摘要:

The rate coefficient of a chemical reaction is given by the equationk= ∫0∞συf(υ)dυ, where σ is an energy dependent cross section, υ is the relative speed of the reactants, andf(υ) is the relative speed distribution. For certain highly energy dependent ionospheric reactions,kis controlled by the population in the high‐energy tail of the relative speed distribution. This leads to problems in the application of laboratory measurements of rate coefficients to the atmosphere wheref(υ) can be significantly different for the same effective temperature. However, we show that the rate coefficients in the laboratory and in the thermosphere are approximately the same for the same value of the mean energy parameterKEcmif a thermal equilibrium apparatus such as a static or flowing afterglow system is used in the laboratory. The rate coefficients are in general not the same in the atmosphere as in drift tube experiments, although for O+in a helium buffer the difference is about 25% or less. As an application of the present work we derive new expressions for the rate coefficients of O+reacting with N2, O2, and NO in the ionosphere, using cross sections published by labor

ISSN:0148-0227    

DOI:10.1029/JA083iA03p00969

年代:1978

数据来源: WILEY

摘要:

Four different rocket techniques provided data on ozone at Wallops Island, Virginia, during the Aladdin 74 program. The entire altitude region from 19 to 108 km was covered, the different techniques providing overlapping profiles that included the afternoon of June 29 and the early morning of June 30 (local time). There were systematic differences between the chemiluminescent sonde and UV absorption techniques, the sonde giving the greater densities. These differences became larger with increasing altitude up to the maximum common altitude, 62 km. Both airglow and absorption techniques indicate a density minimum at 81 km of 1–3 × 107cm−3and agree within the experimental errors in the overlap region down to 72 km. Above 90 km the airglow experiment shows a relatively constant but structured density profile. The mass spectrometer measured a considerably higher ozone density at 90 km with a rapidly decreasing scale height up to 108 km. The experimental results are compared with photochemical‐transport

ISSN:0148-0227    

DOI:10.1029/JA083iA03p00978

年代:1978

数据来源: WILEY

摘要:

The monthly median values of maximum electron densityNmF2in theFregion are harmonically analyzed for a number of high‐latitude and auroral zone stations for each hour of the day during 1958 and 1964. In the high‐activity year 1958 the annual maximum appears in December around 70°N (geographic latitude) for a few hours around noon. The December excess diminishes gradually toward the south, though the duration over which it lasts increases toward the dip equator. By 70°S a slight June enhancement is seen around noon. During the remaining hours of the day a December phase is seen around 70°S, having a large amplitude which decreases toward the north, reaching a slight June excess by 70°N. A 6‐monthly component with equinoctial maximums exists at all stations for all hours of the day, the amplitude being somewhat larger in the south than it is in the north. In the low‐sunspot year 1964 the December phase of the annual component is present in the north with low amplitude for a few hours around noon. The same phase prevails in the south. This is followed in local time by a large‐amplitude June phase in the north and a December phase in the south. The 6‐monthly component is predominant during daytime only and has equinoctial maximums. The current theories are shown to be inadequate to explai

ISSN:0148-0227    

DOI:10.1029/JA083iA03p00983

年代:1978

数据来源: WILEY

摘要:

A theory is developed for ambipolar diffusion in a multiconstituent weakly ionized plasma. The implications of the presence of negative ions and of differing positive ion and negative ion diffusion coefficients are found. In particular, the presence of numerous negative ions is found to enhance the diffusion of the electrons. Furthermore, this theory of multiconstituent ambipolar diffusion is extended to include the nonneutral case in which the scale length of the inhomogeneity is smaller than or of the order of the electron Debye length.

ISSN:0148-0227    

DOI:10.1029/JA083iA03p00989

年代:1978

数据来源: WILEY

摘要:

A sudden commencement of a geomagnetic storm occurred at 1434 UT on September 18, 1974. A traveling ionospheric disturbance was detected about an hour later by the incoherent scatter radar at Millstone Hill, Massachusetts (42.6°N, 71.5°W), and still later by the incoherent scatter radar at Arecibo, Puerto Rico (18.3°N, 66.7°W). Measurements of the vertical distribution of electron temperature, ion temperature, and electron density made during the passage of the disturbance at both stations showed significant perturbations in comparison to the geomagnetic quiet time values obtained on the previous day. We calculated characteristics of the thermospheric gravity wave from a time‐dependent dynamic model of the thermosphere. The wave source is assumed to be enhanced electric currents and particle heating over the polar cap region. The gravity wave generated by the impulsive heating propagates equatorward, and its characteristic structure changes as it progresses to lower latitudes. The calculated neutral temperature and wind perturbations are added to the quiet time variations in a diurnal model of the mid‐latitude ionosphericFregion to calculate the time‐dependent properties of the ionosphere during the passage of the wave over both incoherent scatter radar stations. By requiring agreement between the calculated and observed ionospheric structure we estimated the magnitude of the gravity wave energy source. For the event on September 18, 1974, we obtained reasonably good agreement between the calculated and observed ionospheric structures for a total energy input of about 2 × 1015J, occurring over a period

ISSN:0148-0227    

DOI:10.1029/JA083iA03p00999

年代:1978

数据来源: WILEY

摘要:

Solar wind speeds measured from the Helios 1 solar probe between 0.31 and 1 AU and the earth‐orbiting Imp 7/8 satellites have been correlated with coronal holes as determined fromKcoronal brightness measurements. In March 1975 during perihelion passage, Helios 1 traversed the range of heliographic latitudes from −6° to +6° in a period of only 20 days. During that time the space probe crossed the northern boundary of the high‐speed stream associated with an equatorward extension of the south polar coronal hole. While this same stream continued to be observed by Imp satellites at −5° latitude, it was no longer observable from Helios 1 at +5° latitude. The conclusion is that sharp boundaries separate high‐speed flows from the surrounding solar wind. The thickness of the boundary in latitude appears to be narrower than about 10°. The local latitudinal gradient in flow speed is at least 30 km s−1deg−1. With less confidence it can be deduced from the Helios 1 data that the actual gradients at 0.31 AU might even exce

ISSN:0148-0227    

DOI:10.1029/JA083iA03p01011

年代:1978

数据来源: WILEY

摘要:

A steady three‐fluid model of the solar coronal expansion, in which4He++ions (alphas) are treated as a nonminor species, is developed for nonspherically symmetric flow geometries of the general sort thought to be characteristic of coronal holes. It is found that the very high mass fluxes in the low corona, which are associated with rapidly diverging flow geometries, lead to a locally enhanced frictional coupling between protons and alphas and consequently to a significant reduction of the He/H abundance ratio in the lower corona from that normally predicted by multifluid models. In the models considered, the frictional drag on the protons by the alphas (a process neglected in most studies) is found to play an important role near the sun. Heavy ions, other than alphas, are treated as minor species and are seen to exhibit varying responses to the rapidly diverging flow geometries, depending on the ion mass and charge. As for the protons, the frictional effect of the alphas on the heavier ions is found to be significant in the models considere

ISSN:0148-0227    

DOI:10.1029/JA083iA03p01019

年代:1978

数据来源: WILEY

摘要:

Ogo 5 plasma and magnetic field data are used to compute power spectra of solar wind fluctuations over the frequency interval 10−3‐10−1Hz. We confirm the validity of the assumption made in earlier papers that the power spectra calculated from total flux measurements are approximately equal to the power spectra of density fluctuations times the square of the average solar wind speed. The relative density power spectrum Pn/no² is usually of the same order of magnitude as the power spectrum of speed fluctuations relative to the Alfvén speed, Pv/vA². All cases studied show evidence of the presence of Alfvén waves in this frequency range. In some data sets the density and field fluctuations are consistent with magnetosonic waves. In other sets the ratio of the power in field magnitude fluctuations to that in density fluctuations is inconsistent with magnetosonic waves; for these cases we postulate static inhomogeneities with a balance between electron thermal and magnetic pressures. Finally, we suggest that the power enhancements near 1 Hz reported in earlier papers may be caused by a resonant proton cyclotron instability driven by the proton thermal anisotropy in the s

ISSN:0148-0227    

DOI:10.1029/JA083iA03p01027

年代:1978

数据来源: WILEY

摘要:

The shape of the shock waves associated with the August 1972 solar flares was determined by comparing the plasma measurement data from the Prognoz, Prognoz 2, Pioneer 9, and Pioneer 10 space probes with observations of radio source scintillations and comet brightness. A nearly spherical shock wave form was obtained for two flares on August 2, and essentially nonspherical shock wave forms were obtained for flares on August 4 and 7. The energy and ejected mass determined from the Prognoz 2 measurements of the additional energy and mass flux behind each shock wave are 1032–1033ergs and 1016–1017g, respectively. From the comparison of Prognoz 2 and Pioneer 9 data a significant maximum energy flux near the flare meridian on the shock wave front was deduced for the August 4 fl

ISSN:0148-0227    

DOI:10.1029/JA083iA03p01035

年代:1978

数据来源: WILEY

摘要:

Being fed by the large‐scale magnetospheric convection, the coupled ionosphere‐magnetosphere system is subject to a feedback instability for a conjugate perturbation elongating in the east‐west direction, having a width of several tens of kilometers at the ionospheric level, standing along the magnetic field line. The growth time is as short as several minutes even when no hot electrons are involved in the field‐aligned current. Nonlinear development of the feedback instability is numerically investigated, taking hot electrons into account. The following conclusions are obtained. (1) An auroral arc can develop within a few tens of seconds once hot electrons take part. (2) The induced potential associated with the arc can reach several hundred volts. This predicts that the upward field‐aligned current may be provided by electrons with energies of the order of several hundred electron volts, provided anomalous resistivity or double layers develop. (3) The electron density enhancement is directly connected with the upward field‐aligned current and hence the auroral arc. (4) The downward current is localized equatorward of the upward current, when the background electric field is westward. (5) The electrojet current can grow to a few thousand amperes, which can either be westward or eastward, depending on the direction of the electric field. (6) The induced electric field inside the arc is almost constant and different from outside. These results are consistent with the observatio

ISSN:0148-0227    

DOI:10.1029/JA083iA03p01042

年代:1978

数据来源: WILEY