摘要:

An analysis has been made of the large and rapid Forbush decreases in the cosmic radiation which occurred from 1954 to 1959. Data from the IGY network of cosmic‐ray stations have been utilized to determine the changes in the primary rigidity spectrum, any significant differences in the onset times, and the existence of anisotropies during the decreases. To evaluate changes in the primary spectrum during a decrease it is necessary to know the spectrum before the event. It has been found that this long‐term variation is adequately described by a modulation of the primary spectrum given by 1‐C(t)P−1, where 1≤C(t)≤2.5 andC(t) is a function of time in the solar activity cycle. For individual decreases the modulation is 1‐{C(tF)P−1+kF}, where 0≤kF≤4 per cent for nucleonic detectors at sea level and mountain elevations and 0.6≤C(tF≤2.2. No systematic variations of the onset times were evident, except for the smaller decreases where the effect of any superimposed daily variation is important. The primary radiation remained isotropic during the large decreases. These events were preceded within 3 hours by a sudden commencement geomagnetic storm. These results are discussed in terms of possible sola

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03859

年代:1960

数据来源: WILEY

摘要:

During three large Forbush‐type intensity decreases which occurred on May 12, July 15, and July 18, 1959 the primary cosmic ray α‐particle flux was measured at balloon altitudes. A comparison with the α‐particle flux in an undisturbed period on September 28, 1959, and with the total cosmic‐ray intensity as observed by neutron monitor stations shows a close correlation between the α‐particle flux and the total cosmic‐ray flux during Forbush decreases. This evidence clearly establishes the fact that the proton and α‐particle components are modulated by a common mechanism during the sharp intensity decreases. The measurement of May 16, 1959, exhibits an increase in the α‐particle flux by 30 per cent within approximately 9 hours which is not accompanied by a comparable variation in the proton flux. Similar, independent changes in the α‐particle flux have been noted earlier to follow Forbush decreases. During quiet days the primary α‐particle flux with energies exceeding 560 Mev/nucleon is about 20 per cent higher in 1959 than in 1958. This change in intensity is probably related to the beginning decline

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03881

年代:1960

数据来源: WILEY

摘要:

Low‐energy nucleonic cosmic‐ray data from stations at Lincoln, Mt. Washington, Sulfur Mountain, and Deep River were studied with regard to onset times, time and magnitude of maximum increase, and decay characteristics. The decay behavior underwent a definite transition that is clearly related to the termination of the optical flare. The first part of the decay is clearly exponential, with a time constant in the neighborhood of 17 minutes, whereas the latter part is not distinctly established either as exponential (with a possible time constant of 78 minutes) or as following at−1.5law. Ordinary impact zones do not seem to fit the pattern of increases observed at various stations in the northern hemis

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03889

年代:1960

数据来源: WILEY

摘要:

Results of cosmic noise absorption measurements at 27.5 Mc made at Stanford, California, and Pullman, Washington, during 1958 are presented. A method introduced by Mitra and Shain of extractingF‐layer absorption from total absorption and an extension of this method to removeD‐layer absorption are described. Subtracting these two components from the total absorption leaves an extra component of absorption. The diurnal and annual variation of all these components is presented graphically and discussed. Errors in the cosmic noise curves are discovered and corrected for. The cause of these errors and its relation to assumptions of the cosmic noise absorption method is discus

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03895

年代:1960

数据来源: WILEY

摘要:

It is shown that solar radio emission on any wavelength shorter than 30 cm is good as a solar index for ionospheric studies. The coefficient of correlation betweenE‐layer ionization index and solar radiation decreases to a low value for wavelengths greater than about 30 cm, indicating that a major part of solar X radiation responsible forE‐layer ionization originates in the solar atmosphere below the height of origin of 30‐cm solar radio emi

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03903

年代:1960

数据来源: WILEY

摘要:

Equations are derived for the frequency shift of a radio signal transmitted to the ground from a space vehicle in or above the ionosphere. The principal restriction on the generality of the results is that the ionosphere is treated as quasi‐isotropic; i.e., the ray paths are obtained by methods which would be exact in a slowly varying isotropic medium, but the refractive index is permitted to be a function of ray direction (implying an anisotropic ionosphere).The following conditions prevail: (a) the (slowly varying) ionosphere may be a general function of three spatial coordinates and of time; (b) the vehicle may follow an arbitrary (nonrelativistic) trajectory; (c) the magnetic field, which characterizes the dependence of the refractive index on direction, may have arbitrary for

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03909

年代:1960

数据来源: WILEY

摘要:

Comparison of observed and calculated altitude distributions for the sodium airglow indicates that airglow processes involving combined sodium cannot account for the observations. It is suggested that the airglow results from collisions of neutral atomic sodium with vibrationally excited oxygen. This process can account for the observed altitude distribution and, possibly, the total intensity of the sodium airglow.

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03915

年代:1960

数据来源: WILEY

摘要:

The problem of spreadFis examined statistically, and a resulting theoretical model is obtained to explain the usual spread‐Fionogram. The results are applied in detail to a typical example of arctic spreadF. The statistical model is based on the assumption of Gallet turbulence in the underside of theFlayer under nighttime condition

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03925

年代:1960

数据来源: WILEY

摘要:

The complex refractive index and the state of polarization in a weakly ionized gas with an alternating electric field and a steady magnetic field are given by the ordinary Appleton‐Hartree formulas. In the original derivation a ‘frictional’ term is utilized which is assumed to be independent of the electron velocity,v, and the electron velocity distribution. It represents a first approximation to an effective collision frequency,vAH, for the collisions between electrons and neutral molecules.The present work is an extension of Jancel and Kahan's magnetoionic theory, which is based upon solutions of the Boltzmann equation, whenv=vmf(v). The expression for the complex refractive index and the state of polarization are rederived, utilizing a generalized conductivity tensor for the Lorentz gas. The resulting solutions are shown to be identical with the ordinary Appleton‐Hartree formulas whenv= constant. In the general case,v=vmf(v), a new angular dependent term appears, the coefficient of which vanishes, whenv= constant.The elements of the generalized conductivity tensor are integrals involving the electron velocity distribution function. The general non‐Maxwellian distribution function for the electrons is derived as a function of the alternating electric field and a steady magnetic field, when the two field vectors have anarbitraryinclination to each other. In the ionospheric wave propagation, the electrons are assumed to have a Maxwellian velocity distribution, as the electric and magnetic field effects will be negligible. The elements of the generalized conductivity tensor are then expressible in terms of previously tabulated integrals, when use is made of Phelps and Pack's laboratory results, viz.,v∝v2in air. This greatly eases the computational use of the generalized formulas.Calculations have been carried out for longitudinal and transverse propagation in the cases,vAH=vm=110ω,vAH=vm=ω/2, andvAH=vm= 2ω, and withs(electron gyrofrequency) the same order of magnitude as ω.Generally the birefringent properties of the medium aredecreased, when the velocity dependence of the collision frequency is taken into account through the general theory. In all cases the absorption factors based on the generalized theory differ from those based on the ordinary Appleton‐Hartree formulas by amounts from 30 to 100 per cent.Improved agreement is obtained whenvAHin the Appleton‐Hartree formula is associated with the mean energy instead of the most probable energy as in the generalized theory; i.e. whenvAH=32vminstead ofvAH=vm. In the asymptotic limit,v≪ ω ±s, the ordinary Appleton‐Hartree formula can be retained, provided thatvAH=53×32vm=52vm. In the other asymptotic limit,vω ±s, these same formulas can also be retained whenvAH=32vm. For the intermediate case,v∼ ω ∼s, differences in the absorption factors between the two theories persist with amounts up to 100 per cent, even thoughvAH=32vm. It is concluded that the generalized theory should be utilized in this case

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03931

年代:1960

数据来源: WILEY

摘要:

Using a formula which I derived in 1952 an approximate method is developed for estimating the size and shape of the stationary hollow carved out when a solar corpuscular stream impinges on the geomagnetic field. It is also shown that in a two‐dimensional magnetic field, the breadth of the hollow at infinity is finite and is given by (2πI2/ρυ2)1/2whereIis the current flowing in a permanent inducing system, ρ the density, and υ the velocity of the

ISSN:0148-0227    

DOI:10.1029/JZ065i012p03951

年代:1960

数据来源: WILEY