摘要:

The investigation of the daily variation of cosmic ray intensity has been carried out over the past two decades by either of two approaches: the traditional Fourier series method and the more recently introduced power spectral method. A comparison of the two approaches is essential to the proper understanding of the results derived from them. The present study, for the first time, adopts both approaches for investigating the data from the Sulphur Mountain super neutron monitor for the period of mid‐December 1965 to April 1966 (extending over five solar rotations), when interplanetary magnetic field data from Pioneer 6 were also available. Problems relating to the analyses of both data sets on a day‐to‐day basis and on a statistical basis over a number of days are discussed. The power spectral analysis method cannot provide information on the phase of the diurnal variation or information on the diurnal amplitude on a day‐to‐day basis. This method, however, provides excellent estimates of the diurnal anisotropy amplitude independent of any daily phase shifts in the anisotropy. In addition, this method provides a measure of the ambient anisotropy amplitude which, for the entire period studied, has a mean value of ∼0.1%. The Fourier series method can yield reliable measures of the amplitude and phase on a day‐to‐day basis, provided the time series is reasonably stationary. This method cannot estimate the ambient anisotropy amplitude which, for small amplitudes, contributes to large uncertainties in the Fourier coefficients. We find that there is a general agreement between the observed diurnal variation over each period considered and that predicted theoretically from parameters derived from the interplanetary data. However, for most of the periods examined the ratio of the perpendicular diffusion coefficient to the parallel diffusion coefficient is rather small (K⊥/K∥≲ 0.1). As such the diurnal variation amplitude is generally most sensitive to the interplanetary field direction and the solar wind velocity and not to the calculated values of the diffusion coefficients. Further tests of the theory will require analyses of other periods when perhaps the perpendicular diffusion is larger and/or measurements of cosmic rays outside the atmosphere are available in order to obtain better energy resolution on t

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05139

年代:1978

数据来源: WILEY

摘要:

Diffusion coefficients for cosmic ray propagation in the interplanetary magnetic field are obtained for particles of energies typically observed by ground‐based neutron monitors. The estimates are made in the context of present quasi‐linear and nonlinear theories. Recent observations of the interplanetary magnetic field fluctuations are employed. It is found that the diffusion coefficients derived from the theoretical models generally differ by less than 50%. These differences are less than experimental uncertainties arising from variations in the relevant solar wind observables, where the observables are obtained over scale sizes of the order of a few cosmic ray mean free pa

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05151

年代:1978

数据来源: WILEY

摘要:

Magnetic holes in the interplanetary medium are explained as stationary nonpropagating equilibrium structures in which there are field‐aligned enhancements of the plasma density and/or temperature. Magnetic antiholes are considered to be associated with depressions in the plasma pressure. In this model the observed changes in the magnetic field intensity and direction are due to diamagnetic currents that are carried by ions which drift in a sheath as the result of gradients in the magnetic field and in the plasma pressure within the sheath. The thickness of the sheaths that we consider is approximately a few ion Larmor radii. An electric field is normal to the magnetic field in the sheath. Solutions of Vlasov's equation and Maxwell's equations are presented which account for several types of magnetic holes, including ‘null sheets,’ that have been obs

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05157

年代:1978

数据来源: WILEY

摘要:

The macroscale and mesoscale structure of the interplanetary magnetic field during the primary mission of Helios 1 is discussed. The radial field component behaves essentially in agreement with Parker's theory. The transverse component shows a larger variability than the radial component; its radial variation is in good agreement with Parker's theory for high speeds, but some deviation is found for low speeds. The radial variation of the field variance is also studied. Its dependence upon the heliocentric distanceris expressed by the lawr−3, which is necessary but not sufficient for Alfvén waves. The available data do not allow a unique interpretation of ther−3dependence. No big differences are observed between low (≤500 km/s) and high (≥600 km/s) solar wind velocity

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05161

年代:1978

数据来源: WILEY

摘要:

Helios 1 moved from 1 AU on December 10, 1974, to 0.31 AU on March 15, 1975, and the sun rotated beneath the spacecraft nearly 4 times during the interval. Recurrent high‐speed streams with uniform magnetic polarity were observed, and they were associated with coronal holes of the same polarity. Although they were recurrent, the streams and their magnetic field patterns were not stationary, because the coronal holes which produced them changed in shape and latitude from one rotation to the next. We estimated that the magnetic field intensity of open field lines in some of these holes was of the order of 10'20 G. Recurrent slow flows were also observed. The magnetic field polarity and intensity in these flows were irregular, and they changed from one rotation to the next. Cold magnetic enhancements (CME's) characterized by a twofold to threefold enhancement of magnetic field intensity and a fivefold to sevenfold depression of proton temperature relative to conditions ahead of the CME's were observed in some slow flows. Some of these CME's were contiguous with interaction regions of streams. At perihelion, Helios observed a recurrent stream which was associated with a lobe of the south polar coronal hole. The longitudinal width of the stream was three times that of the hole. We estimate that the width of the eastern and western boundaries of the streams at the coronal holes was only 2.5° ± 1.5°, and we infer that the width at the northern boundary of the stream was ≲5°. We conclude that between the sun and 0.3 AU there was a diverging stream surrounded by a thin boundary layer in which there was a large velocity shear. There is evidence for compression of the magnetic field in the western boundary layer (interaction region), presumably due to steepening of the stream within

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05167

年代:1978

数据来源: WILEY

摘要:

A theory is developed which determines the effect of gravity waves upon chemical reactions in the atmosphere. This theory is then applied in detail to O2(¹Σ) airglow measurements made by Noxon. A theoretical result for OH is given without details. It is shown that fluctuations of O2(¹Σ) airglow can be used to study gravity waves and enhanced diffusion in the vicinity of the atomic oxygen layer (roughly 100 km). This study requires a two‐fluid consideration of gravity waves because the fluctuations of atomic oxygen density are not necessarily in phase with the fluctuations of the major constituent. Neither are the amplitudes equal. It is found that the temperature dependence of the reaction rate constant for O2(¹Σ) and the shape of the atomic oxygen layer both have a major influence on fluctuations of O2(¹Σ) airglow. Inversely, both can be estimated from observations of O2(¹Σ) airglow fluctuations. Eddy diffusion coefficients are estimated from the rate at which the observed airglow intensity increases with time under the assumption that the airglow is horizontally uniform. For OH a separate theoretical calculation is made of the ratio of brightness fluctuations to temperature fluctuations. An important conclusion to be emphasized is that the observed temperature provides a much more reliable diagnostic for studying dynamics than does the observed brightnes

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05175

年代:1978

数据来源: WILEY

摘要:

The first successful measurements of plasma lines in the auroralElayer were made in January 1976 using the Chatanika incoherent scatter radar. Although they are considerably weaker than the signal from the ion component, the plasma line signals are readily detectable. Typical signal‐to‐noise ratios were about 4%. In this series of experiments, plasma lines were observed in the interval between 3.8 and 6.0 MHz, which corresponds to phase energies between 0.55 and 1.4 eV. They were found between 98 and 134 km; the derived plasma wave intensities varied between 0.06 and 1.0 eV, and the enhancements between 4 and 30 times the thermal level. There was a marked altitude dependence: the weakest waves were at the lowest altitudes, and the strongest were just below the maximum altitudes. There was no discernible frequency dependence at the lowest altitudes, but at the highest altitudes the lower‐frequency plasma waves were stronger. These variations are probably related to the altitude variations of the suprathermal electron spectrum and of the electron temper

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05186

年代:1978

数据来源: WILEY

摘要:

On an instrumented rocket payload flown through the polar ionosphere, large‐amplitude electrostatic ELF waves have been measured in the unstableEregion. Using three‐axis instantaneous measurements of the electric vector of the wave field, it was possible to confirm the electrostatic nature of the waves and to make a direct determination of the fullkvector as a function of altitude during upleg and downleg passages through theEregion. Simultaneous measurements were made of electron density and temperature, dc electric field, and ac and dc magnetic field. This allows comparisons to be made with theories of the crossed field two‐stream instability, the conditions for which were well satisfied. The direction of propagation and the frequency range are in agreement with theory, but the phase velocity is lower than predicted, being only about one third of the electron drift vel

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05191

年代:1978

数据来源: WILEY

摘要:

This paper presents observations made with detectors aboard Imp 8 of a unique series of charged particle bursts that occurred on February 16, 1974, while the spacecraft was traversing the dawn magnetosheath region. This event was unlike any other observation of Imp 7 and 8 in 5½ years of operation in orbit, and, to our knowledge, no other observation of this type has been reported. The measurements are most directly interpreted as an intense, 6 × 10³ (cm² s sr MeV/nucleon)−1, highly collimated (≲5° width) beam flowing in the antisolar direction composed of medium (carbon, nitrogen, or oxygen) nuclei. Both the degree of collimation in arrival direction and the composition are unique to this event and have never been observed in the hundreds of magnetospheric bursts or solar and interplanetary events present at these distances (20–35RE) from earth. We present this event as a possibly important signature of terrestrial O+ions escaping from the magnetosphere. Since it is a unique observation, we have examined the instrument performance very carefully and have concluded that i

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05198

年代:1978

数据来源: WILEY

摘要:

Observations of HF‐induced plasma lines in blanketing sporadicEat Arecibo have been reported in the literature. The purely growing instability was found to be the probable source of the plasma lines, although the parametric decay instability could not be ruled out. It was also observed that the upshifted plasma lines tend to be much stronger than the downshifted plasma lines. A calculation of the purely growing and decay thresholds, using typical ray paths of the type thought to be responsible for the Arecibo observations, indicates that the purely growing instability is most likely responsible for the observedEsplasma lines. The purely growing threshold is smallest when it is determined by electron collisions rather than by the density gradient and when the wave normal of the unstable waves is nearly parallel to the earth's magnetic field. It is thus likely that the unstable Langmuir waves are generated where these conditions are satisfied and subsequently propagate to where they are observed by the radar. In order that these waves not be highly damped, the density gradient must be greater than about 10° off the vertical. This indicates that these waves propagate in ionization irregularities embedded in theEslayer. For irregularities with an upward component of density gradient directed north of the antimagnetic field direction, upshiftedEsplasma lines would occur; otherwise, downshiftedEsplasma lines would result. Since the former case covers a much larger range of angles than the latter case, it is not surprising that normally the upshiftedEsplasma line is stronger than the downshiftedEsplasma li

ISSN:0148-0227    

DOI:10.1029/JA083iA11p05207

年代:1978

数据来源: WILEY