Abstract. Energetic electrons can penetrate into the middle atmosphere causing excitation, dissociation, and ionization of neutral constituents, resulting in chemical changes. In this paper, representative electron spectra measured by the Upper Atmosphere Research Satellite particle environment monitor are used to determine the relative contributions of bremsstrahlung X rays and direct electron impact on the energy deposition and ionization production rates for altitudes between 20 and 150 km. Above 50 km most of the ionization comes from direct electron impact. However, in the stratosphere the energy contributed below 50 km is mostly due to bremsstrahlung X rays. In the diffuse aurora the ionization from the bremsstrahlung component exceeds that due to the galactic cosmic ray background to altitudes as low as 30 km during geomagnetically active periods. This paper demonstrates that a diffuse auroral source can input as much or more energy into the upper portion of the lower and middle atmosphere as previously reported for relativistic electron events. The effects of the diffuse aurora (including both the direct electron and the bremsstrahlung contributions) on atmospheric chemistry may be significant.

Bursts of Jovian electrons in the energy range 3-30 MeV have been detected to distances of the order of ! AU from the planet. The duration of each burst was about 2-3 days, and the maximum intensity increased with increasing distance from the sun. These events could not be correlated with known solar activity. The conclusion that these electrons originated at Jupiter and were accelerated within the Jovian magnetosphere is based on the following observations of three of these bursts. (1) The power spectrum of the temporal variations of the 6-to 30-MeV electron flux showed a persistent peak at Jupiter's rotation frequency, 2.8 X 10 -5 Hz (corresponding to the 10-hour rotation period) out to distances > l08 km from the planet; (2) the slope, or spectral. index, of the differential energy spectrum measured as a function of time displayed the 10-hour cyclic variation in the value of the index, which was earlier discovered by our group as being characteristic of the electrons within the Jovian magnetosphere; (3) the value of the spectral index was anticorrelated with the flux level of the 6-to 30-MeV electrons, an effect that was found inside the magnetosphere on the inbound pass; (4) the 10-hour variations of both the spectral index and the number density observed in the bursts analyzed so far are in phase with the corresponding variations inside the Jovian magnetosphere for R >• 50 Ra; and (5) overall, the bursts were anisotropic, their direction of propagation being toward the sun along the average interplanetary magnetic field. We also note that the particles in the bursts propagated across the average interplanetary magnetic field to reach Pioneer 10, and we discuss some of the implications. The analysis of these events provides a new tool for the study of the propagation of particles in the interplanetary medium. 157Pioneer II Launch, Do• 96

Jovian electron flux increases are observed by the University of Chicago experiment on the earth-orbiting satellite Imp 8 throughout five -• 13-month Jovian synodic years during the period from launch of the satellite in late 1973 to 1979. A detailed analysis of these data is presented to define the characteristics of Jovian electron propagation to earth. Corotating interaction regions (CIR) that form at the leading edges of fast solar wind streams continue to modulate the propagation of MeV electrons from Jupiter to the orbit of earth to produce -•27-day recurrent variations in the Jovian etectron flux intensity. Between these CIR's, both the spatial distribution of Jovian electrons around earth's orbit and the time-intensity profiles of the Jovian electron flux induced by the CIR modulation effect are shown to be consistent with the predictions of a simple diffusion model calculation, assuming that Jupiter's magnetosphere is a 'point' source of electrons. A new and significant result of this study is that these time-intensity profiles are more accurately described not by the assumption that Jupiter is a constant source of electrons, but rather by assuming that electron emission is initiated with each passage of a CIR by Jupiter with the emission continuing for several days only. A measurement of the spatial gradient of these electrons demonstrates that there is a significant reduction in the Jovian electron flux between Jupiter and earth even when earth is aligned with Jupiter along the average direction of the interplanetary magnetic field. This observation is inconsistent with 'scatter-free' propagation. telescope on the earth-orbitin• satellite Imp 8 is presented. The purpose of this study is to define the characteristics of Jovian electron propagation to each and to test the propagation model used by Conlon [1978] in his analysis of Jovian electron data obtained on the Pioneer 10 and 11 spacecraft. Conlon [1978] showed that one of the primary mechanisms affecting the propagation of Jovian electrons was the modulation of these electrons by corotating interaction regions (CIR). These CIR's are regions of compression in the solar wind that are formed as a fast solar wind stream overtakes slower plasma [Smith and Wolfe, 1976; Hundhausen and Gosling, 1976]. As Conlon and Simpson [1977] have shown, the effect of a CIR is to inhibit the propagation of Jovian electrons through the CIR, across the average direction of the interplanetary magnetic field (IMF). Conlon [1978] demonstrated that between CIR's, a diffusion model, including the effect of convection by the solar wind and assuming that Jupiter was a constantly emitting 'point' source of electrons, could account for the Jovian electron flux intensity observed at Pioneer 11. ½onlon [1978] concentrated his analysis on data obtained at Pioneer 11 when that spacecraft was within 2 AU of Jupiter, upstream in the solar wind, and across the average direction of the IMF from the planet. At earth, however, every ,-•13 months (the length of the Jovian synodic year) eart...

The Pioneer 11 spacecraft encounter with Saturn (closest approach September 1, 1979) has resulted in the discovery of a fully developed magnetosphere with high-energy trapped radiation around Saturn, as reported in Science, 207, 400-453, 1980, by several investigators with charged-particle instruments on the spacecraft. The present paper contains in detail the final energetic charged-particle measurements and new observations obtained from the University of Chicago instrumentation on Pioneer 11, including the overall characteristics of the trapped electron, proton, and helium radiation, which was found to lie inside ~20 Saturn radii (Rs) from the planet, and the regions extending outward to beyond the planetary bow shocks and into the interplanetary medium. For analytical purposes we divided the magnetosphere into an inner magnetosphere (<5 Rs), where the intensity profiles displayed the near-axial symmetry characteristics of the dipole magnetic field alignment with the spin axis, and an outer magnetosphere whose characteristics on the sunward side inbound were significantly different from the dawn side outbound, indicative of a possible magnetotail but with no dramatic evidence in the charged-particle data for an equatorial current sheet, as observed at Jupiter. The intensities and energy ranges of the protons and electrons were intermediate between the levels found previously at Jupiter by Pioneer 10 and 11 and at earth. Energy spectra for protons and electrons and relative abundances of protons and helium nuclei are presented along with the average characteristics of particle anisotropies. At the time of encounter the magnetosphere was immersed in intense fluxes of electrons, protons, and helium nuclei of solar flare origin which are shown to penetrate from I Rs to 10 Rs into the magnetosphere, where they dominated the flux levels in the far outer magnetosphere. A corotation anisotropy has been measured at the proton energy ~ 1 MeV in the rotating magnetosphere after correcting the observed unidirectional anisotropy for the radial gradient of the proton flux. The principal focus of the paper is on the analysis of the trapped radiation in the inner magnetosphere, where the radiation reaches high intensity, and has a high degree of symmetry in the L shells around Saturn. Consequently, the absorption signatures in the radiation intensity profiles produced by tings and moons of Saturn can be analyzed quantitatively. Among other resuits the observation of the charged-particle absorption features have led to the discovery of satellite 1979 S2 at L --2.53, which corresponds with the optically detected 1979 S I, a concentration of matter probably located at a Lagrangian point in the orbital range of Mimas, and the identification of narrow rings of matter and one or more satellites inside the radial range of the F ring discovered by the optical-imaging investigators. It is pointed out that these discoveries will provide important tests for models of accretion of matter, satellite formation and the stability of narrow r...

Abstract. With its relatively low altitude (520 x 670 km) orbit, SAMPEX is mostly below the stable trapping region where charged particles repeatedly drift around the Earth, especially at midlatitudes. Recent analyses of SAMPEX data have revealed a surprisingly common set of observations of enhanced energetic (>150 keV) electron fluxes at L < 3, during times when SAMPEX was located such that any electrons that it observed were in the drift loss cone (and were thus destined to be precipitated upon reaching