摘要:

It is suggested that hydromagnetic waves generated by the impact of solar plasma on the geomagnetic field may form shock waves in the magnetosphere, thus providing a mechanism for establishing the diamagnetic main‐phase ring current. These shock waves should develop on the night side of the earth and heat the ambient protons (which constitute the normal protonosphere) to approximately the hydromagnetic‐wave velocity (of the order of 500 km/sec). The transfer of hydromagnetic‐wave energy to the protons stresses the geomagnetic field and produces the geomagnetic‐storm main phase; i.e., the kilovolt‐energy protons form a diamagnetic current. The bombardment of the upper atmosphere by energetic hydrogen atoms from the decaying ring current and the possible change in the decay time‐constant of the ring current through the sunspot cycle ar

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03631

年代:1961

数据来源: WILEY

摘要:

A disturbance in the exosphere generates waves in three partially separable modes. The modes are described by considering the vorticity about a line of force, the two‐dimensional divergences of velocity in the plane perpendicular to the line of force, and the component of velocity along the line of force. The propagation of vorticity is one‐dimensional and there is no geometrical attenuation. It is suggested that this mode is associated with the sudden commencement of a magnetic storm. The propagation of the longitudinal component velocity is almost one‐dimensional, but it is heavily damped at high frequencies. In a gravitational field, the medium is no longer uniform, and at low frequencies the modes are coupled in a complicated way. The influence of gravity is characterized by the frequency of oscillation of a small parcel of fluid when displaced from its zero‐order position in the gravitational field. For parallel magnetic and gravitational fields the vorticity mode is still separable, and gravity leads to anisotropic dispersion in the other modes. The propagation at low frequencies is no longer cylindrically symmetrical if the lines of force are at an arbitrary angle to the direction of gravity. Detailed investigations of the influence of the gravitational field on hydromagnetic wave propagation is carried out for the case where the sound velocity is small compared to the Alfvén wave velocity.The principal aim of the study is an attempt to provide a background for the separation of source effects from those of the medium as an aid to the spectral study of magnetic records. The relative proportion of the three modes generated by a specific source is estimated. Consideration of the regions of allowed solutions in frequency‐wave number space show that the vorticity mode will have a narrow spectrum. It is suggested that high‐frequency micropulsations are associated with vorticity mode propagation. Examples of vorticity generating sources include the turbulent region in the vicinity of a finite amplitude wave, the outgassing of a rocket motor, and a wake of a satellite in the lower exosphere. Energy may be trapped within the exosphere in various free vorticity mode oscillations. The free periods of these oscillations are comparable to the periods observed in the low frequency micropulsations.The limiting conditions for the propagation of the various modes in the exosphere are considered. Because of the long‐range nature of the Coulomb forces, the charged particle may travel distances short compared with its mean free path and still exchange a substantial proportion of its momentum. For representative models of the exosphere, disturbances at several earth radii must have a length scale large compared with several kilometers for the propagation of the longitudinal component of velocity. The limiting conditions on the vorticity and transverse modes involve the ratio of the length scale of the disturbance to the Larmor radius. These modes are propagated if the disturbances have length scales of some hundreds of meters in the outer regions of

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03639

年代:1961

数据来源: WILEY

摘要:

The spatial distribution of electrons injected into the geomagnetic field from the beta decay of cosmic‐ray‐produced neutrons leaking out of the atmosphere has been calculated. There is available an IBM 709 code which has been used to calculate the densities of particles trapped by the geomagnetic field for both natural and artificial sources. The spatial distribution of electrons from the neutron decay source in the inner belt has been presented previously. In that calculation losses due to atmospheric scattering were included. In this calculation atmospheric scattering is neglected above 2000 km; but the effect on the mirror‐point distribution of slowing down of the electrons is included. These results are compared with some observed spatial distributions of elec

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03671

年代:1961

数据来源: WILEY

摘要:

Dipole representations of the earth's magnetic field have been found to have insufficient accuracy for the study of magnetically trapped particles. A coordinate system consisting of the magnitude of the magnetic fieldBand the integral invariantIhas been found to organize adequately measurements made at different geographic locations. The present paper shows that a parameterL= ƒ(B,I) can be defined that retains most of the desirable properties ofIand that has the additional property of organizing measurements along lines of force. Since the parameterLis the analog of a physical distance in a dipole field (the equatorial radius of a magnetic shell), it is usually found to present fewer conceptual difficulties than the integral invariantI

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03681

年代:1961

数据来源: WILEY

摘要:

A closed solution of an elementary thermal diffusion equation for solid semi‐infinite conductors is presented which satisfies the black‐body‐radiation boundary condition of proportionality between boundary heat conduction and the fourth power of surface temperature, as imposed by Stefan's law. Theoretical heating and cooling trends are shown to agree satisfactorily with empirical data measured with the aid of Suomi's bolometric equipment onboard Explorer VII for passages into and out of the earth's s

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03693

年代:1961

数据来源: WILEY

摘要:

Evidence from whistlers shows that the outer ionosphere contains columns or ducts of enhanced ionization. The theory of propagation in these ducts shows an upper cutoff frequency at one‐half the gyrofrequency. The average propagation velocity for whistlers trapped in the ducts can be approximated by assuming that the energy follows along the ionization maximum with wave normals aligned with the magnetic fiel

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03699

年代:1961

数据来源: WILEY

摘要:

Data from a number of nose whistlers indicate that the electron density in the outer ionosphere is directly proportional to magnetic field strength. The density has an annual variation of 2∶1 with a maximum near December. The average electron density is given approximately byN= 12,000 ƒH, whereNis the electron density per cubic meter and ƒHis the gyrofrequency in cycles per second. Local variations as large as 40 per cent are shown to exist on occas

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03709

年代:1961

数据来源: WILEY

摘要:

Temperature and relative humidity reported by the radiosonde have long been converted to radio refractive index without regard to sensor time lag. Past studies of radio ducting incidence have shown that under restricted conditions only corrections for humidity sensor lag need be made. It is here shown that lag constants currently in the literature are inadequate under conditions of superrefraction of radio waves. Use of currently available lag constants indicates that, should any correction be made, both temperature and humidity sensor lags must be considered for any climatological comparison of ducting incidence. By ignoring sensor time lag, one tends to underestimate ducting incidence; by correcting only for humidity sensor lag, one tends to overestimate ducting incidence.

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03717

年代:1961

数据来源: WILEY

摘要:

It has been found that ozone heating is capable of producing atmospheric ‘tidal’ oscillations whose semidiurnal component is in close agreement with ground‐level observations, both in magnitude and in phase. No assumption of an atmospheric reasonance is req

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03723

年代:1961

数据来源: WILEY

摘要:

Traveling atmospheric pressure waves with periods from 20 to 80 seconds and pressure amplitude from about 1 to 8 dynes/cm2have been recorded at a microphone station at Washington, D.C., during intervals of high geomagnetic activity. Trains of these waves can be expected at Washington from a quadrant approximately centered on north whenever the magnetic indexKPrises to a value above 5. Their horizontal phase velocity across the station is usually higher than the local speed of sound. During two ‘red’ auroras, clearly visible at Washington and at lower latitudes, the 20‐ to 80‐second‐period waves were accompanied by longer period, higher pressure, and much slower traveling pressure disturbances. Observational data on the wave systems are presented and

ISSN:0148-0227    

DOI:10.1029/JZ066i011p03727

年代:1961

数据来源: WILEY