摘要:

The portion of an anisotropy, in the flux of cosmic rays in the interplanetary medium, that arises from the motion of the solar wind plasma is in the same direction as the flow of the solar wind and isnotperpendicular to the interplanetary magnetic field. The amplitude of this convective component of anisotropy is given by the Compton‐Getting formula (2 + αγ) V/υ. The convective component was calculated for seven events during which the equilibrium anisotropy was observed in the flux of 7.5‐ to 45‐Mev solar flare particles and it accounted for all (in four cases) or most of the anisotropy. From this we conclude that, when the equilibrium anisotropy is observed, low‐energy solar flare particles are being transported mainly by convection in the solar wind. The ∼14‐hour decay time for the particle density, calculated by assuming only convective transport and adiabatic deceleration in a spherically expanding solar wind, is in reasonable agreement with observed values. The diffusive component of anisotropy is toward the sun in one event, thus implying a positive particle density gradient. Convective transport can produce a positive particle density gradient late in a flare event, but diffusive transport alone cannot. The diffusive transport velocity appears to be so small in some cases that the Alfvén velocities of the magnetic irregularities that scatter particles may affect the sc

ISSN:0148-0227    

DOI:10.1029/JA075i016p03147

年代:1970

数据来源: WILEY

摘要:

The integrating ionization chamber on the OGO 2 satellite has measured the quiettime cosmic ray ionization from 430 to 1540 km over the polar regions. After correction for time variations and spacecraft radioactivity, ionization averages have been fitted to analytical functions, which describe the primary and splash‐albedo components of the cosmic rays. Extrapolating to the top of the atmosphere and to infinity, the ionizations are 550±10 and 985±6 ion pairs/(cm³ sec atm), respectively, and splash albedo contributes 10.4 ± 2.3% of the total ionization at the top of the atmosphere. These results apply to early November 1965 and are compared with balloon and interplanetary values obtained for similar intensity levels with similar instruments. An interesting side result is another estimate of the radial gradient of the ionization, 8.5±3

ISSN:0148-0227    

DOI:10.1029/JA075i016p03154

年代:1970

数据来源: WILEY

摘要:

The cosmic ray knee has been observed with the ion chambers on the OGO 2 (October 1965–February 1966) and OGO 4 (August 1967) polar orbiting satellites, using the same graphical definition that applies to balloon observations. The knee is interpreted as a position in the geomagnetic field, which depends on the cosmic ray rigidity spectrum at the time of observation, where the cosmic ray cutoff rigidity has a particular value and is about 1.2 bv for the OGO 2 measurements. The invariant latitude of the knee decreases with altitude of observation at the rate of (2.5±0.5)×10−3degree/km and had the value 59.1° at the surface of the earth in 1965–1966. This invariant latitude should be independent of longitude; in fact, however, a slight longitude dependence of the order of ±1° is observed. Knee latitudes were 0.6° lower (toward the equator) in 1967, according to OGO 4, and 4° to 5° lower in 1961 as measured by other observers. We find a north‐south latitude difference of 0.6°±0.4°, which suggests a seasonal variation with the knee slightly closer to the pole during winter. A small diurnal variation of the knee latitude with amplitude 0.5°±0.4° is indicated; this appears to be consistent with calculations and observations

ISSN:0148-0227    

DOI:10.1029/JA075i016p03159

年代:1970

数据来源: WILEY

摘要:

The Pioneer 8 space probe encountered the extension of the earth's magnetic tail in January of 1968, at downstream distances of 500–800RE. During this period the VLF electric field experiment sporadically detected some characteristic changes in the plasma wave noise spectrum that appeared in close association with tail‐like positive ion energy spectra. In this report, we correlate the Pioneer 8 wave and particle observations in detail and show that during the extended tail crossings the average broadband wave levels were reduced. Enhanced 400‐Hz activity was frequently detected near the tail boundaries, however, and the observations suggest that tail breakup and field‐line reconnection phenomena begin to be important withi

ISSN:0148-0227    

DOI:10.1029/JA075i016p03167

年代:1970

数据来源: WILEY

摘要:

A model for the stormtime ring current, based on a self‐consistent steady state solution of Vlasov’s and Maxwell’s equations for a finite pressure plasma immersed in the earth's dipole field, is described. The particular choice of the particle distribution function is justified by the good fit to OGO 3 particle energy density and the Explorer 26 magnetic field measurements made during moderate geomagnetic storms. The model is then used to calculate a set of self‐consistent equilibrium configurations that correspond to increasing dipole moments of the ring current. These calculations prove the existence of equilibrium solutions that contain a neutral point and regions in which the particle energy density exceeds the undisturbed magnetic field energy density for a factor of up to 27. For a given shape of the particle distribution function in field line space, we show that the particle energy density, the total confined particle energy, and the disturbance field on the earth's surface are limited. For a particle distribution centered around the field line with the shell coordinateL= 3.3 in the undisturbed state, these limiting values were found to be 1.55×10−6ergs/cm³, 5.2×1022ergs, and −230 γ, respectively, where the dependence of these results on the shell coordinate of the undisturbed center field line follows simp

ISSN:0148-0227    

DOI:10.1029/JA075i016p03180

年代:1970

数据来源: WILEY

摘要:

We calculate the potential distribution in the neighborhood of a photo‐emitting plate immersed in a plasma, and we find that two steady state potential distributions can exist. In one the potential decreases from its plate value to zero monotonically, and in the other it decreases from its plate value to a (negative) minimum and then increases slowly to zero. This second ‘over‐shoot’ potential appears to be the stable one. Such over‐shoot effects are expected to play an important role for sheaths around satellites in the interplaneta

ISSN:0148-0227    

DOI:10.1029/JA075i016p03193

年代:1970

数据来源: WILEY

摘要:

In situ measurements of neutral particle and electron density from the Explorer 32 satellite have provided direct evidence that gravity waves in the thermosphere are associated with wave‐like structure in theFregion electron density. The ionospheric wave structure amplitude and spatial extent are consistent with those characteristics for travelling ionospheric disturbances (TID). Although the observed neutral and electron density wave structures are often out of phase, in some cases there was no correlation between the waves. Because of the lack of observation of all of the required ionospheric and neutral wave characteristics, it is not possible to quantitatively interpret the observed phase relationships. However, the observed amplitudes of the wave structure (±10 to ±30% in electron and neutral density) are consistent with theoretical expectations. In the one case where the electron temperature structure could be studied, the electron temperature was out of phase with the electron density. The phase relationship between the electron density and temperature wave structure probably results from local cooling effects in the ionospheric pla

ISSN:0148-0227    

DOI:10.1029/JA075i016p03200

年代:1970

数据来源: WILEY

摘要:

It is suggested that a low‐frequency ‘gradient drift’ instability may be important for the formation of striations in barium ion clouds released in the ionosphere above theElayer. The theory predicts that the trailing edge (with respect to the neutrals) of the plasma cloud will be unstable while the leading edge is stable, in qualitative agreement with observations. The growth time is relatively independent of wavelength and is of orderd/Uo, wheredis the typical density gradient length andUois the velocity of the cloud with respect to neutrals. Predicted growth times varying from seconds in the auroral zone at high latitude to minutes at midlatitudes are also in agreement with observation. Wavelengths of waves with zero phase velocity are found to be given approximately by λ = 2πd, which can be verified by optical obser

ISSN:0148-0227    

DOI:10.1029/JA075i016p03211

年代:1970

数据来源: WILEY

摘要:

The nonequilibrium calculation for various neutral constituents in the mesosphere and lower thermosphere (Hunt, 1966) was extended by including the effects of molecular and eddy diffusion. Nitrogen and its oxides were added, and more recent laboratory data for chemical reaction coefficients were used. A special numerical technique has been developed to simultaneously solve time‐dependent continuity equations for 14 constituents. The preliminary result indicates that vertical eddy diffusion significantly reduces the irregular variations around 80 km and tends to lower the height of these irregular variations. However, the value of the eddy diffusion coefficient acceptable from the consideration of heat balance below ∼100 km cannot entirely smooth out these irregular distributions for atomic oxygen, ozone, and oxygen‐hydrogen compounds, although the smoothing effect for nitric oxide seems to be strong enough to eliminate the irregular variations above ∼70 km. The role of the transport terms for molecular and eddy diffusion in the continuity equation is illustrated explicitly and discussed for some representative cases. We show that the dynamic model fits the observational results for ozone and nitric oxide concentrations better than the static model and also offers a more adequate explanation for the observed diurnal variation in the OH airglow e

ISSN:0148-0227    

DOI:10.1029/JA075i016p03221

年代:1970

数据来源: WILEY

摘要:

The resonances of the earth‐to‐ionosphere cavity are analyzed by considering the different propagation characteristics of day and night hemispheres. The azimuthal unsymmetries cause mode splitting, but the amplitudes of these additional split modes appear to be negligible for normal conditions. Diurnal variations of the resonance frequencies of the vertical electric field differ from the frequency variations of the horizontal magnetic field. The electric field resonance frequencies can explain the complete diurnal variation of the measured fundamental resonance if local equatorial thunderstorm activity, which peaks in late afternoon over land, is changed to a variation, which peaks at night for sources over the Pacific. The frequency variations are caused by the interaction of adjacent resonance modes. An eccentric geomagnetic field may cause comparable frequency changes if the nighttime phase velocity is decreased with an increasing magnitude of the radial geomagnetic field component. Such a phase velocity variation is not observed for nighttime ionosphere models that account for variousF‐layer alti

ISSN:0148-0227    

DOI:10.1029/JA075i016p03237

年代:1970

数据来源: WILEY