Satellite observations of soft particle fluxes in the auroral zone
Electron and proton precipitation measurements in auroral zone by soft particle spectrometer in ISIS-1 satellite
Heikkila, W. J.↗
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Characteristics of sunward flowing proton and alpha particle fluxes of moderate intensity
The diffusive streaming of low-energy protons has been found to be predominately toward the sun during periods between prompt solar particle events. This occurs for essentially all solar wind velocities and proton intensities. The average radial component of this anisotropy (14%) and its dependence on the solar wind velocity agree with values found by a steady-state propagation model. The average radial component (16%) of the diffusive flow of low-energy alpha particles is similar to that observed for protons, suggesting a common origin. The sunward diffusion of alpha particles and protons indicates that these slightly enhanced fluxes contain a positive radial gradient. The direction of the diffusive anisotropy is a function of the magnetic field direction.
Marshall, F. E.↗
A detector for high frequency modulation in auroral particle fluxes
A high time resolution electron detector has been developed for use in sounding rocket studies of the aurora. The detector is used to look for particle bunching in the range 50 kHz-10 MHz. The design uses an electron multiplier and an onboard frequency spectrum analyzer. By using the onboard analyzer, the data can be transmitted back to ground on a single 93-kHz voltage-controlled oscillator. The detector covers the 50 kHz-10 MHz range six times per second and detects modulation on the order of a new percent of the total electron flux. Spectra are presented for a flight over an auroral arc.
Spiger, R. J.↗
An experiment to study energetic particle fluxes in and beyond the earth's outer magnetosphere
This experiment is designed to take advantage of the ISEE Mother/Daughter dual spacecraft system to study energetic particle phenomena in the earth's outer magnetosphere and beyond. Large geometric factor fixed voltage electrostatic analyzers and passively cooled semiconductor detector telescopes provide high time resolution coverage of the energy range from 1.5 to 300 keV for both ions and electrons. Essentially identical instrumentation is placed on the two spacecraft to separate temporal from spatial effects in the observed particle phenomena.
Anderson, K. A.↗
Particle flux decrease-increase events at synchronous orbit and the temporal sequence of aurora during substorms
A systematic temporal correlation has been found between the energetic particle intensity variations measured at 6.6 earth radii and the development of large scale auroral features. The intensification and equatorward drift of eastwest oriented stable discrete homogeneous auroral arc systems coincide with the decrease in energetic particle intensity at 6.6 earth radii as the nightside magnetosphere develops into a more tail-like configuration. The subsequent major breakup of the aurora coincides with the recovery in particle intensity as the field returns to a more dipolar configuration. Since this prominent decrease-increase sequence must be related to the intensification or inward convection of the tail current plasma sheet configuration followed by its diversion or dissipation, the auroral correlation documented here closely links the auroral particle precipitation to the plasma sheet and tail current dynamics.
Erickson, K. N.↗
Rocket-based measurement of particle fluxes and currents in an auroral arc.
The rocket with the experiment was fired from Fort Churchill, Canada, over a homogeneous arc at 2000 local time on Feb. 26, 1969. Detectors measured the pitch-angle distribution of the fluxes of electrons with energies in the range from 2 to 18 and energies above 50 keV, and of protons with energies in the range from 2 to 18 and in the range from 80 to 1000 keV. The total backscattered flux was about 20% of the downward flux in the same energy range. No protons in the range from 2 to 18 keV, or any higher energy particles, were found in significant quantities. It was found that the energetic auroral electrons carry a substantial part of the Birkeland current. The arc extended at least 1500 km in an east-west direction and was not associated with substorm activity.
Vondrak, R. R.↗
Calculated limits for particle fluxes in Jupiter's Van Allen belts
Electron and proton fluxes in Jupiter's radiation belts are calculated, along with the envelopes of dose rates. The following assumptions are made: the particles in the Jupiter belts are influenced only by the magnetic field of the planet; the particles act correspondingly to the particles in the Earth's belts and the Earth's belts can be used as a model; the magnetic field of Jupiter is essentially a dipole; the radiation of a decimetric nature received from Jupiter is synchrotron radiation due to the electrons, and to a first approximation it is emitted isotropically; and the strength of the emission in the decimetric wavelength range gives an upper bound considering how strong the field can be and how many electrons there are. The point dose rates for tissue and 0.1 gram/cm aluminum shielding at about 3 Jupiter radii are 10000 rads/hr for electrons and 1000 rads/hr for protons.
Haffner, J.↗
Long-term particle flux variability indicated by comparison of Interplanetary Dust Experiment (IDE) timed impacts for LDEF's first year in orbit with impact data for the entire 5.75-year orbital lifetime
The electronic sensors of the Interplanetary Dust Experiment (IDE) recorded precise impact times and approximate directions for submicron to approximately 100-micron size particles on all six primary sides of the spacecraft for the first 346 days of the Long Duration Exposure Facility (LDEF) orbital mission. Previously-reported analyses of the timed impact data have established their spatio-temporal features, including the demonstration that a preponderance of the particles in this regime are orbital debris and that a large fraction of the debris particles are encountered as megameter-size clouds, some of which persist for long times. Short-term fluxes within such clouds can rise several orders of magnitude above the long-term average. These finding are consistent with the results of the first catastrophic hypervelocity laboratory impacts on a real satellite, recently reported in the press. Analysis continues on the geometric and evolutionary characteristics of these clouds, as well as on the isolation and characterization of the natural micrometeoroid component in the IDE data, but the unexpectedly large short-term variations in debris flux raises the question of how representative an indication of the multi-year average flux is given by the nearly one year of timed data. It has, therefore, always been one of the goals of IDE to conduct an optical survey of the craters on the IDE detectors, to obtain full-mission fluxes for comparisons with the timed data. This work is underway, and the results presently in hand are significant. Optical scanning of the ram and wake (East and West) panels is complete, and it is clear that the first year was in some respects not representative of the subsequent years. The 5.75-year average flux on East panel was 90 percent of the value predicted by the average flux recorded during the first year, while it was only 34 percent on West panel. This suggests that western hemisphere spacecraft launches are a major contributor to the long-term flux and that their contribution is primarily in the smaller end of the size distribution. This conclusion follows from the fact that a closely-spaced series of launch failures (Titan, Delta, Ariane, and Challenger) caused a virtual hiatus in launch activity during a large part of the later years of the LDEF mission. We hope to provide a quantification of the particle size distribution function in this case.
Mulholland, J. Derral↗
Initial signatures of magnetic field and energetic particle fluxes at tail reconfiguration - Explosive growth phase
The initial signatures of tail field reconfiguration observed in the near-earth magnetotail are examined using data obtained by the AMPTE/CCE magnetometer and the Medium Energy Particle Analyzer. It is found that the tail reconfiguration events could be classified as belonging to two types, Type I and Type II. In Type I events, a current disruption is immersed in a hot plasma region expanding from inward (earthward/equatorward) of the spacecraft; consequently, the spacecraft is immersed in a hot plasma region expanding from inward. The Type II reconfiguration event is characterized by a distinctive interval (explosive growth phase) just prior to the local commencement of tail phase.
Ohtani, S.↗
Energetic solar particle fluxes out to 3 AU during the 7 May 1978 flare event
Simultaneous solar proton flux measurements on IMP 7 and by the world wide neutron monitor network during the May 7, 1978 flare event led to conclusions that in the energy range from 50 MeV to 10 GeV: (1) the propagation of the flare particles in the interplanetary magnetic field (IMF) between the Sun and the Earth was nearly scatter free; and (2) therefore, the intensity time (IT) profiles of the solar proton fluxes observed at Earth for about one hour after onset represent the solar injection profiles even to energies as low as 50 MeV. Observations of the IMF at Helios A indicate that the IMF was undisturbed between the Sun and Helios A at the time of the May 7, 1978 flare event; and, therefore, the solar particle propagation was also scatter free from the Sun to Helios A.
Lockwood, J. A.↗
Measurement of geomagnetic cutoff rigidities and particle fluxes below geomagnetic cutoff near Palestine, Texas.
We report a high-statistics magnetic spectrometer measurement of the geomagnetic cutoff rigidity and related effects at Palestine, Texas. The effective cutoffs we observe are in agreement with computer-calculated cutoffs. We also report measured spectra of albedo and atmospheric secondary particles that come below geomagnetic cutoff.
Pennypacker, C. R.↗
Cosmogenic neon from individual grains of CM meteorites - Extremely long pre-compaction exposure histories or an enhanced early particle flux
This paper presents the results on cosmogenic Ne extracted from individual meteoritic grains by a laser extraction system which used, at different times, two CW lasers: an Ar-ion laser and an Nd:YAG laser, with 20 and 70 W of deliverable power, respectively. Chemical etching was used to select grains exposed to solar flare VH particles. Results show that most of the grains with solar flare VH tracks (but not those which did not exhibit such tracks) contain spallation-produed Ne in significant excess of that due to the nominal cosmic-ray exposure, providing evidence for extensive energetic particle exposure during the precompaction era.
Hohenberg, Charles M.↗
A program of data synthesis from the ALSEP/CPLEE ALSEP/SIDE, and Explorer 35 magnetometer to investigate lunar terminator and nightside particle fluxes and surface interactions
Lunar nightside electron fluxes were studied with the aid of the ALSEP/CPLEE and other instruments. The flux events were shown to be due to (a) electrons propagating upstream from the earth's bow shock, (b) electrons thermalized and scattered to the lunar surface by disturbances along the boundary of the lunar solarwind cavity, and (c) solar wind electrons scattered to the lunar surface by lunar limb shocks and/or compressional disturbances. These electrons were identified as a cause of the high night surface negative potentials observed in tha ALSEP/SIDE ion data. A study was also made of the shadowing of magnetotail plasma sheet electrons by interactions between the lunar body and the ambient magnetic field and by interactions between charged particles and lunar remnant magnetic fields. These shadowing effects were shown to modify lunar surface and near-lunar potential distributions.
Reasoner, D. L.↗
Interplanetary dust-particle flux measurements between 1.0 and 1.56 a.u. from Mariner 4 cosmic-dust experiment
Interplanetary dust flux and mass distributions obtained from Mariner IV flight
INTERPLANETARY DUST↗
Low energy particle fluxes in the geomagnetic tail
Low energy electron and proton fluxes in geomagnetic tail of equatorial magnetosphere forming plasma sheet related to auroral oval
Vasyliunas, V. M.↗
Analysis of auroral particle fluxes
The physical processes which describe the interaction of auroral electrons with the atmosphere appear to be more complex than just the Coulomb scattering of the incident primary electrons with a subsequent loss of energy. The comparison of the measured backscattered electron spectra with spectra predicted using a theoretical scattering calculation has led to a discrepancy for energies below about 1 to 2 keV. It was found that the very high ratio (100%) of backscattered to incident fluxes for these energies could be most reasonably explained by a parallel downward-directed electric field which prevents these lower energy electrons from entering the atmospheric scattering region. This parallel field with potential drop of about 1 keV is thought to have its origin in waveparticle interactions in the turbulent auroral ionosphere.
Chappell, C. R.↗
Energetic particle flux experiment (IMP-F and G)
The technical aspects of the University of California IMP-F experiment aboard the Explorer-34 and the University of California IMP-G (S1) and (S2) experiments aboard the Explorer-41. The experiment detectors and electronics are discussed for each experiment as well as the fabrication, preflight and post-flight history. A description of the ground support equipment is also given for each experiment. These three experiments were essentially all different. The IMP-G experiment was essentially the IMP-F experiment with the addition of four Geiger-Mueller detectors. The IMP-G (S-2) was a supplementary experiment and differed completely from the IMP-F and IMP-G experiments. It was concluded that the ground support equipment approach used for the IMP-F and IMP-G experiments where emphasis was placed on a thorough exercise and monitoring of the experiment operation during various testing phases provided a high degree of confidence and reliability in these experiments. No known electronic failures have occurred during the spacecraft lifetime although some detector problems were experienced.
Anderson, K. A.↗
Analysis of auroral particle fluxes
The study is reported of electron and proton precipitation in different auroral forms from data obtained by the TWINS 1 and 2. The measurement of the energy spectra and pitch angle distributions of auroral electrons is discussed along with the auroral electron code for predicting the scattering and energy loss of electrons covering the complete auroral energy spectrum.
Chappell, C. R.↗