ALBERT

Description: The evolution of whistler mode turbulence and particle participation in a cold plasma release are studied experimentally as part of the Active Magnetospheric Particle Tracers Explorer (AMPTE) program. The investigation used a simple time dependent cold plasma density model, and an atypical ambient radiation belt was assumed. It is shown that a cold lithium injection in the AMPTE parameter range can give rise to whistler mode turbulence with significant gain to the wave amplitude in a single pass through a flux tube. Whistler mode growth results in the pitch angle diffusion of energetic electrons, which are in turn precipitated. The rate of power input into the ionosphere from these precipitating electrons is roughly estimated at 2 ergs per sq cm/s. It is found that this value of the precipitated power is large enough to continue producing a visible aurora until the injected plasma in the flux tube is lost or destroyed by magnetospheric convection or other processes.

Description: Data from the Atmospheric Explorer-C recorded during the rise in solar activity from 1975 to 1978, and Dynamic Explorer-2 data recorded at solar maximum are used to examine how the relation between electron temperature and density in the F-region of the ionosphere is altered by solar activity. It is found that the solar maximum temperature Te is a factor of two larger than the solar minimum Te for the same values of electron density. Temperature does not necessarily increase in response to solar activity because electron density increases enough to approximately cancel the effect of higher solar extreme ultraviolet heating. The effect of solar activity is accounted for by a simple function of the F (10.7 cm) index which multiplies the solar minimum equation from a previous study (Brace and Theis, 1978).

Description: Progress has been made toward the realization of the potential of radio interferometry for measuring crustal motions and global rotations of the earth with accuracies at the centimeter level. In this connection, a series of experiments, primarily with NASA's Deep Space Network (DSN) antennas, has been conducted to develop two generations of very long baseline interferometric (VLBI) systems. A description is presented of the employed techniques, an analysis of the experiments, and the results of geophysical significance. Attention is given to the interferometry technique, the geometric delay model, propagation media calibrations, and the observing strategy.

Description: The crustal deformation patterns associated with the earthquake cycle can depend strongly on the rheological properties of subcrustal material. Substantial deviations from the simple patterns for a uniformly elastic earth are expected when viscoelastic flow of subcrustal material is considered. The detailed description of the deformation pattern and in particular the surface displacements, displacement rates, strains, and strain rates depend on the structure and geometry of the material near the seismogenic zone. The origin of some of these differences are resolved by analyzing several different linear viscoelastic models with a common finite element computational technique. The models involve strike-slip faulting and include a thin channel asthenosphere model, a model with a varying thickness lithosphere, and a model with a viscoelastic inclusion below the brittle slip plane. The calculations reveal that the surface deformation pattern is most sensitive to the rheology of the material that lies below the slip plane in a volume whose extent is a few times the fault depth. If this material is viscoelastic, the surface deformation pattern resembles that of an elastic layer lying over a viscoelastic half-space. When the thickness or breath of the viscoelastic material is less than a few times the fault depth, then the surface deformation pattern is altered and geodetic measurements are potentially useful for studying the details of subsurface geometry and structure. Distinguishing among the various models is best accomplished by making geodetic measurements not only near the fault but out to distances equal to several times the fault depth. This is where the model differences are greatest; these differences will be most readily detected shortly after an earthquake when viscoelastic effects are most pronounced.

Description: Using the unabridged Maxwell equations (including vectors D, E and H) new effects in collisionless plasmas are uncovered. In a steady state, it is found that spatially varying energy density of the electric field (E perpendicular) orthogonal to B produces electric current leading, under certain conditions, to the relationship P perpendicular + B(2)/8 pi-epsilon E perpendicular(2)/8 pi = constant, where epsilon is the dielectric constant of the plasma for fields orthogonal to B. In steady state quasi-two-dimensional flows in plasmas, a general relationship between the components of electric field parallel and perpendicular to B is found. These effects are significant in geophysical and astrophysical plasmas. The general conditions for a steady state in collisionless plasma are deduced. With time variations in a plasma, slow compared to ion-gyroperiod, there is a general current, (j-asterisk), which includes the well-known polarization current, given by J-asterisk = d/dt (E x M) + (P x B) x B B(-2) where M and P are the magnetization and polarization vectors respectively.

Description: In this study, the data set acquired from the vector magnetometer on board MAGSAT during the period October 1979 to June 1980 is examined. Auroral zone crossings were sorted by hourly averaged values of the Interplanetary Magnetic Field. The result is a catalog of sorted data files, from which color-coded magnetic local time invariant latitude plots have been generated that image the auroral Birkeland current pattern, over each prescribed parameter range. These images are used to statistically examine the dynamics of the current pattern. Results indicate that during the periods of B(z) less than 0, the region 1 and 2 current system expands toward lower latitudes accompanied by an expansion of the auroral zones. When B(z) is greater than 0, the region 1 and 2 currents continue to flow with greatly reduced amplitude in the presence of extensive small scale structure.

Description: Stratospheric ozone depressions, following intense solar particle events (SPE) observed by the backscattered ultraviolet (BUV) experiment on the Nimbus-4 satellite, indicate the existence of distinct asymmetries between the Northern and Southern Hemispheres. These asymmetries are observed in the magnitude of the depressions above the 5-mb level, their temporal variations, and the spatial (i.e., latitude and longitude) dependence of these variations. Possible causes of asymmetries, shown by two events on August 4, 1972 and January 25, 1971, can be attributed to: (1) tilt of the interplanetary magnetic field (IMF) with respect to the earth's dipole magnetic field which influences the precipitation of energetic solar particles into the polar atmospheres; (2) differences in ozone chemistry caused by the large change in atmospheric temperature between summer and winter hemispheres; (3) seasonal differences of the stratosphere's dynamic states which are affected by upward propagating planetary waves in winter in contrast to the relatively undisturbed zonal flows in summer; and (4) topographic asymmetry between Northern and Southern Hemispheres. These effects are shown by three-dimensional plots of the events in geographic coordinates and by color contour plots of the stratospheric ozone distributions in geomagnetic and geographic polar coordinates, respectively.

Description: For models of planetary accumulation in the presence of solar nebular gas, the initial surface temperature of the earth is controlled by the grain opacity of the atmosphere. The surface temperature in turn controls the quantity of neon dissolved and trapped within the interior of the earth. To compare accumulation theory with observation, calculations have been made of the grain opacity expected to be associated with accumulation in a gaseous nebula. There are two parameters that are in principle determined by the theory, but actually are at present uncertain: the mean eccentricity(e) of the planetesimal swarm, and the fraction (xi) of the accretional energy that is expended in the release of grains into the atmosphere by ablation of the incoming planetesimal. It is found that if e is low (0.001), rather low values of xi (0.00001) are required to match the observed neon data. In contrast higher values of xi (0.1) are required for the most probable case with e = 0.01. For the high-eccentricity case (e = 0.1), xi must be greater than 0.01. The results show that avoidance of excess trapped neon of solar composition places restrictive, but not necessarily impossible, conditions on the parameters of the accumulation theory.

Description: Mercury and sulphur dioxide analyses were conducted from 1971 to 1980 on air samples collected immediately downwind of Halemaumau, the Kilauea main vent, in Hawaii. On the basis of these measurements, an Hg/SO2 ratio of 0.00051 has been derived which, when applied to the recently determined SO2 mass output of Halemaumau, yields a calculated Hg flux of 2.6 x 10 to the 8th g annually. This rate is consistent with Varekamp and Busek's (1981) evidence suggesting that volcanogenic Hg significantly contributes to the atmospheric total.

Description: OGO 5 triaxial search coil magnetometer data are used to determine the wave propagation directions of postmidnight chorus in the near-equatorial region at L shells of 6 to 7. The methods used to estimate the wave normal directions involved minimum variance, the imaginary part of the cross-spectral matrix, the eigenvector of the Hermitian cross-spectral matrix, and a fitting of dispersion relations for one-wave and two-wave models to the cross-spectral matrix. Wave propagation at all frequencies within chorus tones is found to occur most frequently along the magnetic field with median and average cone angles of 9.1 deg and 12.2 deg, respectively. It is concluded that for waves propagating parallel to B, wave growth is maximum.

Description: The NASA Crustal Dynamics Project has developed very-long baseline interferometer (VLBI) systems and satellite laser ranging (SLR) systems for geodynamics measurements. In VLBI, a radio noise signal from a distant quasar is received by two or more radio antennas and coherently recorded. These recordings are cross-correlated to determine the relative signal delays between stations which are used to derive the vector baselines between the stations. The SLR systems accurately determine the range to a retroreflector satellite as a function of time with short laser pulses. These range measurements from several stations to the same satellite are used in orbit analysis programs to determine the position of the stations and the vector baselines between the stations. Measurements with these systems have achieved precisions of a few centimeters in length for distances of several thousand km. These systems are now operating in a global network for measuring the relative motion of the N. American, Pacific, S. American, Nazca, Eurasian and Australian tectonic plates. Highly mobile VLBI and SLR systems are being operated at many sites in the active earthquake areas in western N. America in order to determine the crustal deformation and strain accumulation.

Description: A theoretical model of the opening of the Cayman Trough is developed on the basis of geological evidence from a wide area. It is proposed that strike slip motion began about 30 Myr ago and proceeded at a rate of 37 + or - 6 mm/yr for a total of 1100 km of relative plate displacement, and that Central America Underwent an anticlockwise rotation with internal plate deformation. Maps of the reconstructed motion are provided.

Description: The presence of large-amplitude magnetosonic waves in the distant plasma sheet boundary layers is demonstrated, and their properties are discussed. The waves for almost all the events examined are right-hand circularly polarized, with the degree of polarization varying from 1.04 to 1.87, i.e., from circular to slightly elliptical. The waves are all propagating nearly along the magnetic field. Their periods vary from 3.7 seconds to as long as 35 seconds, with a median value of about 10 seconds, and are slightly larger than the proton gyroperiod in all but two cases. Most waves have a relatively large compressional component varying from 30 to 90 percent of the wave amplitude. Several possible generation mechanisms are discussed, along with the role that the waves may play in the heating and expansion of the plasma sheet.

Description: Topside-sounder receiver observations by ISIS 1 that reveal examples of o-mode auroral kilometric radiation (AKR) are presented. They correspond to locations outside of the low density source region of intense AKR x-mode emission. The propagation modes are identified by comparing the natural radiation wave cutoffs with the local resonant and wave cutoff phenomena stimulated by the sounder transmitter. The o-mode AKR is the dominant emission in these regions of relatively high electron density, but it is considerably weaker than the intense x-mode AKR observed to emanate from low density cavities above the auroral regions. In addition to the fundamental o-mode, 2nd and 3rd harmonic bands of radiation have also been detected. Harmonics associated with these o-mode AKR are less intense than the harmonics associated with x-mode AKR. It is difficult to explain the variety of harmonic AKR observations (x as well as o-mode) based on present AKR theories. Previously announced in STAR as N83-27517

Description: In the ilmenite-hematite solid solution series, compositions more ilmenite-rich than Ilm(73)Hem(27) are classically thought to be paramagnetic at room temperature. Ilm(80)Hem(20) samples have nevertheless been synthesized that acquire hard saturation remanent and thermoremanent moments. From analysis of AC demagnetization data, the source of the measured remanence is believed to be a single-domain (SD) like material within the IlM(80)Hem(20) grains themselves. On the basis of transmission electron microscope observations, it is suggested that transformation-induced domain boundaries, which in part are enriched in hematite component relative to the bulk composition of the grains, could act as the magnetic carrier of the SD-like remanence.

Description: The importance of the effect of the magnetic shear and the finite size of current channel on the electrostatic ion-cyclotron instability for the space plasmas is illustrated. A non-local treatment is used. When the channel width Lc, is larger than the shear length Ls, there is a large reduction in the growth rate along with a noteworthy reduction of the band of the unstable perpendicular wavelengths. For Lc less than or = Ls/10 the growth rate is not much altered from its local value, however for Lc/pi i less than or = 10 to the second power the growth rate starts falling below the local value and vanishes for Lc pi i. The non-local effects lead to enhanced coherence in the ion cyclotron waves. Previously announced in STAR as N84-14917

Description: Three dimensional measurements from the ISEE-1 low energy electron spectrometer are used to map the location of the inner edge of the plasma sheet and study the anisotropies in the electron distribution function associated with this boundary. Lower energy plasma sheet electrons have inner edges closer to the earth than higher energies with the separations at different energies being larger near dawn and after dusk than at midnight. Lowest energy inner edges are frequently located adjacent to the plasmapause in the dawn hemisphere but are often separated from it in the dusk hemisphere by a gap of at least several Re. The energy dispersion is minimal in the afternoon quadrant where the inner edge is near the magnetopause and frequently oscillating on a time scale of minutes. The location of the inner edge is probably determined primarily by the motion of electrons in the existing electric and magnetic fields rather than by strong diffusion as has sometimes been supposed. Previously announced in STAR as N83-32595

Description: After outlining the constituent parts of the magnetospheric system, a historical review is presented of studies of the earth's magnetic field. It is noted that a connection between the aurora and variations in the magnetic field was first suggested by Halley in 1716. In discussing the magnetosphere, it is pointed out that the geomagnetic field can be thought of as being produced by a huge bar magnet embedded in the earth, with the axis of the magnet tilted away slightly from the earth's rotational axis. Attention is also given to the interplanetary magnetic field, to the relationship between the interplanetary magnetic field and the geomagnetic field, to convective flow, to field-aligned currents, and to Birkeland currents and auroral emissions. Various questions concerning the Birkeland currents are summarized.

Description: Electron beam experiments using rocket-borne instrumentation confirmed earlier observations of fast magnetospheric echoes of artificially injected energetic electrons. A total of 234 echoes were observed in a pitch angle range from 9 to 110 deg at energies of 1.87 and 3.90 keV. Of these, 102 echoes could unambiguously be identified with known accelerator operations at 2, 4 or 8 keV energy and highest current levels resulting in the determination of transit times of typically 300 to 400 ms. In most cases, when echoes were present in both energy channels, the higher energy electrons led the lower energy ones by 50 to 70 ms. Adiabatic theory applied to these observations yields a reflection height of 3000 to 4000 km. The injection process is discussed as the strong beam-plasma interaction that occurred near the electron accelerator appears to be instrumental in generating the source of heated electrons required for successful echo detection.

Description: The calibration standards used in the Atmospheric Lifetime Experiment (ALE) for CFCl3, CF2Cl2, CH3CCl3, and CCl4 are described. This includes the preparation of the primary standards by static dilution and their propagation and stability for the period 1977-1982. Two independent assessments of the absolute concentrations of the primary standards used to initiate the ALE measurements in 1977-1978 are reported. For consistency in the ALE program the values assigned to the primary standards and subsequent working standards used in the field were not altered during the experiment when results of better estimates of the original concentration values were obtained. Rather, the appropriate factors by which the ALE mixing ratios for a given species should be multiplied to obtain the best estimate of the current concentration of a given species, are provided.

Description: Computer simulations have been performed to determine the geographical and temporal coverage of various satellite orbits and scanning and nonscanning radiometers for earth radiation budget measurements. These results were used to simulate the sampling of a diurnally varying cloud and radiation field for several different satellite systems to estimate errors in regional monthly mean reflected radiation. The combined results indicate that coincient observations with a minimum of one sun-synchronous satellite and a midinclined orbit satellite are needed to obtain the required regional, zonal, and global coverage with sufficient temporal sampling for obtaining accurate estimates of monthly mean reflected solar radiation. Overall, the best sampling capability and lowest errors were obtained with a three-satellite system, i.e., two sun-synchronous satellites with different equatorial crossing times combined with either a 46 or 57-deg orbit satellite. The results from these analyses have been used in defining a joint NASA-NOAA multisatellite mission for an earth radiation budget experiment.

Description: Initial results of studies of low-energy plasma using the light ion mass spectrometer (LIMS) on the SCATHA satellite are presented. Results are discussed primarily for plasma flux in the noon to midnight local time sector, examining the behavior of the plasma with geomagnetic activity and local time. Measurements of the ion mass composition in this region for the energy ranges of the LIMS instrument are presented. Results of temperature measurements are given and a possible explanation for the difference between the whistler and OGO 5 plasmapause positions is suggested. The observed pitch angle distributions are presented, limited to a broad characterization of the plasma population. The effects of the spacecraft potential on the low-energy plasma measurements are considered.

Description: Sun photometer and lidar backscatter measurements of the El Chichon volcanic cloud were obtained during an airborne latitude survey. The observations were collected between 46 deg N and 46 deg S from Oct. 19-Nov. 7, 1982. Comparisons between these data sets have been performed. An aerosol optical model was developed for the conversion of the lidar measurements to optical thickness values using numerical aerosol size distribution data and index of refraction information collected with coordinated dustsonde balloon flights. The derived lidar optical thickness values were found to agree with the sun photometer optical thickness values within measurement uncertainties. The lidar derived values ranged from 0.16 at the equator to 0.03 at 30 deg S latitude. Peak values were concentrated between 35 deg N and 10 deg S.

Description: Sun photometer measurements of the spectral optical thickness of the El Chichon eruption cloud were obtained during an airborne latitudinal survey. The measured optical thicknesses were greatly enhanced over background levels for the stratosphere. The observations covered 44 deg N to 36 deg S, and increased optical thickness was found at all latitudes where measurements were made. Significant variations in the magnitude and spectral dependence of the optical thickness were found within the latitude range covered by the observations. The maximum optical thickness was found at 20 deg N and the minimum was found at 30 deg S. The optical thickness values ranged between 0.13 and 0.017 at 870 nm and between 0.15 and 0.044 at 440 nm.

Description: The eruptions of El Chicon in Mexico during March and April, 1982, produced the largest enhancements in stratospheric aerosols, which were experienced in at least the last 20 years. An experimental survey flight was conducted in October-November 1982 to underfly El Chichon's eruption cloud and to map out its latitudinal distribution. A NASA aircraft was flown between 46 deg N latitude and 46 deg S latitude in a coordinated field campaign. The present investigation is concerned with the results of lidar stratospheric measurements taken over the entire mission. The employed airborne lidar system consists of a ruby laser, nominally emitting 1 joule/pulse at 0.5 pulse/sec during flight, and a 35.6-cm receiving Cassegrainian-configured telescope. The lidar data presented are described in two forms, taking into account the lidar backscattering ratio and the integrated aerosol backscattering function.

Description: A quasi-continuous record of atmospheric attenuation is obtained. The data were gathered during a 24-day period in September and October 1982 and a 10-day period in December of that year. The opacity is arrived at by measuring the thermal emission of the atmosphere over a bandwidth of approximately 300 MHz. Using an experimental relationship established by Zammit and Ade (1981), opacity measurements at 1.1 mm are converted to the precipitable water vapor column overhead. With the precipitable water vapor, estimates of opacity due to water vapor can be made for other mm and FIR wavelengths. These estimates require model absorption curves for the atmosphere.

Description: Lead isotope data on whole-rock samples and two feldspar separates for a variety of Pan-African (late Precambrian) igneous rocks for the Egyptian Shield are presented. It is pointed out that the eastern desert of Egypt is a Late Precambrian shield characterized by the widespread occurrence of granitic plutons. The lead isotope ratios may be used to delineate boundaries between Late Precambrian oceanic and continental environments in northeastern Africa. The samples belong to three groups. These groups are related to a younger plutonic sequence of granites and adamellites, a plutonic group consisting of older tonalites to granodiorites, and the Dokhan volcanic suite.

Description: The precise amount of O2 and O3 in the earth's prebiological paleoatmosphere has been a topic of considerable discussion in the past. Since the photolysis of H2O and CO2, the prebiological mechanisms to produce O2, depends on the ultraviolet flux from the Sun, a reliable quantification of the problem requires detailed knowledge of such flux. Using the most recent astronomical observation of young stars from the International Ultraviolet Explorer, as well as a detailed photochemical model of the paleoatmosphere, it is found that the amount of O2 in the prebiological paleoatmosphere may have been as much as a million times greater than previously estimated. Some of the implications of this new value are discussed.

Description: The optical properties of suspended dust particles from the eruption of Mt. St. Helens on July 23, 1980 are investigated using photoelectric observations of standard stars obtained on the 0.76-m telescope at the University of Washington 48 hours after the eruption. Measurements were made with five broad-band filters centered at 3910, 5085, 5480, 6330, and 8050 A on stars of varying color and over a wide range of air masses. Anomalous extinction effects due to the volcanic ash were detected, and a significant change in the wavelength-dependent extinction parameter during the course of the observations was established by statistical analysis. Mean particle size (a) and column density (N) are estimated using the Mie theory, assuming a log-normal particle-size distribution: a = 0.18 micron throughout; N = 1.02 x 10 to the 9th/sq cm before 7:00 UT and 2.33 x 10 to the 9th/sq cm after 8:30 UT on July 25, 1980. The extinction is attributed to low-level, slowly migrating ash, possibly combined with products of gas-to-particle conversion and coagulation.

Description: Data on species of interest in the photochemistry of the ozone layer obtained from balloon flights are presented. The flights made use of remote-sensing instruments that took measurements in the wavelength region from the ultraviolet to millimeter wavelengths. Most of the data were obtained with instruments whose readings were in the midinfrared wavelengths. Descriptions are given of the two techniques generally used in this type of research, namely solar absorption and atmospheric emission. The promise that these techniques hold for providing data on the photochemistry of the ozone layer is discussed.

Description: A method is developed for directly measuring atmospheric winds in the 20-120 km altitude interval from a spacecraft. The wind sensor measures the Doppler shift between the spectral absorption lines of a gas in a cell within the instrument and the thermal emission lines of the same gas in the atmosphere. The wind measurements are performed using a spacecraft-borne gas correlation spectrometer viewing the limb of the atmosphere. The wind-induced Doppler shift between the two spectra, and thus the magnitude of the wind itself, is obtained by phase modulating the incoming thermal radiation (equivalent to frequency modulation) by means of an electrooptically active crystal to determine the frequency shift required to reestablish exact correlation between the lines in the cell and the lines from the atmosphere. Results of numerical simulations of the wind-sensor performance indicate that the noise-equivalent-wind is between 1-5 m/s over most of the stratosphere and mesosphere.

Description: The temperature variations of the neutral gas in the thermosphere are considered as a function of local time and season, taking into account the latitude range from -17.5 deg to +17.5 deg and the altitude range from about 250 km to about 400 km. The temperature measurements were conducted in situ with the Neutral Atmospheric Temperature Experiment (NATE) on the Atmospheric Explorer E (AE-E) spacecraft during the time between December 1976 and January 1979. The altitude of the circular orbit of the spacecraft was gradually increased during this period from 250 to 400 km. A significant result of the reported analysis is the latitudinal (seasonal) variation observed in the semidiurnal and terdiurnal tides during solstice. It is found that this variation is responsible for the seasonal behavior of the midnight temperature maximum.

Description: Attention is given to isotropic distribution, bidirectional field alignment distribution, unidirectional field alignment distribution, and low flux, in a statistical examination of low energy ion data from the ISEE 1 plasma composition experiment whose aim was the study of pitch angle distributions in all local times of the magnetosphere. The isotropic distribution consisting of less than 10 eV ions is a persistent inner region feature, while the bidirectional field-aligned distribution consisting of warm ions is a persistent feature of the outer dayside and is seen just outside the isotropic distribution region of the nightside. On the outer nightside, the unidirectional field-aligned distribution consisting of warm ions is the dominant signature. The 'sources' of ions in various regions are discussed in view of the present and other results.

Description: Using the recently completed JTLA absolute gravity meter, we made a survey of twelve sites in the United States. Over a period of eight weeks, the instrument was driven a total distance of nearly 20,000 km to sites in California, New Mexico, Colorado, Wyoming, Maryland and Massachusetts. The time spent in carrying out a measurement at a single location was typically one day. We report the results of the measurements in this survey along with earlier measurements made with the instrument, discuss the measurement accuracy and compare our results with other measurements. Previously announced in STAR as N83-20480

Description: Previously reported measurements of stratospheric ClO using a balloon-borne laser heterodyne radiometer, launched from Palestine, Texas, are re-evaluated as a result of recent spectroscopic data. A spectral feature which was observed during September, 1978 and November, 1979 flights was incorrectly identified as a ClO absorption line, while a second feature observed during the latter flight with somewhat limited sensitivity is now believed to be due to ClO. This new interpretation results in a measured ClO profile which falls off more rapidly with decreasing altitude than the previous results indicated.

Description: An analysis is undertaken of the properties of a one-level seasonal energy balance climate model having explicit, two-dimensional land-sea geography, where land and sea surfaces are strictly distinguished by the local thermal inertia employed and transport is governed by a smooth, latitude-dependent diffusion mechanism. Solutions of the seasonal cycle for the cases of both ice feedback exclusion and inclusion yield good agreements with real data, using minimal turning of the adjustable parameters. Discontinuous icecap growth is noted for both a solar constant that is lower by a few percent and a change of orbital elements to favor cool Northern Hemisphere summers. This discontinuous sensitivity is discussed in the context of the Milankovitch theory of the ice ages, and the associated branch structure is shown to be analogous to the 'small ice cap' instability of simpler models.

Description: The goal of the study is to calculate numerically the deceleration and heating caused by breaking gravity waves. The effect of the radiative dissipation of the wave is included as vertical-wavelength-dependent Newtonian cooling. The parameterization for zonal deceleration is extended by breaking gravity waves (Lindzen, 1981) to include the turbulent diffusion of heat and momentum. After describing the numerical model, the numerical results are presented and compared with the parameterizations in a noninteractive model of the mean zonal wind. Attention is then given to the transport of constituents by gravity waves and the attendant turbulent zone. It is noted that if gravity wave breaking were not an intermittent process, gravity wave stresses would produce an adiabatic mesosphere with a zonal mean velocity close to the phase speed of the breaking wave.

Description: The present examination of the linear Vlasov stability of a class of electron velocity distributions modeling those observed within the earth's bow shock is restricted to electrostatic waves propagating parallel to the ambient magnetic field B. Two instabilities are identified as driven by free energy in the direction parallel to B: an ion acoustic wave with real frequency below the ion plasma frequency, and an electron acoustic wave whose real frequency is several times the ion plasma frequency. Unstable wave characteristics are in accord with the trend of the observed electrostatic waves toward polarization parallel to the magnetic field. The instabilities identified may contribute to electron dissipation in collisionless shocks.

Description: (Previously cited in issue 08, p. 1248, Accession no. A82-22043)

Description: Analytical solutions to the refraction integrals appropriate for ray trajectories along slant paths through the atmosphere are derived in this paper. This type of geometry is commonly encountered in remote-sensing applications utilizing an occultation technique. The solutions are obtained by evaluating higher-order terms from expansion of the refraction integral and are dependent on the vertical temperature distributions. Refraction parameters such as total refraction angles, air masses, and path lengths can be accurately computed. It is also shown that the method can be used for computing refraction parameters in astronomical refraction geometry for large zenith angles.

Description: The possible contribution by natural hydrocarbon emissions to the total ozone budget recorded in the Tidewater region of southeastern Virginia during the height of the summer period was examined. Natural sources investigated were limited to the primary HC emitters and most prevalent natural vegetation, the forests. Three types and their areal coverage were determined for Region VI of the Virginia State Air Pollution Control Board using remotely sensed data from Landsat, a NASA experimental earth resources satellite. Emission factors appropriate to the specific types (coniferous 0.24 x 10 to the 13th, mixed 0.63 x 10 to the 13th, deciduous 1.92 x 10 to the 13th, microgram/h), derived from contemporary procedures, were applied to produce an overall regional emission rate of 2.79 x 10 to the 13th microgram/h for natural non-methane hydrocarbons (NMHC). This rate was used with estimates of the anthropogenic NO(x) and NMHC loading, as input into a photochemical box model. Additional HC loading on the order of that estimated to be produced by the natural forest communities was required in order to reach certain measured summer peak ozone levels as the computer simulation was unable to account for the measured episodic levels on the basis of the anthropogenic inventory alone.

Description: Magnetic field measurements from the first two passes of the ISEE-3 GEOTAIL Mission have been used to study the structure of the trans-lunar tail. Good agreement was found between the ISEE-3 magnetopause crossings and the Explorer 33, 35 model of Howe and Binsack (1972). Neutral sheet location was well ordered by the hinged current sheet models based upon near earth measurements. Between X = -20 and -120 earth radii the radius of the tail increases by about 30 percent while the lobe field strength decreases by approximately 60 percent. Beyond X = -100 to -1200 earth radii the tail diameter and lobe field magnitude become nearly constant at terminal values of approximately 60 earth radii and 9 nT, respectively. The distance at which the tail was observed to cease flaring, 100-120 earth radii, is in close agreement with the predictions of the analytic tail model of Coroniti and Kennel (1972). Overall, the findings of this study suggest that the magnetotail retains much of its near earth structure out to X = -220 earth radii.

Description: Nimbus 7 LIMS data and a photochemical model are used to show that the observed sharp latitudinal gradients in stratospheric wintertime NO2 are consistent with the conversion of NO2 to N2O5 at high latitudes. This conversion, and the sharp gradients, are brought about by the interaction between transport and photochemistry. Calculated variations show good agreement with observations.

Description: Measurements of atmospheric ozone and water vapor profiles obtained using a differential absorption lidar (DIAL) technique at Haute Provence Observatory are reported. The DIAL technique is based on the comparison of differences in attenuation in backscattered signals at wavelengths centered on strong absorptions or absorption lines of the species in question, and wavelengths corresponding to weaker or no absorption. The system in use is based on three lasers - a Nd:YAG Q-switched laser frequency doubled to emit at 532 nm, and two tunable narrowline dye lasers used to convert this emission into the IR or UV spectral regions. Ozone concentration profiles have been recorded up to a height of 30 km, and reveal large day-to-day variations in number density which were correlated with a decrease in tropopause height. Measurements of water vapor concentrations show a variability of the mixing ratio at heights up to 2.5 km representative of dynamic processes, and a variability above 2.5 km that is within the measurement error. Day-to-day variations in tropospheric mixing ratio were also observed.

Description: In connection with the eccentricity of the earth's orbit, conditions of solar radiation are not strictly symmetrical for the two hemispheres. The intensity of solar irradiation is approximately 6.6 percent higher near perihelion than near aphelion. As the ozone densities in the upper stratosphere and mesosphere are mainly controlled by photochemical processes, the asymmetry of irradiation conditions for both hemispheres could result in corresponding asymmetries regarding the ozone content. The present investigation is concerned with this possibility. The investigation takes into account Nimbus-7 and Nimbus-4 satellite data. It is found that the hemispheric asymmetries of the ozone distribution in the summer mesosphere and upper stratosphere are fully ascribable to the hemispheric temperature differences due to the combined effects of the earth's orbital ellipticity and its tilted spin axis from the ecliptic plane. The wintertime hemispheric asymmetries imply the presence of additional effects.

Description: Ozone transport is calculated for steady, dissipative planetary waves using the Eulerian, Lagrangian mean, and residual circulation. A Lagrangian model of parcel dynamics is used to interpret planetary wave-photochemistry interaction. In chemically active regions the mean field ozone changes are found to be significant only where there are large gradients in chemical sources and sinks along parcel trajectories. The largest changes in the mean field are found in the lower stratosphere and are due to the Lagrangian mean advection. When the Lagrangian mean advection is approximated by the residual circulation, errors in the transport velocities as large as 30 pct may occur.

Description: The eruptions of El Chichon volcano on March 28 and April 3 and 4, 1982 were observed by the Nimbus 7 total ozone mapping spectrometer due to strong absorption by volcanic gases at the shortest wavelengths of the spectrometer (312.5 and 317.5 nm). These ultraviolet pictures permit a measurement of the volume, dispersion, and drift of volcanic gas clouds. The tropospheric clouds were rapidly dispersed in westerly winds while persistent stratospheric clouds drifted in easterly winds at speeds up to 13 m/sec. The spectral reflectance is consistent with sulfur dioxide absorption and rules out carbon disulfide as a major constituent. A preliminary estimate of the mass of sulfur dioxide deposited in the stratosphere by the large eruptions on April 3 and 4 is 3.3 million tons. Prior estimates of volcanic cloud volume were based on extrapolation of locally measured sulfur dioxide concentrations.

Description: Ionospheric and field-aligned sheet current density distributions are presently inferred by means of MAGSAT vector magnetometer data, together with an accurate magnetic field model. By comparing Hall current densities inferred from the MAGSAT data and those inferred from simultaneously recorded ground based data acquired by the Scandinavian magnetometer array, it is determined that the former have previously been underestimated due to high damping of magnetic variations with high spatial wave numbers between the ionosphere and the MAGSAT orbit. Among important results of this study is noted the fact that the Birkeland and electrojet current systems are colocated. The analyses have shown a tendency for triangular rather than constant electrojet current distributions as a function of latitude, consistent with the statistical, uniform regions 1 and 2 Birkeland current patterns.

Description: Magnetospheric electrons precipitated by ground-based coded very low frequency radio transmissions have been detected by rocket measurement of bremsstrahlung X-rays, caused by impact of the electrons with the upper atmosphere. The direct correlations obtained between the very low frequency signals and the X-rays demonstrate the limits of sensitivity required and indicate that this remote sensing technique would be useful for future study of very low frequency effects induced by single lightning strokes.

Description: A new algorithm has been developed which permits, for the first time, real time data reduction of nadir measurements taken with a gas filter correlation radiometer to determine tropospheric carbon monoxide concentrations. The algorithm significantly reduces the complexity of the equations to be solved while providing accuracy comparable to line-by-line calculations. The method is based on a regression analysis technique using a truncated power series representation of the primary instrument output signals to infer directly a weighted average of trace gas concentration. The results produced by a microcomputer-based implementation of this technique are compared with those produced by the more rigorous line-by-line methods. This algorithm has been used in the reduction of Measurement of Air Pollution from Satellites, Shuttle, and aircraft data.

Description: Meteor echoes come from random points in the observation volume, and are irregularly spaced in time. This precludes the use of fast fourier transformations (FFT) techniques on the raw data to give the spectrum of waves that are present. One way around this obstacle is to restrict our interest to a particular class of waves, and fit a corresponding model to the raw data. It is assumed that there is no horizontal variation across the observation volume for tides, but in the vertical this is certainly not the case. If, in addition, we are interested in other types of waves which may be present and whose periods are unknown, then examining the raw line-of-sight velocities does not tell us how to modify the model, since the line-of-sight direction is not fixed. This is the motivation for interpolation. Interpolation takes a temporal series of line-of-sight velocities, and transforms it to a temporal series of wind velocities for each orthogonal direction. The velocities along a given direction can then be examined readily for any waves in addition to tides.

Description: When designing a Mesosphere-Stratosphere-Troposphere (MST) radar antenna one has to trade between the choices to optimize the effective aperture or to optimize the sidelobe suppression. An optimization of the aperture increases the sensitivity. Suppression of side-lobes by tapering attenuates undesirable signals which spoil the estimates of reflectivity and velocity. Generally, any sidelobe effects are equivalent to a broadening of the antenna beam. The return signal is due to a product of the antenna pattern with the varying atmospheric reflectivity structures. Thus, knowing the antenna pattern, it is in principle possible to find the signal spectra, which, however, may be a tedious computational and ambiguous procedure. For vertically pointing main beams the sidelobe effects are efficiently suppressed because of the aspect sensitivity. It follows that sidelobes are a minor problem for spaced antenna methods. However, they can be crucial for Doppler methods, which need off-vertical beams. If a sidelobe is pointing towards the zenith a larger power may be received from the vertical than off-vertical directions, but quantitative estimates of this effect are not yet known. To get an error estimate of sidelobe effects with an off-vertical main beam a 1-dimensional example is considered.

Description: There are many factors affecting the spaced antenna drift results, only one of which is antenna spacing. Generally, good results are obtained at MF for receiver antenna spacings of 1-1.5 lambda, and at VHF (e.g., SOUSY) for spacings approx. 6 lambda. Since one of the factors, local atmospheric/ionospheric conditions, are difficult to predict, this paper will be restricted to a short discussion of relevant factors, and methods for comparing various antenna/analysis configurations.

Description: An attempt is made to draw some quantitative conclusions regarding the anisotropy of the clear-air back-scattering mechanism based on the measured variation of echo power with zenith angle. The measurements were made by the SOUSY group of the Max Planck Institute for Aeronomy at Lindau, FRG. They installed their 47-MHz transmitter and antenna feed in the 300-meter diameter reflector at Arecibo. The resulting 1.7-degree beam was stepped successively through seven 1.7-degree intervals from 1.7 to 11.7 degrees in zenith angle, obtaining about four minutes of data at each setting. This procedure was carried out in an eastward pointing azimuth and in a northward pointing azimuth, the entire set of measurements consuming an hour and twenty minutes. Range resolution was 150 meters.

Description: The Doppler, spaced-antenna and interferometric methods of measuring wind velocities all use the same basic information, the Doppler shifts imposed on backscattered radio waves, but they process it in different ways. The Doppler technique is most commonly used at VHF since the narrow radar beams are readily available. However, the spaced antenna (SA) method has been successfully used with the SOUSY and Adelaide radars. At MF/HF the spaced antenna method is widely used since the large antenna arrays (diameter 1 km) required to generate narrow beams are expensive to construct. Where such arrays of this size are available then the Doppler method has been successfully used (e.g., Adelaide and Brisbane). In principle, the factors which influence the choice of beam pointing angle, the optimum antenna spacing will be the same whether operation is at MF or VHF. Many of the parameters which govern the efficient use of wind measuring systems have been discussed at previous MST workshops. Some of the points raised by these workshops are summarized.

Description: Data from the Jicamarca VHF radar and from a Languir probe fine-structure on a Nike Orion rocket launched from Punto Lobos, Peru, have been compared. A single mesospheric scattering layer was observed by the radar. The Langmuir probe detected irregularities in the electron-density profile in a narrow region between 85.2 and 86.6 km. It appears from a comparison between these two data sets that turbulence in the neutral atmosphere is the mechanism generating the refractive index irregularities.

Description: In both the tropical and extratropical regions there are a large number of dynamical problems which can be addressed by mesosphere-stratosphere-troposphere (MST) radars. The distinct advantage the MST radar has over rocket observations is continuous data acquisition. Without a doubt, the time-space spectrum of the mesospheric flow field is rich in high frequency motions associated with gravity waves rather than turbulent (random) fluctuations, and these events are particularly amenable to analysis with continuous data sets. In addition to the high frequency motions these are longer period fluctuations in the upper stratosphere and mesosphere wind fields which, combined with temperature fields derived from satellite data or lidars, can greatly enhance our knowledge of the upper atmosphere.

Description: During recent decades, the ionospheric D region has been scanned extensively by radar in the frequency range from 1 to 60 MHz. Progress has been made in understanding the reflection/scattering of radio waves in that area. Rocket measurement of ion density irregularities were compared to radar echo observations at 2.75 MHz with the conclusion that the received radar signal was due to scattering from isotropic and homogeneous turbulence in the altitude region between 70 and 95 km. However, scattering cross sections at 2 and 6 mHz suggest that the radar echo from the region below 80 km is in part due to partial reflection from stratified layers. The VHF scattering cross section is aspect sensitive in the D region below about 75 km and tends to be isotropic at higher altitudes. Positive correlations between scattered signal power and signal correlation time (P/C) have been observed by VHF radars in the lower mesosphere, with the conclusion that it might be an additional indication of partial reflection from stratified layers. In the upper mesosphere where the P/C correlation is negative, it is generally believed that the scattering is caused by isotropic turbulence. Radar echoes at the 2.16 and 40.92 MHz ranges are compared, assuming that both result from turbulent scatter. Adjusting the radar Bragg wavelength, it was found that both sets are due to scattering from the same layer of turbulence-generated irregularities.

Description: The structure of unstable planetary waves is computed by a quasi-geostrophic model extending from the surface up to 80 km by means of eigenvalue-eigenfunction techniques in spherical coordinates. Three kinds of unstable modes of distinct phase speeds and vertical structures are identified in the winter climate state: (1) the deep Green mode with its maximum amplitude in the stratosphere; (2) the deep Charney mode with its maximum amplitude in the troposphere: and (3) the shallow Charney mode which is largely confined to the troposphere. Both the Green mode and the deep Charney mode are characterized by very slow phase speeds. They are mainly supported by upward wave energy fluxes, but the local baroclinic energy conversion within the stratosphere also contributes in supporting these deep modes. The mesosphere and the troposphere are dynamically independent in the summer season decoupled by the deep stratospheric easterly. The summer mesosphere supports the easterly unstable waves 1-4. Waves 3 and 4 are identified with the observed mesospheric 2-day wave and 1.7-day wave, respectively.

Description: The propagation of gravity waves from the stratosphere to the mesosphere has important implications both for observers and those who are attempting to parameterize wave breaking in global models. As they propagate from the tropopause to their breaking level (here, assumed to be the mesosphere), gravity waves can encounter a refractive environment since the vertical group velocity is a function of the background wind. They may be focussed or scattered or dissipated before reaching the mesosphere. It is even conceivable that gravity waves may break stop breaking, and begin breaking again at high altitudes with a resultant loss of wave energy in the intervening region. From a modeling viewpoint, the important concern for large-scale flows is the total upward flux of gravity wave (pseudo) momentum entering the stratosphere and mesosphere. The refraction of gravity waves also presents a difficult problem for observers since waves passing through the tropopause may arrive a thousand kilometers upstream in the mesosphere. Since mesosphere - stratosphere - troposphere (MST) radars sense tropospheric and mesospheric conditions most accurately, they are ideally suited to assess the total gravity-wave flux through the tropopause and stratospause. Networks of radars making coordinated measurements may be required to accurately determine the upward flux of momentum as well as the flux convergence between layers.

Description: It is commonly believed that geomagnetic disturbances are caused by external influences connected with the solar wind. The 27-day recurrence of perturbations seems to be a strong hint for this interaction. But frequently geomagnetic disturbances occur without any relation to sunspot numbers or radiowave fluxes. This was one of the reasons for introducing hypothetical M-regions on the Sun and their relation to solar wind activities. Only one half of the variance of the geomagnetic AL-index could be related to the solar wind. Therefore it is concluded that internal processes of the magnetosphere were responsible for additional geomagnetic activity. Arguments, which might lead to the suggestion of geomagnetic disturbances as being caused by internal atmospheric dynamics are discussed and a rather preliminary scenario of those processes is proposed.

Description: Charged particle precipitation in the Earth's atmosphere produces odd nitrogen and odd hydrogen. These species take part in catalytic reactions which destroy atmospheric ozone in the stratosphere and mesosphere. Modeling efforts regarding the impact of these ionization events on the neutral atmosphere describe ozone depletions in good agreement with observations in the stratosphere and mesosphere. The photochemical effects of the solar proton event (SPE) of August 1972 are discussed, and calculations for higher altitudes (70 to 90 km) are presented that indicate after a brief reduction during and immediately following intense particle precipitation, ozone will later reach higher concentrations than those present before the event.

Description: Night-time ionspheric absorption measurements give the possibility to study the precipitation of high energy electrons into the mesosphere during and after magnetospheric storms. The uniform Finnish riometer network was used together with measurements from Kuhlungsborn and Collm (GDR) to investigate the night-time absorption as a function of latitude (L=6.5 to 2.5) and storm-time for seven storms. The common trends visible in all these events are summarized in a schematic average picture, showing the distribution of increased ionospheric absorption as a function of latitude (L value) and storm-time.

Description: Measurements of the integrated atmospheric radio noise field strength at 27 kHz, used here, were made from 1965 to 1975 at Uppsala, Kuhlungsborn, and Prague-Panska Ves. The large scale meteorological situation was considered by comparing solar disturbed and undisturbed periods under similar weather situations. In order to show the effects of the precipitating high energy particle (HEP) flux and of the Forbush decrease on the noise level between pairs of stations were computed as deviations from the monthly median. Delta E (dB), day by day for all six periods was studied. The correlation coefficients for noon as well as for night values were computed. The correlation coefficients were compared with those for solar undisturbed periods.

Description: The precipitation of high energetic electrons during and after strong geomagnetic storms into heights below 100 km in middle and subauroral latitudes is markedly modulated by the structure of the interplanetary magnetic field (IMF). Under relative quiet conditions the D-region ionization caused by high energetic particle precipitation (energies greater than 20 to 50 keV) depends on changes of the interplanetary magnetic field and also on the velocity of the solar wind. To test this assumption, the influence of the IMF-sector boundary crossings on ionospheric absorption data of high and middle latitudes by the superposed-epoch method was investigated.

Description: The precipitation of energetic particles from the magnetosphere produces a remarkable modification of the mid-latitude D-region structure during daytime and at dawn and dusk conditions. Beside the heavily fluctuating precipitation during the main storm phase, there exists a more continuous input of high energy electrons into the mesosphere in the belt between phi= 50 deg and the auroral zone up to ten days after the disturbance. The excessive D-region ionization, the after-effect of geomagnetic storms, is caused at least partly by additional nitric oxide production. The winter anomaly effects are especially amplified and prolonged by this effect. The source of this mid-latitude particle precipitation is thought to be situated in magnetospheric slot region processes.

Description: The fluxes of energetic electrons entering the high-latitude atmosphere during auroral radio absorption events and their effect on the electron density in the auroral D region are discussed. An attempt was made to calculate the radio absorption during precipitation events from the fluxes of energetic electrons measured at geosynchronous orbit, and then to consider the use of absorption measurements to indicate the magnetospheric particle fluxes, the production rates, and electron densities in the D region.

Description: A method by means of which the characteristics of atmospheric turbulence can be determined is discussed. Turbulent diffusivity deduced from ionospheric sporadic E in different altitudes above the ionospheric stations at Bekescsaba and Juliusrah are given. Seasonal variations in different altitudes above Bekescsaba are shown. An attempt was made to determine the variation of the turbulent diffusivity during and after geomagnetic disturbances by computing the horizontal wind velocity from the thermal wind equation. It is argued that the change of the turbulent diffusivity below the turbopause is opposed to that above the turbopause.

Description: Time spectra of the critical frequency f sub o E sub s and blanketing frequency f sub b E sub s for the records of a spaced chain of ionosphere vertical sounding stations were studied by means of a maximum entropy method, while coherence spectra were analyzed with the Blackman and Tukey method. It was found out that the frequency parameters spectrum of E sub s within the range of 1-10 cycles/h are discrete with one or two maxima. The first, a low frequency maximum with T=40 min, is of larger amplitude, stable and exists permanently; the second one with T = 10 min is less stable, occurs irregularly and more often within f sub o E sub s. Further, the first maximum corresponds to a higher level of coherence which decreases as the distance to the stations increases. It is concluded that the low-frequency maximum is induced by cellular eddies, usually interpreted as wind shears with horizontal dimensions of not more than 300 km. Irregularity, small amplitude, and low coherence in the range of the second maximum are indicative of the fact that turbulence must be its only source.

Description: The vibration rotation bands of the hydroxyl radical are the strongest features in the night airglow and are exceeded in intensity in the dayglow only by the infrared atmospheric bands of oxygen. The variation of intensity during evening twilight is discussed. Using a ground-based Fourier Transform Spectrometer (FTS), hydroxyl intensity measurements as early as 3 deg solar depression were made. Models of the twilight behavior show that this should be sufficient to provide measurement of the main portion of the twilight intensity change. The instrument was equipped with a liquid nitrogen-cooled germanium detector whose high sensitivity combined with the efficiency of the FTS technique permits spectra of the region 1.1 to 1.6 microns at high signal-to-noise to be obtained in two minutes. The use of a polarizer at the entrance aperture of the instrument reduces the intensity of scattered sunlight by a factor of at least ten for zenith observations.

Description: There are some increases of the temperature of the hydroxyl emission (delta T approximately 20 K, z approximately 90 km) and of the intensity of the 63000 oxygen emission (delta I/I approximately 20 per cent, z approximately 250 km) for the lee of the mountains at distances about 150 km in the case of the latitudinal direction of the wind (U approximately 10 m/s) at the 3000 m level. Airflow motions over mountains may be one of the possible processes of generation of wave disturbances penetrating into the upper atmospheres (HINES, 1974; LINDZEN, 1971). The purpose here is to study the penetration of orographic disturbances into upper atmosphere. Airplane measurements of emission variations of hydroxyl and atomic oxygen 6300 A near the Northern Ural mountains were made. Several nocturnal flights were carried out in March, 1980 and January to February, 1981 at heights about 3000 m along 64 deg northern latitude in the Ural region. Spectrographs SP-48 with electronic image converters registration for OH ((9,4) and (5,1) bands - 7700 to 8100 A) and OI (6300 A) emissions were used. The zenith region was observed, and exposure time was 2 minutes. This corresponds to averaging of the emission intensities along the airplane trace over a distance of 10 km. Simultaneous measurements of atmospheric temperature variations at the flight altitude were made.

Description: An analysis is made of the wind field structure in the strato-thermosphere over Eastern Siberia during the winter stratwarms of 1975-1977. It is found that coupling between dynamical processes in the stratosphere and lower thermosphere is effected through changes of the temperature regime of the atmosphere. The circulation regime both in the stratosphere and lower thermosphere depends on location of the source of perturbations that cause stratospheric warmings. The effect of warming-induced perturbations on the dynamics of above- and underlying layers and the meridional extent of the processes are determined by the altitude and region where anti-cyclones originate. In conditions of a warmer stratosphere, there is a considerable loss of wind stability in the ionospheric D-region. A time delay of 1 to 2 days of lower-thermosphere processes is found to occur with respect to stratospheric processes of temperature variation at 30 mb level.

Description: When supplemented by absolute reflection height measurements, low frequency wind measurements in the 90-100 km height range become truly competitive in comparison with the more widely used radar meteor wind observations. For example, height profiles of the wind parameters in the so-called meteor zone can be obtained due to the considerable interdiurnal variability of the average nighttime reflection heights controlled by geomagnetic activity. The phase of the semidiurnal tidal wind is particularly height-dependent. The measured vertical gradient of 1/4 h/km in winter corresponds to a vertical wavelength of about 50 km. Wind measurements in the upper atmosphere, at heights between 90 and 100 km, were carried out at the Collm Geophysical Observatory of Karl Marx University Leipzig for a number of years. These measurements use the closely-spaced receiver method and three measuring paths, on 179, 227, and 272 kHz. They take place every day between sunset and sunrise, i.e., nightly. A night in this sense may last as long as 18 hours in winter. Both the measurements and their evaluation are completely automatic, and the prevailing winds and tides are separated.

Description: Some main results of experimental investigations of the dynamical regime of the ionospheric D-region over East Siberia are presented. Regular measurements of horizontal ionospheric drifts by the radio method of closely spaced receivers, using a long wavelength transmitter operating at a frequency of 200 kHz, were carried out near Irkutsk, USSR, since 1975. The seasonal and inter-annual variations of prevailing wind (zonal and meridional), and amplitudes and phases of semi-diurnal tides are investigated. Evidence is presented to show the response of D-region dynamics to stratospheric warmings. Planetary and gravity waves are found in the wind field. Comparison with results of analogous measurements in Central Europe (Collm, GDR) reveals a longitudinal effect on the dynamical regime of the mid-latitude lower thermosphere.

Description: Examples of gravity waves (GW), tides, planetary waves (PW), and circulation effects in the upper middle atmosphere are presented. Energy densities of GW, tides, and PW are compared. Fourier and spectral analyses are applied to the data.

Description: D1 and D2 techniques have been used and are being used for observations at stations located in the high, middle, and low latitudes of both hemispheres. The systematical and wind velocity measurements with these techniques make it possible to specify and to refine earlier mesopause-lower thermosphere circulation models. With this in view, an effort was made to obtain global long term average height-latitude sections of the wind field at 70 to 110 km using the analysis of long period D1 and D2 observations. Data from 26 meteor radar and 6 ionospheric stations were taken for analysis.

Description: A general formula which expresses the distance along the meteoric fireball trajectory 1 as a function of t is discussed. Differential equations which include the motion and ablation of a single nonfragmenting meteor body are presented. The importance of the atmospheric density profile in the meteor formula is emphasized.

Description: In order to understand the lower ionosphere and its probable control by dynamical processes, the behavior of nitric oxide below 100 km was investigated. A two dimensional model with coupled chemical and dynamical processes was constructed. Calculations based on the model reveal that the chemical conditions at the stratopause are related to the state of the thermosphere. This coupling mechanism can be partly explained by the downward transport of nitric oxide during the winter season, and consequently depends on the dynamical conditions in the mesosphere and in the lower thermosphere (mean circulation and waves). In summer, the photodissociation of nitric oxide plays an important role and the thermospheric NO abundance modulates the radiation field reaching the upper stratosphere. Perturbations in the nitric oxide concentration above the mesopause could therefore have an impact in the vicinity of the stratopause.

Description: The heat and momentum flux due to standing planetary waves in the stratosphere were calculated on the basis of satellite data. The convergence of these fluxes was investigated and shows an apparent heating and acceleration of the mean zonal state. The Eliassen-Palm flux divergence calculation shows that the mean zonal state is effectively decelerated. Furthermore, the interaction between ultra long waves and k = 4 - 15 in the troposphere was investigated for a winter period and is discussed in connection with the geopotential wave one amplitude, which increases before a stratospheric warming event occurs.

Description: Data from several sources suggest that between 100 and 200 km in the middle atmosphere, a layer of anomalous circulation must be situated, at least in middle latitudes. The mechanisms responsible for the circulation anomaly in this height region are discussed in terms of hydrodynamic equations. The current state of atmospheric tidal theory is also addressed.

Description: The SOUSY-VHF-radar was used to carry out measurements during minor and a major stratospheric warming in February and March 1980, respectively. Echoes have been received from the stratosphere up to an altitude of about 30 km continuously during day and night, whereas echoes from the mesosphere were restricted to the daytime and occurred sporadically at different heights within the altitude range from 60 to 90 km. The three dimensional velocity vector was derived from Doppler measurements made in three different antenna beam directions with a height resolution of 1.5 km. In particular, the results obtained during disturbed conditions show the change of the zonal winds at mesospheric heights from westerly to easterly. A spectral analysis reveals a diurnal and a weaker semidiurnal tide of the zonal wind component.

Description: Daily zonal wind data of the four pre-MAP-winters 1978/79 to 1981/82 obtained over Central Europe and Eastern Europe by the radar meteor method were studied. Available temperature and satellite radiance data of the middle and upper stratosphere were used for comparison, as well as wind data from Canada. The existence or nonexistence of coupling between the observed large scale zonal wind disturbances in the upper mesopause region (90 to 100 km) and corresponding events in the stratosphere are discussed.

Description: The Middle Atmosphere is coupled to the troposphere during winter because planetary scale waves can propagate upwards if the prevailing winds are from the west. It is during this time of the year that the well-known midwinter disturbances are observed which ultimately affect the whole of the Middle Atmosphere. The mechanism of these disturbances is not completely understood. The large-scale circulation features up to the upper mesosphere are investigated to demonstrate the synoptic-scale behavior of the midwinter disturbances. Ground-based and satellite observations are combined. The interannual variability of the disturbances is discussed briefly. It is shown that the QBO (Quasi Biennial Oscillation) of the equatorial stratosphere appears to modulate the planetary waves during the northern winters, in the troposphere as well as in the Middle Atmosphere.

Description: The main seasonal features of the middle atmosphere are arising from the different dynamical basic states in winter and summer. The development of the two controversial circulation systems and the also different peculiarities of transition between them in spring and autumn create the completely dominant seasonal variations in strato- and mesosphere. Even in the plasma structures of the mesospheric D-region the seasonal variation is towering above the amplitudes of extraterrestrial influences. From standard ionospheric sounding, significant seasonal D- and E-region effects, adhering to equally significant structure changes in the neutral gas in the height region from 20 to 100 km were discovered. Results about such typical seasonal features are summarized.

Description: The winter anomaly in the winter of 1982/83 is compared with the winter anomalies of earlier winters (1960-82) from the point of view of amplitude and timing of the winter anomaly, and geomagnetic and dynamic activity influences. Some evidence of a negative influence of sudden stratospheric warnings on the winter anomaly is given.

Description: Seasonal variations of ionospheric absorption were studied using riometer (A2) measurements over a wide latitude range. In agreement with the results of earlier studies of A1 radiowave absorption, equinoctial maxima of approximately equal amplitude are observed in the auroral zone and near the equator. However, at intermediate latitudes riometer absorption maximizes during the fall season, whereas the A1 data show a semi-annual variation with maxima occurring in summer and winter. The autumn anomaly in riometer absorption is observed at much higher geographic latitude in the Southern Hemisphere, but at comparable geomagnetic latitudes in both hemispheres. The winter anomaly was seen only in absorption values calculated at constant solar zenith angle.

Description: A method to detect stratospheric warmings using ionospheric absorption records obtained by an Absorption Meter (method A3) is introduced. The activity of the stratospheric circulation and the D region ionospheric absorption as well as other atmospheric parameters during the winter anomaly experience an abnormal variation. A simultaneity was found in the beginning of abnormal variation in the mentioned parameters, using the absorption records for detecting the initiation of the stratospheric warming. Results of this scientific experience of forecasting in the El Arenosillo Range, are presented.

Description: It is a well-known fact that in winter the midlatitude lower ionosphere differs considerably from that in summer. Attempts to explain the possible causes of the winter anomaly in the lower ionosphere were made. Integrated ground-based and rocket experiments were performed in the USSR. The rockets M-100B launched in Volgograd (psi = 48.7 deg N; lambda = 44.3 deg E; psi = 43.1 deg) provided weight profiles of electron density, wind and temperature. Radio wave absorption data obtained by a I method in Volgograd and F sub min parameters values obtained at a number of Soviet ionosone stations were used to determine the situation in the lower ionosphere. It was found that a correct interpretation of the midlatitude winter radio wave absorption changes is possible only if the whole spatial-time pattern of the event is taken into account.

Description: Low-frequency propagation experiments for the investigation of the lower part of the ionospheric D region were at first used by BRACEWELL et al. (1951) in the early fifties. Among these was the method of indirect phase height measurements for continuous monitoring of the lower ionosphere. It is based upon field strength measurements of commercial radio transmitters in the frequency range between 50 and 200 kHz at distances from 500 to 1500 km. The field strength records show characteristic diurnal variations with maxima and minima, produced by interference between the ground wave and the ionospherically reflected sky wave, the phase difference between varies in correspondence to the diurnal variation of the reflection height. In order to check the validity of interpretations of indirect phase height data, comparisons were made with simultaneous rocket soundings. Results are summarized.

Description: The concept of so-called meteorological control of the ionospheric D-region is presently undergoing development. According to this concept the electron concentration in this region is governed not only by solar and geomagnetic parameters but strongly depends on the temperature and dynamical regime of the mesosphere and stratosphere. How this connection between D-region and meteorological parameters can be used to obtain some information about middle atmosphere temperature and dynamics is examined. The essential points of the meteorological control concept are reviewed and the influence of turbulence on nitric oxide distribution and thus the ion production rate is discussed.

Description: The increasing discoveries of various manifestations of meteorological control of the D region ionization and the growth of techniques for its measurement provide a challenge to meteorologists to test their insight into middle atmosphere processes with the physical interpretation of D layer phenomena. Models for ion production due to photoionization of minor atmospheric nitric oxide by quasi-monochromatic solar Lyman-alpha radiation are presented. A ground based measuring technique using low frequency radio reflection heights is briefly described and an approach to the interpretation of data acquired by this method is discussed. It is shown that D region electron density variations can provide an efficient diagnostic tool for the detection of perturbations of the circulation state of the middle atmosphere.

Description: A plausible scenario for the existence of a persistent back-ground of turbulence in the free atmosphere is described. The MST radar technique is the only existing technique that can be used to describe the morphology of occurrence of turbulence as a function of altitude, wind speed, shear, weather conditions, geographical location, etc. This technique was used also to assess the degree of universality of shape and amplitude of the buoyancy wave spectrum and the relation between the buoyancy wave spectrum and turbulence.

Description: Gravity waves and their associated breaking into turbulence are very important in producing the overall picture of middle atmosphere global dynamics and associated transport. It is shown in this research that MST radars represent a most powerful technique for obtaining the needed parameters for gravity-wave-induced drag and diffusion effects as well as measuring wave accelerations and diffusion directly. A mathematical solution to this problem is that of radiative equilibrium with a balanced thermal wind.

Description: Winter mesospheric echoes are observed between about 55 and 80 km when auroral absorption is present during daylight hours. Relatively steady auroral absorption during sunrise and sunset periods causes a distinct onset and decay signature in mesospheric echo occurrence. The echo onset and disappearance time are shown versus height by the inclined lines for four different dates. The more vertical lines give the visible sunlight height/time curves for both sunrise (SR) and sunset (SS). The data is combined and replotted to give the morning onset height and the afternoon disappearance height as a function of solar zenith angle. Echoes are not observed at the lowest heights in the morning until the solar zenith angle is less than 90 deg. The afternoon echoes at the lowest heights also start to disappear as soon as the solar zenith angle exceeds 90 deg, implying that the solar component which sustains the mesospheric echo is screened by a layer extending up to about 60 km. The morning echo at 73 km onsets near the time of visible sunrise, but in the afternoon the 73 km echo lasts well past visible sunset.

Description: The reduction of spaced wind measurements taken over a range of heights is described. The equipment used is a medium frequency radar with one site consisting of a vertically pointing transmitter and space receiving antennas, and two remote receiving sites with spaced antennas. Assuming approximately horizontally stratified scatterers, horizontal winds are thus available at the corners of a triangle of side approx. 20 km in the GRAVNET system.

Description: There have been numerous studies addressing the turbulent diffusion in the stratosphere and mesosphere during the last two decades. The motivation for such studies was the need for an understanding of the thermal and constituent structure of the middle atmosphere. Observational estimates of the horizontal and/or vertical diffusion were obtained using chemical release, rocket vapor trail, aircraft, balloon, and radar techniques. During the same period, a number of theoretical studies were performed to infer the level of vertical diffusion needed to account for observed constituent profiles. There appears to be a discrepancy between the level of vertical diffusion required for the dissipation of gravity wave and tidal motions on the one hand and for the maintenance of observed temperature and constituent profiles on the other. A possible explanation of this discrepancy is outlined. Measurements that may help verify this explanation are suggested.

Description: The Arecibo 430-MHz radar was used in the velocity-azimuth display (VAD) mode to obtain radial velocity measurements at 16 azimuth directions from which the three-dimensional wind field and momentum flux can be calculated. The radar was operated on a nearly continuous basis for a seven-day period in May of 1982 and the elapsed time between start and finish of a VAD scan was approximately 35 minutes. Radial velocities were measured in the upper troposphere and lower stratosphere (6-24 km) with at height resolution of 150 meters at a zenith angle of 15 deg. Vertical and horizontal velocities are calculated from the sums and differences, respectively, of radial velocity pairs, i.e., at azimuth directions AZ and AZ + 180 degrees. Momentum flux at a particular azimuth is calculated by taking the difference between the square of radial velocities at AZ and AZ + 180 degrees. It should be noted that measurements of radial velocity pairs are not simultaneous but are time delayed by approximately 15-25 minutes. This period, the time required to rotate the antenna feed and take measurements at AZ and AZ + 180 deg, effectively limits sampling of velocities and momentum fluxes to longer period gravity waves and planetary waves.

Description: Vertical profiles of scalar horizontal winds have been measured at high resolution (10 m) in the 13 to 37 km region of the stratosphere. This resolution (at that range of altitude) represents the state-of-the-art, and is unique. The technique used smoke trails laid by rockets in the stratosphere, and were taken by AFGL at Wallops Island, VA, White Sands Missile Range, NM, and Ft. Churchill, Canada, in the 1977-78 time period. Two or three cameras were used to give the time-lapse photographs. The goal was to ascertain whether or not the internal waves of the stratosphere behave consistently with the Garrett-Munk model which was originally created for oceanic internal waves. Five profiles of horizontal wind are presented. It is concluded: (1) stratospheric internal waves obey the Garrett-Munk model for vertical wave numbers; (2) there is not statistically significant evidence for a break in the curve at high wave numbers when due allowance is made for aliasing effects; and (3) the power density level of the spectra are almost equal on a log-log scale in spite of the difference in time, season, and geographical location.

Description: Using a spaced antenna setup of a VHF radar, the spatial distribution of amplitudes and phases of the radar echoes from the troposphere, stratosphere and mesosphere can be measured. Combining in a suitable analysis procedure the complex digital samples from the different receiving antennas is consistent with the radar interferometer method. In addition to the well-known parameters measured with the commonly applied Doppler and drifts methods, i.e., reflectivity and mean fluctuation velocity, the interferometer technique allows to measure the regular spectrum of the returns. This technique, which was first applied with the spaced antenna system of the SOUSY-VHF-Radar in W. Germany, as well as some first examples of results are described here. These comprise the measurements of the horizontal and vertical velocities of the mean flow as well as of turbulence structures, the aspect sensitivity and the tilt of layers from which the baroclinicity can be estimated. Particularly, results of interferometer measurements of the vertical and horizontal phase velocities and wavelengths of gravity waves in the stratosphere are displayed. The latter results are also discussed in terms of the generation and propagation of these waves.