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The importance of some of the features observed among the nighttime equatorial data of Explorer 31 is discussed with respect to the nighttime thermal structure of the topside ionosphere. The very short-lived photoelectrons being absent, the nighttime measurements represent the background flux due to magnetospheric particles.
Description of a model developed to predict the interactions between multiple electrostatic probes separated by distances that are shorter than or comparable to the characteristic plasma shielding length. The computation involves crude approximations accounting for space charge effects, currents due to the emission and exchange of photoelectrons, and currents from the ambient plasma. Floating potentials are calculated by requiring current balance for each probe and solving by iterating the resulting coupled nonlinear equations. Although only qualitative accuracy is claimed, predictions using the model are found to be in good agreement with observations from the Explorer 45 satellite. The Explorer 45 satellite measures the potential difference between a pair of symmetrical spherical floating probes. The Explorer 45 data show that with increasing altitude, first, the sunward sphere will typically assume a more negative potential than the antisunward sphere; second, the polarities of the probes in the region L = 2 to 4 may switch, sometimes several times; and, finally, near the plasmapause the detector output may saturate, the sunward sphere being more negative.
An RAE-I satellite description is given, taking into account a dynamics experiment and the attitude sensing system. A computer program for analyzing flexible spacecraft attitude motions is considered, giving attention to the geometry of rod deformation. The characteristics of observed attitude data are discussed along with an analysis of the main boom root angle, the bending rigidity, and the damper plane angle.
The concept of a neutral point depends on the physical phenomena described. The regions with B less than about 1 gamma detected by Schindler and Ness may be interpreted as neutral regions for the ion-tearing process. The assumption of the presence of a multiple neutral point structure (with temporal variations) is still the most promising interpretation of the Explorer 34 data. Alternatives suggested by Russell lead to difficulties. Nevertheless, the final answer can come only from multiple satellite systems. A 1-day displacement of the day count in the data discussed by Schindler and Ness is corrected.
Explorer 43 data were used to study 34 bow shock crossings observed from 5 to 16 earth radii upstream of the average bow shock location. Waves with periods of 6 to 130 s having amplitudes up to delta-B/B = 1 were detected. Wave polarization for the low-frequency waves is right-handed in relation to the average field direction when the observer moves from the upstream to downstream direction but is left-handed when the observer moves in the opposite sense. This fact identified the waves as standing whistler waves in the coordinate system of the shock. The waves are in agreement with collisionless low Mach number laminar shock theory. When the measured parameters were used to calculate theoretical wavelengths, the observed wave frequencies could be used to calculate velocities for the shock-wave coordinate system past the spacecraft; such velocities are mostly between 10 and 30 km/s. It is suggested that the higher-frequency propagating whistler waves may evolve from the standing whistler waves through a decay instability.
Electron data from Explorer 47 show a number of quiet-time enhancements in the intensity of interplanetary electrons over the energy range 0.22-2.5 MeV, lasting from 3 to 20 days both in the interplanetary medium and inside the magnetotail. The observed enhancements differ from those associated with solar electron events or magnetospheric bursts in their energy-time profiles and energy spectra, and in the presence of possible intensity fluctuations suggesting a periodicity. The energy spectra are not unlike those obtained in the vicinity of Jupiter by Pioneer 10. These observations, together with the fact that enhancements occurred during times when the earth could be magnetically connected to the magnetosphere of Jupiter, lead to the suggestion that the observed electrons may be of Jovian origin.
Considerations made in developing a model of pulsars are explored. Observational data seems to support the argument that pulsar magnetospheres may contain large masses of plasma. The cascade process resulting from pair creation enables one to interpret the X-ray emission from the Crab and Vela pulsars as synchrotron radiation. On the other hand, the optical radiation from the Crab pulsar is best understood as coherent curvature radiation. Radio emission is interpreted as curvature radiation produced by charge bunches moving along magnetic-field lines. Certain tests of this model are proposed.
The author has identified the following significant results. Analysis of local areas by point-to-point registration was achieved.
From both theoretical and experimental bases, the transmission of Alfven waves through the bow shock is investigated. The theory of Alfven wave transmission through fast MHD shocks is extended to all cases of incident wave vectors. Particular consideration is given to Alfven waves propagating parallel to the ambient magnetic field with field perturbations polarized in the plane formed by the ambient magnetic field and the shock normal. An analysis is also made of magnetic field and plasma data from Explorer-35 in the vicinity of the bow shock. It is suggested that hydromagnetic waves are present in all of the 14 shock crossings studied, and that in upstream regions of at least 6 crossings, predominantly Alfvenic fluctuations exist. Average amplitudes of these fluctuations are measured on either side of the shock and the enhancement is measured by comparing their levels. Theoretical and experimental findings are compared and the apparent discrepancy in amplification factors may be explained by the strong damping of any transmitted magnetoacoustic modes downstream with relatively little damping of any transmitted Alfven waves.
The Atmosphere Explorer (AE) data are reexamined in the light of new laboratory measurements of the N2(+) recombination rate coefficient alpha. The new measurements support earlier measurements which yielded values of alpha significantly lower than the AE values. It is found that the values for alpha determined from the satellite data can be reconciled with the laboratory measurements, if the charge exchange rate coefficient for O(+)(2D) with N2 is less than one-quarter of that derived in the laboratory by Rutherford and Vroom (1971).
There are no author-identified significant results in this report.
There are no author-identified significant results in this report.
Reactions involving metastable ions are difficult to study in the laboratory. Much new information on these reactions has been derived from satellite measurements of aeronomic parameters. In this paper, Atmosphere Explorer D data are used to study charge exchange of metastable O(+)(2D) ions with O2. Using direct measurements of the O2 at 200 km to compute O2 densities at 300 km and supporting ionic concentrations and temperature observations, we find the rate coefficient for this reaction to be 1 + or - 0.6 times 10 to the minus 9th cu cm/sec. The process constitutes a significant source of O2(+) ions in the F2 layer at times when the N2 and O2 densities are enhanced. This finding leads to the conclusion that charge exchange with O2 must be a major sink for O(+)(2D) and an important source of O2(+) ions in the E region, because of the increase in the O2 concentration/N2 concentration ratio with decreasing altitude. The results imply that 80% of all O(+) ions formed in the E region are converted to O2(+) and that only about 20% of the metastable O(+) ions are converted into N2(+) through charge exchange with N2.
There are no author-identified significant results in this report.
There are no author-identified significant results in this report.
The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model nonuniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.
Four methods of investigating the thermal plasma density near the plasmapause are intercompared for the period of July 1 to 15, 1972. These methods are whistlers, the double floating probe on Explorer 45, three IMP I plasma wave signatures, and observations made aboard both Prognoz 1 and Prognoz 2. Explorer 45 data have provided new information on the plasmapause bulge which, during this period, occurs at 16 L.T. This displacement from the accepted time of 18 L.T. or even later is substantiated by the Russian satellites. All methods give the result that the plasmapause is found at an electron number density somewhere between 20 and 120 per cu cm or, alternatively, at 60 per cu cm, to within a factor of 2.
With the addition of magnetic field information to the Atmosphere Explorer C data base it is now possible to make simultaneous observations of charged particles, magnetic field perturbations, and ion drift velocity. The most recently compiled observations from this data set are presented, and attention is given to the observed relationships between the convection reversal boundary, the high-latitude limit of plasma sheet particles, and the high-latitude limit of the region 1 current sheets in the low-altitude ionosphere, taking into account the association with similar boundaries and regions in the distant magnetosphere. The observed relationships between these boundaries are further discussed in light of the current-generating mechanisms considered.