ISSN:0148-0227    

DOI:10.1029/JA074i005p01117

年代:1969

数据来源: WILEY

摘要:

Possible models for the nighttime Venus ionosphere are developed and compared with observations obtained from Mariner 5. The preferred model assumes the presence of a light reactive ion, such as He+or H2+, in the topside ionosphere, and it is shown that all features of the observed ionization profile can be accounted for with this single hypothesis. It is suggested that He+and, or, H2+can be readily supplied by lateral transport from the dayside. Implications of the model with regard to the abundance of He and H2are briefly explored, and some consequences for Venus nightglow are discussed.

ISSN:0148-0227    

DOI:10.1029/JA074i005p01118

年代:1969

数据来源: WILEY

摘要:

The anomalous Lyman‐α glow observed by Mariner 5 between 6500 km and 9000 km from the center of Venus would imply a 10 to 1 deuterium‐to‐hydrogen ratio at 6500 km if it were caused by deuterium. It is pointed out here that because at 650°K the escape of deuterium is only 10−4times as fast as hydrogen, this ratio may only require a planetary abundance ratio of order 10−3. The argument depends on the escape flux of deuterium being determined primarily by the photodissociation rate of deuterium compounds. It is shown that if downward mixing and recombination of atoms is not to compete too seriously with escape, the eddy mixing coefficient on Venus must be much smaller than th

ISSN:0148-0227    

DOI:10.1029/JA074i005p01128

年代:1969

数据来源: WILEY

摘要:

Observations of the relative propagation time of radar pulses to Venus for two frequencies, 40 MHz and 430 MHz, give the columnar electron content between the radar site and the surface of the planet. An independent measurement of the electron content of the earth's ionosphere allows us to obtain the electron content of the interplanetary medium. Assuming an inverse square law for the electron concentration between the orbits of Venus and earth we obtain electron concentrations at 1 AU ranging from 0.9 el cm−3to 8.8 el cm−3with an average over the thirteen days' observations of 4.5 el c

ISSN:0148-0227    

DOI:10.1029/JA074i005p01138

年代:1969

数据来源: WILEY

摘要:

Spectrograms of very low frequency radio noise recorded by University of Iowa satellite Injun 3 at invariant latitudes greater than 50°N are used to determine the behavior of VLF emissions during magnetic storms. Variations in the wide‐band intensity of VLF emissions fromL= 3 toL= 8 are studied for the period from April 28 to August 28, 1963, by means of the automatic gain control levels of the satellite VLF receiver. During a sudden‐commencement magnetic storm the VLF emission called polar chorus characteristically appears at the onset of the storm, may increase in upper frequency extent to ∼5 kHz, may change from spike to burst structure (normal chorus), occurs over the greatest area on the fourth day of the storm, subsequently fades into low‐frequency spike‐structure polar chorus again, and eventually disappears into the ELF hiss band generally present. Chorus occurrence shows symmetry about the 9h 00m–21h 00m, magnetic local time meridian with a large maximum in magnetic morning and a smaller maximum in magnetic evening. Daily regions of occurrence are shown for the duration of a prototypical storm. Contour maps of wide‐band VLF field strength as a function of shell parameterLand universal time are presented for May through August 1963. A correlation withDstis observed. The wide‐band VLF noise intensity rises from the background noise level at the onset of a magnetic storm and peaks during the early recovery phase. The Kennel‐Petschek limiting flux hypothesis is investigated by looking for VLF noise on the appropriateLshells when equatorial ≥40‐kev electron fluxes reach predicted limiting values. The VLF noise levels predicted in the equatorial plane by Kennel and Petschek are not observed at the altitude of the Injun 3 satelli

ISSN:0148-0227    

DOI:10.1029/JA074i005p01144

年代:1969

数据来源: WILEY

摘要:

Protons with energiesE>135 kev were observed in the tail of the magnetosphere after the flare of July 7, 1966. These protons have an isotropic pitch‐angle distribution. The maximum intensity of the protons reached ∼1.2 × 104(cm² sec ster)−1for particles withP>15 Mv between 1000 and 1100 UT and 1400 and 1500 UT July 8, 1966. The energy spectrum of the protons expressed as an exponential in rigidity indicates a monotonic softening: the characteristic rigidity,Po, changing from about 50 to 10 Mv. An hour‐long excursion of the satellite into the magnetosheath during the peak of the proton flux showed that the proton intensity is lower in the magnetosheath than in the magnetosphere by a factor of 2. The observed pitch‐angle distribution is flat in b

ISSN:0148-0227    

DOI:10.1029/JA074i005p01158

年代:1969

数据来源: WILEY

摘要:

A simple model of auroral backscatter from theEregion that includes ordinary ionospheric refraction is developed quantitatively. When the resulting computations are compared with experimental HF auroral backscatter data, a lower limit of 6 db per degree in the 15‐ to 50‐MHz region is found for the aspect‐sensitive decrease in backscatter cross section with off‐perpendicular angle from the geomagnetic field. When combined with recent VHF and UHF results, this result leads to the conclusion that the aspect sensitivity of theE‐layer auroral echoes is almost constant between 15 and

ISSN:0148-0227    

DOI:10.1029/JA074i005p01164

年代:1969

数据来源: WILEY

摘要:

Observations of sporadic‐Eactivity have been carried out during the IQSY from the United Kingdom using a fixed‐frequency, swept‐azimuth oblique backscatter sounder operating at 17 Mc/s. Ground scatter by means of sporadic‐Eionization was presented on a P.P.I. display and recorded on 16‐mm film. Analysis of the film data has shown that, in the north temperate latitudes,Esoccurrence for ƒEs>4 Mc/s is predominantly a daytime phenomenon with a well‐defined peak at the summer solstice. The enhanced activity in summer was characterized by both an increase in the occurrence ofEspatches with ƒEs>4 Mc/s having enhanced electron content and by an increase in the number of such long duration clouds. The azimuthal distribution of the observed activity has been shown broadly to be in accord with the differential land‐sea backscatter; although some deviations from that expected from previous surveys of temperate latitude behavior are indicated. A low occurrence ofEsactivity was generally correlated with magnetically disturbed days. Examination of the individualEsclouds has indicated a most probable patch size of 127 km and a most probable velocity of about 30 m/sec. The directions of motion of clouds showed some prefer

ISSN:0148-0227    

DOI:10.1029/JA074i005p01169

年代:1969

数据来源: WILEY

摘要:

This paper presents a critical study ofD‐region electron concentrations and collision frequencies that were obtained from a high power wave interaction experiment. Daily, mean hourly, and mean midday electron concentration profiles for undisturbed winter 1968 are discussed. The feature of a valley that is consistently observed near 70 km is carefully examined. An average winter collision frequency model is presented. It has been noted that morning and afternoon values of collision frequency are 10% higher than midday value

ISSN:0148-0227    

DOI:10.1029/JA074i005p01184

年代:1969

数据来源: WILEY

摘要:

Continuous records of the electron content of the ionosphere, obtained over a period of several years, have shown that a large disturbance occurs between 10 P.M. and 1 A.M. on about half the nights in summer. After an initial small decrease, the electron content increases rapidly by about 30% and occasionally up to 80%. The increase lasts for 15 to 100 minutes and may be followed by large oscillations. The effects are generally confined to the topside ionosphere, where the electron concentration must fluctuate through a factor of 2 or more. The disturbance consists of an extended wavefront, at latitudes less than 40°S, moving toward the northwest with a velocity of 140 m/sec. The front has a depth of several hundred kilometers and dies out within a few thousand kilometers. There is no relation with magnetic activity, but the occurrence increases with sunspot number

ISSN:0148-0227    

DOI:10.1029/JA074i005p01195

年代:1969

数据来源: WILEY