No abstract

The energy spectra and pitch angle distributions of energetic protons injected into the inner Saturnian magnetosphere by the cosmic ray albedo neutron decay (CRAND) process have been calculated using the nucleon transport code HETC. These calculations predict spectra and pitch angle distributions consonant with the Pioneer and Voyager observations for proton energies above ∼50 MeV assuming that the ring particles are ice, not rock, and that the mean mass seen by the cosmic rays is several tens to a few hundred grams per square centimeter.

Computations on an 80–coefficient model of the earth's field illustrate the ‘topography’ of the magnetic equatorial surface (on which B · ∇B = 0) and the geometry of the drift shells of geomagnetically trapped particles. Individual terms in the spherical harmonic expansion (offset dipole coordinates) of the geomagnetic scalar potential V(γ, θ, ϕ) are either even or odd in cos θ, where θ = π/2 denotes the dipole equator. Terms that (unlike the dipole) are even in cos θ tend to ‘warp’ the equatorial surface, but do not (in first order) distort particle drift shells radially nor split the drift shells of particles having different equatorial pitch angles. Azimuthally asymmetric terms that are odd in cos θ do cause shell splitting in first order. Shell splitting at large L values (neglecting deformation of the earth's field by the solar wind) is found to be dominated by the geomagnetic octupole. At L ∼ 1, shell splitting is strongly enhanced by the South American and South African anomalies. When combined with pitch angle diffusion caused by atmospheric scattering, these results may be able to account for anomalous radial diffusion of inner zone electrons (as observed at L ≲ 1.2).

Measurements of precipitating protons in the energy range 2.5–200 kev have been made on OV1‐15 (1968‐59A), a low‐altitude polar satellite, with a combination of electrostatic analyzers and integral foil detectors. During disturbed times, precipitating proton fluxes in the range 107–108 cm−2 sec−1 are seen. On several occasions, it has been possible to compare the spatial distribution of precipitation with the plasmapause profile taken by Ogo 5 during all phases of magnetic storm activity. It is found that the near‐earth boundary of maximum proton precipitation lies just inside the plasmapause. If observed pitch‐angle distributions are classified according to whether the loss cone is nearly empty or otherwise, it is found that the corresponding 40‐kev flux intensities and L values separate into two classes in a way described by weak versus strong pitch‐angle diffusion.

McIlwain defined the magnetic‐shell parameter L for a point in the earth's magnetic field by the equation L3B/M=F(I3B/M), where I is the integral invariant, B is the mirror point field, M is the earth's dipole moment, and F is a function calculated for a dipole field. A new approximation to F has been found: L3B/M = 1 + a1X1/3 + a2X2/3 + a2X, where X=I3B/M, a1=1.35047, a2=0.465376, and a3=0.0475455. The error in the determination of L is less than 0.01% for all L. The formula is asymptotically correct for X≪1 and X≫1.