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At least 1,387 records · Page 77
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NASA NTRS1972

A solar-wind model including proton thermal anisotropy.

A model of the solar wind is presented which divides the interplanetary space into two regions. It assumes that the solar wind is one-fluid in an 'inner region' of radius less than 0.4 A, and two-fluid and collisionless in an 'outer region' of radius greater than 0.4 A. The second and third moment equations of the Vlasov equation together with conservation equations are used to govern the solar wind flow in the outer region. The model produces solutions for all macroscopic quantities as well as for the microscopic proton distribution function, both as functions of heliocentric distances up to 50 A. Calculated results at 1 A include the solar wind velocity, electron temperature, proton temperature, proton thermal anisotropy and magnetic field magnitude. They are in good agreement with observations.

Whang, Y. C.↗
NASA NTRS1972

A quantitative investigation of the solar modulation of cosmic-ray protons and helium nuclei

The differential energy spectra of cosmic ray protons and He nuclei were measured at energies up to 315 MeV/nucleon using balloon-borne and satellite-borne instruments. These spectra are presented for solar quiet times for the years 1966 through 1970. The data analysis is verified by extensive accelerator calibrations of the detector systems and by calculations and measurements of the production of secondary protons in the atmosphere. The spectra of protons and He nuclei in this energy range are dominated by the solar modulation of the local interstellar spectra. Numerical solutions to the transport equation are presented for a wide range of parameters.

Garrard, T. L.↗
NASA NTRS1972

Shielding of manned space vehicles against protons and alpha particles

The available information on the shielding of manned space vehicles against protons and alpha particles is summarized. The emphasis is placed on shielding against Van Allen belt protons and against solar-flare protons and alpha particles, but information on shielding against galactic cosmic rays is also presented. The approximation methods for use by nonexperts in the space shielding field are those that are standard in the space shielding literature.

Alsmiller, R. G., Jr.↗
NASA NTRS1973

Approximations for neutron emission spectra from proton collisions between 20 and 500 MeV on nuclei of A greater than or equal to 12

When high energy protons from solar proton events or trapped radiation belts impinge on spacecraft structures, secondary particles are emitted. The most pernicious secondaries, from either a biological or physical standpoint, are the cascade and evaporation neutrons because of their reaction with matter leading to radioactive materials in the spacecraft structures. Empirically determined cascade and evaporation neutron emission spectra for protons of energy between 20 and 500 MeV incident on all materials at or above carbon in mass number are presented.

Burrell, M. O.↗
NASA NTRS1972

Remarks on the heating of solar-wind protons.

The heating of solar-wind protons cannot be explained by the thermalization of those protons arising from the ionization of neutral hydrogen atoms traveling in the general direction of the sun. By requiring the heating to satisfy the experimental results of the T sub p versus V sub sw correlation, an efficiency function of thermalization of these incoming protons is obtained, and a value of the 'hot component' of the hydrogen population is about 0.05 per cu cm near 1 AU. This hot component hydrogen density is too high compared to recent estimates by satellite experiments of Lyman alpha radiation and other experiments, and therefore the suggested solar-wind heating mechanism is unimportant in explaining the T sub p versus V sub sw correlation.

Chao, J.-K.↗
NASA NTRS1973

Low-energy cosmic ray protons from nuclear interactions of cosmic rays with the interstellar medium.

The intensity of low-energy (less than 100 MeV) protons from nuclear interactions of higher-energy (above 100 MeV) cosmic rays with the interstellar medium is calculated. The resultant intensity in the 10- to 100-MeV range is larger by a factor of 3-5 than the observed proton intensity near earth. The calculated intensity from nuclear interactions constitutes a lower limit on the actual proton intensity in interstellar space.

Wang, H. T.↗
NASA NTRS1973

Solar proton fluences as observed during 1966-1972 and as predicted for 1977-1983 space missions

The probability with which any given proton fluence level will be exceeded during a space mission is computed for missions to be flown during the active phase of the next solar cycle (1977-1983). This probability is a function of fluence level, proton energy threshold, and mission duration. Data on the major solar proton events of 1966-1972 are given; it is argued that only this data set (and not that of the previous solar cycle) is appropriate for estimating next-cycle fluences. Probable numbers of each of the two types of events are estimated from Burrell's extension of Poisson statistics. Fluences of all future anomalously large events are assumed to have a common spectrum, that given by the August 1972 event. Fluences of the ordinary events are assumed to obey a log normal distribution. It is shown that for much of the confidence-level mission-duration regime of interest, at least one anomalously large event will occur; and given such an occurrence, the ordinary-event contribution to mission fluence is negligible.

King, J. H.↗
NASA NTRS1973

LLL electron and proton spectrometer on NASA's Orbiting Geophysical Observatory 5

The LLL energetic electron and proton spectrometer on NASA's Orbiting Geophysical Observatory 5 (OGO-5) operated successfully from launch - March 4, 1968 - until retirement in August 1971. Data recovery during this time was about 95% of the orbit except for the last few months. The electron spectrometer used a magnetic field for electron momentum selection which served also as an electron broom for a proton range - energy telescope. The energy range was approximately 60 to 2950 keV for electrons (seven channels) and 0.10 to approximately 94 MeV for protons (seven channels). The experiment was scanned relative to the stabilized OGO-5 for obtaining directional information. Excellent data were taken throughout the magnetosphere and in the interplanetary region. Studies were carried out in the areas of equatorial pitch-angle distributions, substorm dynamics and field topology, particle spectra (time history), particle spatial distributions, and solar particle events.

West, H. I., Jr.↗
NASA NTRS1973

A lower limit to the altitude of coronal particle storage regions deduced from solar proton energy spectra

The spectrum of low energy protons observed at 1 AU following solar flares shows little or no evidence of energy degradation down to approximately 0.3 MeV. Such observations may be used to set a lower limit on the altitude of hypothetical coronal particle storage regions, ranging from 2 to 7 R sub s. It is pointed out that closed coronal magnetic loop structures are observed to extend to 2R sub s, so that long-term storage of low energy protons does not take place in the immediate vicinity of the sun. It is further suggested that in the few cases where the proton spectrum appears to be degraded at low energies, the energy loss may be due to adiabatic deceleration in the expanding solar wind. The alternative of continual acceleration is suggested as a plausible substitute for the particle storage hypothesis.

Krimigis, S. M.↗
NASA NTRS1974

The motion of a proton in the equatorial magnetosphere

A proton of low energy moving in the equatorial plane of the earth will experience drift motions due to both the magnetic field (magnetic gradient drift only, if the field is assumed to be that of a dipole) and the electric field. The electric drift again separates into two parts - the drift due to the main electric field (or convection electric field) existing in the frame of the earth, and that due to the earth's rotation. One result indicated by this work is that at distances of 4 - 6 earth radii, a transition from trapped proton orbits to open trajectories leading to the tail occurs at about 10 kev, the precise value depending upon local time. Such a transition also seems to be indicated by particle observations using Explorer 45. The energy spectrum (at magnetically quiet times) of equatorial protons above this energy can be explained by charge exchange but increased flux observed below it seems to be related to the influx of particles on open orbits from the tail.

Stern, D. P.↗
NASA NTRS1974

Flame detector operable in presence of proton radiation

A detector of ultraviolet radiation for operation in a space vehicle which orbits through high intensity radiation areas is described. Two identical ultraviolet sensor tubes are mounted within a shield which limits to acceptable levels the amount of proton radiation reaching the sensor tubes. The shield has an opening which permits ultraviolet radiation to reach one of the sensing tubes. The shield keeps ultraviolet radiation from reaching the other sensor tube, designated the reference tube. The circuitry of the detector subtracts the output of the reference tube from the output of the sensing tube, and any portion of the output of the sensing tube which is due to proton radiation is offset by the output of the reference tube. A delay circuit in the detector prevents false alarms by keeping statistical variations in the proton radiation sensed by the two sensor tubes from developing an output signal.

Walker, D. J.↗
NASA NTRS1973

Polarization of the light from the 3P(1)-2S(1) transition in proton beam excited helium

Measurements of the polarization of the light from the 3 1p-2 1s transition in proton beam excited Helium have shown both a proton beam energy and Helium target gas pressure dependence. Results for the linear polarization fraction range from +2.6% at 100 keV proton energy to -5.5% at 450 keV. The zero crossover occurs at approximately 225 keV. This is in good agreement with other experimental work in the field, but in poor agreement with theoretical predictions. Measurements at He target gas pressures as low as .01 mtorr show that the linear polarization fraction is still pressure dependent at .01 mtorr.

Weinhous, M. S.↗
NASA NTRS1973

Observation of 38-334-keV interplanetary protons during solar quiet times

The observations were from the particle experiment aboard the Apollo 16 subsatellite which was ejected April 24, 1972 into an approximately equatorial lunar orbit from the Apollo 16 lunar science module. The proton fluxes vary by a factor of about 5 over a six-month period. The proton measurements were made with a pair of surface barrier semiconductor telescopes. The accuracy of the proton flux measurements during times when electrons are present is highly dependent on the accuracy of the electronic channel matching.

Lin, R. P.↗
NASA NTRS1974

Production of organic molecules by proton irradiation

Preliminary experiments were carried out to investigate the effectiveness of proton irradiation for producing organic chromophores. The source of the 2 MeV protons used in the experiments was a model Van de Graaff accelerator. The gas cells used were hollow aluminum cylinders. The test results show that energetic protons can be an effective energy source for the formation of complex molecules from simple ones. With the exception of sulfide compounds none of the molecules that were identified are colored. However, coloring agents could be contained in unresolvable fractions.

Scattergood, T.↗
NASA NTRS1973

Solar flare proton spectrum averaged over the last 5000 years

The solar flare differential energy spectrum and integral proton flux above 10 MeV averaged over the last several thousand years are derived from thermoluminescence (TL) data. The dose-rate depth profile is obtained using a new TL equilibrium technique which is independent of the TL decay kinetics. The dose-rate depth profile produced by solar flare protons with a differential energy spectrum of the form dJ/dE = KE to the minus gamma power is calculated for arbitrary gamma. The best fit to the TL data in rock 14310 is obtained for gamma = 2.3 plus or minus 0.2 and an omnidirectional (4 pi) integral flux above 10 MeV of 40 to 80 prot/sq cm/sec. The TL half-life is determined to be 2000 yr. These results are compared to those for Na-22 (half-life of. 2.6 yr) and Al-26 (half-life of 740,000 yr) obtained by Wahlen et al. (1972) and Rancitelli et al. (1972), and it is concluded that the spectral shape and flux of protons in the interval from 25 to 100 MeV is the same within experimental errors when averaged over these three very different time periods.

Hoyt, H. P., Jr.↗
NASA NTRS1974

Instrumental and analytic techniques for separating protons from electrons in the cosmic ray flux

Techniques are being investigated to aid in distinguishing between electrons and the large background of interacting protons which simulate electron-induced electromagnetic cascades. For cosmic ray primaries, incident on the HECRE ionization spectrometer, statistical criteria are employed to test the cascade curves with the incident energy and starting point as free parameters. The physical significance of the distribution of apparent cascade starting points is being studied using Monte Carlo 100-GeV protons. The proposed use of a CsI detector module (totally-active and high Z) to further discriminate against protons is described.

Crannell, C. J.↗
NASA NTRS1974

The protons and electrons trapped in the Jovian dipole magnetic field region and their interaction with Io

Detailed analysis of electrons equal to or greater than 3 MeV and of protons 0.5 to 1.8 MeV and equal to or greater than 35 MeV for both the inbound and the outbound passes of the Pioneer 10 spacecraft. Conclusive evidence is obtained that the trapped radiation in Jupiter's inner magnetosphere is maintained and supplied by inward diffusion from the outer regions of the trapped radiation zone. It is shown that the time required for isotropization of an anisotropic flux by pitch angle scattering inside L approximately equal to 6 is long in comparison with the time required for particles to diffuse inward from L approximately equal to 6 to L approximately equal to 3, that the high-energy protons were not injected at high energies by the Crand (cosmic ray albedo neutron decay) process but were accelerated in the magnetosphere of Jupiter, and that the main conclusions of this analysis are unaffected by use of either the D sub 1 or the D sub 2 magnetic field models. Theoretical studies of the capture of trapped electrons and protons by Io have been carried out, and it is found that the probability of capture by Io depends strongly upon the particle species and kinetic energy.

Simpson, J. A.↗
NASA NTRS1974

Low-energy protons of solar origin and investigation of the interplanetary medium

Experimental data on low energy solar protons are presented. A phenomenological classification of the fluxes of these particles is suggested. Contemporary model conceptions of the propagation of low energy proton fluxes are examined, along with information that has been obtained on the properties of the interplanetary medium from study of solar proton fluxes.

Lutsenko, V. N.↗