SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The flux of secondary protons below 100 MeV in interstellar space is calculated using detailed cross sections and kinematics for proton-proton, and proton-alpha particle interactions.
A comprehensive study of the temporal behavior of trapped protons, alpha particles and ions (Z 2) in outer zone of the earth's magnetosphere has been made. These observations were made by the Injun V satellite during the first 21 months of operation, August 1968 to May 1970. Rapid increases in the observed number of particles followed by slower exponential decay characterize the data. Comparisons are made with the temporal behavior of interplanetary particles of the same energy observed by Explorer 35. Increases in the trapped fluxes generally correspond to enhanced interplanetary activity. The energy spectra of protons and alpha particles at L = 3 have similar shapes when compared on an energy per charge basis while the respective polar cap spectra have similar shape on an energy per nucleon basis. Apparent inward trans-L motion of energetic protons is observed. These particles are diffused inward by a process involving fluctuating electric fields. The loss of trapped low altitude protons, alpha particles and ions (Z 2) is controlled by coulombic energy loss in the atmosphere.
Energetic protons injected into interplanetary space in solar particle events can interfere with spacecraft operations and experiments and can cause permanent degradation of some components. For future long term interplanetary and planetary missions, techniques were developed which use solar particle event data from 1956 through 1970 to predict the probability of exceeding any value of peak proton intensity or mission proton fluence. Dependences on proton energy (near 10 to 100 MeV), heliocentric distance, and phase of the solar cycle are included. The techniques are described and applied to the Mariner Jupiter/Saturn 1977 mission.
Determination of the mean interaction lengths for 9.3-, 13.8-, and 17.8-GeV protons and 9.3- and 17.8-GeV positive pions in iron. The mean interaction length of pions is found to be approximately 20% greater than that of protons. No statistically significant variation of the mean interaction length for protons or pions as a function of energy is observed. With only two exceptions, the data obtained show a systematic 5% difference between measurements of the mean interaction length made with cosmic rays and those made with accelerator-produced protons.
Energetic solar proton observations in the interplanetary medium by Explorer 33 and Explorer 35 and over the polar caps by Injun 5 during the period from September 1968 through March 1970 have been examined in detail. The solar proton intensities observed over the polar regions were compared with the interplanetary intensities on an absolute basis. The high polar latitude (HPL) proton intensities tracked the magnetic field aligned interplanetary intensities well (solar-antisolar intensities as determined from the sectored Explorer data). The tracking was in agreement with the open magnetosphere model about 90% of the time - i.e., the intensities observed on the HPL magnetic lines of force, which would be connected to magnetic lines of force from the sun in an interconnected geomagnetic and interplanetary magnetic field, were in agreement with the maximum intensity of the interplanetary proton pitch angle distribution. The intensities observed at the HPL region of the opposite polar cap were in agreement with the minimum intensity of the interplanetary pitch angle distribution. The low polar latitude intensities generally tracked the maximum interplanetary intensity very well.
Discussion of the energy spectra and pitch angle distributions of ring current protons observed with the solid-state proton detector of Explorer 45 during the main and fast recovery phases of a storm on Dec. 17, 1971. Appearances of characteristic changes in the pitch angle distributions of roughly 100-eV protons are interpreted as pitch angle dispersion of rapidly injected protons during their azimuthal drift at L values above 5.
Energetic particle observations from ATS-5 are presented that directly show asymmetric injection of 30- to 300-keV proton fluxes into the nightside magnetosphere to form the asymmetric ring current. The temporal structure of these substorm-correlated proton bursts is consistent with a westward gradient drift from the nightside acceleration region. The drifting protons tend to be accompanied by nondiamagnetic decreases of the magnetic field at the satellite. Adiabatic decreases of the energetic electron fluxes often occur with these changes in the field strength. Nearly 200 proton-only events have been observed, occurring uniformly between 1500 and 2200 LT and not at all before 1200 LT or after 2300 LT.
Protons of 30 to 100 keV are found upstream from the bow shock whenever interplanetary magnetic fields connect the spacecraft and bow shock. The protons do not appear upstream of a boundary determined by the solar wind speed (the speed at which the interplanetary field is being convected) and an effective upstreaming velocity of 2.5 to 3 times the solar wind speed along the field lines. It is believed that (1) the lower-energy (3-4 keV) protons accelerated and reflected by the bow shock and (2) the Alfven waves observed upstream are in some way responsible for the origin of the 30- to 100-keV protons in very large regions upstream from the bow shock.
Investigations were carried out with the space stations of the Proton series to study the physics of cosmic rays. The SEZ-13 device for the search of particles with a fractional electrical charge and the SEZ-11 device for the measurement of high energy electrons were mounted on the Proton-3 satellite. The mode of action of the SEZ-11 device differed from that of the SEZ-12 device used in the Proton-1 and Proton-2 satellites for similar purposes. Some of the results that were obtained are presented.
Interplanetary plasma data taken near 1 AU by a variety of spacecraft (Imp 1, Vela 2-4, Explorer 33-35, and Heos 1) from 1963 to 1971 are used to study the long-term variations of the solar wind proton properties. An intercalibration among the different experiments is performed in order to obtain a coherent set of data. The most interesting result is a 40% reduction of the proton density between the minimum and the maximum of the solar activity cycle. The observed density variation occurs throughout the velocity range; however, a limited sample of data could suggest that at very low velocities (below 300 km/sec) the density is independent of the solar activity. The proton bulk velocity is remarkably constant during the period considered; small increases of the average speed occurring in 1968 and 1971 cannot be attributed to the solar cycle. No clear trend is exhibited by the proton temperature; differences among the various experiments probably have an instrumental origin.
Auroral and polar cap emissions in a model Jovian atmosphere are determined for proton precipitation. The incident protons, which are characterized by representative spectra, are degraded in energy by applying the continuous slowing down approximation. All secondary and higher generation electrons are assumed to be absorbed locally and their contributions to the total emissions are included. Volume emission rates are calculated from the total direct excitation rates with corrections for cascading applied. Results show that most molecular hydrogen and helium emissions for polar cap precipitation are below the ambient dayglow values. Charge capture by precipitating protons is an important source of Lyman alpha and Balmer alpha emissions and offers a key to the detection of large fluxes of low energy protons.
The effectiveness of low-keV range protons in producing Na line emission from selected sodium-bearing rock and mineral samples is examined. Laboratory experiments show that substantial Na-D line emission is produced by 3- to 5-keV proton bombardment of silicate and halite rock powders. It is found that emission intensity and energy efficiency are directly proportional to sodium content and are dependent on total dose, dose rate, and proton energy. Na-D photon emission is considered to emanate predominantly from sputtered sodium slightly above the target surfaces. It is concluded that the Na-D line emission directly excited during surface sputtering by Jovian magnetospheric protons appears to be an observable component in the Jovian satellite Io emission.
The topology of the boundaries of penetration (or, inversely, the boundaries of the forbidden regions) of 90-deg pitch-angle equatorial protons with energies less than 100 keV are explored for an equatorial convection E-field which is directed in general from dawn to dusk. Due to the dependence of drift path on energy (or magnetic moment), complex structural features are expected in the proton energy spectra detected by satellites since the penetration distance of a proton is not a monotonically increasing or decreasing function of energy. During a storm when the convection E is enhanced, model calculations predict elongations of the forbidden regions analogous to tail extensions of the plasmasphere. Following a reduction in the convection field, spiral-structured forbidden regions can occur. Structural features inherent to large-scale convection field changes may be seen in the nose-like proton spectrograms observed near dusk by instrumentation on Explorer 45. These nose events are modelled by using an electric field model developed originally by Volland (1973). The strength of the field is related to the Kp index through night-time equatorial plasmapause measurements.
A statistical study of the relative abundance of proton to alpha particles at equal energy per nucleon has been carried out on the basis of some hundred solar particle events in the energy range 6-20 MeV/nuc. A small qualitative effect of the coronal propagation has been found for events associated with solar flares away from the observer 'preferred connection region' (20-80 deg W from the central meridian). The variation of the relative abundance of the proton to alpha particle at ejection is analyzed using events for which the coronal transport is minimum. It is found that micro events characterized by small proton intensity, little or no scattering in interplanetary medium and little or no trapping in the corona has an abundance of He-4 of 5-30% relative to proton. Those events frequently display a very high He-3 abundance from 30 to 150% relatively to He-4. For larger particle events, the alpha abundance decreases following a relation which is not valid for flare-associated events that accelerate particles to relativistic energies.
The Energetic Particles Experiment on IMP-7 measures the angular distribution of 50-200 keV solar protons in 16 sectors. The velocity of 50 keV protons may be less than 5 times that of the solar wind. A generalized nonlinear Compton-Getting point transformation into the co-moving frame that contains no assumptions as to the angular distribution of either the spectrum or intensity is presented. Nearly 50 keV proton data in the spacecraft frame exhibit an anisotropy ratio that is large (not less than 5) and radial throughout the October 29, 1972 event lasting more than 9 days at this energy. This anisotropy argues against impulsive injection and diffusive decay in the inner solar system. Application of the transformation to the data reveals a long lasting residual anisotropy in the co-moving frame with protons streaming from the sun. Differences between the co-moving frame and solar wind frame velocities suggest residual electric fields upstream from the bow shock.
Nuclear magnetic resonance (NMR) and relaxation studies of the proton spin-lattice relaxation time (PSLRT) and proton second moment (PSM) are reported. Tetramethylammonium cadmium chloride (TMCC) was selected as a diamagnetic member of the isomorphic series, and hence proton data relate directly to the motion of the tetramethylammonium ion in the absence of paramagnetic ions. In the model adopted, the correlation time for hindered motion of one of the methyl groups differs from that of the other three groups in the low-temperature phase below 104 K. PSLRT and PSM values agree closely with experimental data with this model. Crystallographic phase transitions in TMCC occur at 104 K and 119 K according to the PSLRT measurements. Dipolar interactions between adjacent protons account for the PSLR rates below 104 K.
The rate constants for proton transfer from H3(+) ions to N2, O2, and CO have been measured as function of hydrogen-buffer-gas partial pressure. The rate constant for proton transfer from H3(+) to N2 shows a very large pressure dependence, increasing from 1.0 by 10 to the -9th power cu cm/s at low H2 partial pressures to 1.7 by 10 to the -9th power cu cm/s at high H2 partial pressures. The rate constants for proton transfer from H3(+) to O2 and CO are constant with partial pressure of H2. The roles of excess vibrational energy in H3(+) ions and of equilibrium between forward and back reactions are discussed. Back reaction is observed only for the reaction of H3(+) ions with O2, and an equilibrium constant of 2.0 (plus or minus 0.4) at 298 K has been determined. From these data, the proton affinity of O2 is deduced to be 0.47 (plus or minus 0.11) kcal/mole higher than that of H2.
Using the Mariner 5 solar wind plasma and magnetic field data, we present observations of field-aligned suprathermal proton velocity distributions having pronounced high-energy shoulders. These observations, similar to the interpenetrating stream observations of Feldman et al. (1974), are clear evidence that such proton distributions are interplanetary rather than bow shock associated phenomena. Large Alfven speed is found to be a requirement for the occurrence of suprathermal proton distribution; further, we find the proportion of particles in the shoulder to be limited by the magnitude of the Alfven speed. It is suggested that this last result could indicate that the proton thermal anisotropy is limited at times by wave-particle interactions