摘要:

The most popular concept for the driving force for magnetospheric convection has been that merging of the interplanetary magnetic field with the geomagnetic field at the front of the magnetosphere establishes a good electrically conducting path between the solar wind and the polar ionosphere; the flow of electrical energy then provides the driving force. This model has had impressive success in predicting some phenomena, but it also has some serious defects. The alternative view for the driving force has been that a viscous interaction exists between the solar wind and the outer layer of the magnetosphere. Although mechanisms of viscous interaction have been recognized, they have proved quantitatively inadequate to provide the required driving force. This concept has experienced a recent resurgence of support based on observation, but the conceptual problem in understanding the magnitude of the effect remains. A third possibility suggested by recent observations is that solar wind plasma enters the magnetosphere rather readily around the neutral points, where the flow is turbulent and the geomagnetic field is weak, and then spreads throughout a boundary layer covering virtually the entire inner surface of the magnetopause. This plasma can expand and drive magnetospheric convection by moving tailward around the flanks of the magnetosphere until it escapes out the open tail. The picture is rather similar to the viscously driven magnetosphere, but the driving force is different.

ISSN:8755-1209    

DOI:10.1029/RG016i002p00161

年代:1978

数据来源: WILEY

摘要:

Mass spectrometric composition measurements in the thermosphere form the basis for three global models of upper air composition and temperature: the Ogo 6, the Esro 4, and the MSIS model. The comparison of model predictions reveals differences of up to 25% with respect to mean absolute number densities. In the prediction of thermospheric variations there exists good agreement for the major constituents, but there are notable differences for the minor constituents. A comparison of individual Esro 4 density measurements with the Esro 4 and MSIS models indicates that the observed number density variations are, on the average, equally well represented by either model.

ISSN:8755-1209    

DOI:10.1029/RG016i002p00169

年代:1978

数据来源: WILEY

摘要:

Under the supervision of an international steering committee, basic data for establishing ionospheric profiles were gathered, critically reviewed, and used for establishing vertical profiles of the most important parameters of the ionosphere, namely, electron density, electron and ion temperature, and (positive) ion composition. The data sources used are described in detail, their reliability and coverage is discussed, and remaining problems are reviewed. The International Reference Ionosphere (1978) is to be published soon by URSI in the form of computer programs.

ISSN:8755-1209    

DOI:10.1029/RG016i002p00177

年代:1978

数据来源: WILEY

摘要:

In contrast with the low‐latitude thermosphere, which derives most of its energy from the absorption of solar extreme ultraviolet radiation (EUV), the energy balance of the high‐latitude thermosphere is dependent on processes of magnetospheric origin. Particles precipitating from the magnetosphere deposit energy in the lower thermosphere throughout the high‐latitude region. Processes such as magnetospheric convection drive bulk motions of charged particles; both energy and momentum are transferred to the neutral atmosphere by collisions between neutral constituents and these charged particles. The present paper presents a review of both observational and theoretical investigations of the response of the neutral upper atmosphere to processes which are unique to high latitudes. It also describes in some detail recent three‐dimensional model calculations dealing with the effects of magnetospheric convection on thermospheric dynamics. The three‐dimensional calculations, which treat the effects of viscosity, ion drag, the Coriolis force, thermal conduction, and solar EUV heating, as well as Joule and particle precipitation heating, allow an assessment of the relative importance of processes characteristic of high

ISSN:8755-1209    

DOI:10.1029/RG016i002p00183

年代:1978

数据来源: WILEY

摘要:

This paper reviews what has recently been learned by means of the incoherent scatter radar technique concerning the dynamics of the lower thermosphere (100–150 km). In this region, thermal tides generated in situ and propagating upward from below appear to be the principal source of motions at low and middle latitudes. The winds that they establish can drive ions across magnetic field lines, thereby establishing electric currents and polarization electric fields (which in turn modify the motions of the ions). Efforts to understand this region have traditionally been made through calculations of the tidal amplitudes, from studies of magnetometer records, and from vertical wind profiles observed via chemical releases from rockets. The direct measurements of the temperatures, winds, and electric fields made possible by means of incoherent scatter radar probing have confirmed some early ideas and also have revealed considerably more complexity than had been anticipated. Presently available evidence indicates that the interval 100– 125 km is dominated by upward propagating solar semidiurnal tidal modes (e.g., (2, 4) and (2, 5)) generated in the mesosphere where background winds couple energy out of the (2, 2) mode, which is the mode most strongly excited in the stratosphere‐mesosphere. These higher‐order modes appear to be damped above 120 km by viscous dissipation. In the region 125–150 km the (1, −2) trapped diurnal mode generated by direct absorption of solar EUV seems to be the predominant one at midlatitudes, although some of the energy remaining in the semidiurnal (2, 2) mode appears to leak up to these heights. Nearer the equator it appears that the (2, 2) tide dominates the region below 200–300 km, particularly in summer. These tides create winds that appear capable of explaining a variety of related phenomena including theSq(solar quiet) dynamo current system, the generation of sporadicElayers and layers intermediate between theEandFlayers, and the drift of ions in directions normal to the magnetic field atFregion heights (i.e., electric field induced drifts) seen within the plasmasphere d

ISSN:8755-1209    

DOI:10.1029/RG016i002p00195

年代:1978

数据来源: WILEY

摘要:

The general features, capabilities, and problems of in situ techniques are reviewed. To illustrate these capabilities more closely, examples of recent measurements are presented, including (1) resonance fluorescence for the measurement of O, OH, Cl, and ClO, (2) grab and cryogenic collection of whole air samples for the measurement of N2O, CFCl3, and CF2Cl2, (3) impregnated filters for HCl, and (4) matrix isolation for HO2and NO2.

ISSN:8755-1209    

DOI:10.1029/RG016i002p00217

年代:1978

数据来源: WILEY

摘要:

The measurement capability of the Atmosphere Explorer (AE) satellite series has been used to investigate the detailed chemistry of O(¹D) atoms in the earth's thermosphere. Measurements of the O I (³P‐¹D) transition at 6300 Å on AE have been used to infer the strength of the O2+dissociative recombination source of O(¹D), (β¹D) the quenching rate of O(¹D) by molecular nitrogen (KN2), and the value of the photodissociation rate of O2(Jo2). Values inferred from the measurements for β¹D,KN2, andJo2are 1.33, 3 × 10−11cm³ s−1, and 3 × 10−6s−1respectively. The photoelectron impact source of O(¹D) has also been investigated. A unimolecular rate constant for this process derived from the airglow data agrees well with current theoretical calculations. Morning and evening twilight 6300‐Å data compare favorably with those calculated by a time‐dependent model of

ISSN:8755-1209    

DOI:10.1029/RG016i002p00225

年代:1978

数据来源: WILEY

摘要:

A general discussion is presented of the propagation, attenuation, growth, reflection, scattering, and energy transport of waves in the presence of weak but extensive random media or boundaries. Applications of the theory to various types of long‐period waves in the ocean are given: gravity waves, shear waves, internal and inertial waves, Rossby waves, Kelvin and Poincaré waves, and edge waves. The mathematical methods used in this paper to solve the relevant random differential equations are generally of an asymptotic or approximate nature; however, attempts have been made to assess the validity of these methods. A brief discussion is also given of some recent exact methods which have been developed to study wave propagation in the presence of strong random fluctuations. There has been no attempt to summarize the extensive work done on electromagnetic, optical, and acoustic wave propagation in random media, since a number of reviews and books have already appeared on these topi

ISSN:8755-1209    

DOI:10.1029/RG016i002p00233

年代:1978

数据来源: WILEY

摘要:

We review evidence gathered from theoretical considerations and from measurements on the ground and in space for a 90° rotation of the major axis of the polarization ellipse of geomagnetic pulsation signals between the geomagnetic equator and the ground. The evidence at present supports the existence of the rotation phenomenon, although more observational work is needed. The rotation arises from the nonconducting air on the ground surface and the highly conducting plasma in space

ISSN:8755-1209    

DOI:10.1029/RG016i002p00263

年代:1978

数据来源: WILEY

摘要:

The task of developing empirical models of the thermal ion composition is complicated by the presence of both short‐term temporal and localized spatial variations in the constituents. The requirements of a detailed numerical representation of variable composition patterns such as those detected in the zone of the equatorial anomaly (EA) may exceed either the statistical data available or the numerical modeling resolution, or both. As an illustrative example a correlative test of a parameterized spherical harmonic expansion model of Ogo 6 dayside measurements ofn(H+) is performed, particular characteristics of the observations being used as a basis for comparison. Whereas a review of other research confirms that the Ogo 6 observations of EA variability in longitude and local time are generally consistent with independent experimental and theoretical results, the model reproduces the observed broad‐scale longitudinal behavior but falls short of representing some details of these features. Specifically, the model depicts the persistent prominence of the EA development in the eastern Asian longitude zone relative to the eastern American longitude zone, as Well as the longitudinal shift in the hemispheric asymmetry in EA crests, although the amplitudes of some observed features are not precisely modeled. These results emphasize (1) the limitation in statistical coverage from a single satellite for identifying complex localized and short‐term ionospheric variations and (2) the need for integrating dynamic parameters, e.g., neutral wind and electric field‐ion drift terms, to produce a hybrid empirical‐analyti

ISSN:8755-1209    

DOI:10.1029/RG016i002p00267

年代:1978

数据来源: WILEY