Showing papers in "Geophysical Research Letters in 1983"
TL;DR: Water is essential for the formation of granite and granite, in turn, is necessary for the creation of continents as discussed by the authors, and Earth, the only inner planet with abundant water, is the only planet with granite and continents.
Abstract: Water is essential for the formation of granite and granite, in turn, is essential for the formation of continents. Earth, the only inner planet with abundant water, is the only planet with granite and continents. The Moon and the other inner planets have little or no water and no granites or continents.
292 citations
TL;DR: In this article, a linear 2-D eigenmode analysis was performed to study the Hall current effect on collisional tearing mode instability and the appearance of the dawn-dusk component of the magnetic field in the magnetotail reconnection region.
Abstract: From a linear 2-D eigenmode analysis, it is found that the Hall current effect on collisional tearing mode instability becomes important for the thin magnetic reversal layer whose width is comparable to the ion inertia length; Hall currents produce a three-dimensional field structure and increase the reconnection (growth) rate. Since the magnetaic reversal layer widths both in the magnetopause and in the magnetotail are reported to become as thin as the ion inertial length (several hundred km) when the reconnection process is supposed to occur, the Hall current effect may explain the appearance of the dawn-dusk component of the magnetic field in the magnetotail reconnection region.
241 citations
TL;DR: Soils in an Amazonian rainforest are observed to release N2O at a rate larger than the global mean by about a factor of 20 as discussed by the authors, while emissions from a New England hardwood forest are approximately 30 times smaller then Brazilian values.
Abstract: Soils in an Amazonian rainforest are observed to release N2O at a rate larger than the global mean by about a factor of 20. Emissions from a New England hardwood forest are approximately 30 times smaller then Brazilian values. Atmospheric methane is consumed by soils in both systems. Tropical forests would provide a major source of atmospheric N2O if the Brazilian results are representative.
211 citations
TL;DR: In this paper, the local magnetic field oscillates at its Alfven resonance frequency (ies) in response to a wide band source whose frequency range covers the resonance frequency, where the frequency is found to vary continuously as a function of latitude for a given event.
Abstract: The local magnetic field is shown to oscillate at its Alfven resonance frequency (ies) in response to a wide band source whose frequency range covers the resonance frequency (ies). The proposed mechanism explains certain observations of magnetic pulsations where the frequency is found to vary continuously as a function of latitude for a given event.
165 citations
TL;DR: In this paper, the authors investigated the stratospheric sulfuric acid fraction and mass for the 1982 volcanic eruptions of El Chichon using data from balloon soundings at Laramie (41 deg N) and in southern Texas (27-29 deg N).
Abstract: The stratospheric sulfuric acid fraction and mass for the 1982 volcanic eruptions of El Chichon are investigated using data from balloon soundings at Laramie (41 deg N) and in southern Texas (27-29 deg N). The total stratospheric mass of these eruptions is estimated to be approximately 8 Tg about 6.5 months after the eruption with possibly as much as 20 Tg in the stratosphere about 45 days after the eruption. Observations of the aerosol in Texas revealed two primary layers, both highly volatile at 150 C. Aerosol in the upper layer at about 25 km was composed of an approximately 80 percent H2SO4 solution while the lower layer at approximately 18 km was composed of a 60-65 percent H2SO4 solution aerosol. It is calculated that an H2SO4 vapor concentration of at least 3 x 10 to the 7th molecules/cu cm is needed to sustain the large droplets in the upper layer. An early bi-modal nature in the size distribution indicates droplet nucleation from the gas phase during the first 3 months, while the similarity of the large particle profiles 2 months apart shows continued particle growth 6.5 months after the explosion.
160 citations
TL;DR: F-region vertical drift data from Jicamarca, Peru show that equatorial east-west electric fields are sometimes perturbed 16-24 hours after the onset of geomagnetic storms as mentioned in this paper.
Abstract: F-region vertical drift data from Jicamarca, Peru show that equatorial east-west electric fields are sometimes perturbed 16-24 hours after the onset of geomagnetic storms. These disturbance dynamo electric fields, which must be caused primarily by the action of neutral winds at low and middle latitudes, decrease and sometimes even reverse the quiet time electric field pattern during both daytime and nighttime. The long delay excludes the possibility that gravity waves are responsible and suggests that the thermospheric circulation is disturbed. The data also show that after some storms there are no such delayed disturbances, a fact which may be due to the longitudinal structure of the disturbances at high latitudes and/or that only very strong storms can produce major thermospheric perturbations that extend to middle and low latitudes.
159 citations
TL;DR: When the angle of the IMF to the earth sun line is 15 deg or less, the occurrence rate of dayside Pc 3,4 pulsations in 7-8 times the average at L values of 2.4-2.8.
Abstract: When the angle of the IMF to the earth sun line is 15 deg or less, the occurrence rate of dayside Pc 3,4 pulsations in 7-8 times the average at L values of 2.4-2.8, and 2.2-3.5 times the average at L of 4-4.3. These waves disappear when the IMF is nearly at right angles to the sun-earth line. Such observations are consistent with a source originating in the waves upstream of the subsolar bow shock, which are transported by convection to the magnetopause. There, they couple to oscillations of magnetospheric field lines. Because the magnetospheric plasma's index of refraction decreases with radial distance except at the plasmapause, inwardly propagating waves should be refracted away from the radial direction. To reach low L values, the waves should therefore couple near the stagnation point and propagate nearly radially inwards. The streamline geometry and its connection to the foreshock region is illustrated for various IMF orientations, using a simple approximation to the magnetosheath flow field.
145 citations
TL;DR: The isotopic composition of rainwater near Nahariya, Israel, was measured in 12 individual storms during the winter months of 1980/1981 as mentioned in this paper, and a relatively high correlation coefficient was found between the stable isotopic content of precipitation and the 800 mb temperature.
Abstract: The isotopic composition of rainwater near Nahariya, Israel, was measured in 12 individual storms during the winter months of 1980/1981. Rains most depleted in the heavy stable isotopes and enriched in tritium are associated with air masses which come from North East Europe and have a short, intense interaction with the East Mediterranean Sea. Storms most enriched in 18O and D and depleted in tritium are associated with air masses which come from the Atlantic Ocean and enter the Mediterranean Sea on its western part, travelling along the North African Coast, sometimes with a southerly shift. A relatively high correlation coefficient was found between the stable isotopic content of precipitation and the 800 mb temperature.
130 citations
TL;DR: In this paper, the authors used linear regression to find the relationship between sea-floor age and sea-depth at trenches, and showed that the strength of this correlation is strong evidence in favor of the validity of this simple model.
Abstract: Sea-floor age-depth and age-trench-depth relations suggest that the oceanic lithosphere continues to thicken and subside with age beyond 80 Ma. If so, slab-pull (FS) and ridge-push (FR) forces can be calculated from the age of the sea floor at trenches (t), and if the shear stress acting on the base of the plate increases with absolute velocity (νa), the approximate force balance equation is
Dva2=Svat32+Rt
where D, S and R are constants related to drag, slab pull and ridge push, respectively. The relation between velocity and age is
va2=S′vat12+R′
We have tested this model by linear regression using rate and age data for 15 trenches:
va(mm/a)2=(9.20±.32)vat12+(26±250)
The strength of this correlation (r² = 0.98) is strong evidence in favor of the validity of this simple model. These results suggest that ridge push is just sufficient to overcome drag at the base of the plate, and does not contribute significantly to the motions of oceanic plates, though the value of R′ is consistent with the motions of plates not attached to subducted slabs.
124 citations
TL;DR: The most abundant volatile sulfur compound found in the surface layers of the central equatorial Pacific Ocean (148°W to 170°E) was dimethyl sulfide (DMS) as mentioned in this paper.
Abstract: The most abundant volatile sulfur compound found in the surface layers of the central equatorial Pacific Ocean (148°W to 170°E) was dimethyl sulfide (DMS). Concentrations of DMS ranged from 100-400 ng DMS/L; the highest concentrations occurred at 2°N and 148°W. DMS accounted for more than 97% of the total volatile sulfur species present, and was significantly correlated with chlorophyll ‘a’. Elevated concentrations of DMS near the equator are related to nutrient eutrophication stimulated by equatorial upwelling and the horizontal transport from the east. Vertical profiles taken at 9 stations indicated that maximum DMS concentration occurred at 20-40 m, with concentrations decreasing to < 1 ng DMS/L at 150-200 m.
Flux calculations indicate that the central equatorial Pacific (6°N to 6°S between 148°W and 170°E) supplies about 1.0 Tg DMS/yr, assuming a mean surface concentration of 200 ng DMS/L and a piston velocity of 2.3 m/d.
124 citations
TL;DR: In this paper, it was shown that cold ionospheric electrons, which carry the downward region-1 Birkeland currents on the morning side, are accelerated upward by potential drops of a few tens of eV at altitudes of several thousand kilometers.
Abstract: Measurements made by the High Altitude Plasma Instrument on DE-1 have shown that intense upward electron beams with energies from about 20 eV to about 200 eV are a common feature of the region just equatorward of the morning-side polar cusp. Computations of the currents carried by these beams and by the precipitating cusp electrons show excellent agreement with the simultaneous DE-1 magnetometer measurements for both upward and downward Birkeland currents. The data indicate that cold ionospheric electrons, which carry the downward region-1 Birkeland currents on the morning side, are accelerated upward by potential drops of a few tens of eV at altitudes of several thousand kilometers. This acceleration process allows spacecraft above those altitudes to measure routinely the charge carriers of both downward and upward current systems.
TL;DR: Aerosol evaluation was found to be necessary to explain the 30 mb temperature increases observed in July-Oct. 1982 in comparison with averages for the period 1964-1981.
Abstract: Aerosol evaluation was found to be necessary to explain the 30 mb temperature increases observed in July-Oct. 1982 in comparison with averages for the period 1964-1981. An average difference of 1-1.5 C was determined at 30 mb, coinciding with 1 C deviations at the 50 mb level, for the first half of 1982. The 30 mb differences increased to 4.5-5 C, compared to the 18 yr average, during the July-Oct. period. GOES satellite imagery indicated that material from the El Chichon volcano eruptions had entered the stratosphere. Lidar backscattering ratios indicated the preponderance of the material resided in the 22-28 km interval. Airborne lidar measurements on two occasions confirmed the anomalies' presence south of 30 deg N latitude. Further monitoring of the aerosol evolution is indicated.
TL;DR: In this article, the authors used magnetic field measurements from the first two passes of the ISEE-3 GEOTAIL mission to study the structure of the trans-lunar tail.
Abstract: 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. Neutral sheet location was well ordered by the hinged current sheet models based upon near earth measurements. Between X=−20 Re and −120 Re the radius of the tail increases by about 30% while the lobe field strength decreases by approximately 60%. Beyond X=−100 to −120 Re the tail diameter and lobe field magnitude become nearly constant at terminal values of approximately 60 Re and 9 nT, respectively. These results are consistent with pressure balance across the distant magnetopause equating lobe field pressure, B²L/8π, and external solar wind thermal and magnetic pressure, nk(Te+Ti) + B²/8π. The distance at which the tail was observed to cease flaring, 100-120 Re, is in close agreement with the predictions of the analytic tail model of Coroniti and Kennel. Overall, the findings of this study suggest that the magnetotail retains much of its near earth structure out to X=−220 Re.
TL;DR: In this article, a recent theoretical model for acoustic velocities in dry, disordered sphere packs is discussed and applied to experimental data for both unconsolidated glass beads and Berea sandstone at various confining pressures.
Abstract: Propagation of acoustic waves in earth materials is controlled to a large extent by the properties of the solid frame of the material. In sedimentary materials, interactions at the grain contacts provide a key to understanding the frame properties. In this note, a recent theoretical model by Digby (1981) for acoustic velocities in dry, disordered sphere packs is discussed and applied to experimental data. Central to the model are the normal and tangential stiffnesses at the contacts between grains. We have inverted Digby’s results to give equations for the contact stiffnesses in terms of the measured velocities. These equations have been applied to experimental data from the literature for both unconsolidated glass beads and Berea sandstone at various confining pressures. Taken literally, these results indicate that interactions at real grain contacts are not well described by conventional Hertz-Mindlin contacts or by modified Digby contacts. Alternatively, the results indicate that the theory requires modifications such as additional contact interactions or distributions of grain sizes, coordination numbers, or contact stiffnesses.
TL;DR: In this article, the authors show that if the westward tilts are associated with eastward plasma drifts that decrease with altitude above the F peak, this shear must be set up by a zonal wind pattern of decreasing speed at increasing distances from the equator.
Abstract: Model studies have been carried out to specify the ionospheric conditions and electrodynamical processes required to describe the geometry of westward tilting and bifurcating equatorial plasma depletions inferred from airglow imaging measurements taken on Ascension Island in early 1981. The results indicate that if the westward tilts are to be associated with eastward plasma drifts that decrease with altitude above the F peak, this shear must be set up by a zonal wind pattern of decreasing speed at increasing distances from the equator. Below the peak, calculations of flux tube integrated Pedersen conductivity, including both E and F region contributions, are in agreement with the simulations of Zalesak et al. (1982) that show bifurcated depletions to be associated with a mild gradient in the bottomside conductivity profile.
TL;DR: In this paper, an analysis of the initial neodymium and hafnium isotopic compositions of modern and ancient mantle-derived rocks was performed and it was shown that the divergence of the mantle 143Nd/144Nd and 176Hf/177Hf ratios from the chondritic ratios over the past 2 billion years has been much less than would be expected based on the Sm/Nd, Lu/Hf ratio of the mid-ocean ridge basalt.
Abstract: An analysis of the initial neodymium and hafnium isotopic compositions of modern and ancient mantle-derived rocks shows that the divergence of the mantle 143Nd/144Nd and 176Hf/177Hf ratios from the chondritic ratios over the past 2 billion years has been much less than would be expected based on the Sm/Nd and Lu/Hf ratios of the mantle source of mid-ocean ridge basalt. The most likely explanation is that rock material from the continents has been recycled semi-continuously back into the mantle over this time period. The required rate of return of continents to the mantle, calculated from a simple transport model, is about 0.35±0.15 of the continental mass per billion years (∼2.5 km³/year). This result is consistent with the hypothesis that the mass of the continents has been approximately constant since the late Archean, and implies that recycled continental material must be an important component of the upper mantle.
TL;DR: In this article, the effects of a combined convection and corotation electric field across the Io plasma torus are considered, and the effect of a dawn-to-dusk electric field E sub C will modify the orbits of charged particles shifting them toward dawn.
Abstract: The effects of a combined convection and corotation electric field across the Io plasma torus are considered. A dawn-to-dusk electric field E sub C will modify the orbits of charged particles shifting them toward dawn. The radial drift imposed by the perturbed orbits implies a local time-dependent modulation of low-energy ion and electron temperatures with particles hotter at dusk than at dawn. With E sub C approximately 4 mV/m, the orbits near 6 Jupiter radii would be shifted by approximately 0.2 Jupiter radius. Then the electron temperature would be 20% higher at dust than at dawn, an effect which could explain the local time asymmetry of EUV intensity found by the Voyager ultraviolet spectrometer. The source of the convection electric field is internal to the magnetosphere, and is attributed to the tailward escape of Iogenic and Jovian plasma beyond the Alfven surface.
TL;DR: The solar proton event of July 13, 1982 was the largest to date in the current solar cycle as discussed by the authors, which led to the production of odd hydrogen radicals (H+OH+HO/sub 2/) which catalytically destroy odd oxygen in the mesosphere and stratosphee.
Abstract: The solar proton event of July 13, 1982 was the largest to date in the current solar cycle. Proton fluxes observed by the NOAA-6 satellite have been used to calculate ionization rates during the event, which have been found to be almost as large as those of the August, 1972 event near 70 km, but much smaller at lower altitudes. This ionization leads to the production of odd hydrogen radicals (H+OH+HO/sub 2/) which catalytically destroy odd oxygen in the mesosphere and stratosphee. A one-dimensional time-dependent model has been used to calculate the percentage change in ozone resulting from this event. The calculated ozone depletion is compared to that observed by the Solar Mesosphere Explorer (SME) satellite.
TL;DR: The large-scale thermal structure of the California Current during 1982-83 shows several anomalous conditions: warm sea surface temperature anomalies (∼1-2°C), depression of the thermocline by 50 m or more, and pronounced subsurface warming relative to the 30-year mean as mentioned in this paper.
Abstract: The large-scale thermal structure of the California Current during 1982-83 shows several anomalous conditions: warm sea surface temperature anomalies (∼1-2°C), depression of the thermocline by 50 m or more, and pronounced subsurface warming (∼3-4°C) relative to the 30-year mean. The subsurface anomaly is much greater than the surface anomaly. These persistent (>6 months) structures, coupled with unusually high sea levels along the North American coast, show that a major Californian "El Nino" occurred during 1982-83. The data support the conclusion that the expansion and intensification of the Aleutian low and the decrease in strength of the Pacific high produced an anomalous basin-wide atmospheric circulation which coupled directly to the large-scale oceanic wind-driven circulation to produce the Californian "El Nino." The enhanced transport from the west (offshore California) and south (Baja California), which such a circulation would produce, is consistent with the observed water properties. The equatorial 1982-83 El Nino is probably related to the Californian "El Nino" through an atmospheric teleconnection between equatorial sea surface temperature and the atmospheric Hadley circulations.
TL;DR: In this paper, photographic and television observations made during the third flight of the Space Shuttle in March 1982 reveal the presence of a diffuse optical emission surrounding surfaces of the vehicle exposed to the atmosphere in the ram direction.
Abstract: Photographic and television observations made during the third flight of the Space Shuttle in March 1982 reveal the presence of a diffuse optical emission surrounding surfaces of the vehicle exposed to the atmosphere in the ram direction. The line of sight intensity of this emission is comparable to that of airglow emissions seen at the limb of the earth and competes with the brightness of stars seen within the field of view of the photographic and TV cameras. The glow emission appears to be a manifestation of an atmosphere-vehicle interaction. Light from vehicle thruster operations was also seen, as well as the optical emissions resulting from the operation of a 100 mA electron beam.
TL;DR: The SEEP (Stimulated Emission of Energetic Particles) experiment conducted during May-December 1982 as discussed by the authors showed that approximately 15 to 50 percent of the enhanced electron flux was concentrated near the resonant energies for first order cyclotron interactions occurring close to the magnetic equator with the nearly monochromatic waves emitted from the transmitter.
Abstract: Radiation belt electrons precipitated by controlled injection of VLF signals from a ground based transmitter have been directly observed for the first time. These observations were part of the SEEP (Stimulated Emission of Energetic Particles) experiment conducted during May-December 1982. Key elements of SEEP were the controlled modulation of VLF transmitters and a sensitive low altitude satellite payload to detect the precipitation. An outstanding example of time-correlated wave and particle data occurred from 8680 to 8740 seconds. U. T. on 17 August 1982 when the satellite passed near the VLF transmitter at Cutler, Maine (NAA) as it was being modulated with a repeated ON (3--s)/OFF (2--s) pattern. During each of twelve consecutive pulses from the transmitter the electron counting rate increased significantly after start of the ON period and reached a maximum about 2 seconds later. The measured energy spectra revealed that approximately 15 to 50 percent of the enhanced electron flux was concentrated near the resonant energies for first order cyclotron interactions occurring close to the magnetic equator with the nearly monochromatic waves emitted from the transmitter.
TL;DR: In this paper, the reaction of N2O5 with water vapor, a potentially important nighttime loss reaction for NOx and formation pathway for nitric acid, has been investigated at 298 ± 1 K in two environmental chambers of 3800 and 5800 L volume.
Abstract: The reaction of N2O5 with water vapor, a potentially important nighttime loss reaction for NOx and formation pathway for nitric acid, has been investigated at 298 ± 1 K in two environmental chambers of 3800 and 5800 L volume. From the N2O5 decay rates as a function of water vapor concentration, an upper limit to the N2O5 + H2O rate constant of less than 2.4 × 10−21 cm³ molecule−1 s−1 is derived. However, while gas phase nitric acid was observed to be a major product, its yield, especially at low water vapor concentrations, was significantly lower than the value of 2 expected, indicating that the overall reaction in these chambers involved both homogeneous and heterogeneous components. After allowing for the contribution of the heterogeneous reaction, an estimate of the gas phase homogeneous rate constant for N2O5 + H2O of 1.3 × 10−21 cm³ molecule−1 s−1 was obtained. While this value must still be regarded as an upper limit to the homogeneous rate constant, it is a factor of 10 lower than the only directly measured upper limit reported previously.
TL;DR: The ring plane event detected by the Voyager 1 and 2 Planetary Radio Astronomy experiment is distinct from Saturn kilometric radiation (SKR) and from Saturn electrostatic discharges (SED), it consists of radio noises recorded only during Saturnian ring plane crossings.
Abstract: The ring plane event detected by the Voyager 1 and 2 Planetary Radio Astronomy experiment is distinct from Saturn kilometric radiation (SKR) and from Saturn electrostatic discharges (SED). It consists of radio noises recorded only during Saturnian ring plane crossings. Several models are tested. The electrostatic noise on the antennas resulting from the passage of electrons and ions near the antennas (quasi-thermal noise) leads to order of magnitude much lower than the observed values. Shot noise due to electrons and ions collected and/or emitted by the antennas and spacecraft can explain the noise recorded during Saturn Voyager 1 ring plane crossing and partly what is observed in the case of Voyager 2. For this latter event we must introduce the shot noise due to grain impacts. A quantitative approach of this process gives an estimation of the dust size ∼ 2.3 µm just outside the G-ring.
TL;DR: The spacecraft remained close to or within a previously unexplored part of the distant (60-220 earth radii) geomagnetic tail nearly continuously from January 1 to March 30, 1983.
Abstract: The spacecraft remained close to or within a previously unexplored part of the distant (60-220 earth radii) geomagnetic tail nearly continuously from January 1 to March 30, 1983. Analysis of the data reveals that all of the plasma regimes identified previously with near-earth measurements (plasma sheet, low-latitude boundary layer, plasma mantle, lobe, and magnetosheath) remain recognizable in the distant tail. These regimes, however, are found to be intermingled in a more chaotic fashion than near the earth. Within the plasma sheet at approximately 200 earth radii, typical flow velocities are about 500 km/s tailward, considerably higher than in the near-earth plasma sheet. Earthward flow within the plasma sheet is observed occasionally, indicating the temporary presence of a neutral line beyond 220 earth radii. Also found are strong bidirectional electron anisotropies throughout much of the distant plasma sheet, boundary layer, and magnetosheath.
TL;DR: The axial traces of the major Appalachian orogen change azimuthal direction from a NE-SW orientation to a N-S orientation in the area of the Pennsylvania Salient and swing back to an NE-NW orientation near the Virginia Reentrant as mentioned in this paper.
Abstract: The axial traces of the major Appalachian folds change azimuthal direction from a NE-SW orientation to a N-S orientation in the area of the Pennsylvania Salient and swing back to a NE-SW orientation in the vicinity of the Virginia Reentrant. All available paleomagnetic data from the folded Appalachians have been examined to test the Appalachian orocline hypothesis. Pre-deformational site-mean directions from suitable studies were rotated by the amount required to bring the strike of the sampled beds into coincidence with an average trend of the Central and Southern Appalachians (N35E). A comparison of clustering of site-means before and after this correction, reveals that in all cases unbending of the arc causes site-mean directions to disperse. This dispersal demonstrates that the curvature of the Appalachian orogen is to a very large degree a primary feature rather than a feature which resulted from the bending of initially straight fold axes.
TL;DR: In order to study the mechanism of aerosol sulfate formation, weekly samples of SO2 and aerosol SO4= were collected at Hubbard Brook Experimental Forest, West Thornton, New Hampshire from July to December, 1980.
Abstract: In order to study the mechanism of aerosol sulfate formation, weekly samples of SO2 and aerosol SO4= were collected at Hubbard Brook Experimental Forest, West Thornton, New Hampshire from July to December, 1980. Samples were analyzed for concentration and sulfur isotopes (δ34S). Late summer-early fall samples are characterized by high, variable SO4= levels and low SO2 levels, while late fall - early winter samples exhibit low SO4= and high SO2 levels. These trends suggest that the oxidation rate varies seasonally, with faster oxidation during warmer months. The sulfur isotopic fractionation between aerosol SO4= and SO2 is intermediate between that expected from homogeneous and heterogeneous reactions, indicating that both processes can be important. The isotopic data suggest that homogeneous oxidation reactions are more important than solution reactions, particularly during warm months.
TL;DR: In this paper, the results of an experimental survey flight was conducted in October-November 1982 to underfly El Chichon's eruption cloud and to map out its latitudinal distribution.
Abstract: 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.
TL;DR: In this paper, a model that connects the stress regime in the outer-rise to the behavior of large subduction earthquakes and explains the focal mechanisms and both the temporal and spatial occurrence of outerrise earthquakes was proposed.
Abstract: Outer-rise earthquakes can be separated into two basic categories based on focal mechanism: compressional and tensional events reflecting compressional and tensional outer-rise stress regimes. We propose a model that connects the stress regime in the outer-rise to the behavior of large subduction earthquakes and explains the focal mechanisms and both the temporal and spatial occurrence of outer-rise earthquakes.
We find that compressional outer-rise events tend to occur oceanward of seismic gaps in seismically coupled subduction zones, or equivalently just prior to large subduction zone earthquakes. The compressional stress regime is probably caused by slip in adjacent subduction zone segments. There are two modes of occurrence for tensional outer-rise earthquakes depending on whether they occur in coupled or uncoupled subduction zones. In coupled subduction zones, tensional events tend to occur after large subduction events as tensional stress from slab pull is temporarily transmitted to the outer-rise. In subduction zones that are inherently uncoupled, tensional events can occur at any time. Therefore, in uncoupled subduction zones the outer-rise is always in tension, and only tensional outer-rise events occur there; while in coupled subduction zones, the outer-rise is in a compressional state prior to large subduction earthquakes and a tensional state afterwards due to the large displacements.
TL;DR: In this article, a borehole-to-borehole audiofrequency seismic system using piezoelectric transducers as active elements has been developed and used to investigate crystalline rocks in Canada.
Abstract: A borehole-to-borehole audiofrequency seismic system using piezoelectric transducers as active elements has been developed and used to investigate crystalline rocks in Canada. High-quality seismograms have been recorded for transmitter-receiver distances of up to 230 meters. It has been found that both travel times and signal amplitudes provide diagnostic information about rock quality. Two-dimensional images of seismic velocity and transparency distributions between two boreholes, derived from observed arrival times and amplitudes by simple back-projection tomography, reflect lithology and geological structure. The results indicate the potential usefulness of crosshole seismic imaging as a tool for rock mass characterization.
TL;DR: In this article, the authors examined a similar optical glow by analyzing photometric data taken by the VISible Airglow Experiment on board the Atmosphere Explorer Satellites and found that the glow has a diffuse band or continuum spectrum which peaks in the red and probably in the infrared.
Abstract: Illumination was found recently in the ram direction of the Shuttle Orbiter arising from interaction with the ambient surrounding atmosphere. We have examined a similar optical glow by analyzing photometric data taken by the Visible Airglow Experiment on board the Atmosphere Explorer Satellites. Analysis at six different wavelengths from the ultraviolet to the near infrared suggests that the glow has a diffuse band or continuum spectrum which peaks in the red and probably in the infrared.