摘要:

The solar cosmic ray events of the period July 12–20, 1961, were studied with many simultaneous balloon flights at Fort Churchill, Manitoba, Canada, and Minneapolis and Bemidji, Minnesota. During the low‐energy solar cosmic ray event on July 12–13, γ rays were detected that were produced as the result of nuclear reactions of the solar cosmic rays with air nuclei. The balloon results have been correlated with the Injun 1 results, which showed protons in the range 1 to 15 Mev that could not reach the balloons but that produced the observed γ rays. The observed proton γ‐ray correlation agrees well with theoretical calculations of cross sections, and thus we are able with confidence to reconstruct the proton flux between infrequent passes over northern latitudes of Injun 1. This γ‐ray inferred time history of the event indicated a gradual increase in proton intensity from about 18 hours before the July 13 sudden commencement until shortly thereafter. Then the fluxes dropped sharply, possibly because of an increased geomagnetic cutoff rigidity at Fort Churchill during the initial phase of the magnetic storm, and showed much time structure during the main phase of the storm. In addition to the γ rays, low‐energy X rays were observed coincident with the sudden commencement. These X rays are probably due to electron precipitation, as observed in earlier events.The further events on July 18–20 were studied in their entirety by means of balloons floating at high altitude at Fort Churchill and Minneapolis. Since the complete time history of the solar cosmic rays was obtained, it has been possible to study the mechanisms responsible for the increase and the decay phase of these events. The intensity increase through the time of maximum for particles in a fixed energy region has been found to be well described by the point source infinite medium diffusion equations in interplanetary space. The decay phase, exponential in character, requires the assumption of an escape barrier located at about two astronomical units from the sun. The diffusion mean free path was found to be between 0.025 and 0.04 AU. From diffusion theory, assuming uniform emission from the point source, the number of particles emitted into unit solid angle was found to be about 1032particles/cm2sec ster for the event on July 18 and about an order of magnitude lower for the smaller event on July 20. In addition, we may estimate time of ejection of the solar particles from the sun in finding the best fit to diffusion theory. In these events, the simultaneous flights at different latitudes also enabled us once more to study the geomagnetic cutoff changes associated with the magnetic storm periods. The decrease in cutoff was found to correlate well with negative excursions of the equatorial magnetic field, and, because the particle spectrums were known, the cutoffs at Minneapolis

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02067

年代:1963

数据来源: WILEY

摘要:

This paper describes in detail the results of a series of high‐altitude measurements on 17 balloon flights at Fort Churchill, Manitoba, Canada, and Minneapolis, Minnesota, during the flare event of September 3, 1960. This flare is unique in that it is the only one during the solar cycle in which an east‐limb event produced both a sea‐level and a high‐altitude increase in cosmic ray detectors. Detailed investigation of the radio emission identifies this flare as the most probable source of the cosmic ray particles. An X‐ray burst observed during the flare is shown to be the result of a geomagnetic disturbance and not to have come directly from the solar surface. The particle onset measured by balloons at high latitude was 83 minutes after the microwave burst associated with flare maximum. The increase of intensity during the first five hours of the event can be fitted well by a diffusion model in interplanetary space with a point source in an infinite diffusing medium. The diffusion analysis shows that the interplanetary main free path on the average is 0.02 astronomical unit. Several interplanetary geomagnetic disturbances, however, distorted the particle increase before maximum intensity was observed. The decay of the event followed an exponential relationship for 140 hours after the flare, with a relaxation time of 23 hours. It is shown that this is consistent with the presence of a barrier at about two astronomical units from which particles escape at infinity and do not return inward. Very complex variations of intensity were observed at Minneapolis during the geomagnetic storm associated with cutoff changes for the incident solar particles in the geomagnetic field. These cutoff changes are well correlated with the main phase equatorial field fluctuations observed. A frequency power spectrum analysis of these time variations shows the presence of an eight‐minute period and also longer periods, particularly thirty minutes. The energy spectrum of this event is very flat, which accounts for the particles being observable at sea level even though the high‐altitude intensity was not as high as many other events. The spectrum may be well represented by an exponential rigidity for the integral particle flux, and values for the constants are given here. All the balloon data are presented as rate time charts at both the latitudes at which measureme

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02099

年代:1963

数据来源: WILEY

摘要:

The visual detection of geomagnetically trapped protons in the region of the south Atlantic magnetic anomaly is reported. Protons of energy ≥57 Mev were recorded in nuclear emulsions during a 65‐orbit, oriented flight of a satellite recovered on September 1, 1962. The east‐west asymmetry observed in the flux of geomagnetically trapped protons confirms a prediction by Lenchek and Singer. From measurements of the east‐west asymmetry we obtain a value of 62.0±5.0 km for the scale height of the atmosphere at 364‐k

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02117

年代:1963

数据来源: WILEY

摘要:

Phenomena at and near the boundary of the magnetosphere during the prolonged initial phase of a mild magnetic storm on September 13, 1961, were observed with a variety of magnetic field and particle detectors in Explorer 12. There was an abrupt termination of the regular geomagnetic field and a coincident discontinuity in the intensity of trapped particles at a geocentric radial distance of 8.2 earth radii. A mean directional energy flux of the order of tens of ergs (cm2sec ster)−1was observed outside the boundary. This energy flux is interpreted as being due to an omnidirectional intensity of the order of 1010(cm2sec)−1of electrons having energies of a few kev. From the Chapman‐Ferraro point of view, these electrons are believed to be the observable component of a ‘piston’ of quasi‐thermalized plasma, of the order of 10,000 km thick, which acted as the pressure‐transmitting agent between the directional solar wind and the geomagnetic field. Possible relationships between these observations and the ‘third radiation belt’ of Gringa

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02121

年代:1963

数据来源: WILEY

摘要:

The equations of motion of electrons and ions in the presence of electric, magnetic, and neutral particle velocity fields are derived for conditions likely to exist in an auroral arc. The electric field resulting from charge separation is computed. Electron densities, charged‐particle motion, and electric currents are also computed. It is shown how these computations can account for magnetic bays, electron drifts, and electric field fluctuation observed during auroral disturbances. Analytical expressions for electric field strengths and neutral plasma drift velocities are derive

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02131

年代:1963

数据来源: WILEY

摘要:

Whistlers and VLF phenomena were observed at Godhavn, Greenland (79.9°N geomagnetic latitude), during a period of 4 1/2 years. Of the phenomena observed, only chorus will be treated in this paper. The chorus observed is usually below 1500 cps, and the diurnal variation of the occurrence shows a peak at 1235 UT (0901 LMT) independent of the time of year. The seasonal variation of occurrence shows a maximum in the summer months. The correlation between the daily sum of the localKindex and the number of hours per day with chorus is negative. Since the features of chorus observed at Godhavn are different from those at middle‐latitude stations, we propose to introduce the term ‘polar chorus’ as a name for this type of em

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02141

年代:1963

数据来源: WILEY

摘要:

Two mechanisms are described for the formation of electro jet currents in the auroral zone. Both mechanisms require the existence of magnetospheric convection in which only particles of relatively low energy participate. It is essential to both mechanisms that particles of one sign (positively or negatively charged) should predominate among the energetic ones that do not participate in the convection of the magnetosphere. In the first mechanism the convection of the magnetosphere is taken to be of tidal origin, driven by the electric polarization fields associated with the dynamo current systems. In the second mechanism the convection is assumed to be the corotation of the magnetosphere with the earth, as modified by the solar wind that distorts the geomagnetic field. In both mechanisms the ionospheric currents are a consequence of the relative motion between the less energetic particles that almost fully participate in magnetospheric convection and the more energetic particles whose adiabatic drift motion across the magnetic field is only slightly perturbed by the electric fields associated with the convection of the magnetosphere. If the particles that do not participate are assumed to be the trapped energetic protons observed by Explorer 12 during magnetically quiet days, either mechanism predicts variations of the order of ±50 γ in the horizontal component of the geomagnetic field at auroral latitude

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02147

年代:1963

数据来源: WILEY

摘要:

This paper discusses a possible method for detecting nuclear bursts in space. The method is based on the effects that the bursts should have on the phase and amplitude of high‐frequency radio transmission between separated terminals on the earth's surface. Relations are derived that show how these effects should vary with time after the nuclear detonation and how they are related to bomb temperature, yield, and distance from the earth. The phase shift is independent of bomb temperature over a wide range of temperatures, whereas attenuation decreases by a factor of about 10 (in decibels) for each 50 per cent decrease in bomb temperature. Thus, absorption‐measuring techniques become decreasingly attractive for detecting cooler bombs. It is concluded that measurements of high‐frequency phase and amplitude change, in conjunction with very‐low‐frequency phase measurements, may provide a very sensitive means for detecting nuclear bursts in space by ground‐based radio equipment, even for quite cool bombs. The possibility of determining bomb temperature is

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02159

年代:1963

数据来源: WILEY

摘要:

This paper extends an analysis by C.M. Grain and H.G. Booker of the decay of ionization impulses in theDandEregions of the ionosphere. They pointed out that, considering the ambient ionization in these regions, the lifetime of added ionization such as would result from nuclear bursts in space was greatest near 75 km during the day and 95 km at night. Their limited calculations are here extended to a wider range of altitudes, and detailed results are given for times up to several thousand seconds after the ionization impulsess.

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02167

年代:1963

数据来源: WILEY

摘要:

The total intensity of light scattered by interplanetary dust has usually been directly related to the dust mass lost because of the Poynting‐Robertson effect. The scattered light intensity thus would appear to define a dust supply rate that must be maintained if the dust intensity is to remain constant. This work suggests that comets apparently cannot supply this quantity of dust to the cloud, because radiative pressures prevent most of the comet debris and its secondary collision fragments from entering closed orbits about the sun. More observations on the actual emission rates of very‐short‐period comets may be needed before this can be conclusively established. It is shown that asteroidal collisions can provide sufficient debris, but the injection rate is extremely variable because most of the debris must be produced in very rare collisions between the largest asteroids. It is concluded that no current theory is capable of accounting for a steady cloud. A possible solution might be found in processes that would counter the Poynting‐Robertson drag and permit grains to be long lived. The present comet dust supply rate might then be adequate to account for a stationary cloud. An alternative is a highly variable cloud, with dust produced in asteroidal collisions. The present epoch would then have to be one of unusually high dust

ISSN:0148-0227    

DOI:10.1029/JZ068i008p02171

年代:1963

数据来源: WILEY