摘要:

The equations governing cosmic‐ray modulation allowing for convection, diffusion, and energy changes are approximated with simpler, more manageable equations that describe the particle behavior in a limited energy range. One of these equations determines an excellent approximation to the particle number density in the limit when the particles undergo relatively little modulation or equivalently when , whereare characteristic values of the solar wind speed, the heliocentric distance, and the diffusion coefficient, respectively. This equation describes the behavior of particles with energies above a few hundred Mev/nucleon. Other approximate equations describe the behavior of the number density and radial streaming when , a condition which should be satisfied at energies below about 50–75 Mev/nucleon. Analytic solutions to the exact equations for the number density and streaming are given for cases in which the diffusion coefficient has the formκ = κoTarb, (b>1), whereris heliocentric distance andTis particle kinetic energy. These solutions are used to demonstrate that the approximate equations accurately describe the particle behavior in their respective l

ISSN:0148-0227    

DOI:10.1029/JA074i021p04973

年代:1969

数据来源: WILEY

摘要:

The results of a rocket flight into a quiet evening hydrogen arc at Fort Churchill, Canada, are described and their analysis presented. The Hβvertical emission rate profile, obtained with a two‐channel photometer, is combined with proton measurements above 30 kev to obtain the proton energy spectrum below 30 kev. A result that is consistent with the accepted Doppler Hβprofile can be obtained only by a significant alteration in the cross‐sectional curve for Hβproduction by energetic protons. The derived energy spectrum cuts off sharply below about 25 kev and may have an additional low‐energy component with an energy of a

ISSN:0148-0227    

DOI:10.1029/JA074i021p04987

年代:1969

数据来源: WILEY

摘要:

λ6300 O I pulsations with quasi‐periods of 2 to ∼20 seconds have been observed in pulsating auroras. The percentage modulation was only 0.03–0.9%, compared with modulations of up to 60% in λ5577 O.I and λ4278 N2+. It is shown that rapid quenching of the O¹Dlevel allows a small part of the level population to follow the excitation function. The required quenching rates are derived, and these show that the shorter period pulsations occur lower in the atmosphere and so are associated with more energetic electrons. Pulsation heights can be deduced only if the quenching coefficients

ISSN:0148-0227    

DOI:10.1029/JA074i021p04998

年代:1969

数据来源: WILEY

摘要:

During late December 1966 and January 1967 the elliptically orbiting satellite OGO 3 entered the magnetosphere within 30° of the subsolar point and within 10° of the geomagnetic equator. This permits the measurement ofrb, the distance to the magnetosphere boundary, which is a necessary parameter for the Mead model magnetic field calculations. The electron fluxes measured by an electron spectrometer and an ion chamber of OGO 3 are correlated with electron fluxes on the geostationary satellite ATS 1 at the exact time when both satellites are on the same drift shells as calculated from the Mead model magnetic field with separations in local time up to 180°. During quiet times an absolute comparison of the fluxes from 50–1000 kev gives a linear relationship indicating agreement of the measurements over a three order‐of‐magnitude range of intensities. During substorm increases, the ATS 1 and OGO 3 measurements have similar profiles but are delayed in time with respect to each other. The observed delays are smaller for higher energy electrons and larger for greater separations in local time. As an example, the measured delays for 50, 150, and 400 kev electrons on January 11, 1967, when the local‐time separation was 110° are 26, 13–17, and 5 minutes, respectively. The observed delays are consistent with newly created electrons being produced in a region near local midnight. These newly produced electrons then gradient drift past the two satellites. The production region is shown to be 30°–60° in width and

ISSN:0148-0227    

DOI:10.1029/JA074i021p05005

年代:1969

数据来源: WILEY

摘要:

A correlation study of the sudden intensity increases seen in the 50–150 kev and 150–500 kev energy channels of the ATS 1 electron spectrometer with the occurrence of magnetic substorms recorded at midnight has been made. As a result of this study, the following conclusions applicable for times of moderate magnetic activity are arrived at: (1) Electrons are produced in the 50–150 kev energy range as observed at 6.6REduring a magnetic substorm. The spectrum is soft since electrons are not always observable in the second energy window. (2) The electrons are produced at or near the midnight meridian and then drift on closed field lines around the earth. (3) The electron bunch produced as a result of the substorm in 75% of the 60 events studied is associated with precipitation observed by riometers as it drifts. An apparent dependence of precipitation on the level of substorm activity as given by theAEindex suggests that the electrons are often produced of sufficient intensity to exceed a stable upper limit for trapped electrons at 6.6RE. (4) The frequency of occurrence of such particle substorms indicates that they might represent a quasi‐steady source of electrons for the trapped ra

ISSN:0148-0227    

DOI:10.1029/JA074i021p05019

年代:1969

数据来源: WILEY

摘要:

An analysis is presented of nonlinear interaction in a cold homogeneous magnetoplasma, leading to wave growth in the whistler mode. For such amplification to occur, three waves must generally be involved whose frequencies and wavenumbers satisfy certain synchronism relations. One of these is the energy source and is termed the ‘pump’ wave. It is first established that the synchronism relations can be satisfied for two situations: either for the pump and one other wave in the upper branch of the whistler dispersion relation, and the third wave in the whistler branch, or for all three waves in the whistler branch. A nonlinear theory of the interaction is then described that yields an algebraic expression for the whistler growth rate. The mechanism described is effectively that of traveling‐wave parametric amplification, and the theory demonstrates that for interaction to occur the waves must not all propagate exactly parallel to the static magnetic field. Extensive numerical computations have been carried out for the synchronism conditions and the growth rates over a wide range of magnetoplasma parameters. These indicate that the growth rates are likely to be too weak to be observable over most ranges of magnetospheric and ionospheric parameters. There are, however, situations in which gain might be observable, particularly if a strong pump wave were produced by a transmitter or plasma instability. The paper closes with a discussion of the possible relevance of parametric amplification to whistler amplification and triggered VLF emissions. It is concluded that there are some common features that might repay further study. Extension of the nonlinear theory would be required, to active plasma situations, in which energetic charged particles provide the source of energy analogous to the pump wave in the present t

ISSN:0148-0227    

DOI:10.1029/JA074i021p05029

年代:1969

数据来源: WILEY

摘要:

The intensity and spectrum of cosmic‐ray electrons from 20 Mev to 3 bev has been measured at a depth of 2.5 g/cm² at Fort Churchill in the summer of 1968 at a time when solar modulation effects had reduced the sea‐level neutron monitor rate by ∼12% below its sunspot minimum value. The instrument used was identical to that used in previous flights to study electrons at this location in 1965 and 1966. The total electron intensity at 2.5 g/cm² atmospheric depth at energies ≳1.5 bev in 1968 was essentially the same as that observed in 1966, however, at lower energies the intensity was greatly reduced in 1968. This reduction was a factor of 4 in the 200–400 Mev range. Atmospheric growth curves were used to determine the contribution of atmospheric secondary electrons. The deduced extraterrestrial electron intensity appears to be a factor ∼5 lower in 1968 than in 1966 at energies just above 200 Mev. At higher and lower energies the fractional decrease becomes less. These results confirm and extend earlier measurements of the solar modulation of electrons made in 1965–1966. The energy dependence of the electron modulation is essentially the same in the 1966–1968 period as was meas

ISSN:0148-0227    

DOI:10.1029/JA074i021p05041

年代:1969

数据来源: WILEY

摘要:

The intensities of high‐energy (>64 Mev) protons trapped on very lowL(≤ 1.20) shells have been measured on three satellite flights with similar instruments possessing a large geometric factor and a good separation of protons from electrons and other backgrounds. The data have been analyzed with the expectation that at the extreme lower edge of the inner radiation belt a more complete separation of the various possible source mechanisms might be feasible. The shapes of the spatial flux profiles are found to be in reasonable agreement with the predictions of an injection rate nearly independent of position and a loss rate due to atmospheric interactions. This result suggests that in this region the effects of pitch angle and / orL‐shell diffusion are small, thereby providing a direct measurement of the injection rate by other means, in particular the cosmic‐ray albedo‐neutron decay source. However, the magnitudes of the measured fluxes are found to be higher by about a factor of 20 than those expected for the latter source and are consistent with the findings of other investigators, also for low‐altitude protons but at considerably higherLshells. These discrepancies might be attributed to uncertainties in the many quantities involved, including the cosmic‐ray albedo‐neutron decay source strength. Alternatively, a significant contribution may arise from other source mechanism(s), such as the influx of protons trapped on higherLshells, with special properties resulting in flux profiles at lowLshells consistent with an injection rate nearly independent of position coupled with atm

ISSN:0148-0227    

DOI:10.1029/JA074i021p05054

年代:1969

数据来源: WILEY

摘要:

Recent measurements of the energy spectra of protons and hydrogen atoms in breakup auroras have found significant fluxes at energies near 1 kev. Cross sections for ionization and light emission for collisions of protons and hydrogen atoms with atmospheric gases are useful in analysis of these auroral events. Atomic beam measurements are reported of ionization and charge‐capture cross sections for proton bombardment of N2, of ionization and stripping cross sections for hydrogen atom bombardment of N2, and of the relative cross sections for emission of N2+391.4‐nm radiation in collisions of protons and hydrogen atoms with N2in the energy range 1–2

ISSN:0148-0227    

DOI:10.1029/JA074i021p05065

年代:1969

数据来源: WILEY

摘要:

Neither Venus nor the moon have a significant dipole magnetic field, and their atmospheres are exposed to the solar wind and the interplanetary magnetic field. As the solar wind ions penetrate the atmosphere, photo and charge‐exchange ionization reactions alter the density and velocity of the ion stream. A collisionless reacting hydromagnetic model is used to describe the flow of atmospheric and solar wind ions normal to the interplanetary magnetic field. Because of the ionization reactions, the mass flow increases along the ion stream lines, and the usual adiabatic invariant,P⊥/nB, is not constant. The supersonic solutions obtained show thatE/Bdecreases with penetration of the solar wind into an atmosphere. A critical penetration optical depth, τs, at which a hydromagnetic shock forms, is determined as a function of the ion generation rate in the ionosphere and the ratio of the photon flux to the solar wind flux. Recombination is taken into account and used to establish a minimum optical depth at which a hydromagnetic shock can be maintained in an isothermal atmosphere. In the case of Venus (CO2atmosphere), the hydromagnetic shock forms for 10−9<τs<2 × 10−4, i.e., above the usual Chapman layer. The exact value of τsis strongly dependent on the value of the scale height which is used. For the moon, the lunar atmospheric optical depth is less than that required for the formation of a hydromag

ISSN:0148-0227    

DOI:10.1029/JA074i021p05073

年代:1969

数据来源: WILEY