摘要:

A weak interplanetary magnetic field is shown to be compressed into a boundary layer of high magnetic‐field intensity several earth radii deep at the surface of the magnetosphere. Thus, if the solar wind consisted of streams of plasma interspersed with an interplanetary magnetic field, magnetic intensity beyond the magnetopause would be expected to fluctuate for several earth radii from zero to as high as the value at the boundary of the magnetosphere. The compressed field is tangential to the boundary and, in general, unrelated in direction to the field inside the boundary. Both conclusions are in agreement with satellite measurements. Particles in the solar wind travel smoothly around to the dark side of the earth where their pressure and the compressed interplanetary magnetic pressure may be expected to close the hollow the geomagnetic field creates in the solar win

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01159

年代:1964

数据来源: WILEY

摘要:

The shape of the boundary of the geomagnetic field in a solar wind has been calculated by a self‐consistent method in which, in first order, approximate magnetic fields are used to calculate a boundary surface. The electric currents in this boundary produce magnetic fields, which can be calculated once the first surface is known. These are added to the dipole field to give more accurate fields, which are then used to compute a new surface. This iterative procedure converges rapidly, and the final surface may be tested by finding how close the total fields outside the boundary are to the required value of zero. The result of this stringent test is that the magnetic fields in the plasma outside the fourth surface and within twice the distance to the boundary on the solar side are everywhere less than 1 per cent of the geomagnetic dipole field in the absence of a solar wind. This surface has been used to calculate the perturbation of the geomagnetic field by the solar wind; the results of these calculations, plus a number of applications, are given in an accompanying pape

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01169

年代:1964

数据来源: WILEY

摘要:

From the three‐dimensional numerical solution to the Chapman‐Ferraro problem of a steady solar wind perpendicularly incident upon a dipole field, a simple spherical harmonic description of the distorted field is obtained. From this, a three‐dimensional picture of the field line configuration within the magnetosphere is given. The field lines are found to be compressed on both the daytime and nighttime sides. The behavior of the field lines on the daylight side changes abruptly as one approaches a critical latitude, which ranges between 80° and 85°, depending on the intensity of the solar wind. Above this latitude, lines originating along the noon meridian pass over the north pole and cross the equator along the midnight meridian. The behavior of conjugate‐point phenomena and trapped particles near this critical latitude is discussed. Magnetic changes at the earth's surface due to an increase in the solar wind intensity are calculated. The diurnal variations due to a steady solar wind are also calculated; they are found to be small compared with observe

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01181

年代:1964

数据来源: WILEY

摘要:

The spherical harmonic expansion of the perturbation of the geomagnetic field is calculated, using the magnetopause shape and current system determined previously by the moment technique. The expansion coefficients are compared with those determined by another method by Mead.

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01197

年代:1964

数据来源: WILEY

摘要:

It has been suggested that charge separation electric fields in the Chapman‐Ferraro sheath generate currents large enough to trigger the two‐stream plasma instability. We argue that, as the electric field energy saturates, the drift energy is lowered and the electron temperature rises so that the instability is generally not quenched. Instead, it can change form, leading to growing ion waves. The equilibrium state then involves fluctuating electromagnetic fields which allow ‘fast’ plasma diffusion across the main magnetic field. In this case, the exospheric thermal plasma, together with that part of the solar wind plasma that has attained energy equipartition, can form current systems leading to a broad, disordered transition region between the magnetosphere and the sol

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01201

年代:1964

数据来源: WILEY

摘要:

By means of an idealized elastic string model, the symmetry relations in the magnetic perturbation at a pair of conjugate points due to oscillation of the lines of force of the geomagnetic field are studied. For oscillations of odd modes the change inH(ΔH) is parallel, and that in the east component (ΔD) is antiparallel, at the conjugate points, whereas for oscillations of even modes ΔHis antiparallel and ΔDis parallel at the conjugate points. Hence in the former case the polarizations (as viewed downward) at the conjugate points are mirror images of each other with respect to the meridian plane, and in the latter case they are mirror images with respect to the equator. Several examples indicating these symmetry relations are presen

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01211

年代:1964

数据来源: WILEY

摘要:

Two different methods are discussed for taking geomagnetic effects into account when evaluating the counting rate of a cosmic‐ray detector for a given anisotropic radiation source. The applicability of these methods is studied, and some properties of the asymptotic cone of acceptance are found by performing the transformation through the geomagnetic dipole field of the infinitely small solid‐angle elements that constitute the acceptance cone. A solid angle at the detector is greater than the corresponding asymptotic cone for all latitudes, angles of incidence, and energies except immediately above the geomagnetic cutoff. This focusing effect is especially good for high‐latitude detectors, which thus have the best resolving

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01217

年代:1964

数据来源: WILEY

摘要:

Forbush decrease data recorded by neutron monitors during PCA events support the interpretation of the absorption‐time profiles of PCA events as due to solar particles under the influence of magnetic fields carried by solar plasma. All PCA events showing evidence of strong trapping of solar particles are accompanied by strong Forbush decreases, the magnitudes of which are a function of the delay time from flare to SC storm. Those PCA events showing little evidence of trapping are accompanied by only very weak decreases. The large western excess of these latter events is explained in terms of sun‐earth magnetic linkage set up by earlier flare activity. The relative merits of two models of the interplanetary fields are exami

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01233

年代:1964

数据来源: WILEY

摘要:

Measurements were made of electron fluxes and spectrums above 900 kev at altitudes between 200 and 700 km in early September and October 1962 aboard two near‐polar Air Force satellites. The particle fluxes were observed with shielded solid‐state detectors having a 2π solid angle. The results show that electrons are lost from the radiation belts into the atmosphere along narrow ranges ofLnearL= 1.2 andL= 2 as well as in theL= 3 to 8 region. TheL= 2 andL= 3 to 8 fluxes and spectrums exhibit temporal variations. A typical precipitating flux atB= 0.35 gauss,L= 2.0, is 103/cm2sec withE>0.9 Mev. A typical integral energy spectrum forL= 2,B= 0.35 gauss, isE−3between 0.9 and 1.7 Mev. Comparison of results with pre‐Starfish measurements indicates that the fluxes of electrons observed nearL= 1.2 andL= 2 are not connected with the high‐altitude explosion of Ju

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01239

年代:1964

数据来源: WILEY

摘要:

The role of VLF waves in precipitating fast electrons is studied. It is found that, by Doppler‐shifting whistler frequencies (1–10 kc/s) up to the local Larmor frequency, a resonant interaction of the type proposed by Dragt and Wentzel (for interaction of protons with hydromagnetic waves) can cause the mirror points of the electrons to move randomly. The conditions for resonance lead to a very characteristic dependence onLof the regions of the magnetosphere where VLF waves can effectively precipitate electrons. In general, one expects to see, in a plot of flux versusL, two peaks separated by a broad minimum, the first peak nearL≃ 1.2 and the second near L ≃ 2. Such peaks have been seen by several experimenters. In certain regions of space it may be that whistlers can dominate the lifetimes of trapped electrons, especially fo

ISSN:0148-0227    

DOI:10.1029/JZ069i007p01251

年代:1964

数据来源: WILEY