摘要:

Mariner 2 magnetometer data are presented with a more thorough analysis and discussion than in a previously published preliminary report. No magnetic fields attributable to Venus were detected. An upper bound on the magnetic dipole moment of VenusMvis estimated in several ways, subject to uncertainties regarding the dipole orientation and the nature of the interaction between the solar wind and the planetary field. On the basis of Mariner's not entering the Venus magnetosphere, the upper bound lies between 1/2 and 1/6 ofME, the earth's magnetic dipole moment. However, the absence of field fluctuations near Venus corresponding to the shell of disordered fields detected outside the earth's magnetosphere by satellites and space probes shows thatMvis less thanMEby at least an order of magnitude and makes it probable thatMvis less thanME/20. This result is consistent with qualitative predictions based on the dynamo theory of planetary fields. The energy flux of cosmic radiation above the Venus atmosphere, except perhaps for cosmic rays of the lowest energies, should everywhere approximate the intensity in the earth's polar regions. Any radiation zone of trapped high‐energy electrons is likely to be minor in comparison with the earth'

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01571

年代:1965

数据来源: WILEY

摘要:

The velocity, temperature, and density of the protons in the solar wind are presented for the period when Mariner 2 was near Venus. From these data it is concluded that (a) Mariner 2 never penetrated any magnetosphere associated with Venus; (b) Mariner 2 was probably also outside any shock front associated with the supersonic motion of the solar wind past Venus; (c) the solar‐wind intensity was not especially great during the time of Venus encounter; (d) any shock wave surrounding Venus was probably closer than about 25,000 km to the center of the planet at the subsolar poin

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01587

年代:1965

数据来源: WILEY

摘要:

A comprehensive survey of the spatial distribution of electrons E>40 kev beyond ∼RE(earth radii) with ten months of Explorer 14 observations has revealed that the gross features of the spatial distribution of these electron fluxes are (1) a ‘hard core’ of intensities of ∼107(cm2sec)−1extending from ∼2 to 8REnear the magnetic equatorial plane, which is characterized by small temporal variations compared with those measured at larger radial distances, and a weak latitude dependence; (2) a ‘tail’ of electron fluxes on the night side of the earth confined near the ecliptic plane beyond ∼10RE; (3) an increasing radial extent of electronE>40 kev intensities ≥105(cm2sec)−1as the local time of the satellite position increases (decreases) from local noon (∼11RE) to evening (morning) (≳16RE); and (4) high intensities of electrons at all latitudes of the Explorer 14 trajectory in the day side of the magnetosphere to ∼11REand a relative sparsity of electrons in the night side of the magnetosphere beyond ∼8REat high ecliptic latitudes. TheBandLcoordinates are shown to lose their effectiveness for organizing the observed omnidirectional intensities of electronsE>40 kev andE>1.6 Mev beyond ∼6RE; the observations of electronsE>40 kev beyond ∼10REin the ‘tail‘ of the magnetosphere can be conveniently summarized in an earth‐centered solar‐ecliptic coordinate system. The preliminary result of Frank and Van Allen of a ‘Void’ or sparsity, of electronsE>40 kev on the night side of the earth beyond ∼8REwas a manifestation of the fact that only Explorer 14 measurements at high ecliptic latitudes (∼−40°) were available during the period of the data analyzed in the earlier survey. Several magnetic meridian summaries of the measurements of electronsE>40 kev for a variety of local times offer a detailed view of the spatial distributions and temporal variations of the electron intensities throughout the magnetosphere. Acceleration of electronsE>40 kev within ∼2 or 3REbeyond the sunward side of the magnetospheric boundary is suggested by recurrent ‘spikes’ of intensities in these regions. Sample three‐point integral energy spectrums of electrons (over the energy range 40 kev to 1.6 Mev) are presented for a typical pass of Explorer 14 through the earth's magnetosphere. It was found that the electron spectrum softens with increasing geocentric radial distance and, if the integral spectrums are represented bykE−n, thenn≈ 1 atL= 4.3 andn≈ 2 atL= 7.1. The observation of catastrophic, but apparently rather rare, variations of electron intensities deep within the magnetosphere atL≈ 5 (λm≈ 30°) on December 20–21, 1962, implies a strong source and los

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01593

年代:1965

数据来源: WILEY

摘要:

A sudden increase of the particle intensity and of the magnetic field strength on September 25, 1961, at 1731 UT was detected by the ion‐electron detector and the magnetometer on board Explorer 12 outside the earth's magnetosphere. Comparison of the cyclotron radii of the trapped protons with the distance through which the satellite traveled showed the event to be temporal rather than spatial. Similarities between particle fluxes as well as between magnetic fields during the increase and within the outer belt make it probable that the increase represents an impulse‐like extension of at least a part of the outer belt. A deduced lower limit on the outward radial velocity of the extension is 156 km/sec. Crude calculations show that either the proton density near the outer edge is less than 100 cm−3or the temperature is greater than

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01627

年代:1965

数据来源: WILEY

摘要:

On the basis of 48 random observations of the sun from June through December 1961 with a thin mica window Geiger tube on satellite Injun 1, it is found that: (a) The ‘quiet day’ solar X‐ray flux at 1 astronomical unit in the wavelength range λ<14 A had a minimum value of 0.5×10−3erg (cm2sec)−1, a value which is approximately independent of the assumed blackbody temperature of the emitting areas of the sun over the temperature range 0.8 to 8×106°K. (b) The solar X‐ray flux underwent substantial time variation, from the lowest value quoted in (a) to the highest value on July 20 during a Hα flare of importance 3. The X‐ray flux λ<14 A on July 20 was 0.07 erg (cm2sec)−1. (c) Three other high intensity values also appeared to be associated with visual flares, but no convincing relationship between intensity and flare activity was found among the other 44 cases. (d) The median flux observed in the 48 random observations was 1.7×10−3

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01639

年代:1965

数据来源: WILEY

摘要:

Evidence is presented to support the hypothesis that the low frequency cutoff of a VLF noise band observed by the Alouette 1 satellite is due to a plasma resonance (the lower hybrid resonance) which defines a cutoff frequency for propagation transverse to the earth's field. If this hypothesis is accepted, the observations of this cutoff frequency by the satellite's VLF receiver, and simultaneous measurements of the electron plasma frequency by the topside sounder, can be used to determine an effective mean massfor the ions in the ambient plasma. Thevalues, together with the scale height measured from the electron density profiles, set limits on the ion composition and temperature. The main support for the hybrid resonance hypothesis lies in the plausibility of the temperature and ion mass information that is derived using this interpretation and the agreement between this information and the results of other workers. In general,is found to be larger during the day than at night and to increase with latitude. In polar regionsranges from about 7 at midnight to about 13 at noon; at midnight the composition of the polar ionosphere at 1000 km is more than 60% O+, whereas at noon it is about 95% O+. At middle latitudes,L= 2 to 3,ranges from 1.8 to as high as 7. For low latitudes,L<2, the lowest observed values ofof 1.3 require that the H+ concentration be greater than 68%. An effective ionospheric temperature of about 1200°K is determined for middle latitudes, increasing to high values for high latitudes. A marked diurnal variation of temperature is found at high latitudes

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01647

年代:1965

数据来源: WILEY

摘要:

An experimental study of the proton whistler, a new VLF phenomenon observed in satellite data, is presented, and an explanation of this new effect is given. The proton whistler appears on a frequency‐time spectrogram as a tone which starts immediately after the reception of a short fractional‐hop whistler at the satellite and initially shows a rapid rise in frequency, asymptotically approaching the gyrofrequency for protons in the plasma surrounding the satellite. It is proposed that the proton whistler is simply a dispersed form of the original lightning impulse and that the dispersion can be explained by considering the effect of ions on the propagation of an electromagnetic wave in the ionosphere. The propagation of a wave in a multicomponent plasma for frequencies of the order of the ion gyrofrequencies is discussed. In the ionosphere it is found that, in addition to the right‐hand polarized whistler mode, the left‐hand polarized mode (ion cyclotron wave) is also a possible mode of propagation for certain ranges of frequencies and altitudes. Between each two adjacent ion gyrofrequencies there is a frequency for which both modes of propagation are linearly polarized. These frequencies are called the crossover frequencies. A wave propagating in the ionosphere changes polarization at the altitude where the wave frequency is equal to a crossover frequency. This polarization reversal provides the mechanism by which an upgoing whistler can become an ion cyclotron wave. We show that the proton whistler is an ion cyclotron wave which occurs via this polarization reversal process. The crossover frequency can be measured from spectrograms of proton whistlers and is used to determine the fractional concentration of H+ in the plasma surrounding the satellite. Near the altitude and frequencies for which polarization reversal occurs, it is shown that the right‐hand polarized wave and the ion cyclotron wave may be strongly coupled. For frequencies of the order of the ion gyrofrequencies, this coupling process plays an important part in determining what regions of the ionosphere are accessible to waves from a given source

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01665

年代:1965

数据来源: WILEY

摘要:

A new source of energy for the ionosphere during geomagnetic storms is discussed. Stable auroral red arcs, together with the atmosphere in their vicinity, constitute a major sink of energy for theDstmain phase of a magnetic storm. The intensity of the red arc, the electron density in theFregion, the inferred temperature of electrons in the arc, the inferred transfer of energy from electrons and ions to neutral particles in the region, and the (uninhibited) decay rate of Dstmain phase energy are found to be mutually consistent. Energetic trapped particles causing a major part of theDstmain phase are degraded in energy by Coulomb collisions with a ‘background’ magnetospheric ‘thermalized’ plasma of temperature about 10,000°K. The temperature ofF‐region electrons (about 3200°K in a 100 γ storm), sufficient to excite the arc, is maintained by heat conduction from the magnetosphere along the lines of force. Conduction in the electron‐ion gas proceeds downward to a ‘transition’ level where transfer of heat to neutrals absorbs the heat flux. Below this height, conduction in the neutrals dominates. This source of heat causes the temperature of the neutral particles in the arc to rise by amounts of the order of 100°K in a 100 γ storm. Most of the reported properties of the arc are consistent with the theory. The present paper and a recent paper by the same author provide a coherent theory of (1) the main‐phase decrease of the surface geomagnetic field during storms, (2) the depletion of ionization in the outer magnetosphere during storms, (3) the stable auroral red arc, and (4)Dstvariations of theFr

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01689

年代:1965

数据来源: WILEY

摘要:

Low‐frequency hydromagnetic disturbances which are generated in the sunlit part of the distant magnetosphere and propagate as transverse waves to auroral latitudes are accompanied by pulsating electron precipitation and ionospheric absorption of cosmic radio noise with a similar temporal behavior. The region over which this pulsating activity occurs is belt‐like, ≳1000 km long and ∼100–400 km across. Sometimes the instantaneous pattern of precipitation exhibits spatial structure over these dimensions, but at least on one occasion the pulsations were in phase over a large region near the noon meridian. A unique acceleration process does not appear to be required, as the bremsstrahlung X‐ray spectrums obtained for the pulsations are not essentially different from those observed during activity preceding or following these events. The statically trapped radiation is eliminated as a possible source, and some mechanisms involving local energization are briefl

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01707

年代:1965

数据来源: WILEY

摘要:

This work is a study of charged particle trajectories about a current sheet which is based on Dungey's ‘Open model of the magnetosphere.’ The object of the study is to see if charged particles incident on this model current sheet, coming from the solar wind, and emerging as possible auroral particles, emerge in any kind of complex spatial distributions resembling auroral forms. Adiabatic theory, which is good throughout most of the magnetosphere, breaks down near a neutral point in the current sheet, and particle trajectories must therefore be computed. The computation is done on an IBM 7074 computer. Only proton trajectories are studied extensively, and the results yield accelerated output protons with high intensity in a thin sheet, with perhaps some thin beam structure within the sheet. Such a production of thin sheets or beams of accelerated particles is necessary for an auroral theory. The energy of the output protons is 900 times the energy of the particles comprising the bulk flow, but this energy is still about an order of magnitude smaller than that observed for auroral protons. Preliminary results with a few electron trajectories indicate that the model should yield electron energies of about the right order of magnitude for auroral electrons. Furthermore, a structure for the output electrons thinner than that for protons is suggested by these preliminary resu

ISSN:0148-0227    

DOI:10.1029/JZ070i007p01717

年代:1965

数据来源: WILEY