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An improved re-entrant cosmic-ray albedo calculation.
Reentrant cosmic ray albedo intensity, considering nuclear interaction and trajectory spiraling effects
Latitude and altitude dependence of the cosmic ray albedo neutron flux
Cosmic ray albedo neutron flux latitude and altitude dependence, using OGO-6 polar orbiting satellite
An improved reentrant cosmic ray albedo calculation
Nuclear interaction and trajectory spiral effects in reentrant cosmic ray albedo calculations
Detecting Low-Contrast Features in the Cosmic Ray Albedo Proton Map of the Moon
High energy cosmic rays constantly bombard the lunar regolith, producing (via nuclear evaporation) secondary 'albedo' or 'splash' particles like protons and neutrons, some of which escape back to space. Lunar Prospector and the Lunar Reconnaissance Orbiter (LRO), have shown that the energy distribution of albedo neutrons is modulated by the elemental composition of the lunar regolith, and by ice deposits in permanently shadowed polar craters. Here we investigate an analogous phenomenon with high energy ((is) approximately 100 MeV) lunar albedo protons.
Cosmic ray albedo gamma rays from the quiet sun
We estimate the flux of gamma-rays that result from collisions of high energy galactic cosmic rays with the solar atmosphere. An important aspect of our model is the propagation of cosmic rays through the magnetic fields of the inner solar systems. We use diffusion to model propagation down to the bottom of the corona. Below the corona we trace particle orbits through the photospheric fields to determine the location of cosmic ray interactions in the solar atmosphere and evolve the resultant cascades. For our nominal choice of parameters, we predict an integrated flux of gamma rays (at 1 AU) of F(E(sub gamma) greater than 100 MeV) approximately = 5 x 10(exp -8)/sq cm sec. This can be an order of magnitude above the galactic background and should be observable by the Energetic Gamma Ray experiment telescope (EGRET).
Nuclear cascades in Saturn's rings - Cosmic ray albedo neutron decay and origins of trapped protons in the inner magnetosphere
The nearly equatorial trajectory of the Pioneer 11 spacecraft through Saturn's high energy proton radiation belts and under the main A-B-C rings provided a unique opportunity to study the radial dependence of the greater than 30 MeV proton intensities in the belts in terms of models for secondary nucleon production by cosmic ray interactions in the rings, in situ proton injection in the radiation belts by neutron beta decay, magnetospheric diffusion, and absorption by planetary rings and satellites. Maximum trapped proton intensities measured by Pioneer 11 in the radiation belts are compared with calculated intensities and found consistent with trapping times of roughly 40 years and a radial diffusion coefficient of about 10 to the -15th L to the 9th R sub s squared/s. Differential energy spectra proportional to E to the -2 estimated from integral measurements of trapped photons with E greater than 100 MeV are consistent with the beta decay model, but an inferred turndown of the spectra toward lower energies and reported integral proton anisotropies of a specified form both indicate the need for more realistic calculations of the neutron source from the rings and the radiation belt loss processes.
Measurement of the Charged Splash and Re-entrant Albedo of the Cosmic Radiation
Proton and electron balloon measurements of splash and re-entrant cosmic ray albedo
HIGH-ENERGY ELECTRONS IN THE RADIATION BELT
High-energy electrons in the outer radiation belt produced by the cosmic-ray albedo neutron decay
Cosmic-ray neutron albedo dose in low-earth orbits
An earth albedo neutron environmental model is proposed which provides a way to estimate neutron exposure in low-earth orbit. It is shown that, in the predominantly low inclination orbits (i=28.5 deg) used in the U.S. space program, the neutron exposures are relatively low (0.7 cSv/y). The neutron exposures are more significant for polar orbital missions and even high inclination missions, such as Skylab (i=57 deg).
The edge of the polar plateau for galactic cosmic rays and their charged albedo
Edge of polar plateau for galactic cosmic rays and their charged albedo
Innermost Van Allen Radiation Belt for High Energy Protons at Saturn
The high energy proton radiation belts of Saturn are energetically dominated by the source from cosmic ray albedo neutron decay (CRAND), trapping of protons from beta decay of neutrons emitted from galactic cosmic ray nuclear interactions with the main rings. These belts were originally discovered in wide gaps between the A-ring, Janus/Epimetheus, Mimas, and Enceladus. The narrow F and G rings significant affected the CRAND protons but did not produce total depletion. Voyager 2 measurements subsequently revealed an outermost CRAND proton belt beyond Enceladus. Although the source rate is small, the trapping times limited by radial magnetospheric diffusion are very long, about ten years at peak measured flux inwards of the G ring, so large fluxes can accumulate unless otherwise limited in the trapping region by neutral gas, dust, and ring body interactions. One proposed final extension of the Cassini Orbiter mission would place perikrone in a 3000-km gap between the inner D ring and the upper atmosphere of Saturn. Experience with CRAND in the Earth's inner Van Allen proton belt suggests that a similar innermost belt might be found in this comparably wide region at Saturn. Radial dependence of magnetospheric diffusion, proximity to the ring neutron source, and northward magnetic offset of Saturn's magnetic equator from the ring plane could potentially produce peak fluxes several orders of magnitude higher than previously measured outside the main rings. Even brief passes through such an intense environment of highly penetrating protons would be a significant concern for spacecraft operations and science observations. Actual fluxes are limited by losses in Saturn's exospheric gas and in a dust environment likely comparable to that of the known CRAND proton belts. The first numerical model of this unexplored radiation belt is presented to determine limits on peak magnitude and radial profile of the proton flux distribution.
The flux and source of energetic protons in Saturn's inner magnetosphere
The flux of energetic protons in Saturn's inner magnetosphere was observed in two channels from 48 to 63 and 63 to 160 MeV. Absorption features due to the G ring and the satellites Enceladus and Mimas were easily identifiable. The flux observed in the absorption slot of Mimas can be maintained by the decay of a cosmic ray albedo neutron flux of 0.007/sq cm/s/sr. This flux is entirely consistent with calculations of the neutron flux produced by galactic cosmic ray interactions with the rings of Saturn. The omnidirectional proton flux of 0.0082/sq cm/s at 2.734 R sub s requires a residence time of 30 years. Both the residence time and the energy spectrum are comparable to those found in the inner radiation belt of the Earth. The angular distribution is nearly isotropic in the Mimas slot and beyond 4R sub s. Otherwise the pitch angle distribution is pancake and is approximated by sin(n)theta with n in the range 2 to 7. This distribution is consistent with an isotropic neutron source in the ring plane.
The flux and source of energetic protons in Saturn's inner magnetosphere
The flux of energetic protons in Saturn's inner magnetosphere was observed in two channels from 48 to 63 and 63 to 160 MeV. Absorption features due to the G ring and the satellites Enceladus and Mimas were easily identifiable. The flux observed in the absorption slot of Mimas can be maintained by the decay of a cosmic ray albedo neutron flux of 0.007/sq cm/s/sr. This flux is entirely consistent with calculations of the neutron flux produced by galactic cosmic ray interactions with the rings of Saturn. The omnidirectional proton flux of 0.0082/sq cm/s at 2.734 R sub s requires a residence time of 30 years. Both the residence time and the energy spectrum are comparable to those found in the inner radiation belt of the Earth. The angular distribution is nearly isotropic in the Mimas slot and beyond 4R sub s. Otherwise the pitch angle distribution is pancake and is approximated by sin(n)theta with n in the range 2 to 7. This distribution is consistent with an isotropic neutron source in the ring plane. Previously announced in STAR as N83-22084
Calculation of neutron-decay-proton trapping in the Jovian magnetosphere
Investigations on the possible proton fluxes resulting from cosmic ray albedo neutron decay (CRAND) are summarized. It is recalled that experimental data on the earth's belts are reasonably consistent with a CRAND source for most of the protons with energies 50 MeV in the heart of the inner belt. It is assumed that the CRAND and cosmic ray flux and spectrum for Jupiter are the same as for the Earth, with the significant difference that considerably higher energy particles are needed to reach the Jupiter atmosphere at the same magnetic latitude. The ratio of the CRAND source averaged over an L shell on Jupiter to that on Earth at L = 1.3 is derived from a geometrical calculation. The ratio of average loss rate on Jupiter to that for the Earth is also discussed. The flux around Jupiter is obtained by scaling according to the ratio of source to loss from the flux observed in the Earth's inner belt.
Evaluation of the CRAND source for 10- to 50-Mev trapped protons.
Cosmic ray albedo neutron decay /CRAND/ source for trapped protons, showing disagreement with intensities in inner zone measured on OV1 2 spacecraft
Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays
Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra were calculated using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron-leakage spectrum at the particular latitude considered support the theory that the cosmic-ray-albedo-neutron-decay mechanism is the source of the protons and electrons trapped in the Van Allen belts.
Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays.
Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra in the energy range from about 10 to the minus 8th to about 100,000 MeV at various depths in the atmosphere were calculated by using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron leakage spectrum at the particular latitude considered support the theory that the cosmic ray albedo neutron decay (Crand) mechanism is the source of the protons trapped in the inner radiation belt.