摘要:

The results of the first in‐situ measurement at VLF of the complex permittivities of deep Antarctic ice are presented as functions of depth, projected along the vertical. Measurements made with an electrically short dipole probe at five frequencies to a depth of 1500 m below the ice surface are reported. Temperature is identified as a dominant factor affecting the ice permittivity. This fact, coupled with the measurements of complex permittivity to 1500 m depth, is used to estimate ice permittivities from 1500 m to the bottom of the ice sheet at 2164 m. Comparison of the in‐situ measurements with those of surface measurements is made; it is concluded that for the purpose of VLF antenna and propagation studies the Antarctic ice sheet cannot be considered to be an isotropic homogeneous material, but must be treated at least as a horizontally stratified medium whose dielectric and loss properties vary in the vertical direction with temperat

ISSN:0048-6604    

DOI:10.1029/RS010i008p00763

年代:1975

数据来源: WILEY

摘要:

A quasistatic theory has been constructed for predicting low frequency sheath impedance changes produced on spacecraft sounding antennas as a result of intense RF emissions by them. The theory involves calculation of time‐independent sheath profiles around an infinite cylindrical antenna in a collisionless plasma, using a numerical scheme which includes the time‐averaged repelling force on electrons due to a nonlinear effect of the RF near field of the antenna. These sheath profiles then yield values of static sheath capacitance and conductance per unit antenna length. The theory includes a more accurate electron current calculation than in the earlier treatments by the authors. Results are presented for a range of parameters applicable to spacecraft sounding conditions. In most cases, the quasistatic sheath capacitance and conductance both decrease as RF amplitude increases. At large enough RF amplitudes, the capacitance becomes almost independent of antenna potential and Debye ra

ISSN:0048-6604    

DOI:10.1029/RS010i008p00773

年代:1975

数据来源: WILEY

摘要:

The multifrequency satellite radio beacon enables the measurement of the columnar electron content of the ionosphere and plasmasphere along the ray path and its spatial and temporal structure. Measurements include modulation phase, Faraday rotation, and amplitude. The characteristics of the beacon transmitter and its design are presented together with the design of the Boulder receiver and antennas and the calibration procedures. A shape factorFis defined which depends on the electron density and geomagnetic field distributions. It is found thatFvaries by about 30% from day to night. It is shown that the ratio of the plasmaspheric content to total content varies from about 0.08 during the day to about 0.35 at night. Other examples which are presented to illustrate the uses of the radio beacon include sunrise effects, solar flare enhancements of total content, and the ionospheric storms of early July 1974.

ISSN:0048-6604    

DOI:10.1029/RS010i008p00785

年代:1975

数据来源: WILEY

摘要:

The solution of the wave equation for a plane stratified medium is obtained by using a fourth‐order accurate numerical integration technique. The general solution thus obtained is described in terms of four characteristic waves, two upgoing and two downgoing. A compact expression for the coupling coefficients Γij(i≠j), which is suitable for numerical calculation, is also derived. These techniques are then used in a quantitative study of transmission coefficients, coupling factors, and wave structures through the crossover region where the proton whistlers are generated. The negligible influence of collisions upon the transmitted energies in the two upgoing modes is discussed. The results are then compared with previous works in which the thin‐slab full‐wave method

ISSN:0048-6604    

DOI:10.1029/RS010i008p00801

年代:1975

数据来源: WILEY

摘要:

During the period 1000–1030 UT on March 16, 1972, a very dynamic auroral event occurred in the latitudinal region from College to Fort Yukon, Alaska. Simultaneous observations of this auroral event were made with an all‐sky camera, a geomagnetic meridian scanning photometer, an incoherent scatter radar, a three‐component magnetometer, a 30‐MHz riometer, and two VHF/UHF auroral radars. The basic purpose of this report is to illustrate the advantages of such coordinated measurements and the possibilities for future experiments. These preliminary results point out many relationships which, although not hitherto unknown, are important to the understanding of the auroral ionosphere. Paramount among these are (1) intense discrete auroral forms (>25 kR in 4278 Å) are associated with enhancedE‐layer electron densities near 106electrons/cm3; (2( the riometer data and the height of maximumNefrom the incoherent scatter radar suggest that few energetic (>40 kev) particles were precipitating during this event; (3) enhanced regions of VHF backscatter seem to be associated with eastward and westward electrojet current systems but do not spatially correspond to the regions of highNeor bright auroral forms; and (4) the collective data yield a description which indicates that this period is associated with the Harang discontinuity region of the auroral curre

ISSN:0048-6604    

DOI:10.1029/RS010i008p00813

年代:1975

数据来源: WILEY

摘要:

The antenna problem consisting of exciting an infinitely long horizontal thin wire with an arbitrary distribution of impressed electric field along the axis of the wire is discussed. The special case of excitation by a delta function voltage source is solved. The current on the antenna is found as a sum of two residue (discrete) contributions and two branch integration (continuous) contributions. The far field and orthogonality properties of both the discrete and continuous modes are discussed. Finally, expressions are given for the current on the antenna. From this current the input conductance of the antenna can be obtained.

ISSN:0048-6604    

DOI:10.1029/RS010i008p00823

年代:1975

数据来源: WILEY

摘要:

In this paper, properties of stationary waves of the transverse magnetic (TM) type which have two electric field components, i.e., axial and transverse ones, in a nonlinear self‐focusing medium are discussed. Waves of the TM type are categorized into a solitary wave and several types of waves oscillating in the transverse plane. Analytical expressions of oscillating waves are obtained by using an asymptotic expansion and its extension for the large nonlinearity as well as the small one of the medium. A solitary wave is also discussed numerically, and some differences between the solitary waves of TE and TM types are mentione

ISSN:0048-6604    

DOI:10.1029/RS010i008p00833

年代:1975

数据来源: WILEY