Research in particles and fields

The astrophysical aspects of cosmic and gamma rays and the radiation environment of the Earth and other planets investigated by means of energetic particle detector systems flown on spacecraft and balloons are discussed. The theory of particles and fields in space is also addressed with particular emphasis on models of Saturn's magnetic field

Research in particles and fields

Cosmic rays and astrophysical plasmas, NASA spacecraft experiment activities, and gamma rays are discussed

Research in particles and fields

The astrophysical aspects of cosmic radiation and the radiation and electromagnetic field environment of the Earth and other planets are investigated. Energetic particle and photon detector systems flown on spacecraft and balloons are used. Galactic, solar, interplanetary, and planetary energetic particles and plasmas are also studied with emphasis on precision measurements with high resolution in charge, mass, and energy

Analytic Approximations in the Study of the Solar Modulation of Electrons

Numerical solutions to the transport equation of galactic cosmic rays in the interplanetary medium have been used to investigate the applicability of commonly used approximate analytic solutions for electrons (10 MeV to 10 GeV). We find that for a given cosmic-ray diffusion coefficient: (a) the "force-field" approximation is in reasonable agreement with the numerical solution at energies ≳ 200 MeV, but deviates significantly at lower energies, depending on the shape of the interstellar electron spectrum, (b) the "diffusion-convection" approximation agrees generally with the numerical solution within a factor of ~ 2 over the entire energy range

Interplanetary Diffusion Coefficients for Cosmic Rays

Information on the cosmic-ray diffusion coefficient, κ, derived from near-Earth observations of the solar modulation of galactic electron fluxes and from the near-Earth power spectra of the interplanetary magnetic field, has been used to study the heliocentric radial dependence of κ and to derive limits on the spatial extent of the solar modulation region. Representing κ as a separable function of radius r and rigidity, and assuming κ(r) ∝ r^n, we can place a limit on the power law exponent, n ≾ 1.2. The distance of the modulation boundary is a function of n, and, e.g., for n = 0, falls into the range of 6-25 AU

Research in particles and fields

The astrophysical aspects of cosmic rays and gamma rays and of the electromagnetic field environment of the Earth and other planets are investigated. These investigations are carried out by means of energetic particle and photon detector systems flown on spacecraft and balloons

Interstellar Electron Spectrum from the Galactic Non-Thermal Radio Emission

A range of interstellar electron spectra at energies between 100 MeV and 5 GeV has been derived from an analysis of the observed galactic non-thermal radio spectrum and from consideration of the existing uncertainties in the other relevant physical parameters of the galaxy. We find that for energies larger than ~ 300 MeV the electron spectrum is uncertain to a factor of 4 due to uncertainties in the galactic magnetic field strength and the total line-of-sight emission length. The uncertainty in the electron spectrum increases towards lower energies, exceeding a factor of 50 near 100 MeV, primarily due to uncertainties in the galactic parameters affecting interstellar radio absorption

Space Trajectory Error Analysis Program (STEAP) for halo orbit missions. Volume 2: Programmer's manual

The six month effort was responsible for the development, test, conversion, and documentation of computer software for the mission analysis of missions to halo orbits about libration points in the earth-sun system. The software consisting of two programs called NOMNAL and ERRAN is part of the Space Trajectories Error Analysis Programs. The program NOMNAL targets a transfer trajectory from earth on a given launch date to a specified halo orbit on a required arrival date. Either impulsive or finite thrust insertion maneuvers into halo orbit are permitted by the program. The transfer trajectory is consistent with a realistic launch profile input by the user. The second program ERRAN conducts error analyses of the targeted transfer trajectory. Measurements including range, doppler, star-planet angles, and apparent planet diameter are processed in a Kalman-Schmidt filter to determine the trajectory knowledge uncertainty

Relation of the Radial Gradient of Cosmic-Ray Protons to the Size of the Solar-Modulation Region

The radial intensity-gradient of cosmic-ray protons has been calculated for a range of values of the distance to the boundary of a spherically symmetric solar-modulation region. We find that the radial dependence of the gradients may be described in terms of two characteristic domains of the modulation region: (a) an "inner region" where the gradients are relatively small and constant, and (b), an "outer region"' where the gradients are large and show a strong radial dependence. The magnitude of the gradient in the inner region is small for reasonable values for the physical parameters of the modulation mechanism