bluuebunny/crossref_metadata_2025 huggingface dataset:
A magnetic cloud and a coronal mass ejection
Authors: Burlaga L. F. , Klein L. , Sheeley N. R. , Michels D. J. , Howard R. A. , Koomen M. J. , Schwenn R. , Rosenbauer H.
Published: February 2008

An interplanetary magnetic cloud observed by the Helios 1 spacecraft was found to be associated with a coronal mass ejection observed by the NRL Solwind coronagraph on the spacecraft P78‐1. The magnetic cloud was observed on June 20, 1980 when Helios 1 was at 0.54 AU and nearly 90° west of the earth‐sun line. This was associated with a large loop‐like coronal mass ejection observed over the west limb on June 18, 1980, moving toward Helios 1. The speed of the front of the event at Helios 1 was (470 ± 10) km/s, which is close to the mean transit speed (∽ 500 km/s). The magnetic cloud was similar to others described in the literature: The magnetic field strength was higher than average; the density was relatively low; the magnetic pressure greatly exceeded the ion thermal pressure; and the magnetic field direction changed through the cloud by rotating parallel to a plane which was highly inclined with respect to the ecliptic.
Plasma turbulence in the downstream ionosheath of Venus
Authors: Intriligator D. S. , Scarf F. L.
Published: February 2008

We compare observations made by the Pioneer Venus Orbiter plasma analyzer and the plasma wave instrument in the Venus ionosheath. Large increases in plasma wave turbulence levels appear to be connected with changing plasma distributions and interpenetrating plasma beams. We identify some of these plasma waves as Doppler‐shifted ion acoustic waves due to beam/beam interactions, but different forms of instabilities are probably also operative. The changes in the temperature, intensity and energy of the peak in the PVO plasma distributions are similar to those observed by Venera 10 closer to the planet and appear to be evidence for rarefaction and compression in the downstream ionosheath. Some of the changes in the PVO plasma distributions may be related to the presence of a second ion population or the acceleration of protons.
Variability of the Harang discontinuity as observed by the Chatanika radar and the IMS Alaska magnetometer chain
Authors: Kamide Y. , Vickrey J. F.
Published: February 2008

The relative location of ionospheric parameters and ground magnetic perturbations in the vicinity of the Harang discontinuity is examined. For this purpose, we use combined observations of the Chatanika incoherent scatter radar and of the IMS Alaska meridian chain of magnetometers, which were continuously measuring the crucial ionospheric parameters near the Harang discontinuity when a sizeable substorm took place. The Harang discontinuity, as defined by the reversal of the north‐south electric field, is found to be located at 1‐2° poleward of the discontinuity identified by the conventional method of using ground magnetic perturbations. It is also found that the relative location of auroral conductivity enhancements is quite variable, depending perhaps upon substorm time. During relatively quiet times and the early stage of a substorm, a conductivity enhancement occurs only on the poleward side of the Harang discontinuity defined by the electric field reversal, whereas the enhancement surges equatorward extending beyond the discontinuity during the maximum to recovery phase of a substorm.
Charge‐exchange in the magnetosheaths of Venus and Mars: A comparison
Authors: Russell C. T. , Gombosi T. I. , Horanyi M. , Cravens T. E. , Nagy A. F.
Published: February 2008

The amount of solar wind absorption due to charge‐exchange in the Martian magnetosheath is evaluated and found to be about an order of magnitude less than that in the Venus magnetosheath. This difference might explain the observed difference in the scaled position and shape between the shocks at Venus and Mars. The lower solar wind absorption for Mars is attributable to the less dense hot oxygen corona of Mars compared to Venus.
Atomic oxygen emissions observed from Pioneer Venus
Authors: Meier R. R. , Anderson D. E. , Stewart A. I. F.
Published: February 2008

Atomic oxygen features at 1304 and 1356 Å detected by the Orbiting Ultraviolet Spectrometer (OUVS) on Pioneer Venus are compared to theoretical emission models. Limb scans from three orbits of the OI 1304 Å emission were analyzed using an improved model which removes the restrictive assumptions of complete frequency redistribution and isothermal multiple scattering. Data‐model comparisons indicate the OI 1304 Å emission rates observed are consistent with an O density 40% of the BUS model. It is also found that the emission at 1356 Å is consistent with the sum of the CO fourth positive band at 1352 Å and the OI doublet at 1356, 1358 Å, if an O density equal to 40% of the BUS model is used to calculate the OI emission rate.
Radon and rilt anomalies detected before the Irpinia (south Italy) earthquake of November 23, 1980 at great distances from the epicenter
Authors: Allegri L. , Bella F. , Della Monica G. , Ermini A. , Improta S. , Sgrigna V. , Biagi P. F.
Published: February 2008

Some Investigators of Istitute of Physics and Istitute of Geology of the University of Rome are carrying out measurements of tilt and groundwater radon content in sites located in Central Italy. Beginning from June to November 1980 anomalous variations in the radon content have been detected in Rome and Rieti sites. Water samples for discrete measurements of radon content were drawn periodically from underground strata. The amplitude of the anomalies were 25% and 170% compared with the background level. From about March 15 a bubble type tiltmeter installed at L'Aquila site showed a first anomalous tilting with a time scale of about two mounths and an amplitude of 15 µrad. A second anomalous tilting, about 20 µrad in amplitude, was observed from the middle of May to November. The seismicity (M=4.0‐4.7) within about 100 Km of the sites seems to justify only the first anomalous tilting. On November 23, 1980 a strong (M=6.5) earthquake took place in Irpinia (Southern Italy) at about 250 Km from Rome, Rieti and L'Aquila sites. We suggest to assume both the radon content anomalies and the second anomalous tilting as precursors of the Irpinia earthquake.
On the recent variations of the apparent westward drift rate
Authors: Le Mouël J. L. , Ducruix J. , Ha Duyen C.
Published: February 2008

Quantitative study of the westward drift (w.d.) was initiated by Bullard et al (1950) and then followed by many others, using more or less similar methods (e.g. Yukutake, 1962; Harwood and Malin, 1976). More recently, MAGSAT results have enhanced the interest in the subject (see for example fig. 1 of Peddie, 1982). In the present paper, we compute the w.d. rate in the 1950‐1980 time interval, using different methods, and we establish that the 1969‐1970 secular acceleration impulse (the so‐called "jerk") clearly shows up in the results.
Eddy intrusion of hot plasma into the polar cap and formation of polar‐cap arcs
Authors: Chiu Y. T. , Gorney D. J.
Published: February 2008

We present plasma and electric field data obtained by the S3‐3 satellite over the polar caps. We demonstrate that: (1) plasma signatures in the polar cap arc formation region near 5000 km altitude show clear intrusions of plasma sheet ( ∼ keV) and magnetosheath ( ∼ 100 eV) plasma into a background of low‐energy polar cap plasma; (2) the combined plasma and electric field signatures (electron inverted‐V, ion beam and ▽ •
< 0) are exactly the same as in the evening discrete arc. We interpret this equivalence of polar cap and evening discrete arc signatures as indication that their formation processes are identical. The spatial structures of polar cap electric fields and the associated plasma signatures are consistent with the hypothesis that plasma intrusion into the polar cap takes the form of multiple cellular eddies. This hypothesis provides a unifying view of arc formation and arc configurations.
Geocoronal imaging with Dynamics Explorer: A first look
Authors: Rairden R. L. , Frank L. A. , Craven J. D.
Published: February 2008

The ultraviolet photometer of the University of Iowa spin‐scan auroral imaging instrumentation on board Dynamics Explorer 1 has returned numerous hydrogen Lyman alpha images of the geocorona from altitudes of 570 km to 23,300 km. Attempts were made to fit these observations with a spherically symmetric isothermal Chamberlain model of the exosphere using numerical solutions to the radiative transfer equation. The removal of a substantial portion of the satellite component at higher altitudes was necessary to obtain the required functional dependence of hydrogen density with radial distance. The optimum fit utilizes a Chamberlain model of temperature 1050°K, with exobase rc at 1.094 RE (600 km altitude), exobase density of 40,000 cm−3, and a satellite critical level rcs equal to 3.5 rc. This model is accurate from the exobase to 4.5 RE, beyond which an exponential decrease in density N(r) = 3300 exp(−r/1.46 RE) cm−3 is found. This corresponds to the removal of an increasing percentage of the satellite component of the geocoronal population, ranging from 10% lost at 5 RE, through 50% at 6.5 RE, to 100% beyond 9 RE. Departures of the observed emission rates from the spherically symmetric model are consistent with a diurnal variation with lower densities on the dayside than on the nightside.
Ionospheric conditions affecting the evolution of equatorial plasma depletions
Authors: Anderson D. N. , Mendillo Michael
Published: February 2008

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.
Heating of heavy ions on auroral field lines
Authors: Nishikawa K.‐I. , Okuda H. , Hasegawa Akira
Published: February 2008

Heating of heavy ions is studied in the presence of a large amplitude hydrogen cyclotron wave. A three wave decay process, in which a large amplitude pump hydrogen cyclotron wave decays into a daughter hydrogen cyclotron wave and a low frequency oxygen cyclotron wave, is studied theoretically and by numerical simulations. The numerical simulations show a decay instability resulting in strong heating of both the oxygen ions and the hydrogen ions. In particular, the high energy tail of the oxygen ions is observed in the perpendicular distribution.
Characteristics of two types of beam plasma discharge in a laboratory experiment
Authors: Boswell R. W. , Kellogg Paul J.
Published: February 2008

Experiments on the Beam Plasma Discharge (BPD) using an electron beam traveling along a magnetic field have been carried out in a large volume laboratory vacuum chamber. Two different types of BPD have been observed, and scaling laws for varying neutral gas pressure, axial magnetic field, interaction length and electron flux, deduced. The second type of BPD occurs when the beam current is increased well above the threshold for the first type. The transition from the first type to the second, like the ignition of the first, is distinguished by abrupt changes of luminosity, discharge diameter, and wave emission signature.
The modulated precipitation of radiation belt electrons by controlled signals from VLF transmitters
Authors: Imhof W. L. , Reagan J. B. , Voss H. D. , Gaines E. E. , Datlowe D. W. , Mobilia J. , Helliwell R. A. , Inan U. S. , Katsufrakis J. , Joiner R. G.
Published: February 2008

The first direct observations of the precipitation of radiation belt electrons by the controlled injection of VLF signals from a ground based transmitter were recently reported from data acquired in the SEEP (Stimulated Emission of Energetic Particles) experiment. That outstanding example of time‐correlated wave and electron data has now been enhanced by the finding of four additional modulated events out of 65 satellite passes when one of the U. S. Navy VLF transmitters at Cutler, Maine (NAA) or at Annapolis, Maryland (NSS) was being modulated in a 3s ON/2s OFF format. During each of these events the fluxes of precipitating electrons were observed repeatedly to display a characteristic time behavior with respect to the transmitter modulation: a relatively slow rate of increase after start of the ON period leading to a maximum about 2 seconds later. Details of this consistent pattern and the statistics of occurrence of modulation events are presented along with comparisons of the absolute fluxes of precipitating electrons observed during normal transmitter operation with those recorded when one of the transmitters was modulated.
Frequency gap formation in electromagnetic cyclotron wave distributions
Authors: Mauk B. H.
Published: February 2008

This letter addresses in detail the structure of the gap near the helium cyclotron frequency observed within the statistical distribution of the frequencies of electromagnetic cyclotron waves encountered at synchronous altitudes. It is shown that, at most, two‐thirds of the gap (the high frequency portion) results from linear dispersion effects. It is suggested that at least one‐third of the gap (the low frequency portion) results from nonlinear, off‐resonant absorption of the waves by means of near cyclotron resonance with singly charged helium ions.
Drift boundaries and ULF wave generation near noon at geostationary orbit
Authors: Korth A. , Kremser G. , Roux A. , Perraut S. , Sauvaud J.‐A. , Bosqued J.‐M. , Pedersen A. , Aparicio B.
Published: February 2008

Coordinated observations on board GEOS 2 of energetic particles (20 to 400 keV), plasma particles (300 eV to 20 keV), dc electric fields, and ULF waves (0.2 to 10 Hz) at the geostationary orbit reveal several occasions on which sharp increases in particle flux occurred near 1400 LT without any appreciable energy dispersion for ions at 90° pitch angle. The intensity increases of ions with pitch angles away from 90° preceded those at 90° and showed clear energy dispersion that is consistent with the idea that these particles are injected in the midnight sector and drift toward noon. The global electric field establishes boundaries that particles of given adiabatic invariants cannot penetrate. A change or reversal of the electric field moves these boundaries so as to permit their observation at GEOS 2. Such boundaries seem to be associated with intense ULF waves observed close to the proton gyrofrequency and its harmonics. The waves may be compressional drift waves destabilized by plasma pressure gradients.
Generation of Alfven‐ion cyclotron waves on auroral field lines in the presence of heavy ions
Authors: Lysak Robert L. , Temerin Michael A.
Published: February 2008

Observation of electromagnetic waves in the low‐altitude auroral zone at frequencies between the proton and helium gyrofrequencies suggests that Alfven‐ion cyclotron waves modified by the presence of helium ions are being excited. Estimates of the growth rates for this mode indicate that the auroral electron beam can provide the free energy for the instability. The effect of the heavy ions is to decrease the group velocity of the waves, leading to larger convective growth. Theoretical wave spectra are computed in the local approximation, which assumes that the gradient scale lengths in density and magnetic field are constant over the ray paths. Narrow banded spectral peaks similar to observations may be produced when the thickness of the electron beam is small (200 m at 3000 km altitude). Narrow beams also limit growth of whistler mode waves, which compete for the free energy of the electron beam.
Experimental modelling of satellite wakes in auroral arcs
Authors: Wild N. , Stenzel R. L. , Gekelman W.
Published: February 2008

Preliminary measurements have been made in a large laboratory discharge device configured to simulate plasma wake phenomena. A large relative electron drift impinging on a nonconducting disc gives rise to a perturbed density structure downstream, as well as a reflected beam of electrons upstream. Velocity distribution measurements were made using a novel energy analyzer with angular resolution.
Determination of timing of volcanic events by secular variation and thermal modeling
Authors: Furlong Kevin P. , Shive Peter N.
Published: February 2008

The length of time between emplacement of successive lava flows is difficult to determine with high resolution except in regions of very recent or current activity. In paleomagnetic studies, a tacit assumption of the relative timing is made by considering the effects of secular variation to be averaged in samples from a series of flows, a condition which may not in fact be met. Through the combined use of numerical modeling of the cooling history of sequences of lava flows (erupted at any set of arbitrary time intervals) and detailed measurements of the magnetization directions from field samples, constraints can be placed on the length of time between flows.

As individual flow units in a sequence cool, the position within each flow of the last point to pass through the blocking temperature is a function of the relative timing of the flows in the sequence. Additionally, the depth into an underlying flow to which magnetic directions are reset is also a function of this relative timing.

In addition to the timing information, the approach appears promising for determination of rates of secular variation in the past.
Geos 2 plasma drift velocity measurements associated with a storm time Pc5 pulsation
Authors: Walker A. D. M. , Junginger H. , Bauer O. H.
Published: February 2008

The Geos 2 electron gun experiment has been used to obtain electric field data during the compressional Pc5 pulsation event of Day 300, 1979. The phase relationships between the electric field and magnetic field observations show that the oscillation in the meridian plane appears to be a transverse Alfvén standing wave in the second harmonic, while the compressional oscillation is symmetrical about the equatorial plane. Computations of the fields of a guided poloidal wave fit the transverse oscillation well. The oscillation is not completeley explained by existing theories. A comprehensive model of the oscillation is presented.
ALHA 81005 Meteorite: Chemical evidence for Lunar Highland Origin
Authors: Laul J. C. , Smith M. R. , Schmitt R. A.
Published: February 2008

Based on the well‐established characteristic lunar and meteoritic ratios of FeO/MnO, Cr2O3/V and K/La, and REE patterns, ALHA 81005 meteorite is undoubtedly of lunar highland origin. The ALHA 81005 meteorite is an anorthositic gabbro (72% Pl) and matches closely in chemical composition to Apollo 15 15418 and Luna 16 21013 highland rocks. The rock is a non‐KREEPY and VLT type. The siderophiles Au, Ni and Ir content is high (1.5% Cl equivalent) and similar to other lunar highland breccias. The clast has a different ancient meteorite component than the bulk and matrix. The meteorite has a young terrestrial age implying a recent lunar cratering event. Therefore, during major lunar basins formation in early eons, the earth must have received a significant amount of lunar material which is now mixed in the crust. The finding of a lunar meteorite lends credibility to the suggestion that SNC achondrites may come from Mars.
Laboratory simulation of Venusian lightning
Authors: Borucki W. J. , Orville R. E. , Levine J. S. , Harvey G. A. , Howell W. E.
Published: February 2008

Evidence of lightning activity in the Venusian atmosphere has been obtained from the Venera 9, 11, and 12 spacecraft, and from the Pioneer Venus Orbiter (PVO). However, a search for optical pulses expected from Venusian lightning using the star sensor on the PVO did not detect any signals. It has been suggested that the star sensor did not detect lightning because Venusian lightning does not radiate in the 500‐ to 900‐nm spectral region detected by the star sensor. In this paper, we discuss spectra obtained from a laboratory simulation of Venusian lightning. Both the laboratory spectrum and the results of a theoretical calculation of line intensities show that Venusian lightning can be expected to radiate strongly in the 600‐ to 900‐nm spectral region. Hence, the failure of the star sensor to detect lightning must be caused by the low flashing rate or by the low intensity of Venusian lightning.
Longitudinal asymmetry of the Io plasma torus
Authors: Hill T. W.
Published: February 2008

Remote observations of the Io plasma torus have revealed a persistent longitudinal asymmetry in the brightness of optical S+ emission lines but not of ultraviolet S++ emission lines. The S+ asymmetry (with respect to the corotating System III coordinates) has been attributed to an asymmetric plasma source; the question then arises, why do the higher ionization states of sulfur not reflect a similar asymmetry? The explanation proposed here is based on the fact that torus ions do not quite corotate at the System III rate because of mass loading. If the resulting System III drift period of the ions is intermediate between the ionization lifetimes of S+ and S++, then the asymmetry of the source will be obscured by longitudinal drift for the relatively long‐lived multiply‐ionized sulfur ions, but not for the short‐lived S+.
Archean komatiites and geotherms: Solution to an apparent contradiction
Authors: Jarvis Gary T. , Campbell Ian H.
Published: February 2008

The high liquidus temperatures of Archean komatiites and the low geothermal gradients in Archean continents appear to give contradictory indications of temperatures in the Archean mantle. We resolve this contradiction in terms of an idealized model of convection in the Archean mantle. We suggest that temperatures in the Archean mantle were no more than 100°C higher than at present, that komatiites originate from the hot lower boundary layer of a non‐steady convection cell and that Archean continents were formed near subduction zones where near‐surface temperature gradients were lower than elsewhere in the convecting mantle.
The fallout rate of PB‐210 on the western coast of the United States
Authors: Fuller Christopher , Hammond Douglas E.
Published: February 2008

The deposition rate of atmospheric Pb‐210 has been measured during a one year period using plastic funnels as collectors. Observed rates were 0.15 dpm cm−2 yr−1 at a site in Palo Alto, California and 0.21 dpm cm−2 yr−1 at a site in Los Angeles. The Palo Alto value agrees well with a long‐term average of 0.14 dpm cm−2 yr−1, obtained from a nearby salt marsh core. These rates are only one‐third of those previously estimated using global models for Pb‐210 fallout and indicate the need to consider both longitude and precipitation as factors controlling fallout rates. More than 75% of the Pb‐210 fallout occurs as wet deposition at the Los Angles site.
Radiative effects of the Arctic haze
Authors: Valero Francisco P. J. , Ackerman Thomas P. , Gore Warren J. Y.
Published: February 2008

During the recent Arctic Gas and Aerosols Sampling Project (AGASP) flight series, the absorption of solar radiation by the Arctic haze was measured directly for the first time. Absorption was measured in three narrow‐band channels, and the measurements were used to calibrate a high‐resolution solar‐flux model, which was then used to compute atmospheric heating rates. Analyses of data from three flights with estimated optical depths of 0.26, 0.17, and 0.31 at 500 nm produced instantaneous solar heating rates of the order of 1.1 to 1.5 K day−1. These rates are greater by a factor of 2 to 3 than heating in the absence of the haze. Possible climatic implications are briefly discussed.
Electric field evidence on the viscous interaction at the magnetopause
Authors: Mozer F. S.
Published: February 2008

Electric field measurements during 28 magnetopause crossings by the ISEE‐1 satellite within 2 hours of local dusk in 1980 are examined for the presence of dusk‐to‐dawn electric fields just inside the magnetopause, since such fields are proposed to be produced by a viscous interaction or other processes occurring in a closed magnetosphere. Although dusk‐to‐dawn fields containing few kV potentials were often observed, it is concluded that less than 10% of the typical magnetospheric electric potential resulted from the viscous interaction or similar processes.
Aqueous low‐temperature oxidation of titanomagnetite
Authors: Worm Horst‐Ulrich , Banerjee Subir K.
Published: February 2008

In an attempt to find conditions suitable for aqueous oxidation of titanomagnetite in submarine basalts, synthetic titanomagnetite powders have been exposed to solutions with different pH's and gas fugacities at different temperatures. Analysis of dissolved Fe and Ti, thermomagnetic measurements, and x‐ray measurements all confirm that aqueous oxidation by Femigration does occur. Furthermore, it is, in the first order, pH dependent, implying that ‘maghemitization’ of ocean floor basalts proceeds most favorably under what geochemists call water‐dominated conditions, where basalt‐seawater interaction leads to an increase in acidity.
A new approach to the theory of single domain TRM
Authors: Smith Guy M.
Published: February 2008

While the theory of single domain TRM has been very successful in describing qualitative behavior, it has been less so quantitatively. It is argued here that at least some of the discrepancy between theory and experiment derives from inadequacies in the theory. An analysis of the conventional dynamical model used in TRM theory in terms of the statistical mechanics of thermal fluctuations shows that it is internally inconsistent. Calculation of the distribution of thermal energy shows that, counter to the usual assumption, only a small fraction of the energy goes into producing uniform rotation of magnetization, suggesting that non‐uniform modes are more likely to be the controlling factor in TRM. One possible non‐uniform mode is suggested: reversal by passage of a domain wall through the grain.
Magnetic remanence and fabric properties of laboratory‐deposited hematite‐bearing red sandstone
Authors: Løvlie R. , Torsvik T.
Published: February 2008

Redeposition experiments of disintegrated hematite bearing sandstone have confirmed a tangent relationship between inclinations of the DRM and ambient magnetic field. Pronounced variations of DRM‐intensities with field inclination are attributed to processes acting during the depositional formation of laminated sediments. Coinciding azimuthal distributions of remanence and maximum susceptibility directions reflect intrinsic properties of flaky hematite grains in which the magnetic moment is parallel to the direction of maximum susceptibility. This parallelism probably depends on magnetic domain configurations.
Surface acetonitrile near Tucson, Arizona
Authors: Snider Jefferson R. , Dawson G. A.
Published: February 2008

Eighteen measurements of acetonitrile have been made at two rural sites about 40 km from Tucson, Arizona. Mean mixing ratio was 56 (± 20) ppt; no value greater than 84 ppt was observed. Limit of detection was between 10 and 20 ppt. Allowing for some contamination from Tucson, the results are compatible with observed stratospheric mixing ratios, small tropospheric loss, and a small global surface source.
Implications of the hydrodynamic analogue for the solar‐terrestrial interaction and the mapping of high latitude convection pattern into the magnetotail
Authors: Rostoker Gordon
Published: February 2008

In the past, attempts have been made to relate magnetospheric geometry to that expected for the hydrodynamic analogue involving high speed flow past an obstacle. For this analogue, the region behind the obstacle can be divided into two distinct regions ‐ a separation bubble immediately behind the obstacle and a laminar wake further downstream. The purpose of this paper is to examine the implications of such an analogue in terms of convective flow patterns in the magnetotail and how these flow patterns might be expected to map down to ionospheric levels. We contend that magnetic field lines which thread the plasma mantle never reach the region of sunward convection normally associated with the auroral oval. We further claim that, during extended periods of southward interplanetary magnetic field, magnetic flux piles up near the poleward border of the morning sector auroral oval and that return flow occurs across the polar cap only after the interplanetary magnetic field turns northward. This effect should be observed in comparing the cross polar cap potential drop to the potential drop across the auroral oval for periods of northward and southward interplanetary magnetic field. Our model also explains the origin of field‐aligned currents and theta auroras in what would conventionally be called the polar cap.
Auroral X‐ray images from DMSP‐F6
Authors: Mizera P. F. , Gorney D. J. , Roeder J. L.
Published: February 2008

X‐ray images of auroral arcs for consecutive north and south polar crossings of the DMSP‐F6 satellite are presented. On January 18, 1983, the north polar region was in the earth's shadow and the south polar region was in complete sunlight. The X‐ray images of both polar cap regions show features of the dawn and dusk auroral oval that are quite similar. However a strong polar cap structure appears only in the north pole image. Near simultaneous measurements of precipitating electrons obtained by instruments aboard the NOAA‐6 and NOAA‐7 satellites crossing the south pole, show no indication of polar auroral structures. These examples illustrate the utility of X‐ray imaging in both sunlight and in darkness for studying auroral boundaries and morphology.
Average flow between ∼70 RE and ∼220 RE in the geomagnetic tail
Authors: Scholer M. , Hovestadt D. , Klecker B. , Gloeckler G. , Ipavich F. M.
Published: February 2008

The ISEE‐3 spacecraft was transferred in 1982 into the magnetotail, where it was kept for about 1 year via succesive lunar swingbys. The Max‐Planck‐Institut/University of Maryland sensor on ISEE‐3 provides energetic ion measurements above ∼30 keV/charge. Assuming that the energetic protons are convected with the local plasma flow we are able to determine the convection velocity from the measured angular distributions and the differential spectrum. A statistical analysis of the flow magnitude and direction at various distance ranges reveals the following: The average tailward flow velocity between 203 and 220 RE is 567 km/s and earthward flow occurs in less than 1% of all cases. At a radial distance of 117 to 153 RE the result is similar; the average tailward flow velocity is found to be 665 km/s and earthward flow occurs in less than 6% of all measurements. This is in contrast to findings at radial distances of 61 to 76 RE. Here, equal probability for earthward and tailward flow has been found and average flow velocities are 336 km/s in both directions. These results indicate that magnetic neutral lines rarely move or form beyond ∼100 RE.
A comparison of photolysis and substitution decomposition rates of methyl iodide in the ocean
Authors: Zika Rod G. , Gidel Louis T. , Davis Douglas D.
Published: February 2008

Measurements of the quantum yield of methyl iodide (CH3I) in seawater and other solvents were made in order to determine the potential of direct photolysis to compete in global surface waters with the decomposition of CH3I via SN2 (substitution, nucleophilic, bimolecular) reaction with Cl− ion. As a decomposition pathway it is potentially significant because photolysis does not yield methyl halides as products and may thus modulate the degree of supersaturation of surface water with respect to methyl chloride and methyl bromide. However the reduction in quantum yield (factor of 10) and the large hypsochromic shift (116 cm−1) for methyl iodide in going from nonpolar solvents to water reduces the importance of the direct photolysis in surface waters over most of the globe. Because of the temperature dependence of the SN2 reaction of Cl−, the halflife of CH3I increases with depth and latitude from 5‐6 days in tropical surface water to 150 days at high latitudes. This increase means that correlations in concentrations of CH3I and its decomposition products, CH3Cl and CH3Br, may be destroyed by either faster transport or primary production processes for CH3I.
Features of aerosol optical depth observed at Barrow, March 10‐20, 1983
Authors: Dutton Ellsworth G. , DeLuisi John J. , Bodhaine Barry A.
Published: February 2008

Total vertical aerosol optical depth over Barrow, Alaska, during March 1983 was up to four times greater than the average for recent years, with part of the excess being due to stratospheric debris from El Chichon. The variability in optical depth during a 10‐day period spanning the aircraft flights of the Arctic Gas and Aerosol Sampling Program (AGASP) suggests a major tropospheric aerosol event on March 12 and 13, which accounts for the maximum observed optical depths. Occurrence of the tropospheric event is substantiated with independent aerosol data from aircraft, surface sampling, and synoptic scale meteorological data. Analysis of the Barrow optical depth data yields information on the climatic effects of both the stratospheric aerosol from El Chichon and the tropospheric aerosol commonly called Arctic haze.
Organic gases in the Norwegian Arctic
Authors: Hov Ø. , Penkett S. A. , Isaksen I. S. A. , Semb A.
Published: February 2008

Air samples for determination of halocarbons and light hydrocarbons were collected at Spitsbergen in July 1982 and in March 1983. With the exception of ethene and propene, which appear to originate mainly from natural sources, hydrocarbon concentration levels were generally one order of magnitude higher for the March 1983 samples than for the summer samples. This is explained by difference in atmospheric reactivity, and particularly by direct transport of polluted air masses from the Soviet Union during March 1983.

The spring samples from Spitsbergen were more abundant in alkanes and less abundant in solvents than air sampled at Barrow by Rasmussen et al. (1983) in March 1982. Ny‐Ålesund is a good site to measure air coming off the Soviet Union and Europe. Continued sampling could provide valuable information about questions related to global climate, Arctic haze and the chemical composition of the troposphere.
Major ions in Spitsbergen snow samples
Authors: Semb A. , Brækkan R. , Joranger E.
Published: February 2008

Chemical analysis of Spitsbergen snow cores sampled in spring 1983, reveals a spatial pattern consistent with orographic deposition of major anthropogenic pollutants with air movements from southeast towards northwest. The highest concentrations of pollutant species were found at an altitude of 700 metres above sea level, and are higher than for any other recorded snow samples from the Arctic.
The vertical structure of Arctic haze as determined from airborne net‐flux radiometer measurements
Authors: Ackerman Thomas P. , Valero Francisco P. J.
Published: February 2008

From net‐flux radiometer measurements and model results, we deduce the vertical layer structure of the Arctic haze encountered during two of the AGASP flights. We find the total value of the absorption optical depth to be on the order of 0.065 for both flights, with the majority of the absorbing aerosol concentrated in the lowest 1.6 km of the atmosphere. A comparison of these results with measurements of the carbon concentration (Rosen et al., 1984) leads to a value of the specific absorption of carbon of 24 m²/g. While higher than expected, this value is shown to be consistent with an internally‐mixed aerosol of carbon cores and sulfate shells.
Mesospheric wind determinations and the P1 (2)c,d lines of the X ²∏ OH (8‐3) band
Authors: Hernandez G. , Smith J. L.
Published: February 2008

Mesospheric winds have been determined from ground‐based optical measurements of the nighttime sky emission of the P1(2) lines of the X ²∏ OH (8 ‐ 3) band. The measured winds indicate a 12‐hour periodicity with amplitude near 30 m/s, and presumably associated with tidal motions. The frequencies (wavelengths) of these Λ‐doubled P1 (2)c,d lines have been measured to be 13 664.444 K (731.6428 nm) and 13 664.310 K (731.6320 nm), with a standard deviation of the mean of 0.001 K (0.00007 nm). The spacing between the two P1 (2) lines is found to be 0.1346 ±0.00005 K. Incidental to this study is the determination of the frequency (wavelength) of a Xenon line in this region of the spectrum found at 13 663.274 K (731.6874 nm), with the same uncertainty level as the OH lines.
COS in the stratosphere: El Chichon observations
Authors: Leifer R. , Juzdan Z. R. , Larsen R.
Published: February 2008

During April 1982, based on filter and impactor samples, we intercepted the plume from the eruption of El Chichon. Our measurements of the trace gases in the plume show no enhancement of carbonyl sulfide (COS) over background. It is apparent from the data that strong vertical mixing occurred during this period. Some of the lowest concentrations of COS to date were measured in the lower polar stratosphere during this mission.
The appearance of carbon aerosol oarticles in the lower stratosphere
Authors: Chuan R. L. , Woods D. C.
Published: February 2008

Very small carbonaceous particles, thought to be meteoritic, have been found in small quantities in the lower stratosphere during aircraft sampling flights. The sampling was accomplished using a quartz crystal microbalance (QCM) cascade impactor operating on a U‐2 aircraft as it flew stratospheric sampling missions. Post flight analyses of the samples using scanning electron microscopy, x‐ray energy spectroscopy and Auger electron spectroscopy have identified carbon particles 0.1 µm aerodynamic diameter and smaller in 16 of 28 sets of samples obtained between 1979 and 1983. The presence of such carbon particles in the stratosphere has implications relating to global climate, to the conversion of SO2 to sulfuric acid, and to the phenomenon of the Arctic haze.
Density spectra as a function of altitude in an ionospheric barium release
Authors: Lebeda Charles , Gary S. Peter , Pongratz Morris B.
Published: February 2008

Plasma column density fluctuation spectra observed from the Buaro ionospheric barium release have been analyzed as a function of altitude over the range 285 km to 345 km. The wavenumber spectra become steeper with increasing altitude, the first time this has been shown in any ionospheric injection experiment. The source of these steepened spectra is argued to be wave‐particle scattering due to the universal density drift instability.
Paleomagnetism of the Lower Jurassic Copper Mountain intrusions and the geotectonics of terrane I, British Columbia
Authors: Symons D. T. A. , Litalien C. R.
Published: February 2008

The 198 Ma Lower Jurassic Copper Mountain intrusions outcrop in the Quesnellia Subterrane of Terrane I in the Canadian Cordillera. Thermal demagnetization at 550 ± 10°C defines a single stable remanence component of 25.9°, 41.2° (α95=3.6°) in 11 reliable sites. The resulting pole position of 11.8°E, 57.3°N (δp = 2.7°, δm = 4.4°) is discordant for the North American craton and reflects 39 ± 6° of clockwise rotation and 9 ± 5° of northward translation. Combined with previous paleomagnetic and geologic data, a consistent model for the geotectonic evolution of Quesnellia and Terrane I emerges.
Centimeter scale heterogeneities and microstratifaction in sedimentary rocks
Authors: Murphy W. F. , Roberts J. N. , Yale D. , Winkler K. W.
Published: February 2008

Two dimensional acoustic images of sedimentary rocks were generated in order to characterize centimeter‐scale heterogeneities and microstratigraphy. The images are based on dense sampling of the compressional phase velocity at frequencies near 1 MHz. The acoustic observations are compared to visual and x‐ray images of the same samples. The results are intrepreted in terms of microscopic compositional variations. Sedimentary rocks are more variable on the scale of a centimeter than we expected. The homogeneous Berea sandstone exhibits a ±3% random variation in velocity. Heterogeneous rocks show 20 and 30% velocity variations. In the particular case where porosity is the sole compositional inhomogeneity, the acoustic and radiographic images agree. In general however, the acoustic images yield different information from the visual and radiographic images.
Seasonal adjustments in the equatorial Atlantic during 1983 as seen by surface moorings
Authors: Weisberg R. H.
Published: February 2008

Upper ocean seasonal variations in velocity and temperature observed with current meters on surface moorings along the equator in the Atlantic during February ‐ September 1983 are shown. The longitudinal variation in the duration of upwelling and downwelling responses to zonal wind stress changes are discussed. These responses exhibit an integral character dependent upon longitudinal position which is consistent with forced linear long wave theory.
Drifting buoy trajectories in the Atlantic North Equatorial Countercurrent during 1983
Authors: Richardson P. L.
Published: February 2008

During 1983, 21 freely drifting buoys measured trajectories in the vicinity of the Atlantic North Equatorial Countercurrent. These provide a visualization of the flow field and the first direct measure of the seasonal variation of the velocity during a single year. From February to May the buoys moved gradually westward. From June to December the buoys moved swiftly eastward with maximum speeds of 90 cm sec−1 located in the western Atlantic. The seasonal variation in current was similar to that measured by historical ship drifts except that the onset of the Countercurrent in 1983 was about a month earlier than usual. Of the buoys that drifted eastward in the Countercurrent, three went into the North Equatorial Current, two into the South Equatorial Current and seven into the Guinea Current.
Moored current meter measurements in the Atlantic North Equatorial Countercurrent during 1983
Authors: Richardson P. L.
Published: February 2008

Current meters were moored at depths of 20, 50, 75 and 150 m near 6N, 28W from February 25 to September 13, 1983. From February to May the low frequency zonal velocity was slow and westward. From May to September the zonal velocity was eastward with peak (low passed) speeds up to 60 cm sec−1. During July the eastward flow was approximately 40 cm sec−1 at all four depths. The surface and subsurface North Equatorial Countercurrent disappeared on a seasonal basis during 1983. Strong fluctuations were observed with periods in the bands 1‐2 months and 4‐5 days. The amplitude of these fluctuations appeared to be maximum during the period of swift eastward Countercurrent flow.
Instability waves observed on the Equator in the Atlantic Ocean during 1983
Authors: Weisberg R. H.
Published: February 2008

A packet of surface confined westward propagating waves apparently generated by barotropic instability of the surface currents was observed in the equatorial Atlantic during 1983. Initial wavenumber analyses and energetics calculations are presented. Local working by the horizontal Reynolds stress was large enough and at the correct time to account for the wave packet's existence. The amplitude of the waves was comparable to the mean currents implying that the waves are of primary importance in the momentum balance of the seasonally varying equatorial surface currents.
Near equatorial eddies in the North Atlantic
Authors: Bruce John G. , Kerling Jeffrey L.
Published: February 2008

Surveys of the large scale near equatorial eddies (≃400km across) off the northeast coast of South America with expendable bathythermographs from ships of opportunity and aircraft indicate that a large eddy (6N‐11N) to the north and a southern eddy‐like feature (2N‐6N) probably are a permanent part of the circulation. Both features were observed during the periods of seasonal extremes, March and September, although during the latter period the structure of the eddies had enlarged and deepened, indicating a pronounced seasonal variability.
Seasonal variation of the Gulf of Guinea thermal structure
Authors: Houghton Robert W.
Published: February 2008

Data from 6 temperature sections are combined with other SEQUAL/FOCAL data along 4°W from the coast (5°N) to 3°S to study the seasonal variation of the temperature field in the Gulf of Guinea during 1983. The equatorial upwelling begins during mid‐April approximately 1 1/2 months before the climatic mean but has a normal amplitude and duration. The upwelling on the coast at Abidjan occurs approximately 1 1/2 months after the equatorial upwelling and precedes its climatic mean by 2 weeks. At the equator vertical displacements of isotherms within the thermostad are complicated by an anomalous warming of the thermostad in May. Between the thermostad and the deeper thermocline at 230 m the seasonal isotherm displacement amplitude has a minimum. At greater depths it increases again. In all respects the fluctuation of the thermal field at the equator is similar to the climatic mean but displaced forward in time by 1 1/2 months.
High frequency oscillations and their correlation with the wind forcing during the first sequal year
Authors: Garzoli Silvia L.
Published: February 2008

Two arrays of inverted echo sounders, one along the equator and the other across the North Equatorial Countercurrent, are analysed together with a wind record from St. Peter and St. Paul rocks. The dominant high frequency feature along the equator is an energetic oscillation with a period of 5.8 days that shows strong coherence with the meridional component of the wind. The sounder at 3°N 28°W, on the other hand, shows a high degree of coherence with the zonal component of the wind at a period of 4.5 days. Comparison of these measurements in 1983 with measurements made in 1979 suggest considerable non‐stationarity.
Lidar observations of the El Chichon cloud at λ = 10.6 µm
Authors: Post Madison J.
Published: February 2008

Coherent CO2 lidar observations of the El Chichon stratospheric event were made in the Boulder‐Denver area and are reported for a two year period, together with supportive Mie calculations and ruby lidar comparisons. The data, after proper filtering and statistical analysis, show properties that should help modelers test hypotheses and assumptions on the larger particles that produce 10.6 µm backscatter.
Particle concentrations at the South Pole, on meteorological and climatological time scales; Is the difference important?
Authors: Hogan A. , Kebschull K. , Townsend R. , Murphey B. , Samson J. , Barnard S.
Published: February 2008

Sulfur and dust layers in glacial ice cores have been associated with volcanic activity. Particles collected on the South Polar Plateau during January of 1983 show the maximum concentration of sulfur aerosol to arrive at the surface, from the lower troposphere at the beginning of a storm, and the maximum dust concentration to arrive from the upper troposphere as the storm weakens. The sulfur and dust particles did not arrive simultaneously on the meteorological time scale, posing a question to interpretation of the climatic aerosol record, and the glacio‐climatic record.
A dynamo theory prediction for solar cycle 22: Sunspot number, radio flux, exospheric temperature, and total density at 400 km
Authors: Schatten Kenneth H. , Hedin A. E.
Published: February 2008

Using the "dynamo theory" method to predict solar activity, a value for the smoothed sunspot number of 109 ± 20 is obtained for solar cycle 22. The predicted cycle is expected to peak near December, 1990 ± 1 year. Concommitantly, F10.7 radio flux is expected to reach a smoothed value of 158 ± 18 flux units. Global mean exospheric temperature is expected to reach 1060 ± 50K and global total average total thermospheric density at 400km is expected to reach 4.3 × 10−15 gm cm−3 ± 25%.