摘要:

A large increase in the atmospheric neutron flux was observed at balloon altitudes on September 3, 1966, during a solar proton event. The flux and energy spectrum of the solar particles are known with some precision from satellite detectors, as well as from our balloon measurements. From these data quantitative comparisons have been made with the predictions of Lingenfelter and Flamm (1964) on the production of neutrons in the atmosphere by proton interactions. The theory is in satisfactory agreement with the observations, although there is considerable uncertainty about the fraction of neutrons that leaked out of the atmosphere.

ISSN:0148-0227    

DOI:10.1029/JA075i025p04595

年代:1970

数据来源: WILEY

摘要:

Changes in the geomagnetic cutoff latitude for low‐energy (>2 Mev) solar protons have been compared with changes in the high‐latitude boundary of trapped energetic electrons during a magnetically disturbed period. These changes have been measured with good time resolution. The observations suggest that the depression of the cutoff latitude is partly due to an enlargement of the region of direct access, as indicated by the depression of the trapped electron boundary. In addition, solar protons become trapped and are transported to lower latitudes during magnetospheric substo

ISSN:0148-0227    

DOI:10.1029/JA075i025p04605

年代:1970

数据来源: WILEY

摘要:

Three simple photodiodes on the Spades satellite (1968‐059A) have measured the near‐earth solar flux in three broad wavelength intervals: 300–1150 A, 1150–1600 A, and 1600–2100 A. During the first 27 days of the satellite's lifetime, the signals in the two longer wavelength intervals showed nonrandom variations of more than 50% from the mean, and the short wavelength flux varied by 40%. Except for the 1150–1600 A channel, the variation did not correlate well withF10.7; all three channels showed a much stronger correlation with the area times intensity of calcium plage regions. The data are consistent with a model in which the effective plage temperature is about 1250°K higher than the background sun at all wavelengths in the 300–2

ISSN:0148-0227    

DOI:10.1029/JA075i025p04613

年代:1970

数据来源: WILEY

摘要:

Two days after the widely studied solar flare of July 7, 1966, an attempt was made to measure the average free‐electron number density of the solar wind between earth and Pioneer 6, by running the ‘dual frequency experiment’ beyond its design range. A recent detailed re‐examination of the raw data revealed that a worthwhile measurement could be inferred from part of the apparatus response; however, this measurement is ambiguous because of our inability to count the full cycles of the modulation phase of the radio signals. Three average‐density versus time curves were drawn from the same data. The average number density along the earth‐Pioneer line was compared with local number density measured at each end of the line. During these measurements, a large plasma cloud, preceded by a shock, engulfed the Pioneer and passed beyond. Timing and orientation were consistent with the theory that the cloud was ejected by the July 7 flare. Plasma‐cloud models were constructed in accordance with these data, following guidelines established by others who have attempted to determine the probable shape of shocks attributable to some solar flares. From these comparative studies, the most credible of our three possible measurements was selected

ISSN:0148-0227    

DOI:10.1029/JA075i025p04623

年代:1970

数据来源: WILEY

摘要:

The large‐scale properties of 19 flare‐associated solar wind disturbances observed by Vela 3 and Vela 4 satellites between August 1965 and June 1967 have been examined. It is generally found that the solar wind flow speed rises above the value measured immediately after the shock at the leading edge of such disturbances and remains elevated for at least 1 day. The mass and energy fluxes may either rise or fall after the discontinuous change at the shock. Integration of the excess of these fluxes above the preshock or ambient level gives the total mass and energy in the interplanetary disturbance. The average mass is found to be 3×1016g; the average energy (at 1 AU) is 5×1031ergs. Both the mass and energy are smaller for disturbances in which the energy flux falls after the shock than for disturbances in which it rises. Both quantities are larger for disturbances observed in early 1967 than for those observed in late 1965, thus suggesting that the mass and energy deposited in the solar wind by individual flares increased with the rise in solar activity during the period under discussion. The energy released by the flare (obtained by correcting for the solar gravitational potential at 1 solar radius) is found to be proportional to the mass released, despite variation of more than an order of magnitude in both quant

ISSN:0148-0227    

DOI:10.1029/JA075i025p04631

年代:1970

数据来源: WILEY

摘要:

Observations of the solar wind proton component made between July 1965 and June 1967 on the twin Vela 3 satellites are analyzed to give a statistical description of solar wind properties. Distributions of the observed proton density, flow speed, flow direction, thermal anisotropy magnitude, and anisotropy orientation are displayed; average values, standard deviations from the averages, median values, and ranges are given for this set of measured properties. Relationships among the solar wind properties are discussed. The distributions of the logarithm of the proton temperature, at differing flow speeds, are nearly normal, with a constant standard deviation from an average that increases with increasing flow speed. Statistical description of several basic plasma parameters and the measured solar wind properties under ‘quiet conditions’ are also presen

ISSN:0148-0227    

DOI:10.1029/JA075i025p04643

年代:1970

数据来源: WILEY

摘要:

The dispersion relation for ion acoustic waves that can propagate in a plasma, with the geometry corresponding to a collisionless perpendicular shock wave, is investigated. We find that for (k∥/k⊥)>(me/mi)1/2these modes behave as ion sound waves in an unmagnetized plasma. In the presence of ion sound turbulence, electrons diffuse rapidly. As a consequence, the distribution function becomes square‐shaped with spherical symmetry, and the electrons are heated. The heating rate is small, however, over a typical shock thickness. By comparing the results with measurements of the electron distribution function at the earth's bow shock, we find qualitative agreement regarding the shape off, whereas the observed jump of the electron temperature seems to be due essentially to adiabatic he

ISSN:0148-0227    

DOI:10.1029/JA075i025p04659

年代:1970

数据来源: WILEY

摘要:

We find that slow magnetoacoustic waves produce the magnetic field perturbations of the largest amplitude in the 0.01‐ to 0.1‐Hz frequency range within the ‘highly disturbed’ magnetosheath. The frequencies quoted are frequencies seen by the satellite. Rotational Alfvén waves with periods of several minutes and longer are also detected on most orbits. The power spectrum of rotational waves usually rises much more steeply below 0.01 Hz than the power spectrum of magnetoacoustic waves. We conclude that the magnetoacoustic waves are produced or strongly amplified at the earth's bow shock or in the outer magnetosheath. The observed rotational waves may be produced beyond the bow shock and carried into the magnetosheath by the so

ISSN:0148-0227    

DOI:10.1029/JA075i025p04666

年代:1970

数据来源: WILEY

摘要:

Convective flow of plasma in the magnetosphere is apparently driven by the interaction between the solar wind and the magnetosphere, but the flow pattern is regulated by the ionosphere and by pressure gradients in the magnetospheric plasma. The equations for conservation of ionospheric currents are used here to deduce theoretical flow patterns. The currents caused by the pressure of magnetospheric plasma are neglected. When all merging and friction processes are assumed to take place in the tail, and the dayside magnetopause is assumed to be an equipotential, computed trajectories of plasmasphere particles generally exhibit bulges in the dusk‐to‐midnight sector; if the conductivity model includes a sharp drop in conductivity at sunset, the computed bulge has a sharp onset near local sunset. When convection is assumed to be caused by merging or some other friction process operating near the nose of the magnetosphere, the outer‐plasmasphere trajectories have pronounced bulges in the dusk‐to‐midnight sector, with sharp onset near local sunset, if the conductivity model includes a sharp drop in conductivity at local sunset and a band of substantially enhanced Pedersen and Hall conductivities in the auroral zone. Vasyliunas' observations indicate that the plasma sheet is generally well defined throughout the evening and afternoon sectors of the magnetosphere, to about 1300 LT. Comparing the observed plasma‐sheet region with the regions of the computed flow patterns that are accessible to kilovolt electrons from the tail, we find agreement only in cases where the day‐night asymmetry is included in the conductivity model, and only when a potential drop ≳35 kv is assumed to exist across the nose region of the magnetosphere. Throughout most of the afternoon and evening sectors, the computed shape of the inner edge of the plasma sheet is insensitive to the assumption about the rate of precipitation. The computed ionospheric current patterns resemble observed currents only if the auroral‐zone Pedersen and Hall conductivities are assumed to be enhanced by an order of magnitude or more over the midlatitude nightside conductivities. When peak auroral‐zone enhancements of the Pedersen and Hall conductivities are taken to be 3.3 and 10 mhos, respectively, current patterns computed assuming a large voltage drop across the nose of the magnetosphere are roughly consistent with observedDP2 fluctuations; currents computed assuming that all merging activity takes place in the tail then generally

ISSN:0148-0227    

DOI:10.1029/JA075i025p04677

年代:1970

数据来源: WILEY

摘要:

Ring current protons (<50 kev), which are unaffected by ion cyclotron waves outside the plasmapause, undergo strong turbulent diffusion just inside the plasmapause. Lifetimes from ion cyclotron turbulence are predicted to be of the order of 1 hour, as observed by Frank for 3≤L≤5. During the main phase of a geomagnetic storm, the protons rapidly diffuse across the plasmapause (probably at the Bohm rate) and are lost before reaching the noon meridian, thus giving rise to the asymmetric part of the ring current. During recovery phase the ring current decays on a time scale of a day or less, as the turbulent region moves outward with the expansion of the plasmapause. Further decay takes place on a charge exchange time sc

ISSN:0148-0227    

DOI:10.1029/JA075i025p04699

年代:1970

数据来源: WILEY