepley, 1962] (also private communications from H. Benioff and G. Bodvarsson concerning unpublished work at California Institute of 'Technology). The term 'emission' was introduced to suggest an analogy between these signals and the so-called 'VLF emissions,' which are generated above the ionosphere [Gallet and Helliwell, 1959; Gallet, 1959]. The terms 'hm emission' and 'noise burst' are defined below. In the appendix, they are again considered in relation to nomenclature (pearls, SIP, IPDP, type A and Wpe B oscillations, and solar whistles) currently employed by other workers to describe signals in the same general frequency range.

Because of its long lifetime below 45 km, ozone can deviate markedly from the concentration given by photochemical equilibrium considerations. Hence the ozone concentration can be used as an indicator of the motion of air masses, particularly in the stratosphere. The meteorological implications can be fully realized only by synoptic measurements, for which an artificial earth satellite is ideally suited. The method described employs the optical absorption properties of ozone in the ultraviolet region around 2900Å. A detector looking down towards the earth will receive solar ultraviolet scattered by the atmosphere which has been attenuated both by scattering out and by ozone absorption. Calculations are presented to illustrate the effective depth in the atmosphere to which the detector “sees,” the effective depth being defined as the point above which 90 per cent of the contribution to the detector response is made. The sensitivity of the method to changes in the ozone concentration at various altitudes is also demonstrated.