摘要:

On at least three occasions, marked enhancement has been observed in the intensity of polar‐cap absorption of radio waves before sudden commencement of a geomagnetic storm. During the most recent of the events, on September 30, 1961, equipment on board the satellites Explorer 12 and Injun 1 confirmed an earlier suggestion that the enhanced absorption is due to an increase in the flux of low‐energy solar cosmic rays. The available evidence about the pre‐SC enhancements is presented in detail, and the effect is interpreted in terms of a compression of the particles between two shock waves in the interplanetary medium. One of these shock waves, associated with the geomagnetic storm, approaches the earth with a speed of the order of 1000 km/sec, whereas the other is a ‘standing’ shock wave set up by the motion of the solar wind past the magnetosphere. The net effect of the compression is to cause the particles to crowd together and to increase their energy by Fermi acceleration. Both effects tend to increase the flux above a given energy in the vicinity of the earth. It is shown that many of the observed features can be explained by this inter

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01793

年代:1963

数据来源: WILEY

摘要:

Spectrums of solar protons and a particles as determined from emulsions are given for the May 10, July 14, and July 16, 1959, flares, and the July 13, and July 18, 1961, flares. These spectrums are expressed as exponentials in rigidity. The fluxes have been measured at several different times during each flare. The proton to α‐particle ratio can be determined at six different times during these five flar

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01805

年代:1963

数据来源: WILEY

摘要:

The proton energy spectrum in the inner Van Allen zone has been investigated in the range 30 to 40 Mev with the two Geiger counters aboard the satellite Explorer 4. It has been found that an exponential spectrumdN=I0 e−E/E0dEis suitable for describing the variation of the ‘hardness’ of the spectrum with the magnetic coordinateL. The present data yield the following variation ofE0withL:E0= (306 ± 28)L−(5.2±0.2)Mev. An extrapolation of this function also gives the correct order of magnitude forE0for almost all values ofL. It is believed that the relationship determined betweenE0andLsupports the theory of a breakdown of the adiabatic conditions for the protons trapped in the earth's magne

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01811

年代:1963

数据来源: WILEY

摘要:

The transport equation pertaining to cosmic‐ray neutrons in the atmosphere was solved for neutron flux by means of the numerical multigroupSnmethod. Flux values were obtained at geomagnetic latitude 57°N as a function of altitude and energy group in the range from thermal to 20 Mev. These results, and continuous neutron flux distributions over energy determined from them, are presented for several representative altitudes. On the basis of the fluxes and appropriate neutron cross sections, averaged world rates for production of carbon 14 and tritium by neutron absorption processes in the atmosphere were calculated to be 2.1 atoms C14cm−2sec−1and 0.07 atom T cm−2sec−1. All results obtained are compared with oth

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01825

年代:1963

数据来源: WILEY

摘要:

A three‐component magnetometer was carried on Explorer 12, launched on August 16, 1961. The boundary of the geomagnetic field on the sunlit side of the earth was observed. During magnetically quiet periods the boundary, near the earth‐sun line, was at approximately 10 earth radii distance. During the period of observation a field of magnitude 30 to 40 gammas existed outside the boundary; it was usually directed downward, or southward, from the ecliptic plane. The boundary was stable, and magnetic fluctuations inside the geomagnetic field were relatively small although often large outs

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01835

年代:1963

数据来源: WILEY

摘要:

Six tin dipoles (length ≈34 cm, diameter ≈0043 cm) have been placed in a near‐polar, near‐circular orbit at a mean altitude of about 3100 km. Radar observations made at the RCA facility at Moorestown, N. J., over a period of about two months, while the dipoles were continuously in sunlight, indicate that charge drag has not produced a decrease in mean altitude at an average rate greater than 0.3 km/year. (The actual charge drag may be far less since, in fact, no systematic change in mean altitude is clearly discernible from the experimental results.) If an approximate scaling law is invoked, it is found that the corresponding upper bound on the decrease in mean altitude of 1‐mil‐diameter microwave dipoles is about 90 km/year. Making additional assumptions about the plasma leads to establishing an upper limit of 0.6 volt for the average magnitude of the electrostatic potential of the dipoles during this

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01845

年代:1963

数据来源: WILEY

摘要:

Radio signals on a frequency of 20 Mc/s from a satellite in a polar orbit over a period of one month were recorded at two sites in. southeastern Australia to locate regions causing scintillation of signals. Very little scintillation was present during daytime transits between 1200 and 1800 h local time, but between 1900 and 2300 h local time it was observed consistently. The indications are that between latitudes 20°S and 40°S the scintillation was patchy, arising in regions a few hundred miles in north‐south extent and more than 1000 miles in east‐west extent. A marked increase in the incidence of scintillation with increasing latitude began at 38°S and between 40°S and 50°S, the region responsible for scintillation here being apparently more continuous in both time and latitude. Heights of the scintillation region deduced by triangulation from the two sites ranged from 200 to 350 km. It is shown that, although this method of observation imposes some limitation on the accuracy of these values, much of the scintillation observed must have originated within this heig

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01851

年代:1963

数据来源: WILEY

摘要:

The relative bending effects on a radio ray of the horizontal and vertical gradient of refractivity are investigated. With the use of ray‐curvature formulas developed by Wong, convenient differential equations governing the three‐dimensional ray path are derived. It is also shown that the ratio of ‘horizontal to vertical’ bending effects is maximum when the ray is propagated in the vertical plane containing the horizontal gradient of refractivity. In a two‐dimensional example, computations of path height as a function of horizontal distance are obtained by numerical integration, For this purpose, a regional space‐time averaged exponential model drawn from climatologieal studies of Bean and Thayer has been used. Even though this smoothed model and an extreme version of it derived synthetically by increasing the horizontal gradient everywhere by a factor of 10 have comparatively strong horizontal gradients, the ‘horizontal bending’ effect is virtually negligible. It is not implied, however, that this conclusion is necessarily applicable to an atmosphere exhibiting small‐scale fluctuations in the refractivity pattern. The ray paths corresponding to the nonhomogeneous model are significantly different from those in a horizontally uniform atmosphere. The problem of replacing a nonhomogeneous model by an equivalent horizontally uniform one is also investigated. The choice of the best uniform atmosphere depends upon minimizing the rms height error over a designated horizontal path length, and this in turn requires the specification of several ray‐propagation parameters in addition to the distribut

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01861

年代:1963

数据来源: WILEY

摘要:

Telluric‐current micropulsations were recorded at Barrow, College, Fort Yukon Meanook, and Palmer. The diurnal variation data suggest a spiral pattern of occurrence in the auroral zone for the aurorally associated micropulsations (T= 3–20 sec). A spiral pattern of pearl‐type micropulsation occurrence may exist at lower latitudes. Many pearl events having sudden onsets and very large amplitudes were found to be well correlated with simultaneous cosmic noise absorption. Simultaneous pearl ‘necklaces’ were recorded. The occurrence of pearls at College seems to be negatively correlated with the occurrence of aurora. Evidence was found of increased ionisation in theFlayer at times of extremely large‐ampli

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01871

年代:1963

数据来源: WILEY

摘要:

Red (6300 A) auroral arcs were observed during twenty‐three nights at Rapid City, South Dakota, for the 1957–1958 IGY period. It is shown that they are strongly concentrated at an invariant latitude of 53° (sheet parameterL= 3), whereas visual auroral features occur predominantly at an invariant latitude of 67° (L=

ISSN:0148-0227    

DOI:10.1029/JZ068i007p01885

年代:1963

数据来源: WILEY