ISSN:0148-0227    

DOI:10.1029/JA073i013p04133

年代:1968

数据来源: WILEY

摘要:

It is shown that energy in the form of magnetic field can be converted with essentially 100% efficiency into synchrotron radiation and cosmic rays under conditions expected to be present in astrophysical objects such as the Crab Nebula. The radiation reaction from synchrotron radiation provides an effective resistance that allows merging of magnetic field lines. The induction electric field generated by this merging accelerates the electrons to restore the energy lost as radiation. In astrophysical applications this mechanism can maintain the relativistic electron energies.

ISSN:0148-0227    

DOI:10.1029/JA073i013p04135

年代:1968

数据来源: WILEY

摘要:

Measurements made between May 1965 and November 1967 of the Balmer‐α emission arising from Lyman‐α scattering in the geocorona have been normalized to remove the effects of geometry of scattering. The remaining variations are interpreted in terms of variations in the column abundance and distribution of hydrogen in the geocorona, variations in the intensity of the line center of the solar Lyman‐β flux, and possible variations in molecular oxygen distribution. Diurnal, annual, and solar cycle variations are found, together with probable fluctuations with periods of a few days. It is pointed out that there may be significant variations in hydrogen production rate that affect the column a

ISSN:0148-0227    

DOI:10.1029/JA073i013p04139

年代:1968

数据来源: WILEY

摘要:

The Rice University suprathermal ion detector aboard the ATS 1 synchronous orbit satellite has established the existence of occasional bulk motion of the magnetospheric thermal ions. This conclusion is based on the observation of a highly directional flux of positive ions, moving with a flow velocity of approximately 30 km/sec with a thermal energy substantially less than the flow velocity energy. The flow direction and magnitude observed are generally consistent with present theories of magnetospheric convection. The electric field required to account for the observed flow velocity is 5 millivolts/meter, and the electric field direction is across the magnetosphere from the dawn to dusk side. A gross pattern of magnetospheric convection that is consistent with this, as well as previously reported ATS 1 data, is presented. Implications of the requisite electric field for the energetic trapped radiation in the outer portion of the outer zone of the Van Allen radiation belt are briefly discussed.

ISSN:0148-0227    

DOI:10.1029/JA073i013p04151

年代:1968

数据来源: WILEY

摘要:

The direction of the cosmic‐ray anisotropy during solar proton events and the concurrent direction of the interplanetary magnetic field vector are compared, using data obtained in 1966 by the Pioneer 6 spacecraft. It is shown that the nonequilibrium cosmic‐ray anisotropy (normally observed to exhibit an amplitude in the range 20–50%) is field‐aligned, while the equilibrium anisotropy (normally observed to exhibit an amplitude in the range 5–15%) is independent of the direction of the magnetic field vector. Two anomalous proton events during which pronounced anisotropies were observed with their maximum cosmic‐ray fluxes directed toward the sun are discussed. It is shown that during these proton events there were synchronous reversals of 180° in the direction of the magnetic field vector and the cosmic‐ray anisotropy in association with the passage of a magnetic sector boundary past the spacecraft. These observations are interpreted as possible evidence for there being a complex loop in the

ISSN:0148-0227    

DOI:10.1029/JA073i013p04159

年代:1968

数据来源: WILEY

摘要:

Fluxes and energy spectra are presented for electrons above an energy of ∼0.4 Mev on a worldwide basis over the range ofLvalues 1.6–7, as measured in the fall of 1963 on a low‐altitude polar‐orbiting satellite. The data have been subjected to a systematic analysis in terms of the longitude variations in intensity and spectral shape. In contrast to the behavior atL≲ 1.7, significant fluxes of electrons are observed in the outer radiation belt at virtually all longitudes, and the energy spectra of the precipitating electrons are comparable to those of electrons trapped at minimum altitudes of 200–350 km. For the precipitating electrons, the data have been analyzed in terms of the interval of longitude drift between the measurement location and the point where theB, Ltrace of the observation point was last below 100 km in altitude. The rates of flux buildup with longitude drift are rather slow in the inner belt, whereas in the outer belt regions, the intensities rapidly build up to near equilibrium values. Comparisons have been made of the rates of flux buildup with calculations of pitch‐angle diffusion, using the Fokker‐Planck formalism. Over a rather wide range of magnetic latitudes covering the outer radiation belt and slot regions, where the low‐altitude precipitations vary enormously in magnitude, the diffusion coefficient varies by only a factor of 4 and is consistent with the dominant loss mechanism for trapped electrons being pitc

ISSN:0148-0227    

DOI:10.1029/JA073i013p04167

年代:1968

数据来源: WILEY

摘要:

A coordinated experiment with rocket‐borne particle detectors and ground‐based photometers has shown that the ratio of the differential flux of alpha particles withEa∼ 200 kev to protons withEp∼ 100 kev was approximately 1.6% in an aurora on February 9, 1967. This value is consistent with ratios observed at that time by spacecraft in the solar wind but is not consistent with the ratio He++/H+of thermal ion densities measured between the ionosphere and an altitude of 20,000 km. These data argue that the energetic auroral ions were originally constituents of the solar wind and were accelerated at altitudes above 20,000 km by a mechanism that gives an energization proportional to the charge of the ion. The measured proton energy spectrum between a few hundred ev and 650 kev was used to predict the Hβ optical intensity; calculated limits of 35–105 rayleighs were in good agreement with the measured value of 46 R. An experimental upper limit of 1 R for the λ5876 He I intensity is not inconsistent with the alpha‐particle flux. Theoretical implications of these several results

ISSN:0148-0227    

DOI:10.1029/JA073i013p04185

年代:1968

数据来源: WILEY

摘要:

Measurements of the photoelectron spectrum at White Sands Missile Range in June 1965 are reported and compared with theory. The agreement is satisfactory and shows that a realistic treatment of photoelectrons, at least at low altitudes, is feasible with current information on atmospheric structure, solar fluxes, and cross sections. The theoretical model is also compared with measurements by Hinteregger in August 1959. Theory and experiment agree satisfactorily in this case also if one assumes a solar cycle variation of extreme ultraviolet solar radiation comparable with that observed for the 10‐cm radio flu

ISSN:0148-0227    

DOI:10.1029/JA073i013p04199

年代:1968

数据来源: WILEY

摘要:

A stable auroral red (SAR) arc was recorded the night of September 28/29 from stations at Fritz Peak, Colorado, and Richland, Washington. The first direct determination of position and altitude of an SAR arc was accomplished by triangulation from these two stations. The appearance of this arc marks the definite recurrence of this phenomenon after an apparent absence of four years. The arc occurred southward of an intense auroral display, and it was aligned parallel to lines of constantL. Average intensity of [O I] 6300 A emission in the brightest part of the arc was approximately 150 R. Altitude of the brightest region was determined from angular coordinates at the two stations to be 400 km at 0745 UT. A typical width across the narrow dimension of the arc was 160 km between half‐maximum intensity values. A sector of the arc almost 4200 km long was simultaneously within the combined range of the two stations. The arc occurred during a period of high magnetic activity, and though a comparably intense aurora borealis occurred the night before (September 27/28), no SAR arc was observed from either statio

ISSN:0148-0227    

DOI:10.1029/JA073i013p04213

年代:1968

数据来源: WILEY

摘要:

Evidence is presented that suggests that geomagnetic bay disturbances occur in two stages. The onset of each stage is accompanied by a Pi 2 micropulsation; the fact that a Pi 2 occurs almost synchronously over the earth's surface allows the onset of this micropulsation to be used to define the onset of each stage of a bay. The time lag between the onsets of the two stages ranges from about 10 to 30 minutes. The delay between the two stages is suggested to be the time required for the transfer of information from the front of the magnetosphere to the region of reconnection in the magnetotail. The recognition of the first stage of a bay as a precursor can facilitate high‐resolution studies of auroral phenomen

ISSN:0148-0227    

DOI:10.1029/JA073i013p04217

年代:1968

数据来源: WILEY