bluuebunny/crossref_metadata_2025 huggingface dataset:
The evolution of ozone with changing solar activity
Authors: Chakrabarty D. K. , Chakrabarty P.
Published: February 2008

An examination of the Umkehr ozone data of Mt. Abu from 1953 onwards shows that at the upper stratosphere there is an increasing trend of ozone with increasing level of solar activity. At the lower stratosphere, however, this trend is seen only when analysis is made with the monthly averaged values of ozone separately for separate solar cycle. The ozone values of one solar cycle are found to be different from those of others. From the trend of variation of ozone at the upper and the lower stratosphere, it appears that the changes due to dynamical processes in the lower stratosphere are in phase with the changes due to photochemical processes in the upper stratosphere.
Predicted diurnal variations of electron density for three high‐latitude incoherent scatter radars
Authors: Sojka J. J. , Schunk R. W.
Published: February 2008

We have used a high‐latitude ionospheric model to predict the diurnal variations of electron density that should be observed by the EISCAT, Chatanika and Millstone Hill incoherent scatter facilities. Our calculations were for a strong convection model without substorms. Our results provide an indication of the quantitative differences in measured electron density that are expected when the three radars probe the high‐latitude ionosphere simultaneously. The differences are significant and vary with altitude, latitude, local time, and season, and are associated with the UT dependence of the high‐latitude ionosphere which results from the displacement between the geomagnetic and geographic poles.
Tertiary paleomagnetism of the North Cascade Range, Washington
Authors: Beck Myrl E. , Burmester R. F. , Schoonover Ruth
Published: February 2008

We have obtained paleomagnetic data for the southern tip of the middle Tertiary Chilliwack Composite Batholith, located on the Canada‐United States border about 125 km E of Vancouver, B.C. Thirty‐four separately oriented samples were collected along a road traverse 1.5 km long located along State Highway 22, about 20 km NE of Marblemount, Washington. The mean direction after magnetic cleaning is: D, 182.8°; I, −65.0°; α95, 1.5°. This corresponds to a paleomagnetic pole at 87.5°N, 267.5°E, close to other poles for Tertiary plutons from the North Cascades and only slightly displaced from Tertiary reference poles from the craton. We conclude that the North Cascades block has not been rotated or suffered major internal disruption since perhaps late Eocene time, in marked contrast to all the terranes that surround it.
Diffusion processes in the magnetopause boundary layer
Authors: Tsurutani Bruce T. , Thorne Richard M.
Published: February 2008

Anomalous cross‐field diffusion of magnetosheath ions and electrons is a direct consequence of cyclotron‐resonant scattering by electrostatic and electromagnetic emissions which are continuously present within the magnetopause boundary layer. Expressions for the rate of cross‐field diffusion involving either type of wave are developed and expressed in terms of the absolute upper limit referred to as Bohm diffusion. For the typical average intensity of waves observed in the boundary layer, resonant electron cross‐field diffusion is always insignificant. However, magnetosheath ions, resonant with low frequency electrostatic waves, may be transported inward at a rate approaching one tenth the Bohm rate (D⊥⊥ ≈ 10³ km²/s). While this is not the only mechanism capable of explaining the presence of the low latitude boundary layer it is adequate to account for the typical boundary layer thickness and it should occur at all local times and under all interplanetary conditions. It consequently provides a continuous mechanism for significant mass and momentum transfer across the magnetopause under conditions when field merging is inoperative.
Heavy metal pollution, Part VII. Emissions from Mount Etna Volcano
Authors: Cimino Giuseppe , Ziino Marisa
Published: February 2008

From June 1980 to December 1981 lava dust samples from the eastern slope of Mt. Etna were periodically collected in order to estimate the volcanogenic contribution to environmental pollution. The heavy metal composition of these dusts suggests that this volcano does not basically modify the surrounding basaltic soil, but is a polluting agent of the remote Sicilian environment. In the lava‐ash the level of leachable elements is negligible. Furthermore, the amount of heavy metals enriched in volatiles relative to that in ash falling to at ground‐level appears to be significant.
Altitude, thickness and charge concentration of charged regions of four thunderstorms during trip 1981 based upon in situ balloon electric field measurements
Authors: Byrne G. J. , Few A. A. , Weber M. E.
Published: February 2008

Balloon borne corona probes designed to measure vertical electric fields have yielded data on the vertical electric structure of four thunderstorms studied during the Thunderstorm Research International Program (TRIP), 1981. All four thunderclouds exhibited a bipolar charge structure with an upper positive charge region and a lower negative charge region. The negative region was consistently centered between the 0° C and −10° C isotherm altitudes. The altitudes of the concentrated positive regions varied considerably. The average vertical extent of the negative regions was 1 km with estimated average charge concentrations ranging from −.7 nC/m³ to −1.8 nC/m³. The average thickness of the positive regions was 1.5 km with estimated charge concentrations averaging .5 nC/M³ to 1.7 nC/m³.
Critique of “Elastic thickness of the Venus lithosphere estimated from topography and gravity” by A. Cazenave and K. Dominh
Authors: Reasenberg R. D. , Bills B. G.
Published: February 2008

Cazenave and Dominh compare the topography in a portion of the rolling plains province of Venus with a measure of the corresponding gravity perturbations, the residual acceleration of the Pioneer Venus Orbiter. They ignore substantial geometric factors and make unsubstantiated geophysical assumptions to draw conclusions which we consider logically invalid and numerically implausible.
Enormous increase of stratospheric aerosols over Fukuoka due to volcanic eruption of El Chichon in 1982
Authors: Hirono M. , Shibata T.
Published: February 2008

Large increases of stratospheric aerosol particles caused by the eruption of Mexican volcano El Chichon in early April 1982 were observed by a Yag lidar system at two wavelengths (1.06 µm and 0.53 µm) over Fukuoka for three months since April 18. Most of the observations show high concentrations of aerosols in the altitude regions from 15 to 33 km, with highest concentrations between 21 and 30 km. The aerosol optical thickness at 0.55 µm is about 0.1 ‐ 0.3; this is about 10 to 30 times the maximum monthly mean values that were observed after the Mt. St. Helens event in 1980.

The mean radius of aerosols in the densest part of the El Chichon cloud is estimated to be approximately 0.1 µm. This estimate is based on the slow settling velocity of the peak of the cloud and from information obtained by comparison of the two‐wavelength lidar returns.

A significant impact of the presence of the cloud on the climate through variations of atmospheric circulation is suggested.
Possible enhancement of previously unobserved (NII) emissions in the mid‐day aurora associated with nightside substorm activity
Authors: Myrabø H. K. , Deehr C. S. , Sivjee G. G.
Published: February 2008

We report here the presence of previously unobserved NII emissions in several spectra of aurora from the dayside cusp region taken near Longyearbyen, Spitzbergen (74.3°N geomagnetic). The presence of the 3d³P° ‐ 4p³S transition giving rise to the triplet (6809, 6834, 6847A) is particularly obvious, but the spectra also show strong evidence of other NII emissions such as those from the 3d³D° ‐ 4p³D level. The forbidden [NII] (6548, 6584A) doublet seems also to be present, but less obvious than the NII (6809, 6834, 6847A) triplet. The presence or the enhanced level of these permitted emissions seems, on two occasions, to coincide with a sudden decrease in the characteristic energy of the local particle precipitation and with a high latitude substorm on the nightside. Integration time is so large (30 min) as to preclude a more exact correlation with the substorm. However, two otherwise identical situations occurred with no nightside substorm and neither increased NII emissions nor decreased particle energies were observed on the dayside.
A rocket observation of the 6300 Å/5200 Å intensity ratio in the dayside aurora: Implications for the production of O(¹D) via the reaction N(²D) + O2 → NO + O(¹D)
Authors: Link Richard
Published: February 2008

An analysis of rocket AMF‐VB‐41 measurements of the spatial variation of the I6300/I5200 intensity ratio in the dayside cleft and polar cap ionosphere is reported. The measured variation of the I6300/I5200 ratio is not consistent with significant production of 6300 Å emission via the reaction N(²D) + O2 → NO + O(¹D). An upper limit to the O(¹D) yield of 0.1 is obtained for this mechanism.
Stratospheric sulfuric acid fraction and mass estimate for the 1982 volcanic eruption of El Chichon
Authors: Hofmann D. J. , Rosen J. M.
Published: February 2008

From balloon‐borne particle counter data at Laramie (41°N) and in southern Texas (27‐29°N), the total stratospheric mass of the eruptions of El Chichon is estimated to be ≈ 8 Tg about 6½ months after the eruption with possibly as much as 20 Tg in the stratosphere about 45 days after the eruption. The aerosol as observed in Texas was primarily in two layers, both highly volatile (⩾ 98%) at 150°C. Aerosol in the upper layer at ≈ 25 km was composed of an ≈ 80% H2SO4 solution while the lower layer at ≈ 18 km was composed of a 60‐65% H2SO4 solution aerosol. An H2SO4 vapor concentration of at least 3 ×107 molecules cm−3 is estimated as needed to sustain the large droplets in the upper layer. An early bi‐modal nature in the size distribution suggested droplet nucleation from the gas phase during the first 3 months and similarity of the large particle profiles 2 months apart indicated continued particle growth 6½ months after the eruption. By December, the aerosol layers had largely spread to the latitude of Laramie (41°N).
Atomic nitrogen abundance in polar upper thermosphere
Authors: Sivjee G. G.
Published: February 2008

In night‐time auroras the intensity of highly excited (n ⩾ 3) NI line emissions is much less than 1% of the red and near‐IR N21PG as well as N2+M Δv = 3 band emissions, while in mid‐day cusp auroras the ratio is greater than 10%. These observations point to electron impact on N (rather than on N2) as the main source of some of the mid‐day auroral NI line emissions. To produce the measured level of NI 6945‐51 and 6979‐82A emissions, by cusp electrons impacting on N, requires the daytime polar thermospheric density of atomic nitrogen, above 200 km, in excess of 107cm−3.
A 550 km long moho traverse in the Tyrrhenian Sea from O.B.S. recorded PN waves
Authors: Steinmetz L. , Ferrucci F. , Hirn A. , Morelli C. , Nicolich R.
Published: February 2008

Six OBS deployed on a 550 km line in the Tyrrhenian sea furnish reversed and overlapping profiles from 43 shots at 12 km intervals. Head waves recorded from a 8 km/s refractor, the Moho, permitted the computation of the crustal thickness, which shows this basin to be underlain by an oceanic type of crust, at least in two 100 km wide regions. Variations of Pn arrival times mirror strong topographical changes of the Moho. Differences in dips at the extremities towards Corsica and Calabria are documented.
Increasing backscattered light from the stratospheric aerosol layer after Mt. El Chichon Eruption laser radar measurement at Nagoya (35°N, 137°E)
Authors: Iwasaka Yasunobu , Hayashida Sachiko , Ono Akira
Published: February 2008

The increase of backscattered light from the stratospheric aerosol layer was measured by laser radar at Nagoya during the period from the end of April to early July, 1982. On the basis of much information (e.g., SEAN Bull., 1982), this is certainly due to the volcanic eruptions of Mt. El Chichon (Mexico) in March and April 1982. The effect of the Mt. El Chichon eruption on the stratospheric aerosol layer is longer lasting than that of Mt. St. Helens (Washington, USA) in May of 1980.
Observations on GEOS‐1 of whistler mode turbulence generated by a ground‐based VLF transmitter
Authors: Neubert T. , Lefeuvre F. , Parrot M. , Cornilleau‐Wehrlin N.
Published: February 2008

Signals launched by the NLK Jim Creek transmitter in Alaska on 18.60 and 18.65 kHz have been observed on GEOS‐1. Data for one pass over Alaska on June 11, 1977, are presented here. The peak amplitude of the signals is ∼5 pT (0.6 mV/m), which is received when the satellite is close to exact conjugacy at 7500 km altitude. While the weaker signals received at some distance from conjugacy behave as expected from linear theory, the stronger signals received closer to conjugacy have features which indicate that some non‐linear process is active. These features are: 1) a turbulent electric frequency spectrum 2) an increased electrostatic character of the waves. The threshold field amplitude of the supposed (but unidentified) non‐linear interaction is ∼1 pT.
Plasma drift measurements with the electron beam experiment on GEOS‐2 during long period pulsations on April 7, 1979
Authors: Junginger H. , Bauer O. H. , Haerendel G. , Melzner F. , Higel B. , Amata E.
Published: February 2008

During almost the whole day of April 7, 1979, wave activity with frequencies between 2 and 5 mHz and amplitudes between 5 and 20 km/sec has been observed with the electron beam experiment on GEOS‐2. No corresponding activity showed up in the magnetic field data. The waves observed in the dayside magnetosphere are nearly toroidal and elliptically polarized. Their polarization is left‐handed in the forenoon sector and right‐handed in the afternoon sector of the magnetosphere. The orientation angles of the polarization ellipses on average change sign near local noon. A comparison between the electron number density as measured on the same spacecraft and the observed wave frequencies shows that these waves are consistent with fundamental mode eigenoscillations of the magnetic field. The model according to which solar wind driven surface waves at the outer boundaries of the magnetosphere are the energy sources for this kind of pulsations is supported by the tilt of the polarisation ellipses and by a switch in the sense of polarization near local noon. GEOS‐2 should be located on the earthward side of the resonance in terms of this model.
Ferromagnetic resonance and magnetic properties of ALHA81005
Authors: Morris Richard V.
Published: February 2008

Seven chips of primarily matrix material from the Antarctic meteorite ALHA81005 were analyzed by ferromagnetic resonance (FMR) and magnetic hysteresis techniques. The FMR spectra of two chips have a resonance at g∼2.1 that resembles the g∼2.1 resonance that is characteristic of lunar soils. Thus the FMR spectra are consistent with the lunar regolith being a progenitor for the matrix material. For the two chips, Is/FeO∼5 units which is equivalent to a value for an immature lunar soil. The total concentration of metallic iron is on the order of 0.11 equivalent wt. % which is within the observed range for Apollo 16 rocks and soils.
Natural remanent magnetization of the Wellman Meteorite
Authors: Hamano Yozo , Matsui Takafumi
Published: February 2008

Magnetic measurements revealed that the NRM of the Wellman meteorite (H5) varies with the position within the meteorite. In the outer part with a thickness of about a few cm, the intensity of the NRM is high (∼100 Am−1) and the remanence consists of almost a single component. On the other hand the NRM intensity in the internal part is as low as 10 Am−1 and consists of three components. The directions of these three components are coherent among multiple samples. The two components with the lower coercivities are magnetically very soft, and must have been acquired on the earth’s surface. The magnetic stabilities of the surface magnetization and that of the hard component of the internal remanences are high and similar to each other. The stable direction of the internal magnetization is almost antipodal to the surface magnetization. These observations suggest that all the remanences of the Wellman meteorite have been acquired during the fall through the earth’s atmosphere and on the earth’s surface.
Possible effects of the El Chichon volcanic cloud on the radiation budget of the northern Tropics
Authors: Pollack James B. , Ackerman Thomas P.
Published: February 2008

We have carried out a series of calculations with a one‐dimensional, time‐marching, radiative‐convective model to assess the impact of the El Chichon volcanic cloud on the radiation budget of the northern tropics during the 6‐month period following the injection of volcanic material into the stratosphere. Extensive measurements of the cloud obtained from airborne, spacecraft, and ground platforms were used to define the model parameters and to test the predictions of the model. The El Chicon cloud is predicted to have caused an increase in planetary albedo of 10%, a decrease in total solar radiation of 2‐3% at the ground on cloudless days, and an increase in temperature of 3.5 K at the 24 km (30 mb) level. These predictions are compatible with relevant observations, within their respective error bars.
18 months of UV irradiance observations from the Solar Mesosphere Explorer
Authors: London Julius , Bjarnason Gudmundur G. , Rottman Gary J.
Published: February 2008

Daily solar irradiance measurements in the spectral interval 120‐305 nm have been made since 6 October 1981 with an instrument on the Solar Mesosphere Explorer. The instrument operates with a spectral resolution of about 0.75 nm. Analysis of the observed data for the period 6 December 1981 to 3 June 1983 (20 solar rotations) shows that during this period there was an apparent decrease in irradiance at all wavelengths observed (−19.7% ± 9.7% at Ly‐α) but the decrease was not significantly different from zero at wavelengths longer than 210 nm. The cross correlations between daily values of the solar irradiance and 10.7 cm flux varied from 0.7 (Ly‐α) to 0.5 (210‐215 nm) and ∼0 (290‐295nm). Calculations of the % range (i.e., highest to lowest value) of the irradiance within each solar rotation showed that for Ly‐α the range varied between 6% and 30% over the 20 solar rotations studied. At longer wavelengths the % range was smaller—about 7% at 180 nm and about 2% beyond 240 nm. The percent range values indicate representative variations useful as input data for model calculations of stratosphere/mesosphere responses to short period solar variability.
The resolving power of cross‐borehole tomography
Authors: Menke William
Published: February 2008

The data collected in a cross‐borehole tomography problem is inherently incomplete, since the boreholes do not completely surround the media under study. The ability of the experiment to resolve structure is therefore limited by poor experimental geometry. We use the method of Backus and Gilbert to investigate the ability of this technique to resolve variations in acoustic velocity and attenuation between the two boreholes. Both integrals that appear in the Backus‐Gilbert formulation can be performed analytically, thus expediting the calculations. The resolving kernels have significant horizontal width, demonstrating that the horizontal position of structures can be only poorly resolved.
High temperature stability of maghemite (γ‐Fe2O3)
Authors: Özdemir Özden , Banerjee Subir K.
Published: February 2008

The temperature stability of acicular maghemite (γ‐Fe2O3) was studied between 20°C and 600°C by x‐ray diffraction and magnetic measurements. Synthetic monodomain maghemite was found to be stable with respect to hematite (α‐Fe2O3) at temperatures as high as 500°C, inverting to α‐Fe2O3 between 510‐660°C. However, a complete inversion of the γ to α form for the sample was not achieved even at 660°C, the final product was a two‐phase mixture, with 65% of the original γ‐Fe2O3 unchanged. Two conclusions are made: (a) the absence of maghemite in a natural sample cannot be proven if heating has been restricted to moderate temperatures (300°‐400°C) and (b) the true Curie point of pure maghemite is close to 645°C.
Airborne observations of Arctic aerosols. II: Giant particles
Authors: Bailey Ian H. , Radke Lawrence F. , Lyons Jamie H. , Hobbs Peter V.
Published: February 2008

Airborne measurements made in the vicinity of Barrow, Alaska during early spring have revealed relatively large concentrations of giant (>2 µm diameter) particles in the air. Their concentration varied approximately with the inverse cube of the particle diameter. These particles were not well correlated with the layers of visible haze observed. They appeared to be approximately uniformly distributed from altitudes of 0.3 to 5 km regardless of the presence or absence of arctic haze.
Elemental composition of Arctic particulate matter
Authors: Cahill Thomas A. , Eldred Robert A.
Published: February 2008

Measurements were made of the elemental composition of particulate matter collected in flights in the Arctic in spring 1983 as part of the Arctic Gas and Aerosol Sampling Program (AGASP). Ten samples of size‐selected particles were analyzed by four nondestructive techniques at Davis. Concentrations were determined for H, C, N, and O by Forward Alpha Scattering Techniques (FAST) and for elements heavier than fluorine by Particle Induced X‐ray Emission (PIXE). Total mass was measured gravimetrically, and optical absorption was measured using the Laser Integrating Plate Method (LIPM). Results of the analyses show dramatic differences in concentrations and elemental ratios from the Alaskan arctic to the Norwegian arctic, with indications of wood smoke and sulfuric acid in the arctic atmosphere.
Energetic (>100 keV) O+ ions in the plasma sheet
Authors: Ipavich F. M. , Galvin A. B. , Gloeckler G. , Hovestadt D. , Klecker B. , Scholer M.
Published: February 2008

We present the first measurements of very energetic (112 ‐ 157 keV) O+ ions in the earth's magnetosphere. The observations were made with the UMd/MPE ULECA sensor on ISEE‐1 on 5 March 1981 at geocentric distances ∼20 RE in the earth's magnetotail. During this time period an Energetic Storm Particle event was observed by our nearly identical sensor on the ISEE‐3 spacecraft, located ∼250 RE upstream of the earth's magnetosphere. The ISEE‐1 sensor observed a similar temporal profile except for several sharp intensity enhancements, corresponding to substorm recoveries during which the plasma sheet engulfed the spacecraft. During these plasma sheet encounters we observe O+/H+ abundance ratios, at ∼130 keV, as large as 0.35. In between plasma sheet encounters the O+/H+ ratio at this energy is consistent with zero.
Herzberg continuum cross section of oxygen in the wavelength region 193.5‐204.0 nm: New laboratory measurements and stratospheric implications
Authors: Cheung A. S.‐C. , Yoshino K. , Parkinson W. H. , Freeman D. E.
Published: February 2008

The absorption cross section of oxygen at 300 K and at pressures in the range 50‐760 torr has been measured throughout the wavelength region 193.5‐204.0 nm with a 6.65 m scanning spectrometer having an instrumental full width at half maximum of 0.0013 nm. The absorption features in this region are the discrete lines of some Schumann‐Runge bands and two underlying dissociation continua, viz., the weak Herzberg continuum of oxygen and a pressure dependent continuum involving two molecules of oxygen. The instrumental width is small enough to permit measurement of the total continuum cross section, as a function of pressure, at a number of wavelengths at which interference from the discrete lines is negligible. Analysis of the pressure dependence of the total continuum cross section yields the Herzberg continuum cross section, which decreases monotonically from 14 barn at 193.58 nm to 5.5 barn at 204.06 nm. At all wavelengths in this region, our values of the Herzberg continuum cross section are smaller than previous laboratory values, much smaller than values used in many photochemical models, and consistent with recent in situ stratospheric values. The acceptance of reduced Herzberg continuum cross sections implies significant changes in photochemical modelling predictions of the stratospheric concentrations and altitude profiles of ozone, chlorofluorocarbons and nitrous oxide.
Semiannual oscillation of stratospheric ozone
Authors: Maeda Kaichi
Published: February 2008

By applying spherical harmonic analysis to the ozone data obtained from the Nimbus‐7 solar backscattered UV‐radiation (SBUV) measurements for the period from November 1978 to October 1980, the following features of the semiannual oscillation (SAO) in stratospheric ozone are revealed: (1) The equatorial ozone SAO has a broad maximum of the order of 0.5 (mixing ratio in µg/g) between the 10 mb and 3 mb levels, and the maximum shifts downward from 1 mb in June (and December) to 40 mb in November (and May). (2) Amplitudes of polar ozone SAO's are larger than that of the equatorial SAO with a major maximum at 2 mb which is 2 µg/g at 75°N and 0.8 µg/g at 75°S, respectively. (3) The inverse phase between the polar and tropical SAO which occurs around the 3 mb (∼40 km) level can be interpreted in terms of the temperature dependent ozone chemistry and the poleward meridional transport of ozone by dynamical processes in the atmosphere.
Evidence for slow‐mode shocks in the deep geomagnetic tail
Authors: Feldman W. C. , Schwartz S. J. , Bame S. J. , Baker D. N. , Birn J. , Gosling J. T. , Hones E. W. , McComas D. J. , Slavin J. A. , Smith E. J. , Zwickl R. D.
Published: February 2008

Plasma and field data from the ISEE‐3 space probe provide evidence that the lobe‐plasma sheet boundary in the central part of the distant geomagnetic tail is often a slow‐mode shock. Such shocks are predicted by Petchek's model of reconnection. If this model applies, then the ISEE‐3 observations place the general location of the reconnection diffusion region closer to the earth than x ≈ −100 RE.
Atlantic Equatorial sections during July, 1983
Authors: Perkins Henry , Saunders Kim
Published: February 2008

Two cross‐equatorial sections of current, temperature and salinity were made in the Atlantic during July, 1983. The first, along 24°W, extended from 10°N to 10°S and the second, along 28°W, from 3°S to 10°N. Measurements extended from the surface to 300 m in the case of currents and to 800 m for temperature and salinity. On the large scale, these measurements agree well with historical data. On a smaller scale, the closely spaced stations across the equator reveal a complex structure in the equatorial currents.
A trans‐Atlantic upper‐ocean temperature section along 11°15′S in March 1983
Authors: Collins Curtis A.
Published: February 2008

The temperature structure of the upper 500m was resolved with an average station spacing of 29 km along 11°15′S across the Atlantic in March 1983. To the east of 5E, an intense thermocline was observed with 18C to 24C isotherms lying within 20 m of 45 m. Elsewhere, the temperature distribution was consistent with a pattern of southward flow above 300 m at the South American Coast as well as southward flow in intermediate waters (10‐12C) to the east of 5E and in the region between 32W and 34W; from 34W to Brazil, northward flow was indicated for intermediate waters. Mesoscale variability was not observed.
Temperature variations in the Equatorial Atlantic as revealed by drifting buoys
Authors: Reverdin Gilles , Gonella Joseph , Fieux Michèle , McPhaden Michael
Published: February 2008

From May through September 1983, surface buoys deployed as a component of the FOCAL experiment (Programme Français Océan et Climat dans l'Atlantique Equatorial) drifted in the cold waters of the South Equatorial Current in the equatorial Atlantic Ocean. The surface temperature (SST) is analysed along the buoy tracks. In late May, the strong temperature drop near 4°W and 3°S is associated with vertical mixing as cold patches appear near the equator. Horizontal advection is important in June and July, as the cold water tongue expands southwards and westwards. It is also important later in the western Atlantic south of the equator, where the cooling by advection is balanced primarily by heating from the atmosphere.
Sea surface dynamic height topography and the North Equatorial Countercurrent as inferred from a linear model
Authors: du Penhoat Yves , Treguier Anne‐Marie
Published: February 2008

Hellerman and Rosenstein's (1983) climatological winds are used to force a linear, continuously stratified model of the tropical Atlantic. The dynamic height topography relative to 500 meters is compared with available data. Special attention is paid to the computed North Equatorial Countercurrent. We conclude that most of the observed seasonal variations can be explained using simple linear theory.
Magnetic properties of a columnar basalt from central Mexico
Authors: Urrutia‐Fucugauchi J. , Radakrishnamurty C. , Negendank J. F. W.
Published: February 2008

The variation of low‐field magnetic susceptibility with low temperature (between ˜77°K and ˜300°K) observed for a vertical columnar basalt from central Mexico shows a rare pattern for continental basalt ‐ i.e. susceptibility decreases with temperature to about 40‐70% of room‐temperature value, and then increases up to about 60‐100% at 77°K. These results combined with other rock‐magnetic measurements, including AF and thermal demagnetization, IRM experiments, Lowrie‐Fuller tests, thermomagnetic analysis, and optical and SEM observations suggest the presence in the columnar basalt of predominantly single domain and pseudo‐single domain titanomagnetites with composition around TM60, and a small amount of very fine‐grained particles.
Boron as a tracer of aerosol from combustion of coal
Authors: Fogg Thomas R. , Rahn Kenneth A.
Published: February 2008

Atmospheric boron was found to be predominantly gaseous in ambient samples and in stacks of coal‐fired power plants. Typical gas/particulate ratios ranged from 20 to more than 100, with stack ratios above 100 and ambient ratios generally below 100. In the stacks, B/SO2 ratios were lower than expected from bulk U.S. coals, consistent with volatilization of 20‐80 percent of the boron during combustion. Midwestern ambient B/SO2 ratios were at or above stack values, with the lowest ratios associated with highest concentrations. SO2 was always more variable than gaseous boron. These observations are consistent with coal combustion as the major source of atmospheric boron (and SO2) in the Midwest. In northern Vermont, concentrations of gaseous boron and SO2 were several times lower than in the Midwest, but the B/SO2 ratio was several times higher. Both species passed through quasiweekly in‐phase cycles of concentration with the relative amplitudes being greater for SO2 than for gaseous boron. All major pulses of boron and SO2 came from the direction of the Midwest, on the backsides of high‐pressure areas. Since the ocean is also a source of gaseous boron, its anthropogenic tracer potential for acid deposition studies will be most useful in the interior of continents.
Ionospheric currents and F‐region plasma boundaries near the dayside cusp
Authors: Vennerstrom S. , Friis‐Christensen E. , Jorgensen T. S. , Rasmussen O. , Clauer C. R. , Wickwar V. B.
Published: February 2008

Observational evidence of the location of a dayside high‐latitude ionospheric current (DPY current) with respect to the different regimes of the high‐latitude magnetosphere is obtained by analyzing data from the magnetometer chain along the west coast of Greenland in conjunction with simultaneous measurements from the newly established incoherent‐scatter radar facility at Sondre Stromfjord. The latitudinal location of the DPY current is compared with the location of the maximum F‐region electron temperature and with the location of the plasma convection reversal from sunward to antisunward. The maximum in the F‐region electron temperature roughly coincides with the velocity reversal boundary, while the DPY current is always located more poleward, penetrating deep into the polar cap. When UT variations are examined, a correlation of 70 to 80 percent is found between the three locations.
Unusual auroral features observed on January 10‐11, 1983 and their possible relationships to the interplanetary magnetic field
Authors: I‐Akasofu S. , Tsurutani B.
Published: February 2008

We report unusual auroral features observed by the DMSP‐F6 satellite on January 10 and 11, 1983. These features include the shift of the most active region to the morning sector, the shift of the polar cap center toward the evening sector, a large number of sun‐earth aligned arcs and the oval‐shaped diffuse glow without bright oval arcs. The simultaneous magnetic field observations by the ISEE‐3 and IMP‐8 satellites, together with a simple magnetospheric modeling result, suggest that the unusual features result from both the unusually large By and a large positive Bz component of the IMF.
Evidence for atmospheric carbon dioxide variability over the Gulf Stream
Authors: Bufton Jack L.
Published: February 2008

Two airborne surveys of atmospheric carbon dioxide (CO2) concentration have been conducted over the Gulf Stream off the east coast of Virginia and North Carolina on September 7‐8, 1983. In‐situ CO2 data were acquired at an aircraft altitude of 300 m on trajectories that transected the Gulf Stream near 36°N 73°W. Data show evidence of a CO2 concentration increase by 4 ppm to 15 ppm above the nominal atmospheric background value of 345 ppm. These enhanced values were associated with the physical location of the Gulf Stream prior to the passage of a weak cold front.
Acetonitrile in the troposphere: Residence time due to rainout and uptake by the ocean
Authors: Hamm S. , Hahn J. , Helas G. , Warneck P.
Published: February 2008

Henry's law coefficients for the binary system acetonitrile‐water are reported as a function of temperature from 279–303 K. The results are used to estimate the tropospheric residence time of acetonitrile due to wet precipitation (3±1.5 years) and the dry deposition velocity over the ocean (0.5 cm/s).
The response of the continental crust‐Mantle boundary observed on broadband teleseismic receiver functions
Authors: Owens Thomas J. , Zandt George
Published: February 2008

Broadband receiver functions derived from teleseismic P‐waveforms recorded on Regional Seismic Test Network (RSTN) stations in Eastern North America contain detailed information about the crust‐mantle boundary. This paper examines receiver functions from three stations (RSCP, RSNY, and RSON) to illustrate the variability in response of the continental "Moho" and to demonstrate the utility of broadband data in studying these variations. Of particular interest is the clear evidence for frequency‐dependence of the amplitudes of converted phases arriving from the crust‐mantle boundary. The shear velocity structures for these stations obtained by inverting the radial component of the receiver functions in the time domain indicate that this frequency‐dependence is a measure of the "sharpness" of the crust‐mantle boundary region.
Charge state distributions of oxygen and carbon in the energy range 1 to 300 keV/E observed with AMPTE/CCE in the magnetosphere
Authors: Kremser G. , Stüdemann W. , Wilken B. , Gloeckler G. , Hamilton D. C. , Ipavich F. M. , Hovestadt D.
Published: February 2008

Observations of charge state distributions of oxygen and carbon are presented that were obtained with the charge‐energy‐mass spectrometer (CHEM) onboard the AMPTE/CCE spacecraft. Data were selected for two different local time sectors (apogee at 1300 LT and 0300 LT, respectively), three L‐ranges (4 ⩽ L ⩽ 6, 6 ⩽ L ⩽ 8, L > 8), and quiet to moderately disturbed days (Kp ⩽ 4). The charge state distributions reveal the existence of all charge states of oxygen and carbon in the magnetosphere. The relative importance of the different charge states strongly depends on L and much less on local time. The observations confirm that the solar wind and the ionosphere contribute to the oxygen population, whereas carbon only originates from the solar wind. The L‐dependence of the charge state distributions can be interpreted in terms of these different ion sources and of charge exchange and diffusion processes that largely influence the distribution of oxygen and carbon in the magnetosphere.
Eastward propagation of a plasma convection enhancement following a southward turning of the interplanetary magnetic field
Authors: Lockwood M. , van Eyken A. P. , Bromage B. J. I. , Willis D. M. , Cowley S. W. H.
Published: February 2008

On October 27th 1984, high‐latitude ionospheric convection was observed by the European incoherent scatter (EISCAT) radar. For a nine‐hour period, simultaneous observations of the interplanetary magnetic field (IMF) were obtained sunward of the Earth's bow shock. During this period, the IMF abruptly turned southward, having previously been predominantly northward for approximately three hours, and a strong enhancement in convection was observed 11 ± 1 minutes later. Using the very high time resolution of the EISCAT data, it is shown that the convection enhancement propagated eastward, around the afternoon magnetic local time sector, at a speed of the order of 1 kms−1. These results are interpreted in terms of the effects of an onset of steady IMF‐geomagnetic field merging and are the first to show how a new pattern of enhanced convection is established in the high latitude ionosphere.
On the influx of small comets into the Earth's upper atmosphere I. Observations
Authors: Frank L. A. , Sigwarth J. B. , Craven J. D.
Published: February 2008

Images of the earth's dayglow emissions at ultraviolet wavelengths, primarily those of atomic oxygen at 130.4 nm, reveal regions of transient intensity decreases to ∼ 5% to 20% of surrounding values over areas estimated to be ∼ 2,000 km². The duration of these transient decreases in intensities is ∼ several minutes. Approximately 10 of these events occur each minute in the dayside upper atmosphere. The diurnal variation of the rate of occurrence is qualitatively similar to that for radar meteors.
Density of Martian north polar layered deposits: Implications for composition
Authors: Malin Michael C.
Published: February 2008

Mariner 9 and Viking Orbiter observations of the topography and mass of layered deposits in the north polar region of Mars suggest a density of about 1 gm/cm³. Consideration of the self‐compaction of these deposits further suggests that this low density cannot be explained by a high porosity sediment. Rather, a significant component of ice is probably required to account for the low value. The density further implies that the silicate fraction, regardless of its density (i.e., its composition), represents a volumetrically almost negligible component of the deposit. The most likely values, 5% silicate dust and 95% ice, agree well with a theoretical model for the formation of the deposits through cyclic incorporation of the perennial polar ice cap. Additional tests of this model may be posed in advance of future spacecraft missions to Mars.
Spectroscopic detection of CH3CL in the upper troposphere and lower stratosphere
Authors: Park J. H. , Zander R. , Farmer C. B. , Rinsland C. P. , Russell J. M. , Norton R. H. , Raper O. F.
Published: February 2008

Absorptions due to the ν1 band of CH3Cl have been identified for the first time in infrared solar absorption spectra of the upper troposphere and lower stratosphere. The spectral data were obtained with the ATMOS Fourier transform spectrometer onboard Spacelab 3 in May 1985 during four solar occultation events near latitudes of 30°N, 26°N, 25°N, and 49°S. Volume mixing ratio profiles of CH3Cl retrieved for the altitude range 12 to 23 km at these four latitudes do not show appreciable differences. Vertical mixing ratio distributions vary from 6 × 10−10 at 12 km to 3 × 10‐10 at 23 km with an average uncertainty of about 25%. The retrieved mixing ratio does not decrease with altitude as rapidly as the data obtained by in situ techniques.
Hydromagnetic waves near O+ (OR H2O+) ion cyclotron frequency observed by Sakigake at the closest approach to comet Halley
Authors: Yumoto Kiyohumi , Saito Takao , Nakagawa Tomoko
Published: February 2008

Long‐period HM waves with 150‐ 380 s periods were observed by Sakigake at 7 × 106 km upstream from comet Halley. The wave amplitudes were as great as ∼2 nT peak to peak. The long‐period waves were of an approximately linearly polarized transverse mode and propagated parallel to the ambient magnetic field. Dominant periods of the waves were found to be consistent with the local O+ (or H2O+) cyclotron period and to change as a function of the ambient magnetic field. The long‐period HM waves are believed to be excited by a resonant instability with high‐energy cometary heavy ions. The necessary cometary ion density for excitation at a distance of 7 × 106 km from the comet can be inferred to be of the order of 10−3 ‐ 10−4 cm−3 for 10¹ ‐ 10² keV O+ (or H2O+) ions.
Activity of comet Halley observed in the ultraviolet
Authors: Kaneda E. , Hirao K. , Shimizu M. , Ashihara O.
Published: February 2008

The time variation of the water production rate of comet Halley during this apparition has been deduced from observations of the Ultraviolet Imager on board Suisei. The preperihelion production rates were a factor of 2 ∼ 3 smaller than postperihelion rates, suggesting a postperihelion heating of the cometary nucleus. Some fine intensity structure in the Lyman alpha photometry data taken at encounter, which indicates spatial variation of the atomic hydrogen density in the coma, may correspond to shell structures in the Lyman alpha images so far obtained and is ascribed to the presence of a hydrogen source other than water in the cometary gas or dust particles. The velocity of these hydrogen atoms is estimated to be about 11 km s−1.
Rapid pickup of cometary ions due to strong magnetic turbulence
Authors: Wu C. S. , Winske D. , Gaffrey J. D.
Published: February 2008

Magnetic turbulence observed with the ICE spacecraft near Giacobini‐Zinner indicates that the energy density of the fluctuating field is higher than the thermal energy density of the solar wind plasma. We show that in the presence of such strong turbulence the newly created ions are assimilated into the solar wind very rapidly. The time scale for the assimilation process is estimated and shown to be on the order of 100 sec which is consistent with the ICE results for the H2O+ cometary ions.
EISCAT observations of bursts of rapid flow in the high latitude dayside ionosphere
Authors: Todd H. , Bromage B. J. I. , Cowley S. W. H. , Lockwood M. , van Eyken A. P. , Willis D. M.
Published: February 2008

Observations are presented of short‐lived, highly structured bursts of rapid plasma flow observed with the EISCAT radar in the high latitude dayside ionosphere. It is shown that the properties of the bursts are consistent with ionospheric perturbations caused by impulsive, localized reconnection at the Earth's magnetopause, i.e. by flux transfer events.
An evolution of antiparallel merging
Authors: Crooker N. U.
Published: February 2008

In the past it was suggested that the geomagnetic field and the interplanetary magnetic field (IMF) merge at the dayside magnetopause along lines formed by the loci of points where the fields are antiparallel. These antiparallel merging lines curve outward from the cusps, one in each hemisphere. Here we describe a 3‐D magnetopause model in which the antiparallel merging lines become chains of neutral points. The model is constructed by overlapping shielding currents of the geomagnetic field and the IMF in a layer of finite thickness. The neutral points away from the cusps allow complete cancellation of the merging fields across much of the magnetopause. The global topology of the model explains the observed disappearance of flux transfer events when the IMF turns northward and the dearth of flux transfer events in the subsolar region.
Recent measurements of Antarctic ozone depletion
Authors: Gardiner B. G. , Shanklin J. D.
Published: February 2008

Measurements of total ozone at Halley Bay, Antarctica, are presented for the six most recent observing seasons, 1980‐86, showing the consistency and progress of the spring ozone depletion. The principal ozone minimum of October 1985 was as deep as that of 1984, if not deeper. However, the period of depletion was affected by strong wave activity, giving rise to four distinct minima. A cusped maximum in total ozone was observed at Halley Bay on 19 October 1985, confirmed by temperatures in the lower stratosphere and by a similar ozone maximum at Faraday station, Argentine Islands. In the presence of such fluctuations, it is not possible to say whether the ozone depletion has reached its limit or not: indeed several years' data will yet be needed before that question can be answered. Ozone amounts recorded in the summer period December 1985 to February 1986 remain marginally lower than in the past.
The 1979‐1985 ozone decline in the Antarctic as reflected in ground based observations
Authors: Bojkov Rumen D.
Published: February 2008

Since 1979, from late September to the end of November, the total ozone over the southern polar region has declined by up to 30%, compared with the ozone average for 1957‐78. During the rest of the year there are no indications of a major decline. Neither are there significant changes in the middle latitudes surrounding Antarctica except those related to the QBO. More than 85% of the entire ozone deficiency is observed between 10 and 24 km. The rapid ozone and temperature increase in spring usually occurs in mid October and shows a 2 month lag, compared to the Arctic. The increase is related to the time of the breakdown of the winter stratospheric polar vortex. During the last six years the breakdown has occurred around mid‐November, extending the period with circumpolar circulation by 3‐4 weeks. It is suggested that weak upward motions within the vortex, in the order of 0.1 cm sec−1 during September and October, could cause part of the ozone decline.
The development of shell‐like distributions from newborn cometary ions
Authors: Gary S. Peter , Hinata Satoshi , Madland Christian D. , Winske Dan
Published: February 2008

The evolution of newborn cometary ions that interact self‐consistently with the solar wind are studied with one‐dimensional hybrid computer simulations. Cometary ions are injected at a constant rate and in a constant direction; the associated free energy leads to growing electromagnetic fluctuations which scatter these ions. At relatively low fluctuating field amplitudes, this scattering leads to shell‐like velocity distributions that subtend approximately 4π in solid angle, but have relatively small spread in speed. Shell‐like distributions are favored when the ion injection rate is comparatively slow (i.e. thin shells should be observed at relatively large distances from the cometary nucleus), when the injected ion mass is relatively light (i.e. protons develop a thinner shell than oxygen ions), and when the energy density of the fluctuating magnetic fields exhibits linear, rather than exponential, temporal growth.