摘要:

Variations of three‐dimensional anisotropy of cosmic rays during Forbush decreases are examined by a spherical harmonic method and by constructing successive isointensity contour maps in the solar ecliptic coordinate system. The east‐west and north‐south anisotropies are studied statistically and for several individual events; the data are based on cosmic ray records from about 24 stations for the 3‐year period from 1966 to 1968. For the individual events the high anisotropies of ∼4% are examined in terms of the convective, diffusive, and density gradient components of the differential streaming as well as the interplanetary magnetic field and solar wind. In each case, vector gradients are derived that lead to the observed anisotropies, and the magnitude of these gradients is typically 10–20 times that of the quiet time interplaneta

ISSN:0148-0227    

DOI:10.1029/JA078i028p06409

年代:1973

数据来源: WILEY

摘要:

In three sets of irradiations at Texas A&M's Variable Energy Cyclotron, stacks of thin Mg, Al, Si, Ca, Ti, and Fe foils were bombarded with 1016to 1018protons of energies 14 to 45 Mev to determine cross sections of He and Ne and of certain radionuclides. The22Na activity in the Mg and Si target foils, the48V activity in the Ti foils, the57Co,51Cr, and52Mn activities in the Fe targets, and the47Sc activity in the Ca targets were measured by gamma ray spectrometry. Cross sections were calculated by using the22Na activity in the Mg foils as an internal monitor.

ISSN:0148-0227    

DOI:10.1029/JA078i028p06428

年代:1973

数据来源: WILEY

摘要:

The procedure for mapping solar wind fluctuations observed at earth (1 AU) to other heliocentric distances under the assumption that they are corotating structures has been applied to Explorer 35 solar wind data to obtain solar wind structure between 20Rsand the orbit of Mars. Mappings were obtained for each of nine lunations. Two cases are shown here that best illustrate the structure associated with high‐speed streams. Main conclusions are as follows: when the structure is mapped back toward the sun from 1 AU, the velocity amplitude increases slightly but maintains constant phase relative to the corotation spiral; the preceding density peak decreases toward the sun and essentially disappears by 20Rs; the temperature amplitude changes only slightly and maintains its phase relative to the velocity maximu

ISSN:0148-0227    

DOI:10.1029/JA078i028p06443

年代:1973

数据来源: WILEY

摘要:

Arguments are presented that associate the proton thermal anisotropy observed in the solar wind at 1 AU with nonthermal effects. In particular, (1) dimensionless third momentsqpof the proton velocity distribution are occasionally measured to be larger than the saturation limit; consequently, corresponding values of the third momentQpcannot be reasonably interpreted in terms of a ‘heat’ flux; (2)qpis observed to increase with decreasing temperature and to be linearly related toT∥/T⊥,qp= (−0.095 ± 0.006) + (0.192 ± 0.006)* (T∥/T⊥); (3) largeqpandT∥/T⊥are associated with either double‐peaked velocity distributions or distributions with pronounced distortions of the high random energy tail alongB; and (4) the linear least squares fits of the observed velocity distributions to the simplest mathematical form proposed by Whang to describe a steady state, spherically symmetric thermal solar wind evolution are in general unacceptably poor. Analysis of the cause for the poor fits suggests that Whang's general mathematical form may not adequately characterize measured proton velocity distributions as well. It is concluded that a major contribution to the solar wind proton temperature and thermal anisotropy comes from inhomogeneities in its bulk convection energy and/or heat transfer from electrons to protons by way

ISSN:0148-0227    

DOI:10.1029/JA078i028p06451

年代:1973

数据来源: WILEY

摘要:

The Vela 3 proton data have been examined to determine the extent to which interplanetary compressions and rarefactions affect the large‐scale nonshock statistics of the solar wind temperatureTand densityn. Considered as a joint function of velocityVand velocity gradient ΔV/Δt, the temperature is found to be much more strongly related to the velocity. The density shows significantVdependence, but ΔV/Δtappears to be more important. Simple analytic functions are derived from flow parameter values obtained during times of little velocity change (|ΔV/Δt| ≤ 1 km sec−1hr−1) to describe the averageT‐Vandn‐Vdependencies. Fluctuations about these norms in bothnandTare demonstrated to be positively correlated with ΔV/Δton a time scale of 9–12 hours. However, more rapid (≤6‐hour) variations inTduring periods of highV, lown, and negative ΔV/Δt(corresponding to the rarefaction phase of interacting stream events) lack this association. The large‐scale compressional perturbation ofnandTis not limited in importance to the relatively infrequent large interacting streams, but should be regarded as a fundamental and widely occurring solar wind process. The implication is that much, perhaps most, nonshock solar wind activity can be viewed as a steady succession of interacting streams of varying intensities. This circumstance limits the usefulness of the average relations in identifying the physical processes dominating the flow in the acce

ISSN:0148-0227    

DOI:10.1029/JA078i028p06469

年代:1973

数据来源: WILEY

摘要:

A variation of a procedure developed by Davis and Smith (1968) is presented for the in‐flight determination of spacecraft magnetic fields. Both methods take statistical advantage of the observation that fluctuations in the interplanetary magnetic field over short periods of time are primarily changes in direction rather than in magnitude. During typical solar wind conditions between 0.8 and 1.0 AU a statistical analysis of 2–3 days of continuous interplanetary field measurements yields an estimate of a constant spacecraft field with an uncertainty of ±0.25γ in the direction radial to the sun and ±15γ in the directions transverse to the radial. The method is also of use in estimating variable spacecraft fields with gradients of the order of 0.1γ/day and less and in other special circu

ISSN:0148-0227    

DOI:10.1029/JA078i028p06480

年代:1973

数据来源: WILEY

摘要:

The behavior of the Lyman α 1216‐A intensity on Mars is presented for a range of atomic hydrogen density distributions below 200 km. Two sets of radiative transfer calculations have been performed. The first is based on spherical geometry and includes the effect of pure absorption of the resonance photons by CO2. The second set is based on the simpler plane parallel geometry and includes the effects of both pure absorption and a varying Doppler width associated with the planetary Lyman α line. From the plane parallel solutions we are able to estimate and account for the effect of a varying Doppler width on our spherical model results. When pure absorption and a varying Doppler width are incorporated in the theory, the maximum change in the Lyman α disc intensity is a factor of ∼2 over the range of hydrogen density models considered. Limb intensities above several hundred kilometers are unaffected by the model changes below

ISSN:0148-0227    

DOI:10.1029/JA078i028p06491

年代:1973

数据来源: WILEY

摘要:

An analytic theory is developed for the time‐dependent magnetic fields inside the moon and the diamagnetic cavity when the interplanetary electromagnetic field fluctuation propagates parallel to the cavity axis. The moon model has an electrical conductivity that is an arbitrary function of radius. The lunar cavity is modeled by a nonconducting cylinder extending infinitely far downstream. For frequencies less than about 50 Hz, the cavity is a cylindrical waveguide below cutoff. Thus cavity field perturbations due to the moon do not propagate down the cavity but are instead attenuated with distance downstream from the moon. Far from the moon, the cavity electromagnetic field is a cylindrical TE mode propagating downstream with the same frequency and wavelength as the interplanetary field. Thus the magnetic field in the far downstream cavity has a component parallel to the cavity axis that is 90° out of phase with the incident magnetic field. The far cavity field is the result of a surface wave on the cylindrical boundary induced by the interplanetary field and moving downstream with it. Cavity surface currents and charges accompany the far field surface wa

ISSN:0148-0227    

DOI:10.1029/JA078i028p06496

年代:1973

数据来源: WILEY

摘要:

The total hemispherical emittance of a section of polished aluminum support tubing from the Surveyor 3 spacecraft was measured by a calorimeter. The values found, 0.090 at 25°C and 0.089 at 50°C, are lower than was expected from a visual estimate but are in good agreement with an estimate based upon scanning electron microscopy of the tubin

ISSN:0148-0227    

DOI:10.1029/JA078i028p06507

年代:1973

数据来源: WILEY

摘要:

Low‐light‐level television systems have shown considerable promise in the optical extension of meteor flux measurements to faint magnitudes. In particular, the secondary electron conduction vidicon has demonstrated its ability to detect fast, faint meteors. Such a system has been calibrated and used to obtain the cumulative flux of meteors above threshold masses of 10−1–10−3gram. The results indicate a basic continuity with photographic and satellite measurements. The observed data were further analyzed for diurnal and directiona

ISSN:0148-0227    

DOI:10.1029/JA078i028p06511

年代:1973

数据来源: WILEY