摘要:

It is useful to express spectra of modulated galactic cosmic rays in terms of the Compton‐Getting coefficientC. This parameter can reveal the energy range over which the force field approximation is valid and the range where convection effects dominate over those of diffusion. A value ofCnear zero over an extended low‐energy range (according to recent observations this is the situation for protons) implies that the radial gradient at low energies cannot be large. This small gradient may imply, in turn, that the diffusion coefficient increases beyond 1 AU less rapidly than if it were proportional to heliocentric radial distance and/or that there is essentially no scattering for a sizeable distance from the sun to earth. The behavior ofCwith rigidity (or energy) is discussed in terms of the omnidirectional distribution function ƒ0. Contours of constant ƒ0in the heliocentric distance versus rigidity plane are useful for illustrating the mean rigidity loss experienced by cosmic rays in the interplanetary m

ISSN:0148-0227    

DOI:10.1029/JA078i007p00995

年代:1973

数据来源: WILEY

摘要:

A new radial solution has been obtained to the Fokker‐Planck equation for solar flare particle propagation that includes the effects of convection, energy change, and anisotropic diffusion with κγ= constant. It is assumed that the particles are injected impulsively at a single point and that there is a free escape boundary. In addition, the azimuthal solution derived by Burlaga, which was based on κθ∝ γ², has been modified to include some of the effects of solar rotation. With an outer boundary at ∼2.7 AU, a solar wind velocity of ∼400 km/sec, and κγ≈ 2 to 8 × 1020cm²/sec, the complete solution gives reasonable fits to the time profiles of 1‐ to 10‐Mev protons from ‘classical’ flare‐associated events observed with the Caltech solar and galactic cosmic ray experiment aboard Ogo 6. It is not necessary to invoke a scatter free region near the sun in order to reproduce the fast rise times observed for west limb events, indicating that κγ= constant is a better description of conditions inside 1 AU than is κγ∝ γ. The radial solution also provides insight into the possible dependence of the observed decay times on various parameters and can be used as the basis for an illustrative calculation of th

ISSN:0148-0227    

DOI:10.1029/JA078i007p01007

年代:1973

数据来源: WILEY

摘要:

By using Explorer 35 interplanetary observations of solar protons ofEp>0.3 Mev during ten selected solar events (1967‐1970) the time dependence of intensity and of the angular distribution of intensity has been studied for the first time in the sub‐Mev range of energy. The respective contributions of diffusive and convective transport are resolved. Results are qualitatively similar to those of McCracken et al. (1968, 1971) in the energy range 7.5

ISSN:0148-0227    

DOI:10.1029/JA078i007p01019

年代:1973

数据来源: WILEY

摘要:

Energetic solar proton observations (Ep≳ 300 kev) in the interplanetary medium by Explorer 33 and Explorer 35 and over the polar caps by Injun 5 during the period September 1968 through March 1970 have been examined in detail. The solar proton intensities observed over the polar regions were compared with the interplanetary intensities on an absolute basis. The high polar latitude (HPL) proton intensities tracked the magnetic field aligned interplanetary intensities well (solar‐antisolar intensities as determined from the sectored Explorer data). The tracking was in agreement with the open magnetosphere model about 90% of the time. That is, the intensities observed on the HPL magnetic lines of force, which would be connected to magnetic lines of force from the sun in an interconnected geomagnetic and interplanetary magnetic field, were in agreement with the maximum intensity of the interplanetary proton pitch angle distribution. The intensities observed at the HPL region of the opposite polar cap were in agreement with the minimum intensity of the interplanetary pitch angle distribution. The low polar latitude (LPL) intensities generally tracked the maximum interplanetary intensity very well. The solar protons appear to have access to the LPL regions via the neutral sheet region of the magnetotail. Interplanetary proton intensity structures were used to estimate the delay in access to the polar caps. Based on the assumption that the interplanetary intensity structures are convected past the earth at solar wind speeds, the estimated delay times correspond to access regions with distances from the earth of about 100REfor the north LPL region and 260REfor the north HPL region. No evidence was found to indicate that the delays in access depend on the direction of the interplanetary magnetic fi

ISSN:0148-0227    

DOI:10.1029/JA078i007p01036

年代:1973

数据来源: WILEY

摘要:

For quiet (C9 ≤ 2) and quiet to moderately disturbed (C9 ≤ 4) conditions in the period 1964‐1968, the following sector structure dependence of auroral zone positive and negative bay activity, as measured by theAEcomponentsAUandAL, is noted. (1) There is a broad summertime peak inAUfor both sector polarities, withAUhigher for toward sectors during the first half of the year and with no apparent sector dependence during the second half of the year. (2) A stronger sector dependence is evident forAL, which peaks for toward sectors in the spring and for away sectors in the fall. (3) In a single 6‐month period, negative bay magnitudes at College and at its southern hemisphere conjugate station, Macquarie Island, followed the same sector dependence asAL. (4) During this same period the ratio of College to Macquarie Island negative bay magnitudes was higher for away sectors than for toward sectors, and this asymmetry persisted through the midwinter crossover in sector dependence that occurred for each individual station. A similar N‐S asymmetry is found in the polar cap. The ratio ofDP2 type activity at Vostok to that at Thule was greater by a factor of about 1.75 for toward sectors than for away sectors for periods near the 1967 spring and fall

ISSN:0148-0227    

DOI:10.1029/JA078i007p01047

年代:1973

数据来源: WILEY

摘要:

Variable intensities of geomagnetically trapped protons with energies between 12.4 and 500 kev were observed during times encompassing the magnetic storms on March 20 and 24, 1969. These proton fluxes were measured for 1.0

ISSN:0148-0227    

DOI:10.1029/JA078i007p01058

年代:1973

数据来源: WILEY

摘要:

A survey of the equatorial pitch angle distributions of energetic electrons is provided for all local times out to radial distances of 20REon the night side of the earth and to the magnetopause on the day side of the earth. In much of the inner magnetosphere and in the outer magnetosphere on the day side of the earth, the normal loss cone distribution prevails. The effects of drift shell splitting (that is, the appearance of pitch angle distributions with minimums at 90°, called butterfly distributions) become apparent in the early afternoon magnetosphere at extended distances, and the distribution is observed in to 5.5REin the nighttime magnetosphere. Inside ∼9REthe pitch angle effects are quite energy dependent. Beyond ∼9REin the premidnight magnetosphere during quiet times the butterfly distribution is often observed withj⊥/j∥<1/100. It is shown that these electrons cannot survive a drift to dawn without being considerably modified. The role of substorm activity in modifying these distributions is id

ISSN:0148-0227    

DOI:10.1029/JA078i007p01064

年代:1973

数据来源: WILEY

摘要:

High‐frequency electrostatic microinstabilities in magnetospheric plasmas are considered in detail. Rather special plasma parameters are found to be required to match the theoretical wave spectrum with satellite observations in the magnetosphere. In particular it is necessary to have a cold and a warm species of electrons such that (1) the warm component has an anomalous velocity distribution function that is nonmonotonic in υ⊥and is the source of free energy driving the instabilities, (2) the density ratio of the cold component to the hot component is greater than about 10−2, and (3) the temperature ratio of the two components for cases of high particle density is no less than 0.1. These requirements and the corresponding instability criteria are satisfied only in the trapping region (4 ≤L≤ 10); this is also the region in which the waves are most frequently observed. The range of unstable wavelengths and an estimate of the diffusion coefficient are also obtained. The waves are found to induce strong diffusion in velocity space for low‐energy electrons (≲1 kev) during periods of moderate wave amplitude (≲10 mv/m). Electrons with energies of up to 100 kev can be strongly diffused when the wave amplitude is large (∼100 mv/m). Geophysical implications are discussed; predicted results compare favorably with available observations pertaining to electrostatic waves, the particle distribution function, particle acceleration, and pitch angle diffusion in

ISSN:0148-0227    

DOI:10.1029/JA078i007p01082

年代:1973

数据来源: WILEY

摘要:

The magnitude of the westward‐directed auroral zone electric field is inferred from the measurement of the southward drift of moderately bright auroral arcs. In a sample of 43 events recorded over a period of 15 months at Fort Smith (68.1°N corrected geomagnetic) it was found that southward‐drifting arcs were predominantly associated with the decay phase of polar magnetic substorms, and no evidence was found for the association of southward‐drifting arcs with the so‐called growth phase of substorms. It is suggested that the southward‐drifting arcs are generated through the precipitation of energetic plasma affected by the limit on stably trapped particle fluxes proposed by Kennel and Petsc

ISSN:0148-0227    

DOI:10.1029/JA078i007p01100

年代:1973

数据来源: WILEY

摘要:

Two photometers with bandpasses of 170–500 and 170–800 A were employed to observe dayglow emissions in the extreme ultraviolet (EUV) over an altitude range of 90–186 km. We have identified the emissions observed with these photometers as resonantly scattered He I 584‐A and He II 304‐A radiations. At 186 km, 209 ± 70 rayleighs of 584‐A and 9.3 ± 3.1 rayleighs of 304‐A radiation were measured. We have compared these observations to theoretical calculations of resonance scattering of solar emissions from geocoronal He and He+. Using the Jacchia (1971) atmospheric model for He, we find that the observed brightness of the 584‐A emission requires that the solar 584‐A line width be 0.014 ± 0.004 A. In this model the maximum overhead brightness of 584‐A dayglow would occur at 900 km, and its magnitude would be 1.9 ± 0.6 kR. Our observation of 304‐A brightness requires that the overhead column density of the He+ions be 4.2 × 1011ions/cm² column. This value is consistent with a constant‐density plasmasphere model with a He+ion density of 320 ions/cm³ in the plasmasphere. There is evidence of additional EUV dayglow emission in the 500‐ to 800‐A band near

ISSN:0148-0227    

DOI:10.1029/JA078i007p01107

年代:1973

数据来源: WILEY