摘要:

A nonlinear perturbation theory is formulated for the solution of the multicomponent equations of energy, mass, and momentum conservation in the atmosphere. The theory is three dimensional and includes the effects of heat conduction and advection, viscosity, ion drag, and diffusion. The theory is described as a superposition of mathematical modes, obtained by expanding the physical quantities into vector and spherical harmonics. The coupling between the various modes, both linear and nonlinear, is included. Hence the theory provides a basis for the treatment of the thermosphere and its interaction with the lower atmosphere, where ‘mode coupling’ is most important. As an example, a comparison is presented between one‐dimensional and three‐dimensional calculations of the fundamental mode of the diurnal component in the thermosphere, which illustrates the importance of thermospheric circulation. Coupling between the lowest modesP1¹ andP3¹ is considered to describe the physical conditions of the lower thermosphere where inertia and Coriolis forces become dominant over the ion drag and viscous forces. In this region the latitude structures of the temperature, wind field, and diffusively controlled oxygen are shown to change sign

ISSN:0148-0227    

DOI:10.1029/JA080i028p03925

年代:1975

数据来源: WILEY

摘要:

The photoelectron spectrometer experiment on Atmosphere Explorer C has obtained high‐resolution spectra of the energy distribution of 2‐ to 500‐eV electrons in the thermosphere at altitudes above 155 km. The photoelectron spectrum in the day airglow has been measured in detail over a wide range of altitude, latitude, and local time. Structure observed near 27 eV is assigned to photoelectrons ejected from atomic oxygen by the intense solar He II (304 Å) radiation. The photoelectron energy distribution is shown to have a sharp cutoff near 60 eV. In addition to the day airglow data, spectra are also presented showing low‐energy (100–500 eV) electron precipitation near the polar boundary of the auroral oval at magnetic local times near 0830. The precipitation is a low‐energy inverted ‘V’ type event occurring over an extremely narrow range of invariant latitude (ΔΛ ∼ 0.3°). The electron stream is about 50 eV wide at the half‐maximum intensity points and changes in energy from 100 to 500 eV. Instrument calibration in the laboratory, performance of the experiment in orbit, and plans for further analysis of the large body of data which now exists

ISSN:0148-0227    

DOI:10.1029/JA080i028p03934

年代:1975

数据来源: WILEY

摘要:

Diurnal variations of number densities of oxygen, nitrogen, hydrogen, carbon, and ionic minor constituents in the mesosphere and lower thermosphere are investigated using the simultaneous solution of photochemical‐diffusive equations. Special account is taken of the mutual coupling of nitrogen compounds with ions. Quantum yield of N(²D) production in the dissociative recombination of NO+and the photodissociation of N2, which are the main sources of NO in the lower thermosphere, must be ≳0.5 in order to reproduce the NO density around 100 km deduced from γ band airglow measurements. The NO density shows no substantial diurnal variation between the heights of 75 and 110 km and shows the day‐to‐night variation of a factor of greater than 2 above 120 km, whereas NO changes almost completely into NO2at night below ∼70 km. The calculated NO density is smaller than that observed in the height range of 60–80 km, although it explains the observed electron density according to currently known ion chemistry. A larger rate coefficient recently measured for the conversion of NO+into NO+·N2, which eventually will be hydrated to NO+·H2O, can be used to adequately model the height where the dominant ion changes from hydrated ions to NO+. Disagreement of the calculated atomic oxygen density profiles with the observed ones in the lower thermosphere is discussed in connection with the eddy diffusion coefficient and the solar flux. Dynamical transport of atomic oxygen such as the general circulation may be invoked to resolve th

ISSN:0148-0227    

DOI:10.1029/JA080i028p03945

年代:1975

数据来源: WILEY

摘要:

A Nike Tomahawk sounding rocket was launched into a 400‐γ auroral substorm on February 7, 1972, from Esrange, Kiruna, Sweden. The rocket instrumentation included a split Langmuir probe plasma velocity detector and a double‐probe electric field detector. Above 140‐km altitude the electric field deduced from the ion flow velocity measurement and the electric field measured by the double probe agree to an accuracy within the uncertainties of the two measurements. The difference between the two measurements at altitudes below 140 km provides an in situ measurement of current density and conductivity. Alternatively, if values for the conductivity are assumed, the neutral wind velocity can be deduced. The height‐integrated current was 0.11 A/m flowing at an azimuth of 276°. The neutral winds were strong, exhibited substantial altitude variation in the east‐west component, and were predominantl

ISSN:0148-0227    

DOI:10.1029/JA080i028p03961

年代:1975

数据来源: WILEY

摘要:

By using magnetic data measured at a network of stations extending fromL∼ 3.2 toL∼ 4.4 and at a station in the conjugate area, ellipticities in the three orthogonal planes (H‐D,H‐Z, andD‐Z) for the frequency range 2–5 mHz were computed continuously by the cross‐spectral matrix method over 10 days with various levels of magnetic activity. The ellipticity diagrams in theH‐Dplane show that except for the time interval during the main phase of a major magnetic storm, the sense of polarization reverses every day across local noon, with a left‐hand polarization observed during local morning hours and a right‐hand polarization observed during local evening hours, regardless of the level of magnetic activity. The second reversal of the sense of polarization occurs generally around ∼2000 LT. The ellipticity diagrams in theH‐Zplane show a predominantly clockwise polarization throughout the day, while the diurnal variation of the ellipticity in theD‐Zplane tends to be confused. As to the latitude dependence of the wave phase, it is found that theDcomponent oscillations are almost in phase at all latitudes, while theHcomponent oscillations have advanced phase shifts at the lower‐latitude stations. As to the conjugate dependence of wave phase, it is found that theDcomponent oscillations are almost out of phase, while theHcomponent oscillations are almost in phase at the conjugate pair stations. These polarization characteristics are discussed in terms of external driving sources coupling to the shear Alfvén waves of the local resonant field lines. Possible energy sources of Pc 5 waves are also discussed on the basis of the local time dependence

ISSN:0148-0227    

DOI:10.1029/JA080i028p03973

年代:1975

数据来源: WILEY

摘要:

Detailed Explorer 45 equatorial observations of the storm and poststorm structure of radiation belt electrons (35–560 keV) for 1.7 ≲L≲ 5.2 are presented. Injection during major storms results in electron pitch angle distributions and radial profiles that are greatly distorted from their quiet time equilibrium structure. Following storms the pitch angle distributions return to their prestorm shape over a period of several days. This shape is maintained as electron fluxes decay back to the quiet time levels. The equatorial radial profiles slowly return to their prestorm equilibrium structure over a period of a few weeks and then maintain that stru

ISSN:0148-0227    

DOI:10.1029/JA080i028p03985

年代:1975

数据来源: WILEY

摘要:

The triggering and saturation mechanisms of the electrostatic waves having frequencies near 1½ times the electron gyrofrequency in the magnetosphere are studied. Also studied is the corresponding evolution of the electron distribution function caused by the wave‐particle interaction. The linear instabilities supporting these waves are found to require a cold species of electrons having density between 0.1 cm−3and 1 cm−3and a warm species whose distribution function has a relatively weak positive slope in the velocity space perpendicular to the background magnetic field. The corresponding unstable wavelengths are short and thus result in much smaller diffusion coefficients than those derived previously. Such instabilities when triggered by an enhanced injection of ionospheric cold electrons into the warm plasma clouds can support wave amplitudes that grow to nonlinear saturation levels much greater than 10 mV/m and as large as a few hundred millivolts per meter. The majority of the observed wave activity (1–10 mV/m) can be explained as marginal instabilities maintained by a convection‐induced slow increase of the cold electrons in the plasma clouds. The evolution of the waves and plasma is described in a simple physical model for different plasma

ISSN:0148-0227    

DOI:10.1029/JA080i028p03995

年代:1975

数据来源: WILEY

摘要:

A model for the motion of flare‐generated shocks through interplanetary streams is presented, illustrating the effects of a stream‐shock interaction on the shock strength and geometry. It is a gas dynamic calculation based on Whitham's method and on an empirical approximation for the relevant characteristics of streams. The results show that the Mach number of a shock can decrease appreciably to near unity in the interaction region ahead of streams and that the interaction of a spherically symmetric shock with a spiral‐shaped corotating stream can cause significant distortions of the initial shock front geometry. The geometry of the February 15–16, 1967, shock discussed by Lepping and Chao (1972) is qualitatively explained by thi

ISSN:0148-0227    

DOI:10.1029/JA080i028p04004

年代:1975

数据来源: WILEY

摘要:

The ionospheric configuration of the vertical Birkeland currents associated with an auroral arc is calculated from a model based on the assumption that the auroral electrons constitute a net current into the ionosphere. It is further assumed that the return vertical current out of the ionosphere is impeded along the field lines which connect the arc to the magnetosphere. The magnitude, location, and structure of the return Birkeland current calculated from the model agree well with measurements of these parameters by a rocket‐borne experimen

ISSN:0148-0227    

DOI:10.1029/JA080i028p04011

年代:1975

数据来源: WILEY

摘要:

During the Mercury flyby of Mariner 10, observations of large fluxes of energetic electrons (E>0.3 MeV) and protons (0.53

ISSN:0148-0227    

DOI:10.1029/JA080i028p04015

年代:1975

数据来源: WILEY