摘要:

An approximate method of computing cosmic‐ray cutoff rigidities is presented. The geomagnetic field is represented by the combination of a sixth order magnetic field whose origin lies entirely within the earth, and that due to a filamentary equatorial ring current of various radii and magnetic moments. The sixth order spherical harmonic expansion of the scalar magnetic potential is that obtained by Finch and Leaton by numerical analysis of surface magnetic field measurements for epoch 1955. Vertical cutoff rigidities have been computed for all IGY stations of geomagnetic latitude greater than ±45° listed in theAnnals of the International Geophysical Year, vol. 8. In addition, the vertical cutoff rigidities have been calculated for geographic latitude steps of 5° in geographic longitude steps of 10° for the sixth order field alone in regions of geomagnetic latitude greater than ±45°. The results are compared with the values given by Quenby and Webber, and by Quenby and Wenk, and with those derived from the magnetic shell parameterL. Comparisons of the values of vertical cutoff rigidity obtained for Port aux Francais, Northern Italy, and Minneapolis with those obtained by McCracken, Lynch, and Kellogg, respectively, by calculation of particle trajectories, are consistent with the 5 per cent precision claimed for the present

ISSN:0148-0227    

DOI:10.1029/JZ068i004p00957

年代:1963

数据来源: WILEY

摘要:

The magnetic momentMRof the ring current is calculated for model ring current belts, together with their magnetic fields along an equatorial radius. A graph shows the relation between the ratioMR/ME(ME= the magnetic moment of the earth) and the intensity ΔHof the ring current field at the equator on the earth's surface. It gives possible ranges of the ratioMR/MEfor observed values of ΔHand approximate upper limits of bothMR/MEand ΔHfor each belt. On the basis of diagram, the entry of low‐energy solar protons is discussed, and it is shown that the ring current alone cannot produce the drastic reductions of apparent cutoff rigidity of solar protons observed by detectors carried by balloons and satell

ISSN:0148-0227    

DOI:10.1029/JZ068i004p00973

年代:1963

数据来源: WILEY

摘要:

The positron annihilation line at 0.5 Mev has been found to be a prominent feature of the low‐energy γ‐ray spectrum produced in the atmosphere by cosmic rays. The measurement, which covered the energy range between 37 kev and 3.5 Mev, was made with a phoswich scintillation counter carried on a balloon to a depth of 6 g/cm2over Minneapolis. The flux at 0.5 Mev was found to be 0.31±0.03 photon/cm2sec at 6 g/cm2, and, when extrapolated to zero depth, gave a residual of 0.18±0.03 photon/cm2sec. All components of the spectrum, including the line at 0.5 Mev, were observed to have a transition maximum at 90 g/cm2and a length for absorption of 180 g/cm2. These indicate the origin of the low‐energy γ rays to be associated with the electronic component of secondary cosmic rays. Evaluation of the source function at 0.5 Mev over the entire atmospheric column gives 8.6 positrons per incident primary cosmic ray at λ = 55° geomagnetic. Since no statistically significant time variations were observed during the seven hours of constant depth balloon flight, an upper limit on the flux of certain possible extraterrestrial point sources, which made high elevation meridian transits, can be obtained. The flux at 0.5 Mev from the quiet sun and from the Crab nebula must be less than about 0.1 photon/cm2sec a

ISSN:0148-0227    

DOI:10.1029/JZ068i004p00979

年代:1963

数据来源: WILEY

摘要:

The satellite Injun 1 was used to find the high‐latitude termination of trapping of electrons with energyE≳40 kev at 1000‐km altitude over North America. On the average, this termination is atL∼16 or Λ∼75° in the local day and atL∼8 or Λ∼69° in the local night. As a consequence, in the range 8≲L≲16 or 69° ≲ Λ ≲75°, the average intensity of trapped electrons is some 100 times greater in the local day than at local night. Several explanations are suggested, but none is proved. The results show that McIlwain'sLparameter loses its simple a

ISSN:0148-0227    

DOI:10.1029/JZ068i004p00989

年代:1963

数据来源: WILEY

摘要:

The high‐latitude boundary (LN) of energetic electrons (E≳40 kev) quasi‐trapped at an altitude of 1000 km was studied with the satellite Injun 1 over North America during periods of magnetic quiet and magnetic storms in 1961. The boundary was very sharp during disturbed periods, and it moved farther from the pole during larger disturbances. The electron intensity south ofLNincreased during magnetic disturbances, and the electron spectrum was much softer than normal just at the boundary. Throughout two magnetic storms in October and December 1961, the boundary (LN) of the energetic electron flux coincided with the boundary of the auroral absorption of radio waves. Quantitative correlation of the intensities of the two phenomena is disc

ISSN:0148-0227    

DOI:10.1029/JZ068i004p00997

年代:1963

数据来源: WILEY

摘要:

Magnetograms from Eights, Antarctica, were compared with those taken at three close‐spaced stations bracketing the calculated conjugate point in Quebec, Canada, and with records from other nearby stations in the northern hemisphere. A very close association among all variations save theSqwas found for the two‐month period studied. Detailed analysis of the storm of January 10, 1962, yielded the conclusion that the region of closest association may be localized to within a few tens of kilometers for such disturban

ISSN:0148-0227    

DOI:10.1029/JZ068i004p01011

年代:1963

数据来源: WILEY

摘要:

Some general properties of geomagnetic tubes are considered in an exploration of the possibilities of excitation of auroral 5577 A by the release of trapped electrons. Two mechanisms are considered: the release of energetic electrons from the tubes; and the acceleration of low‐energy electrons after release from the tubes. The possibility that one or both of the mechanisms is operative from the equatorial to the auroral regions is discusse

ISSN:0148-0227    

DOI:10.1029/JZ068i004p01015

年代:1963

数据来源: WILEY

摘要:

Auroral zone X‐ray pulsations in the 1‐ to 15‐second period range, observed at Macquarie Island, Australia, on March 5, 1962, and College, Alaska, on June 29, 1962, are described. Both observations indicate that the time intervals between the X‐ray bursts are not unique; theaverageintervals over the pulsation events were 7.8 and 8.8 seconds, respectively. These observations indicate that the pulsation periods in this range are determined by acceleration or pitch‐angle redistribution processes in the equatorial plane rather than any fundamental, periodic motion of the electrons along lines of force in the geomagne

ISSN:0148-0227    

DOI:10.1029/JZ068i004p01023

年代:1963

数据来源: WILEY

摘要:

An investigation of recombination in the nighttimeFregion is described in which use was made of electron‐density profiles of the region up to the maximum of the layer obtained from ionosonde records. Several models of the region above the maximum were compared to reconstruct the entire profile. Profiles of theFlayer were reconstructed for several successive hours during the night. The recombination coefficient was then assumed to vary as a function of height in accordance with the scale height of either molecular oxygen or molecular nitrogen, and values of the recombination coefficient at 300 km were calculated. Marked percentage changes of β with temperature, of the same order as current estimates of the changes in neutral‐particle density with temperature, were observed. Estimated values of β as a function of temperature are pres

ISSN:0148-0227    

DOI:10.1029/JZ068i004p01031

年代:1963

数据来源: WILEY

摘要:

The radio horizon of satellite signals for an observer on earth is measured with a satellite of 780‐km average altitude and a beacon frequency of 108 Mc/s. The analyzed data consist of measurements from 295 orbits from July 13, 1961, to December 4, 1961. The statistical distribution of radio horizon data differs considerably from the geometric horizon and from the radio horizon calculated to allow for refraction effects using an equivalent radius of 4/3 the earth's radius. The observed radio horizon depends on seasonal changes as well as on the topographical regions along which the radio waves travel when the satellite is at low elevation. During summer the data are sporadic, in contrast to fall and winter when the data are more uniform. The either sporadic or uniform nature of the data is ascribed to the seasonal variation of the ionosphere. However, whereas the average radio horizon along sea is at all times longer than the corresponding geometric horizon by approximately 300 miles, the one along land was always found to be considerably shorter during the summer and late fall and only slightly longer during the winter. The lengthening along sea goes beyond the radio horizon calculated with 4/3 the earth's radius. It is suggested that a tropospheric duct, facilitated by the Gulf stream near our station and greater abundance of water vapor above sea, is responsible for lengthening the radio horizon along se

ISSN:0148-0227    

DOI:10.1029/JZ068i004p01039

年代:1963

数据来源: WILEY