摘要:

A supersonic disturbance in nonionized air cannot be directly detected by an observer outside the shock wave. The analogous limitation on detection of disturbances in the solar wind is discussed, and the limiting Mach angle is computed in a convenient coordinate system. Recent interpretations of the Imp 1 data (i.e. observation of the moon's wake) are discussed in view of the above restrictions.

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00001

年代:1965

数据来源: WILEY

摘要:

It is proposed that after a solar wind enhancement the wind‐magnetosphere interface becomes unstable with respect to production of ion acoustic waves. The high frequency electric oscillations then allow plasma to diffuse across the magnetic field, and the waves interact with the electron population via the cyclotron resonance. A small fraction of the electrons are accelerated to kev energies, and the energy distribution function is also distorted in the thermal region. Ultimately, the solar wind becomes locally subsonic with respect to the ion acoustic wave speed, and the waves travel upstream spreading the region of electron thermalization. Various stages in this relaxation process are described, and the theoretical predictions are compared with available experimental result

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00009

年代:1965

数据来源: WILEY

摘要:

The ion acoustic wave‐electron gyrofrequency resonance is examined quantitatively, and the results are used to discuss the plausibility of invoking this mechanism to explain the production ofE>30 kev electrons in the solar wind‐geomagnetic field transition region. The wave is represented by a potential distribution ϕ = ϕ0sin (k · r ‐ ωt+ ψ) with 0<ω<Ωp(ion plasma frequency), 0

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00021

年代:1965

数据来源: WILEY

摘要:

IGY magnetograms from eleven stations in Alaska and Siberia were compared with Macquarie Island records for correlation. The conjugate area defined by contours of equal correlation coefficient varies in size, shape, and location with time, but is generally elongated along a line of constantLvalue. Some definite departures from conjugacy were found and are discussed. No pronounced daily or seasonal change was found in form correlation between Macquarie Island and Kotzebue. The relative size of afternoon and early evening disturbances definitely varies with season, probably as a result of seasonal changes of ionospheric conductivity. The coherence of magnetic disturbances was investigated using Alaska net magnetograms, since this affects the size and shape of a conjugate area. Tight coherence was always noted in a group of stations spread 350 km east‐west and 125 km north‐so

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00029

年代:1965

数据来源: WILEY

摘要:

The conjugacy of bay‐type magnetic variations at midlatitude was investigated using data from the Cold Bay, Alaska, and Oamaru, New Zealand, pair (L= 2.6). Of twenty‐four intervals representing positive bay activity which were examined, the majority showed substantial agreement. Eleven intervals could be considered anomalous in all or some features. At midlatitude positive bays seem to result from the return current part of auroral zone electrojets. Intervals showing noncorrelation indicate departures of the primary electrojet from a conjugate pattern. Short period magnetic pulsations were also observed as a conjugate phenomenon. They could not be studied in detail owing to the insensitivity of the magnetomet

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00043

年代:1965

数据来源: WILEY

摘要:

Data from theL= 1.4 conjugate pair San Juan, Puerto Rico, and Trelew, Argentina, were used to study the conjugacy of low latitude magnetic variations. The majority of low latitude variations have essentially a worldwide distribution. Positive bays, however, are more limited in areal extent, and are thus of interest to a study of conjugacy. All bays examined showed similar and simultaneous variations at the conjugate stations.

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00049

年代:1965

数据来源: WILEY

摘要:

Expressions for group and phase velocity are derived for left‐ and right‐hand circularly polarized waves propagating along the static magnetic field of a magnetoplasma composed of electrons, positive ions, and negative ions. It is shown that a small percentage of negative ions can have pronounced effects on the propagation characteristics of the right‐hand wave near the negative ion gyrofrequency. In particular, the wave becomes evanescent in a frequency band just above the gyrofrequency, exhibits a ‘nose effect’ below the gyrofrequency, and above the stop band the wave's group velocity is strongly influenced by the negative ions. Some experimental observations consistent with negative ion effects are

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00053

年代:1965

数据来源: WILEY

摘要:

A model for the generation of pearl‐type micropulsations in the 0.1–5 cps range is presented. Under a different set of conditions, the model is also applicable to the generation of VLF emissions in the whistler mode. It is proposed that a beam of trapped protons atL≥ 4, supersonic with respect to the local Alfvén speed, emits hydromagnetic waves at a frequency corresponding to the occurrence of a cyclotron instability. These hydromagnetic waves propagate along the earth's field lines and are reflected back along the line at the ionosphere. On each pass of a wave packet through the proton beam, energy is supplied to the wave by the particles via the instability. Certain features of the observed fine structure of micropulsations are explained with the concept of bouncing hydromagnetic wave packets. A possible candidate for the necessary proton beam is the belt of 200–500 kev protons observed by Davis and Williamson, but there are other candidates as well, including low‐energy ring currents atL≃ 6. VLF emission in the 1–10 kc/s range may be produced by a similar instability if a beam of energetic electr

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00061

年代:1965

数据来源: WILEY

摘要:

Examination of very low frequency records of the Alouette 1 satellite has revealed the presence of an unusual band of noise. This band shows several features that distinguish it from other VLF emissions which are observed both in the satellite and on the ground. It is suggested that this noise is generated in the immediate vicinity of the satellite as a result of a resonance in the plasma surrounding the satellite. From a knowledge of the resonance frequency and the ambient plasma and gyrofrequencies, an inverse mean of the ionic mass can be determined.

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00071

年代:1965

数据来源: WILEY

摘要:

Radar reflections from artificial earth satellites tracked at a frequency of 425 Mc/s have at times revealed unusual amplitude scintillations in certain spatial regions of the orbital trajectories. The experimental observations were conducted at the U.S. Air Force Trinidad Test Site, West Indies (22° geomagnetic north latitude) during 1961. An analysis of the scintillation data has indicated that the perturbations were most likely caused by the presence of ionospheric irregularities along the radar‐satellite transmission paths. An estimate is made of the possible extent of the irregularities. The scintillations appeared only during the nighttime and when the antenna beam was oriented in a southerly direction toward the equatorial ionosphere. The correlation of the experimental data with solar‐geophysical conditions existing during the time of the radar measurements is also prese

ISSN:0148-0227    

DOI:10.1029/JZ070i001p00081

年代:1965

数据来源: WILEY