摘要:

We describe the satellite Injun 3 and its scientific payload, which has been used in geophysical studies reported in the accompanying papers. The satellite was launched on December 13, 1962, into an orbit with apogee altitude 2785 km, perigee altitude 237 km, orbital inclination 70.4°, and period 116 minutes. One axis is continually aligned to within a few degrees of the local geomagnetic field vector by a permanent magnet. Eight directional detectors point at right angles to this axis and therefore measure trapped, or Van Allen, radiation. There are three omnidirectional particle detectors. Six particle detectors point upward in the northern hemisphere and therefore detect particles that are being precipitated to cause auroras. Two photometers, with 5577 A and 3914 A filters, point down the axis to view these auroras in the northern hemisphere, while another 5577 A photometer serves the same purpose in the southern hemisphere. With a loop antenna, very‐low‐frequency electromagnetic radiation in the frequency range about 500 cps to about 10 kc/s is detected, and a frequency and amplitude analysis is performed. The characteristics of the proton detectors which cover the energy range ∼50 kev to more than 100 Mev and the electron detectors which cover the range ∼5 kev to ∼5 Mev are

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00001

年代:1964

数据来源: WILEY

摘要:

The precipitation of electrons with energyEe≥ 40 kev into the atmosphere over North America is analyzed. Measurements were made principally with three directional Geiger tubes on the magnetically oriented satellite Injun 3. It is shown that the intensity of electrons mirroring at the satellite altitude increases rather than decreases when precipitation occurs, for example, over an aurora. The precipitation process is such that the angular distribution of electrons tends to approach isotropy over the upper hemisphere at the satellite altitude. The flux of electrons withEe≥ 40 kev backscattered by the atmosphere is about ten per cent of the precipitated flux. No events have been found where the upflux exceeded the downflux, and it is concluded that most acceleration processes take place high above the satellite, accelerating electrons preferentially parallel to the magnetic field lines. It is shown that electrons withEe≥ 1 Mev trapped aroundL∼ 4 are not perturbed when electrons withEe≳ 40 kev are precipitated at the same place, and so it is considered that the precipitation is not caused just by a gross change in the magnetic field producing lowered mirror points. The dependence of precipitation onKp, local and real time,L, and so on is summarized and the implications are

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00013

年代:1964

数据来源: WILEY

摘要:

Photometric observations of auroras were made with the satellite Injun 3 at altitudes of 250 to about 600 km over North America early in 1963. The magnetically oriented satellite simultaneously observed the precipitated electrons which caused the aurora and trapped electrons. The auroral zone, as defined on some fifty latitude surveys of the brightness of the N2+emission at 3914 A, showed an average maximum brightness of about two kilo‐rayleighs at an invariant latitude (Λ) around 69° on the magnetic shellL= 7.8. Several visible auroras are discussed in detail. It is suggested that the auroras delineated the outer edge of the region of durable trapping of Van Allen electrons, and that the electrons causing the auroras and having an isotropic angular distribution over the upper hemisphere at the satellite altitude were mostly freshly accelerated rather than old electrons of the Van Allen belts with similar energy. In two auroras measured by the satellite near perigee, less than 0.1 per cent of the oxygen 5577 A emission came from altitudes above 250 km. Hence the flux of electrons of energy ∼10 ev was no larger than the flux of those with

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00045

年代:1964

数据来源: WILEY

摘要:

This is a preliminary report of very‐low‐frequency (VLF) electromagnetic radiation measurements made by the Injun 3 satellite in the altitude range 250 to about 2000 km over North America from December 1962 to March 1963. The radiation is received by a loop antenna on the magnetically oriented satellite. Amplitude is measured with narrow‐band filters at six frequencies, the lowest being 0.7 kc/s and the highest being 8.8 kc/s. A wideband amplitude over the frequency band from 0.5 to 7.0 kc/s is also measured. In addition, the VLF signal modulates the telemetry transmitter so that a detailed spectral analysis can be made on the ground. It is found that the amplitude of naturally occurring VLF signals is commonly tens of decibels stronger at Injun 3 than on the ground, and this is to be understood as due to strong absorption of VLF energy in the ionosphere, as has been found previously in other experiments. The maximum observed signal strength over the band 0.5 to 7.0 kc/s is 5 × 10−2gamma. The amplitude of VLF chorus, considered for local times between 0800 and 1300, shows a maximum atL= 5 over the three‐day period studied. Simultaneous occurrences of VLF electromagnetic emission, auroral optical emissions, and particle precipitation into the atmosphere have been repeatedly observed. Two specific instances are discussed. In the more stable of the two, it is concluded that the auroral hiss was generated in the same magnetic shell in much the same region of the magnetosphere (near the outer boundary of trapping) as were the precipitated particles that caused the aurora. For this event it is estimated that, for the VLF radiation having frequencies less than 10 kc/s, the VLF energy flux at the satellite was about 8 × 10−7erg cm−2sec−1, the energy flux of precipitated electrons was about 10 ergs cm−2sec−1, and that from the auroral light was about 0.6 erg cm−2sec−1. These measurements suggest that, in this event, the electrons caused both the visible aurora

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00065

年代:1964

数据来源: WILEY

摘要:

Proton intensities and energy spectrums in the inner Van Allen belt have been measured with shielded plastic scintillators on three satellites and an Atlas pod. Omnidirectional fluxes of protons above 59, 95, and 148 Mev are given at the equator forLvalues of 1.25 and 1.48–1.60, and isoflux contours are given inB,Lspace for protons above 59 Mev. The counting rates of three scintillation counters having threshold energies of 46, 76, and 128 Mev have been analyzed in terms of assumed energy spectrums of the formdф/dE=AE−nanddф/dE=Ae−E/E0. The second form produces a dependence on the geomagnetic parameterLgiven byE0= 460L−4.8Mev. For the theoretical spectral shapes of Lenchek and Singer, cutoff energies have been derived from the ratios of counting rates in the three detectors. The results are in moderately good agreement with the calculations of Singer (in which, because of nonadiabatic effects, the cutoff momentum was found to be of the formPmax=POL−2), with a best fit valuePO=

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00091

年代:1964

数据来源: WILEY

摘要:

We have developed a method for accurate calculation of the distribution of electron energies in the ionosphere under the influence of an electric field. From this calculation we can predict rates of excitation of radiating states of N2, O2, and O as a function of the strength of a hypothetical applied field. We find that it is unreasonable to expect that electric fields are the source of the normal night airglow and that some of the consequences of fields adequate to generate the airglow are incompatible with observed facts. On the other hand, we present evidence that certain auroral forms (especially the so‐called midlatitude red arcs), in which the red lines 6300–6364 A of atomic oxygen dominate the spectrum, are almost certainly caused by local electric fields, perpendicular to the magnetic field, and of the order of 1 mv/cm in strength. This hypothesis, as well as explaining quantitatively the preferential excitation of low‐lying electronic levels in such auroral forms, is consistent with the observed height profiles of the red emission and with the increased drift velocity and decreased density of electrons that are observed to accompany midlatitude red arcs. A field of the magnitude required could be caused by separation of charge in the magnetosphere due to the solar wind. Because the conductivity parallel to the geomagnetic field is very much greater than that perpendicular to the field at all altitudes above 120 km or so, the electric field would exist everywhere in the ionosphere and magnetosphere above this altitude. This mechanism of generation would be consistent with the observed correlation of the occurrence of red arcs with other geomagnetic phen

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00101

年代:1964

数据来源: WILEY

摘要:

The worldwide ionospheric current system predicted by a previously described theory of the auroral electrojets is computed. Tidal air motions are neglected at first, and the high‐latitude current system is assumed to be due entirely to the interaction of magnetospheric rotation with the belt of energetic protons trapped in the distorted geomagnetic field. For a given geomagnetic distortion and trapped proton distribution, the computed current system strongly resembles Chapman's idealizedDs, current system, if sufficiently highE‐region electron concentrations independent of geographical position are assumed. As the assumed electron concentrations are decreased, however, the intensity of the computed current system is reduced, first in the auroral zone and then at all latitudes; at the same time the phase of the current system is advanced in the polar cap and is retarded at low latitudes. In view of this limitation of the current system by the available electron concentrations, the large disturbance variations observed during an intense geomagnetic storm can be explained by the present theory only if, in addition to an enhancement in the trapped proton density, greatly enhancedE‐region electron concentrations are assumed, particularly in the auroral zone. Such enhanced electron concentrations are known to occur when blanketing sporadicEis observed. The observed correlation between blanketing sporadicEand the strength of the electrojet current is thus predicted by the present theory. The interaction of the tidal wind system with the belt of trapped protons is also considered. The resulting auroral electrojet currents oppose theDsa current system if the usually accepted pattern of upper atmospheric tidal winds is assumed; the existence of a different wind pattern at high latitudes, at least during geomagnetic storms, is a possibility that cannot altogether be excluded, although it appears unlikely. If the majority of energetic particles in the radiation belt were electrons, their interaction with the usually accepted tidal wind pattern would result in the correct phase for theDscurrent system; satellite observations indicate, however, that the majority of the energetic particles are protons. The present theory can also account for the generation of meridional static electric fields of the type that, according to a theory of Megill and Carleton, cause midlatitude red

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00123

年代:1964

数据来源: WILEY

摘要:

The propagation and geometric attenuation of hydromagnetic waves in the earth's magnetic field are calculated by the methods of geometrical optics. The waves are assumed to be generated by point sources located at a distance of 6 earth radii from the center of the earth. It is shown that the ray tracing method cannot be used to explain the rise time of sudden commencements of geomagnetic storms. However, the calculated propagation times of hydromagnetic disturbances can give an understanding of delay times and latitude dependence of arrival times. If extended sources are considered, the following conclusion results from our analysis: According to geometric optics, hydromagnetic disturbances of the fast mode produced at 6 earth radii by the interaction of a solar plasma front with the earth's magnetosphere will reach the earth only if they are produced in a region within a radius of a few thousand kilometers of the subsolar point.

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00139

年代:1964

数据来源: WILEY

摘要:

The diffusion‐limited flow of hydrogen in the thermosphere is obtained by a Monte Carlo calculation. The resulting density distribution has a steeper gradient than current theories predict, even taking omission of gravity into account. The departure is ascribed to increasing nonvalidity of the Chapman‐Enskog diffusion coefficient as density changes over a mean free path become signific

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00157

年代:1964

数据来源: WILEY

摘要:

In previous models of the greenhouse effect in the Venus atmosphere it has been assumed that infrared‐absorbing atmospheric gases provide the sole contribution to the infrared opacity of the Venus atmosphere. In the present study the influence of an extensive cloud cover, opaque to infrared radiation, is also included in the greenhouse model. The magnitude of the greenhouse effect, which is defined here as the ratio of the surface temperature produced by the greenhouse to the surface temperature of an atmosphereless Venus, is computed as a function of infrared opacity of the atmosphere, and amount and height (actually ratio of cloud‐top pressure to surface pressure) of clouds. It is assumed that the Venus atmosphere is gray, that the absorbing gas has a constant mixing ratio, and that the temperature variation with altitude is linear. Calculations are made for two temperature lapse rates: the adiabatic lapse rate and nine‐tenths of the adiabatic lapse rate. The adiabatic lapse rate maximizes the greenhouse effect; for this case estimates of the minimum infrared opacity required to maintain the observed surface temperature can be determined. For a surface temperature of 700°K, 99 per cent cloudiness, and cloud‐top temperature of 240°K, the minimum required infrared opacity is 6. Uncertainties and questionable side effects of the model are discussed. The model is quite general and can be applied to other planetary atmospheres; sample calculations are shown for the earth

ISSN:0148-0227    

DOI:10.1029/JZ069i001p00165

年代:1964

数据来源: WILEY