摘要:

The Princeton University telescope on the Orbiting Astronomical Observatory 3 was used for occultation measurements of upper atmospheric species. The target star, β Cen, and observing date, July 26, 1975, were selected so that the line of sight grazed the earth's limb at local midnight. Observations at 2580, 2825, 2997, 3100, and 3428 Å produced ozone absorption data of high statistical accuracy between 48‐km and 114‐km tangent altitude. Near‐exponential density profiles are obtained up to 85 km. Near 100 km a significant density excess above the extrapolated low‐altitude profile is observed. Near‐equatorial observations at altitudes up to approximately 75 km agree well with theoretical calculations. Ozone densities measured at 6.5°–12.5°S above approximately 75 km exceed our theoretical calculations and are not understood at the present time. A search for the 1188‐Å chlorine line in the 1187‐Å O2absorption feature was carried out at tangent altitudes of 96–116 km. An upper limit to the atomic chlorine mixing ratio at 106 km of 3 ppb is found. This upper limit exceeds the expected value for atomic chlorine by a fact

ISSN:0148-0227    

DOI:10.1029/JA081i028p04997

年代:1976

数据来源: WILEY

摘要:

Waves in the neutral upper atmosphere have been measured by the open source neutral mass spectrometer (Oss) during both the elliptical and the circular phases of the Atmosphere Explorer‐C mission. Typical peak‐to‐peak wave amplitudes seen in [N2] are 30%, although amplitudes of 55% have been recorded. The amplitudes are mass dependent, Ar showing the largest perturbation. Helium is typically found to be out of phase with the heavier constituents. A survey of Oss data from 338 circular orbits shows that the highest wave amplitudes and the greatest number of occurrences are found in both the northern and the southern high‐latitude regions. The near‐simultaneous measurements of waves in both hemispheres at high latitudes also point toward a source related to conjugate phenomena. A possible second class of lower‐amplitude waves peaks at high latitudes; however, a secondary peak near ±25° magnetic latitude may be due to waves generated near the equatorial region. A study of wave amplitudes and occurrences during a magnetic storm shows a possible transpolar propagation of waves from a magnetically active region near local midnight. The assumption of horizontal propagation would explain the observed high‐latitude distribution of large‐amplitude waves. The results of this study are compared with previous measurements of neutr

ISSN:0148-0227    

DOI:10.1029/JA081i028p05002

年代:1976

数据来源: WILEY

摘要:

The simultaneous measurements of neutral composition both from Esro 4 and from Aeros‐A have provided a complementary set of data for studying the temporal and spatial characteristics of the thermosphere during a major geomagnetic storm on April 1–2, 1973. From the correlative studies of Ar and N2number densities, the magnetic indexap, and ground‐based magnetograms, it is found that the indexaponly reflects the gross features of the atmospheric disturbances. Superposed on the global component are localized regions of ‘hot spots’ which appear correlated with ground‐based magnetograms. Because of these localized disturbances the interpretation of the atmospheric response to geomagnetic storms become

ISSN:0148-0227    

DOI:10.1029/JA081i028p05013

年代:1976

数据来源: WILEY

摘要:

A comparative study of thermospheric storms for the equinox and winter conditions is presented based on the neutral composition measurements from the Aeros‐A Nate (Neutral Atmosphere Temperature Experiment) experiment. The main features of the two storms as inferred from the changes in N2, Ar, He, and O are described, and their implications to current theories of thermospheric storms are discussed. On the basis of the study of theFregion critical frequency measured from a chain of ground‐based ionospheric stations during the two storm periods, the general characteristics of the ionospheric storms and the traveling ionospheric disturbances are described. It is suggested that the positive and negative phases of ionospheric storms are the various manifestations of thermospheric sto

ISSN:0148-0227    

DOI:10.1029/JA081i028p05018

年代:1976

数据来源: WILEY

摘要:

The temporal variation of the solar flare particle alpha to proton ratio during energetic storm particle events is investigated within the framework of a model where a particle gains energy by successive reflections at the moving interplanetary shock front. The basic parameter which produces ratio changes is the energy dependence of the interplanetary diffusion coefficient and by inference the power spectral slope of the fluctuations in the interplanetary magnetic field. For a power spectrum of the typeP∼f−nwithn= 1 the diffusion coefficient is proportional to rigidity times velocity, and the alpha to proton ratio is therefore constant at equal energy per change. Monte Carlo simulation of the particle‐shock interaction shows that even for power spectral slopes as high as 4/3 the ratio at equal energy per charge does not vary greatly during the event. It is concluded that composition changes during energetic storm particle events reflect (at least in part) the power spectral slopenof the magnetic fluctuations responsible for the particle scatt

ISSN:0148-0227    

DOI:10.1029/JA081i028p05027

年代:1976

数据来源: WILEY

摘要:

A comprehensive analysis of the transient north‐south anisotropy that is a characteristic feature of Forbush decreases has revealed that the direction of axial anisotropy is determined by the inclination of the associated interplanetary shock wave with respect to the ecliptic plane. The study included all recorded cosmic ray events (15) for which the sense of the anisotropy vector could be determined by a rigorous statistical procedure and for which the associated shock orientation is known. In contrast, similar examinations of the same set of events showed that there is no correlation between the sense of the north‐south anisotropy and either the heliolatitude of the associated solar flare or the inclination of the interplanetary magnetic field. An additional investigation of the collection of heretofore puzzling events during which the direction of anisotropy flips suddenly has shown that the reversal is associated with the arrival of a second shock, presumably having an inclination that is opposite to that of the earlier one associated with the onset of the Forbush decrease. These results provide new insight into the key role played by shocks in the transient modulation mechan

ISSN:0148-0227    

DOI:10.1029/JA081i028p05032

年代:1976

数据来源: WILEY

摘要:

Trapped protons in the outer radiation belt of the earth can be removed through charge exchange by collisions with neutral exospheric hydrogen. The neutralized energetic particles escape into interplanetary space as well as to low altitudes. At low altitudes these particles constitute a copy of the outer radiation belt and have been repeatedly observed. It is proposed that the energetic neutral hydrogen escaping into interplanetary space is responsible for the recently observed highly anisotropic hydrogen flux at energies 0.29–0.5 MeV during solar quiet time. The expected energy spectrum of the neutral hydrogen flux in interplanetary space is derived from low‐altitude measurements obtained on board the Esro 4 satellite and is compared with the observations. The result supports the hypothe

ISSN:0148-0227    

DOI:10.1029/JA081i028p05039

年代:1976

数据来源: WILEY

摘要:

Effects of the time dependence of the sun's magnetic field upon the interplanetary field in the solar wind are considered. General expressions for the interplanetary field are developed under the assumptions that the radial component of the sun's field at some reference surfacer0can be described in terms of spherical harmonics with coefficients which are functions of time represented by Fourier series and that the solar wind expands radially in a steady state flow. Some of the simplest field configurations are examined in additional detail. It is shown that the variation in the sun's field may produce elliptically polarized fluctuations in the interplanetary field; may generate field strengths in the θ direction, i.e., the north‐south direction, that are comparable in magnitude to the spiral field; may produceBθwith nonzero averages over significant periods of time; and may produce systematic deviations from the nominal steady state spiral angle over such peri

ISSN:0148-0227    

DOI:10.1029/JA081i028p05043

年代:1976

数据来源: WILEY

摘要:

The dependence of solar wind speed on latitude as influenced by the magnetic field configuration of the inner corona is studied. It is found that in general, a dipolelike field geometry characteristic of a minimum‐type corona tends to produce a solar wind speed distribution which increases with heliographic latitude, in accordance with observations. At very high coronal base densities and temperatures, however, this effect is minimal or even inverted. Physically, the field affects the wind speed through its area divergence, a larger divergence resulting in correspondingly lower speeds. During solar minimum, eclipse photographs suggest that the field divergence increases from pole to equator, a characteristic not apparent during solar maximum. Hence we expect the latitudinal increase in speed to be most pronounced at the minimum phase of solar activit

ISSN:0148-0227    

DOI:10.1029/JA081i028p05049

年代:1976

数据来源: WILEY

摘要:

In order to develop a more realistic set of constraints for theories of solar wind high‐speed streams a detailed study was made of the fastest streams observed at 1 AU during the time period spanning March 1971 through July 1974. Streams were accepted for study only if (1) the maximum speed exceeded 650 km s−1; (2) effects of stream‐stream dynamical interaction on the flow parameters could be safely separated from the intrinsic characteristics of the high‐speed regions; (3) the full width at half maximum (FWHM) of the stream when mapped back to 20 solar radii by using a constant speed approximation was greater than 45° in Carrington longitude; and (4) there were no obvious solar‐activity‐induced contaminating effects. Nineteen streams during this time interval satisfied these criteria. Average parameters at 1 AU for those portions of these streams aboveV= 650 km s−1were as follows: (1) the maximum speed and FWHM were 741 ± 49 km s−1and 89° ± 34°, respectively; (2) proton and electron temperatures were (2.3 ± 0.9) × 105K and (0.99 ± 0.08) × 105K, respectively; (3) the convected proton enthalpy flux of (24 ± 5) × 10−3erg cm−2s−1was nearly an order of magnitude larger than the radial component of conducted electron heat flux of (2.8 ± 0.9) × 10−3erg cm−2s−1and a factor of 2 greater than the inferred convected Alfvén wave energy flux of (11.6 ± 4.7) × 10−3erg cm−2s−1; (4) the proton particle flux wasNV= (3.3 ± 0.5) × 108cm−2s−1; and (5) the convected energy flux, including the flux of work done against the sun's gravitational field in traveling from the sun's surface to 1 AU, was 2.4 ± 0.4 ergs cm−2s−1. Not only is it not presently known why the electrons are significantly cooler than the protons within high‐speed regions, but also observed particle fluxes and convected energy fluxes for speeds greater than 650 km s−1are substantially larger than those values predicted by any of the existing theories of solar wind high‐speed streams. More work is therefore needed in refining present solar wind models to see whether suitable modifications and/or combinations of existing theories based on reasonable coron

ISSN:0148-0227    

DOI:10.1029/JA081i028p05054

年代:1976

数据来源: WILEY