摘要:

Twenty‐seven‐day averages of the solar‐wind density and flow speed, observed by Vela 3 and 4 spacecraft between July 1965 and July 1968, are found to vary with the heliographic latitude of observation. High average densities and low average flow speeds were measured near the solar equator; low average densities and high average flow speeds were measured near the northern and southern extremes of the earth's heliographic latitude excursion. Possible instrumental and statistical explanations of this pattern of variations are discussed and found to be unlikely. The variations can be reasonably interpreted in terms of a latitude‐dependence in the structure of high‐speed solar‐wind streams related to sol

ISSN:0148-0227    

DOI:10.1029/JA076i022p05145

年代:1971

数据来源: WILEY

摘要:

The equations for a linearly polarized Alfvén wave, propagating parallel to the direction of the average magnetic field in a perfectly conducting fluid, are solved to second order in the wave quanities for cases where the fluid obeys single adiabatic or double adiabatic equations of state. To this order, we find no change in the wave magnetic field or transverse wave velocity, but longitudinal wave velocity and density fluctuations appear, driven by gradients in the wave magnetic‐field pressure. This is in contrast to the common belief that even large‐amplitude Alfvén waves remain purely transverse. The density fluctuations can become quite large when the Alfvén speed is close to the ion sound speed in the fluid; this condition may at times exist in the solar wind at 1 AU. We suggest that part of the density fluctuations observed in the solar wind by satellites and interplanetary scintillation may be associated with large‐amplitude Alfvén waves. Heating of the solar wind might result if the ion sound waves, which are driven by the Alfvén waves, are apprecia

ISSN:0148-0227    

DOI:10.1029/JA076i022p05155

年代:1971

数据来源: WILEY

摘要:

We use Ogo 5 interplanetary particle and wave observations from March 11 and 12, 1968, to demonstrate that oscillations near the characteristic upper hybrid and electron plasma frequencies are produced when nonthermal electrons (Ee≳700–800 ev) flow upstream. The results are discussed in terms of resonant interactions, with the streaming particle speed set equal to the wave phase speed. The nonthermal electrons can interact with long‐wavelength longitudinal electron plasma oscillations, or with relatively short‐wavelength transverse waves. Other Ogo 5 measurements favoring the electromagnetic wave‐particle interaction are cited, and the relations between these observations and some theories of type II solar radio bursts are discusse

ISSN:0148-0227    

DOI:10.1029/JA076i022p05162

年代:1971

数据来源: WILEY

摘要:

The response of the moon to a large discontinuity in the interplanetary magnetic field with |ΔB| = 6 γ, observed by the lunar satellite Explorer 35, is examined on the basis of presently available theoretical models. A simplified model of the poloidal mode response of the moon to such a discontinuity predicts that its effects will be undetectable at satellite altitude. Ness has earlier presented an interpretation with respect to the electrical conductivity of the lunar interior. The absence of a bow or limb shock wave suggests that the toroidal mode response of the moon is also undetectable at satellite altitude

ISSN:0148-0227    

DOI:10.1029/JA076i022p05172

年代:1971

数据来源: WILEY

摘要:

A numerical study was made of the confinement of a uniform magnetic field by a warm plasma with a net velocity parallel to the confined field. Parker's assumptions of a vanishing electric field and vanishing trapped‐particle currents and pressures were adopted. For a given proton temperature equilibriums were found whenever the electron temperature exceeded a certain critical value. This result is in qualitative agreement with an estimate presented by Parker, but it is in direct conflict with Lerche's nonexistence proof. A crucial error in that proof is identified. The properties of the equilibrium solutions are discussed. Finally, the equilibrium confinement with the incident streaming plasma tangential to the magnetopause but perpendicular to the confined field is treated. It is concluded that in the geomagnetic equatorial plane equilibriums of Parker's type are possible on the morning side but not on the afternoon side of the magnetospher

ISSN:0148-0227    

DOI:10.1029/JA076i022p05181

年代:1971

数据来源: WILEY

摘要:

A detailed signature for individual substorms is sought in the interplanetary medium. Hourly values of interplanetary field and plasma parameters are correlated with hourly averages of theAEindex. An interplanetary variable involving the southward component of the interplanetary field in the solar magnetospheric coordinate system is shown to be singularly important for the generation of substorms. The parameter best correlated withAE(0.8 correlation coefficient) is the integral or summation ofBzsouth over time for the hour preceding theAEhourly average. The magnitude of this integral appears to be linearly related to the hourly average ofAE. The linearity suggests that the southward interplanetary field represents a continuing dynamic mechanism for the production of substorms rather than just being a trigger for the release of energy that has been stored in the magnetospheric tail. Furthermore, the additional energy that the southward component of the interplanetary field apparently puts into the tail is not accumulated for longer than about 1 hour before it appears as a substorm. A linear fit toAEthat uses interplanetary parameters is obtained for two time intervals of data.

ISSN:0148-0227    

DOI:10.1029/JA076i022p05189

年代:1971

数据来源: WILEY

摘要:

First observations of the plasmas in the dayside polar magnetosphere were obtained with the earth‐satellite Imp 5 during July‐August 1969. Several of the more important observational results are the following. (1) The polar neutral ‘points’ that appear at the high‐latitude magnetopause in mathematical models for the shape of the geomagnetic cavity formed by the interaction of the solar wind with the geomagnetic field are observationally ‘bands’ with width ∼1REacross the dayside high‐latitude magnetopause (one band in the northern hemisphere and presumably a second in the southern hemisphere). (2) These two bands, or regions of the magnetopause through which the magnetosheath plasma has direct access to the magnetosphere, and the corresponding extension of these bands from magnetopause to auroral altitudes have been designated herein as the ‘polar cusps.’ (3) At all other positions of the dayside magnetopause, the magnetopause appears to be an effective barrier against the direct entry of magnetosheath plasma. (4) During periods of relative magnetic quiescence the intersection of the dayside polar cusp with the auroral zone is positioned at invariant latitude Λ=79° (±1°) and its latitudinal width is 20 to 400 km projected onto the auroral zone. (5) During periods of the relative magnetic disturbance the position of the polar cusp moves equatorward by several degrees in invariant latitude without a large increase in its latitudinal width, i.e., by factors ≲2. (6) The high‐latitude termination of energetic trapped electron (E>45 kev) intensities in the high‐latitude dayside outer radiation zone occurs coincident with the polar cusp, albeit these intensities are small and of irregular profile with radial distance in this region. (7) No measurable intensities of energetic electrons (E>40 kev), magnetosheath protons and electrons, and ring‐current protons were observed at latitudes above the polar cusp, i.e., in the polar cap region. (8) The proton and electron differential energy spectrums as viewed in the solar direction in the distant polar cusp (within several earth radii of the magnetopause) are identical to those observed within the magnetosheath to within observational accuracy. (9) The bulk velocity of protons in the distant polar cusp as deduced from the angular distributions appears to be lower than that of the magnetosheath plasma near the magnetopause by factors ∼2 or 3. (10) In the midaltitude polar cusp at ∼4 to 5REgeocentric radial distances, the proton spectrum differs from that at the magnetosheath in that protons with energies ≲500 ev are severely less than those observed in the magnetosheath. (11) The proton spectrums in the midaltitude polar cusp are similar to those in the distant plasma sheet with the exception that the proton number densities in the polar cusp are typically larger by factors ∼20 to 200. (12) The angular distributions of proton intensities in the midaltitude polar cusp are strongly peaked along the local magnetic field (i.e., down into the auroral zone); the dimensions of the atmospheric loss cone at these altitudes appear to be insufficiently large to account for the observed anisotropy; and (13) the magnetosheath plasma in the midaltitude polar cusp is observed to be separated into two thin sheets, one of magnetosheath proton intensities and the other populated with magnetosheath electrons; these sheets are immediately adjacent to each other with the electron sheet equatorward of the proton sheet; their latitudinal widths as projected into the auroral zone are roughly equal, ∼10 to 200 km. These observations, along with recent measurements from other earth satellites, have been interpreted in terms of a proposed magnetospheric model with several new features, among which are the following. (1) Plasma sheet protons gain access to the magnetospheric field lines via the dayside polar cusps. (2) All magnetic field lines threading the distant plasma sheet beyond ∼20 or 30REwere convected from the polar cusps. (3) Magnetic field lines in the polar cap region of the magnetotail

ISSN:0148-0227    

DOI:10.1029/JA076i022p05202

年代:1971

数据来源: WILEY

摘要:

Measurements of precipitating protons in the energy range 2.5–200 kev have been made on OV1‐15 (1968‐59A), a low‐altitude polar satellite, with a combination of electrostatic analyzers and integral foil detectors. During disturbed times, precipitating proton fluxes in the range 107–108cm−2sec−1are seen. On several occasions, it has been possible to compare the spatial distribution of precipitation with the plasmapause profile taken by Ogo 5 during all phases of magnetic storm activity. It is found that the near‐earth boundary of maximum proton precipitation lies just inside the plasmapause. If observed pitch‐angle distributions are classified according to whether the loss cone is nearly empty or otherwise, it is found that the corresponding 40‐kev flux intensities andLvalues separate into two classes in a way described by weak versus strong pi

ISSN:0148-0227    

DOI:10.1029/JA076i022p05220

年代:1971

数据来源: WILEY

摘要:

Recent experimental determinations of the total proton γ‐ray production cross sections are used together with equatorial proton fluxes measured on ATS 1 to calculate the predicted diurnal variations in the precipitating low‐energy solar proton‐produced γ rays. Reasonable agreement is obtained in the relative diurnal variations for observations separated 2 hours in local time and on approximately the sameLshell. However, the predicted γ‐ray fluxes, using the equatorial data, are approximately 10 times less than those actuall

ISSN:0148-0227    

DOI:10.1029/JA076i022p05235

年代:1971

数据来源: WILEY

摘要:

The equatorial solar protons measured on ATS 1 during the January 28, 1967, solar event are used together with the ionosphere model of Potemra et al. (1969) to calculate the expected daytime 30‐MHz riometer absorption. The computed absorption values compare favorably with the riometer observations at Byrd, Antarctica, located on approximately the sameLshell (L=7) as ATS 1 (L=6.4). The latitude profiles measured by the polar‐orbiting satellite 1963‐38C show that during the decay of the event Byrd was within a latitude region where fewer protons precipitated in comparison to higher latitudes. The absorption measured at Byrd during this period was systematically lower than the absorption measured at either South Pole (L=13) or McMurdo (L=32), stations well within the polar cap. Absorption values computed from the 1963‐38C proton fluxes at the latitude of Byrd compare favorably with the observed absorption at this station. Empirical linear relationships between the square root of the 2π‐omnidirectional ATS 1 proton fluxes greater than someEminand the daytime 30‐MHz riometer absorptions are also studied, with an excellent correlation found forEm i nover a wide

ISSN:0148-0227    

DOI:10.1029/JA076i022p05244

年代:1971

数据来源: WILEY