bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of tidal h Love number parameters in the diurnal band using an extensive VLBI data set
Authors: Mitrovica J. X. , Davis J. L. , Mathews P. M. , Shapiro I. I.
Published: February 2004

We use over a decade of geodetic VLBI data to estimate parameters in a resonance expansion of the frequency dependence of the tidal h2 Love number within the diurnal band. The resonance is associated with the retrograde free core nutation (RFCN). We obtain a value for the real part of the resonance strength of (−0.27±0.03) × 10−3; a value of −0.19 × 10−3 is predicted theoretically. Uncertainties in the VLBI estimates of the body tide radial displacement amplitudes are approximately 0.5 mm (1.1 mm for the K1 frequency), but they do not yield sufficiently small Love number uncertainties for placing useful constraints on the frequency of the RFCN, given the much smaller uncertainties obtained from independent analyses using nutation or gravimetric data. We also consider the imaginary part of the tidal h2 Love number. The estimated imaginary part of the resonance strength is (0.00±0.02) × 10−3. The estimated imaginary part of the nonresonant component of the Love number implies a phase angle in the diurnal tidal response of the Earth of 0.7°±0.5° (lag).
Spatiotemporal patterns of clustered and non‐clustered seismic activity in the Shin‐etsu and Tokai regions, central Japan
Authors: Yoshida Akio , Maeda Kenji , Takayama Hiroyuki
Published: February 2004

We investigated spatiotemporal patterns of seismicity in the Shin‐etsu region and Tokai region, central Japan, by separating the seismicity into clustered and non‐clustered activity. We found that clustered activity occurred at various sites during short periods in each investigated region and that an alternation of active and quiet periods was clear for the clustered activity. In contrast, non‐clustered earthquakes occur at an almost constant rate, and active or quiet periods can not be distinguished in the non‐clustered activity. Some evidence suggests that an increase of clustered activity indicates a buildup of the regional stress field.
Evolution of Pinatubo aerosol near 19 km altitude over western North America
Authors: Goodman Jindra , Snetsinger K. G. , Pueschel R. F. , Ferry G. V. , Verma S.
Published: February 2004

Stratospheric aerosols, collected near 19 km altitude on wire impactors over western North America from August 20, 1991 to May 11, 1993, show strong influence of the June 1991 Mt. Pinatubo eruption. Lognormal size distributions are bimodal; each of the mode radii increases and reaches maximum value at about 15 months after eruption. The second (large particle) mode becomes well developed then, and about 40% of the droplets are larger than 0.4 µm radius. The eruption of Mt. Spurr (Alaska) may also have contributed to this. Sulfate mass loading decays exponentially (e‐folding 216 days), similar to El Chichon. Silicates are present in samples only immediately after eruption. Two years after eruption, sulfate mass loading is about 0.4 µg/m³, about an order of magnitude higher than background pre‐volcanic values. Aerosol size distributions are still bimodal with a very well‐defined large droplet mode.
Hybrid simulations of whistler waves generation and current closure by a pulsed tether in the ionosphere
Authors: Chang C. L. , Lipatov A. S. , Drobot A. T. , Papadopoulos K. , Satya‐Narayana P.
Published: February 2004

The dynamic response of a magnetized collisionless plasma to an externally driven, finite size, sudden switch‐on current source across the magnetic field has been studied using a two dimensional hybrid code. It was found that the predominant plasma response was the excitation of whistler waves and the formation of current closure by induced currents in the plasma. The results show that the current closure path consists of: a) two antiparallel field‐aligned current channels at the end of the imposed current sheet; and b) a cross‐field current region connecting these channels. The formation of the current closure path occured in the whistler timescale much shorter than that of MHD and the closure region expanded continuously in time. The current closure process was accompanied by significant energy loss due to whistler radiation.
Dust streams from comet Shoemaker‐Levy 9?
Authors: Grün E. , Hamilton D. P. , Baguhl M. , Riemann R. , Horanyi M. , Polanskey C.
Published: February 2004

In 1991 and 1992, the dust detector onboard the Ulysses spacecraft detected several dust streams apparently originating from the jovian system. The timing and measured speeds of the final two dust streams are compatible with dust from comet Shoemaker‐Levy 9's (SL9) disruption in 1992. Our further investigations of stream characteristics and dust acceleration mechanisms, however, shed some doubt that two of the eleven dust streams are of SL9 origin. In July 1994 when SL9 impacts Jupiter, the Galileo spacecraft will be about 3500 jovian radii away from the planet. Submicron‐sized dust released into, and accelerated by, the jovian magnetosphere during this event may reach Galileo and impact its dust detector between September and November 1994. We also discuss the possibility of directly sampling dust from SL9 during Galileo's orbital tour.
Reconnection layer at the flank magnetopause in the presence of shear flow
Authors: Lin Y. , Lee L. C.
Published: February 2004

We present hybrid simulations of reconnection layer at the flank magnetopause, where a large plasma flow speed is present in the magnetosheath. It is found that there exists a threshold flow speed υ* such that for the magnetosheath flow speed υs < υ* (υs > υ* ), the rotational discontinuity with a larger field rotation angle exists on the magnetosheath (magnetospheric) side of the reconnection layer. The threshold speed is found to be υ* = υAm ‐ υAs, where υAm (υAs) is the Alfvén speed on the magnetospheric (magnetosheath) side of the reconnection layer. Furthermore, for υs << υ*, the rotational discontinuity on the magnetosheath side is very thin, and an accelerated high‐speed flow is located earthward of the rotational discontinuity, as observed at the dayside magnetopause. For υs ∼ υ*, the magnetic field transition region is thick, and the accelerated flow is present in the entire field transition region, as observed at the flank magnetopause.
Heterogeneous reaction of HOBr with HBr and HCl on ice surfaces at 228 K
Authors: Abbatt Jonathan P. D.
Published: February 2004

Motivated by the recent observations of springtime ozone loss in the Arctic boundary layer, we have studied the heterogeneous reactions HOBr + HBr → Br2 + H2O and HOBr + HCl → BrCl + H2O using a low temperature flow tube coupled to a mass spectrometer. By monitoring the decay of HOBr in an excess of either HBr or HCl, both reactions have been shown to occur readily on ice surfaces at 228 K with reaction probabilities of 0.12 (±0.03) and 0.25 (+0.10/−0.05), respectively. The gasphase reaction products, Br2 and BrCl, have been observed. Also, it has been shown that HOBr interacts strongly with supercooled 60 wt % sulfuric acid solutions, being taken up with a sticking coefficient of greater than 0.06. The atmospheric implications of the heterogeneous reactivity of HOBr and HBr are discussed.
Freja UV imager observations of spatially periodic auroral distortions
Authors: Murphree J. S. , Johnson M. L. , Cogger L. L. , Hearn D. J.
Published: February 2004

Freja UV imager measurements of distortions of discrete arcs within the auroral distribution reveal a number of examples of periodic intensifications. Analysis of these features reveals a clear peak at 152 km separation between the intensifications with a less well defined peak at approximately twice that value. No observations at separations less than 100 km were found. Theories relating such features to shear flow regions suggest a relationship between wavelength and shear layer width. A statistical analysis indicates that the product of the wave number and the arc system width yielded a value of .7 which is consistent with theoretical predictions. The periodic features were found to occur throughout the afternoon/midnight sector with no apparent dependence on MLT. As well they appeared at a variety of locations within the auroral distribution implying the common existence of shear layers.
Shock synthesis of light hydrocarbon gases from H2 and CO: Its role in astrophysical processes
Authors: Sugisaki Ryuichi , Mimura Koichi , Kato Manabu
Published: February 2004

Impact experiments for CO and H2 mixtures showed that hydrocarbon gases up to C4H10 are synthesized by shock. The conversion of CO to hydrocarbons increases with increasing shock energy but the composition of synthesized hydrocarbons depends on that of the reactant (H2/CO). From the results, geneses of some light hydrocarbons in planetary materials were inspected: Hydrocarbon gases contained in regoliths on the Moon's surface and in atmospheres of Jovian planets might have been produced by shocks that were caused by frequent meteorite falls and condensation‐accretion of primitive solar nebulae into planets, respectively. Besides Fischer Tropsch reaction, impact‐derived shock syntheses must have played an important role in the chemical evolution of astrophysical materials.
A possible signal of the El Niño‐Southern Oscillation in time series of the diurnal tide
Authors: Vial François , Lott François , Teitelbaum Hector
Published: February 2004

Long time series of diurnal pressure variations, S1(p), at Macao (22° N,113°E) and Batavia (now Djakarta: 6°S, 107°E) are analysed, and, at both locations, a correlation is found between S1(p) and El Niño‐Southern Oscillation (ENSO). Some possible physical explanations for this correlation are given.
Corotating particle enhancements out of the ecliptic plane
Authors: Simnett G. M. , Sayle K. , Roelof E. C. , Tappin S. J.
Published: February 2004

We have studied > 40 keV ion and electron enhancements seen at Ulysses from a series of corotating interaction regions (CIR), from mid‐1992 until the end of 1993. The event intensity increased up to latitude 20°S; after that the ion flux maxima decreased by ∼23%/deg while the electron maxima decreased more erratically, and more slowly, during the last half of 1993. After April, 1993, the electron increases lagged the ions by up to four days. The electron energy spectrum hardened both towards the end of the events and as the latitude went above ∼35°. The electron/ion delays and the electron spectral hardening are related to the three‐dimensional structure of the reverse shocks at high latitudes. The H/He ratio at ∼0.4‐1.2 MeV/nucleon decreased towards the end of each event; the mean minimum value was 3.5±0.3, lower than observed in earlier studies of CIR‐associated events near the ecliptic plane. The He increases have recurred with a period of 26.0 days. There have been two phase changes: +4.3 days (February 1993) and +2.4 days (August 1993), related to changes in the coronal structure of the source regions for the high speed solar wind streams.
Possible radio wave precursors associated with the comet Shoemaker‐Levy 9/Jupiter impacts
Authors: Farrell W. M. , Kaiser M. L. , Desch M. D. , MacDowall R. J.
Published: February 2004

We suggest that prior to its impact with Jupiter, comet Shoemaker‐Levy 9 will behave as an electrical generator in the Jovian magnetosphere, converting planetary rotational energy to electrical energy via a dust/plasma interaction. This electrical energy will then be deposited in the dayside auroral region where it may drive various auroral phenomena including cyclotron radio emission. Such emission could be detected by spacecraft like Ulysses and Galileo many hours prior to the actual comet impact with the upper atmosphere. We apply the theory originally developed to explain the spokes in Saturn's rings. This theory allows us to quantify the driving potential associated with the comet and, consequently, to determine the radio power created in the auroral region. We conclude that if enough fine dust is present in the cometary system, comet‐induced auroral radio emissions will reach detectable levels. This emission should be observable in the dayside hemisphere about 12–24 hours prior to each fragment impact.
Solar wind oscillations with a 1.3 year period
Authors: Richardson John D. , Paularena Karolen I. , Belcher John W. , Lazarus Alan J.
Published: February 2004

The IMP‐8 and Voyager 2 spacecraft have recently detected a very strong modulation in the solar wind speed with an approximately 1.3 year period. Combined with evidence from long‐term auroral and magnetometer studies, this suggests that fundamental changes in the Sun occur on a roughly 1.3 year time scale.
Magnetic reconnection ahead of a coronal mass ejection
Authors: McComas D. J. , Gosling J. T. , Hammond C. M. , Moldwin M. B. , Phillips J. L. , Forsyth R. J.
Published: February 2004

On 29 November 1990 the Ulysses spacecraft passed through a series of interplanetary structures which suggest that reconnection had occurred on open field lines ahead of a coronal mass ejection (CME), changing the magnetic topology of the upstream region. We observe in sequence 1) a heat flux dropout, 2) a region of counterstreaming halo electrons which does not appear to be a CME, and 3) a region of counterstreaming halo electrons which is a CME. We suggest an interpretation in which upstream of the CME Ulysses passed first through a region magnetically disconnected from the Sun and then through a region magnetically connected back to the solar corona at both ends, both of which were created by reconnection of open field lines ahead of the CME. Such reconnection provides a method for producing a heat flux dropout / counterstreaming suprathermal electron pair of signatures in interplanetary space that has not been previously described.
On the relationship between the population of the fine structure levels of the ground electronic state of atomic oxygen and the translational temperature
Authors: Sharma R. , Zygelman B. , von Esse F. , Dalgarno A.
Published: February 2004

Using a recent calculation of the cross sections for fine structure changing collisions during an encounter between two oxygen atoms in the ground electronic state, we determine the population of the fine structure levels of oxygen as a function of altitude for four model atmospheres representing conditions at 0° longitude, 45° latitude, at midday and midnight, and high and low solar and geomagnetic activity. We include the effect of electron impacts. The fine structure levels are shown to be in local thermodynamic equilibrium (LTE) at the local neutral atom translational temperature for altitudes up to 350 km and 400 km for midnight and midday, respectively, at low activity, and up to at least 600 km at high activity. At higher altitudes spontaneous emission causes deviation from LTE and overpopulates the lowest (J=2) level at the expense of the other two levels.
Tropospheric ozone measurement at the top of Mt. Fuji
Authors: Tsutsumi Yukitomo , Zaizen Yuji , Makino Yukio
Published: February 2004

Since August of 1992, tropospheric ozone has been measured at the top of Mt. Fuji to investigate the background ozone feature of middle troposphere over Japan. During one year, the maximum concentration of monthly mean ozone at Mt. Fuji was 59.3 ppbv in May and minimum was 30.9 ppbv in August. The secondary minimum was recorded in January. The seasonal behavior showed a bi‐modal trend. The diurnal amplitude of ozone in summer showed slight effect from the mountain and valley winds, but the amplitude around 2 ppbv is a lot smaller compared to other mountain data. The amplitude of other seasons did not show any significant variations. The effect of the mountain and valley winds were small at the top of Mt. Fuji because of the steep and windy summit. Day‐to‐day summertime variations varied wildly and often recorded low concentrations of ozone less than 20 ppbv. This low concentration of ozone sometimes continued for 3–5 days. This summer ozone minimum of the lower free troposphere was due to horizontal advection of the ozone poor air. In wintertime, the deviation of ozone concentration was very small. High peaks which lasted only a few hours were observed in spring. Analyzing the cross section chart on the 14th May 1993, the high peak of ozone on this day must have come from the stratosphere along the isentropic surface.
Stratospheric denitrification due to polar aerosol formation: Implications for a future atmosphere with increased CO2
Authors: Pitari Giovanni , Ricciardulli Lucrezia
Published: February 2004

The amount of stratospheric denitrification produced by NAT aerosol formation is studied with a photochemical two‐dimensional model which includes the effects of zonal asymmetries of the temperature field. The model photochemistry is coupled with a microphysical code for aerosol formation and growth, so that the permanent loss of stratospheric nitric acid and water vapor may be taken into account. The model results for nitric acid relative to the atmospheric chemical composition of 1980 are compared with LIMS data. We show that the level of denitrification may rise substantially if the polar vortex cools down, as it could be the case in a future atmosphere richer in carbon dioxide. A three‐dimensional model is used to calculate the temperature perturbation due to an increase of CO2 from 335 ppmv of 1980 (baseline) up to 500 ppmv (predicted for 2050). The photochemical model adopting these new temperatures predicts an average 20% HNO3 column decrease poleward of 45N with respect to baseline. One consequence is that the relative weight of the NOx catalytic cycle for O3 destruction decreases with respect to the present atmosphere.
Large‐scale current and thermohaline structures along 156°E during the COARE intensive observation period
Authors: Eldin Gérard , Delcroix Thierry , Hénin Christian , Richards Kelvin , du Penhoat Yves , Picaut Joël , Rual Pierre
Published: February 2004

From December 1992 to February 1993, 18 meridional sections of temperature, salinity, and current were collected along 156°E, from 5°S to 5°N, during the Intensive Observation Period of the Coupled Ocean‐Atmosphere Response Experiment. The average conditions were characteristic of the ongoing El Niño event, with a relatively shallow thermocline and fresh surface waters. Alternating westerly and easterly wind forcing was observed, and the warm surface layer (the “Warm Pool”) responded in a time scale of a few days by corresponding alternating flows; the equatorial current system was less affected at depth. The upper‐layer oceanic temperature variability involved several mechanisms, including surface cooling by evaporation during westerly winds and entrainment from the thermocline.
The global hotspot distribution and instability of D″
Authors: Ribe N. M. , de Valpine D. P.
Published: February 2004

We present a new spherical harmonic expansion of the global hotspot distribution, with the contribution of each hotspot weighted by its buoyancy flux. The resulting power spectrum, normalized to that expected for a random distribution, has statistically significant peaks only at degrees 1 and 2. To explain this, we study a simple model for the origin of mantle plumes in the D″ layer at the base of the mantle: the Rayleigh‐Taylor instability of two superposed fluid layers with different viscosities and densities in a spherical shell. The wavelength of the fastest growing instability greatly exceeds the thickness of D″ and increases as the viscosity contrast γ across this layer increases. These results are consistent with the hotspot spectrum if γ ∼ 106.
X‐ray photoelectron spectroscopic studies of the heterogenous reaction of gaseous nitric acid with sodium chloride: Kinetics and contribution to the chemistry of the marine troposphere
Authors: Laux J. M. , Hemminger J. C. , Finlayson‐Pitts B. J.
Published: February 2004

We report here the first measurement of the reaction probability (ϕ) at 298 K for the reaction (1) HNO3(g) + NaCl(s) → HCl(g) + NaNO3(s), ϕ = (4±2) × 10−4, which was determined using X‐ray photoelectron spectroscopy to follow the formation of nitrate on the surface of single crystals of NaCl. Along with recent kinetic data for the reaction N2O5(g) + NaCl(s) → ClNO2(g) + NaNO3(s), we show that in the dark with typical relative concentrations of N2O5 and HNO3, the N2O5 reaction should be competitive with, and may exceed, that of HNO3. The reactions of NO2 and ClONO2 with NaCl are expected to be much less important. Thus, the tropospheric production of chlorine atoms via photolysis of ClNO2 from the N2O5 reaction is anticipated, which has the potential to impact the ozone balance in the troposphere.
Plasma effects on the interaction of a comet with Jupiter
Authors: Kellogg Paul J.
Published: February 2004

I consider some plasma effects to be expected when the fragments of Comet Shoemaker‐Levy 9 crash into Jupiter. Emphasis is put on pre‐impact effects, and on the possibility of significant radio emission. It is shown that an ionizing shock will develop at altitudes below about 600 km, and that significant ionization will exist above that altitude. The incoming comet and its surroundings will then represent a rapidly moving conductor in a strong magnetic field and will induce large currents in Jupiter's magnetosphere, similar both qualitatively and quantitatively to a way in which Io interacts with Jupiter's magnetic field and with the plasma of the torus. This process is thought to be involved in the generation of decametric radiation, so that the impact of the comet may also produce such radiation. The power involved in this interaction is estimated to be at least 1/15th of the power due to Io, and its duration to be for 10‐20 s before the comet's impact with the surface of Jupiter.
Some interactions between dust from comet Shoemaker‐Levy 9 and Jupiter
Authors: Dessler A. J. , Hill T. W.
Published: February 2004

Dust components of Comet Shoemaker‐Levy‐9 will traverse Jupiter's magnetosphere for an extended period surrounding the July 1994 impact of the nuclear fragments with Jupiter's atmosphere. We focus here on three interactions that are, in principle, visible from Earth: one in which the magnetosphere could affect the comet, one in which the comet could affect the magnetosphere, and one caused by dust impacting the upper atmosphere. These interactions are (1) electrostatic disruption of dust grains, which could permit remote optical imaging of the magnetosphere, (2) energy degradation of trapped relativistic electrons, which might produce observable changes in their synchrotron emission spectrum, and (3) a coma‐induced meteor shower in view of Earth‐based telescopes. We find these various interactions may be weak, possibly unobservable. If these interactions prove detectable, they can provide unique diagnostic tools for the magnetosphere, the comet/magnetosphere interaction, and the mass flux and size distribution of dust striking the upper atmosphere.
New Jovian ring?
Authors: Horányi Mihály
Published: February 2004

We follow the orbital evolution of small dust particles generated from the break up of comet Shoemaker‐Levy 9. In addition to the usual perturbations, we also consider electrostatic charging and the consequent magnetospheric effects. We show, that in about ten years following the break up, a small fraction of the dust will settle into orbits well inside the magnetosphere. The forming ring will be comprised of dust particles with radii in the range of 1.5 < a < 2.5 µm that follow retrograde orbits in the radial range of 4.5 < r < 6 RJ. We estimate the peak optical depth of this new ring in the range of 10−8 < τmax < 2 × 10−6.
In‐situ measurement of the Schmidt number within a PMSE layer
Authors: Lübken Franz‐Josef , Giebeler Jochen , Blix Tom , Thrane Eivind , Singer Werner , Bremer Jürgen
Published: February 2004

During the SCALE campaign in July and August 1993, rocket borne in situ measurements of neutral and electron small scale density fluctuations were performed in the mesosphere over Andøya (69° N16°E) at the same time as the EISCAT 224 MHz radar in Tromsø observed strong polar mesosphere summer echoes (PMSE). Strong neutral air turbulence was observed in the height of the PMSE with a turbulent energy dissipation rate of ϵ = 630mW/kg. In the same altitude range, electron density fluctuations were observed extending to scales smaller than found in the neutrals. From a comparison of the neutral and electron density fluctuation spectrum we obtained a Schmidt number Sc of 6.8 (Sc = ν/D ; ν = kinematic viscosity ; D = molecular diffusion coefficient for the electrons). From the above numbers we deduced ℓoD&K = 5.2m (ℓoD&K is the ‘break‐off’ scale between the viscous‐convective and the viscous‐diffusive subrange of the turbulence spectrum). The half wavelength of the EISCAT 224 MHz radar (λ/2 = 0.67m) is therefore well located in the viscous‐diffusive subrange of the turbulence spectrum, despite the fact that Sc > 1, which shifts ℓoD&K towards smaller scales. Our results indicate that the theoretical model of Driscoll and Kennedy [1985], frequently used in this context, is not appropriate under PMSE conditions at scales significantly smaller than ℓoD&K.
ERS‐1 altimetry on the Greenland Ice Sheet: Preliminary investigations of annual variations
Authors: Andersen Ole Baltazar
Published: February 2004

The existence of an annual signal in the ERS‐1 35‐day repeat altimetry measurements over the Greenland ice sheet is investigated in this paper.

Spectral analysis from a collinear set of long tracks indicates, that the timevarying part of the elevation signal is rather constant at a level around 20 cm at frequencies higher than 1 cycle per degree. At lower frequencies the presence of a stationary signal can be seen. This signal can be estimated in a collinear analysis from the entire set of 35‐day altimetry data over the ice sheet spanning one and a half years.

Separation of an annual signal revealed a signal highly correlated with topography. The mean amplitude is around 40 cm, with amplitudes between 10–20 cm around the summit of the ice, rising to between 50–80 cm approaching the ablation zone of the ice sheet.
Tropical cirrus cloud radiative forcing: Sensitivity studies
Authors: Jensen E. J. , Kinne S. , Toon O. B.
Published: February 2004

We have performed one dimensional radiative transfer calculations to evaluate the impact of cirrus clouds on the tropical radiation budget. We investigate the sensitivity of solar and infrared fluxes to cloud optical depth, particle size distributions, and cloud height. If the observed solar cloud forcing in excess of 100 W‐m−2 is to be attributed to cirrus anvils alone, then the optical depth of these anvils must be at least 5 (assuming 50% cloud cover and an ice crystal effective radius of 15 µm). The net radiative forcing of cirrus near the tropical tropopause is positive (heating) for cloud optical depths less than about 16 and negative (cooling) for larger optical depths. If cirrus clouds alone are responsible for the equal and opposite shortwave and longwave cloud forcing in excess of 100 W‐m−2 observed by ERBE, then the cirrus must typically take the form of deep, optically thick clouds with relatively small particles (radii of 10‐20 µm) and cloud‐tops well below the tropopause. The maintenance of this balance on monthly time scales can be attributed to a variety of correlations: The cloud cover of optically thick cirrus or thin cirrus overlying low‐level stratus clouds could vary; or cirrus anvil height could increase along with a decrease in the ice crystal effective radius and an increase in optical depth. It would be of great interest to determine observationally which of these correlations is responsible for the observed lack of variation in cloud forcing.
Energetic helium particles trapped in the magnetosphere
Authors: Chen Jiasheng , Guzik T. Gregory , Sang Yeming , Wefel John P. , Cooper John F.
Published: February 2004

High energy (∼40‐100 MeV/nucleon) geomagnetically trapped helium nuclei have been measured, for the first time, by the ONR‐604 instrument during the 1990/1991 CRRES mission. The helium events observed at L < 2.3 have a pitch angle distribution peaking perpendicular to the local magnetic field and are contained in peaks located at L = 1.2 and 1.9. The events in each peak can be characterized by power law energy spectra with indices of 10.0±0.7 for L = 1.9‐2.3 and 6.8±1.0 for L = 1.15‐1.3, before the large storm of 24 March 1991. CRRES was active during solar maximum when the anomalous component is excluded from the inner heliosphere, making it unlikely that the observed events derived from the anomalous component. The trapped helium counting rates decrease gradually with time indicating that these high energy ions were not injected by flares during the 1990/91 mission. Flare injection prior to mid‐1990 may account for the highest energy particles, while solar wind injection during magnetic storms and subsequent acceleration could account for the helium at lower energies.
Comment on “By fluctuations in the magnetosheath and azimuthal flow velocity transients in the dayside ionosphere” by Newell and Sibeck
Authors: Lockwood M. , Cowley S. W. H. , Smith M. F.
Published: February 2004

Newell and Sibeck [1993] (hereafter N&S) list some objections to our interpretation of dayside auroral transients and associated azimuthal flow bursts in terms of pulsed reconnection [e.g. Lockwood et al., 1989; 1993a]. They present what they term an “apparently overlooked” alternative explanation in terms of steady reconnection and fluctuations in the magnitude of the By component of the magnetosheath field. The objections of N&S can all be answered by reference to our previous publications and their alternative explanation was only “overlooked” in so far as it fails to explain the observations. Here we discuss just some of the reasons why the objections of N&S are invalid, and then give reasons why the events are not simply due to magnetosheath |By| changes.
Nonlinear studies of coronal heating by the resonant absorption of Alfvén waves
Authors: Ofman L. , Davila J. M. , Steinolfson R. S.
Published: February 2004

The first nonlinear study of the instability of the resonant absorption is presented in this paper. The nonlinear evolution of the resonant absorption of Alfvén waves in an inhomogeneous plasma is studied via solution of the time‐dependent 3‐D, low‐β, resistive MHD equations. Highly sheared velocities that are subject to the Kelvin‐Helmholtz like instability are found at the narrow dissipation layers. Three dimensional Kelvin‐Helmholtz like vortices appear at and near the dissipation layers and propagate along the slab of plasma. The narrow resonant heating layers are deformed by the self‐consistent shear flow. In the solar active regions where the resonant absorption of Alfvén waves is believed to occur the instability may lead to turbulent enhancement of the dissipation parameters and account for the observed turbulent velocities inferred from the non‐thermal broadening of x‐ray and EUV emission lines.
The population of the magnetosphere by solar winds ions when the interplanetary magnetic field is northward
Authors: Richard Robert L. , Walker Raymond J. , Ashour‐Abdalla Maha
Published: February 2004

We have examined some possible entry mechanisms of solar wind ions into the magnetosphere by calculating the trajectories of thousands of non‐interacting ions in the magnetic and electric fields from a three dimensional global magneto‐hydrodynamic (MHD) simulation of the magnetosphere and the magnetosheath, under northward interplanetary magnetic field (IMF) conditions. Particles, launched in the solar wind, entered the magnetosphere and formed the low latitude boundary layer (LLBL), plasma sheet and a region of trapped particles near the Earth. The densities and temperatures we obtained in these regions were realistic, with the exception of trapped particle densities. The dominant entry mechanism was convection into the magnetosphere on reconnecting field lines.
Fractal fracture scattering origin of S‐wave coda: Spectral evidence from recordings at 2.5 km
Authors: Leary Peter , Abercrombie Rachel
Published: February 2004

Local earthquake seismograms recorded at a depth of 2.5 Km in the Cajon Pass borehole near the San Andreas fault, southern California, yield body‐wave and coda‐wave amplitude spectra at frequencies between 10 and 200 Hz without interference from either near‐surface attenuation or surface waves. The coda‐wave spectra resemble the shear‐wave source spectra except that above the corner frequencies fo ≈ 20–30 Hz coda spectra decay by power‐law exponent n ≈ −2.3±0.1 while the source shear‐wave spectra decay by cubic power‐law (mean power‐law exponent n ≈ −3.1±0.1). Assuming a cubic source power‐law spectral decay, the high frequency power‐law enrichment of coda amplitudes relative to source amplitudes implies a power‐law distribution of scatterers that increases with frequency as ≈ f0.7±0.1. The distribution of acoustic reflectivity deduced from the Cajon Pass well log has a power‐law density ≈ ν0.6 at the relevant spatial frequencies ν. The agreement between the temporal and spatial frequency power‐law exponents may be explained by first order scattering in fractal fracture‐heterogeneous material.
High altitude bottomside bubbles?
Authors: Hanson W. B. , Urquhart A. L.
Published: February 2004

The ion drift meter on the polar orbiting DMSP F‐10 spacecraft observed bubble‐like features near the magnetic equator that have remarkably continuous transitions in ion concentration (Ni) and drift velocity, where there is a high positive correlation between upward velocity and decreased Ni. This is in marked contrast to the virtually discontinuous transitions that are characteristics of most bubbles. We conclude that these new features were probably observed on the bottomside of the F‐layer at DMSP altitudes (750–850 km), much higher than normally accepted values. These observations were made during Feb.‐Mar.‐Apr. of 1991, when Ni exceeded 106cm−3 on nearly every equator crossing.
3‐D Simulation of high‐latitude interaction regions: Comparison with Ulysses results
Authors: Pizzo V. J. , Gosling J. T.
Published: February 2004

A three‐dimensional (3‐D) magnetohydrodynamic (MHD) numerical model is used to simulate the global evolution of a steady, tilted‐dipole solar wind flow configuration similar to that prevalent in interplanetary space in 1993. Systematic latitudinal changes in the structure of a corotating interaction region (CIR) near 5 AU is shown to agree well with recent Ulysses observations. The abrupt disappearance of forward shocks and continued persistence of reverse shocks poleward of the latitude where Ulysses crossed the southern edge of the coronal streamer belt is explained as a natural consequence of the 3‐D flow geometry.
Classical dynamics of the N(4S) + O2 (X³ Σg−) → NO(X²II) + O(³P) reaction
Authors: Duff James W. , Bien Fritz , Paulsen Duane E.
Published: February 2004

Classical trajectory calculations have been performed to determine the reaction rate constants and NO final vibrational‐rotational distributions of the N(4S) + O2 reaction at hyperthermal translational energies. The reaction occurs on two electronic potential energy surfaces, both of which must be considered for a realistic description of the N(4S) + O2 dynamics. The calculations, which are in good agreement with the available experimental data, show that the reaction has a very strong translational energy dependence and produces NO with extensive vibrational and rotational excitation. The present study provides the N(4S) + O2 reaction attributes necessary to predict NO formation and emission from translationally hot N(4S) in the thermosphere.
VHF backscatter radar observations of type I waves during a counter electrojet event
Authors: Somayajulu V. V. , Selvamurugan R. , Devasia C. V. , Cherian Ligi
Published: February 2004

The paper presents simultaneous observations made at Trivandrum (Dip ‐ 0.5°N) during a strong counter electrojet event using VHF backscatter radar, Ionosonde and Magnetometer. The VHF backscatter radar observations of 2.7 m scale size irregularities have shown that Type I waves with phase velocities in the range of 180–220 ms−1 can be generated in the presence of a destabilizing gradient. This gives direct experimental evidence that the electron density gradient will affect the type I threshold velocity, sometimes substantially.
Shock synthesis of polycyclic aromatic hydrocarbons from benzene: Its role in astrophysical processes
Authors: Mimura Koichi , Kato Manabu , Sugisaki Ryuichi , Handa Nobuhiko
Published: February 2004

It was experimentally shown that shock waves generated by projectile impact cause a reaction between benzene molecules to produce heavier aromatic hydrocarbons such as naphthalene, biphenyl, phenanthrene, and chrysene. Most of these shock induced‐molecules are detected in meteorites and cosmic dusts; some in interstellar environments. Such processes may have operated during shock events in interstellar environments.
Irregular, long‐period boundary oscillations beyond ∼100 Re: GEOTAIL plasma observations
Authors: Siscoe G. L. , Frank L. A. , Ackerson K. L. , Paterson W. R.
Published: February 2004

Near the tail boundary beyond about 100 Re, GEOTAIL often measures irregular, long‐period oscillations in plasma velocity and density. Flow speed and density oscillate between magnetosheath values and values an order of magnitude less. The oscillations can persist for days. A typical oscillation lasts 100 minutes, but the range is large. The oscillations are highly asymmetric in that the increasing phase of the oscillation is an order of magnitude faster than the decreasing phase. This asymmetry shows that they are a distinct class of oscillations, not previously explicitly reported, and that they are not mere consequences of tail flapping in a variable solar wind. The changes in flow direction through an oscillation imply that the oscillation results from a motion of the boundary toward and away from the spacecraft with an amplitude between 5 and 10 Re. A consideration of options suggests that the most plausible cause of these oscillations is the ‘breathing’ of the magnetotail that attends the substorm cycle.
Mode radius and asymmetry factor of Mt. Pinatubo volcanic aerosols from balloon‐borne optical measurements over Hyderabad during October 1991
Authors: Ramachandran S. , Jayaraman A. , Acharya Y. B. , Subbaraya B. H.
Published: February 2004

Using Sun‐tracking photometers onboard balloon, the Pinatubo volcanic aerosol layer has been studied over Hyderabad (17.5°N) in October 1991, about 4 months after the eruption. From the aerosol extinction coefficients the mode radius and from the angular distribution of the scattered radiation intensity measurements the asymmetry factor g are determined. Mode radii are found to be in the range of 0.22±0.05 µm within the aerosol layer while g values are found to be 0.83±0.04, indicating the presence of larger particles. The mass determination reveals that the mass of the Pinatubo layer is about 0.053 gm−2 which is 3.75 times higher than the earlier reported value for El Chichon layer, about 4 months after the eruptions.
Seismic velocities of upper oceanic crust
Authors: Chapman N. R. , Hannay D. E.
Published: February 2004

New measurements are reported for the seismic velocities in upper oceanic crust (layer 2A) at off‐axis sites along a track at 34° N in the Pacific where the sediments were thin (< 33m) and the crustal age increased from 42 to 63 m.y. The data were obtained in experiments designed to measure the reflection coefficient at each site using a horizontal line array. The reflection coefficient versus angle information was inverted for the seismic velocities using a nonlinear inversion technique based on a simulated annealing search algorithm. The p wave velocity increased from 2.7 to 3.1 km/s along the track, and the shear velocity in‐creased from about 1.0 to 1.6 km/s. These results suggest that the aging process controlled by passive hydrothermal circulation is continuing at these sites.
Topside observation of gravity waves
Authors: Mende S. B. , Swenson G. R. , Geller S. P. , Spear K. A.
Published: February 2004

The AEPI (Atmospheric Emissions Photometric Imager) experiment on the ATLAS‐1 shuttle mission (launched March 24, 1992) imaged the earth night airglow emission in the O2 Atmospheric (0,0) bands, at 762.0 nm. Earthward views of O2 A bands show structure from gravity waves which exhibit extended horizontal structure with horizontal wavelengths on the order of 50–100 km. These observations of the O2 A (0,0) bands are particularly interesting since in this wavelength the lower atmosphere absorbs all the earth‐reflected emissions and most of the spectrally diffuse backgrounds. Herein we present observations of gravity waves using a topside airglow imaging technique.
Application of the coded long‐pulse technique to plasma line studies of the ionosphere
Authors: Djuth Frank T. , Sulzer Michael P. , Elder John H.
Published: February 2004

Recently, the coded long‐pulse radar technique was tested at Arecibo Observatory, Puerto Rico using photoelectron‐enhanced plasma lines in the daytime ionosphere. The technique immediately proved to be a powerful diagnostic tool for studying natural ionospheric phenomena. Our initial observations indicate that extremely accurate measurements of absolute electron density (0.01 to 0.03% error bars) can be achieved with an altitude resolution of 150 m and a temporal resolution of ∼2 s. In addition, the technique provides information about electron density structure within a 150‐m altitude cell and yields parameters from which the energy spectrum of suprathermal electrons (≥ 5 eV) can be deduced. Our earliest measurements are used to illustrate applications of the coded long‐pulse technique to several aeronomic/ionospheric areas of current interest. These include studies of neutral wave motions in the lower thermosphere, measurements of ion composition in the F1 region/upper ionosphere, and investigations of electron‐gas thermal balance and photoelectron energy loss processes. The technique can be utilized to examine irregularity formation in the F region, probe electron acceleration processes in ionospheric modification experiments, verify the magnetic field dependence of Langmuir wave damping, and more generally test higher order corrections suggested for the Langmuir dispersion relation. It is anticipated that the latter tests will facilitate measurements of ionospheric currents.
Macroscale coherence of the heliospheric current sheet: Pioneers 10 and 11 comparisons
Authors: Siscoe George , Intriligator Devrie
Published: February 2004

We use the near radial alignments of Pioneers 10 and 11 during 1974 to study the macroscale geometry of the heliospheric current sheet (HCS). The interval of near alignment gave eight analyzable cases of encounters of both spacecraft with the same HCS and one case in which the IMP and Pioneer 11 spacecraft, while nearly radially aligned, encountered the same current sheet. The degree of macroscale coherence of the HCS was judged by comparing observed solar wind speeds against solar wind speeds calculated on the bases of HCS encounter times and ideal Parker spiral geometry. The correlation coefficient between the two sets of speeds is 0.53. The difference between the calculated and observed speeds can be understood in terms of observed deviations from ideal spiral geometry in the ecliptic plane or in terms of typical corrections to the calculations from small latitudinal factors. One case, however, defies explanation in these terms. This range of behavior demonstrates that the HCS is a useful probe of heliospheric dynamics.
Atmospheric rivers and bombs
Authors: Zhu Yong , Newell Reginald E.
Published: February 2004

Filamentary structure is a common feature of atmospheric water vapor transport; the filaments may be termed “atmospheric rivers” because some carry as much water as the Amazon [Newell et al., 1992]. An extratropical cyclone whose central pressure fall averages at least 1 hPa hr−1 for 24 hours is known in meteorology as a “bomb” [Sanders and Gyakum, 1980]. We report here an association between rivers and bombs. When a cyclonic system is penetrated by a river, the cyclonic center moves to be close to the position occupied by the leading edge of the river twelve hours previously and the central pressure falls. If the river then moves away from the cyclone, the central pressure rises. Based on a pilot study of pressure fall and water vapor flux convergence for two winter months, the cause of the explosive deepening appears to be latent heat liberation. This is substantiated by composite maps of seven Atlantic and seven Pacific bombs which show that the flux convergence near the bomb center has a comma cloud signature. The observed association may be useful in forecasting 12‐hour direction of motion and pressure change of rapidly developing cyclonic systems; the incorporation of better moisture data into numerical forecasting models may be the reason for the reported increase of skill in the prediction of bombs in recent years.
Quasi‐biennial and semi‐annual oscillations in equatorial wind fields constructed by data assimilation
Authors: Swinbank Richard , O'Neill Alan
Published: February 2004

Since October 1991, the U.K. Meteorological Office has used the technique of data assimilation to produce global meteorological analyses of the troposphere and stratosphere. These analyses are constructed from conventional meteorological measurements in the troposphere and lower stratosphere, and temperature soundings from NOAA polar‐orbiting satellites. The analyses show very clear quasi‐biennial and semi‐annual oscillations in equatorial winds. The quasi‐biennial oscillation has its maximum amplitude of about 20 ms−1 near 30 hPa, and exhibits descending easterly and westerly shear zones. Analysed winds compare well with radiosonde observations in the lower stratosphere. The semi‐annual oscillation has its peak amplitude of about 30 ms−1 near the stratopause. Winds near the equatorial stratopause show strong longitudinal variations on a planetary scale during both the westerly and easterly phases of the semi‐annual oscillation.
First geodetic measurement of convergence across the Java Trench
Authors: Tregoning P. , Brunner F. K. , Bock Y. , Puntodewo S. S. O. , McCaffrey R. , Genrich J. F. , Calais E. , Rais J. , Subarya C.
Published: February 2004

Convergence across the Java Trench has been estimated for the first time, from annual Global Positioning System (GPS) measurements commencing in 1989. The directions of motion of Christmas and Cocos Islands are within 1° of that predicted by the No‐Net Rotation (NNR) NUVEL‐1 plate motion model for the Australian plate although their rates are 25% and 37% less than predicted, respectively. The motion of West Java differs significantly from the NNR NUVEL‐1 prediction for the Eurasian plate with a 21° difference in direction and a 40% increase in rate. We infer that either West Java moves with a distinct Southeast Asian plate or this region experiences plate margin deformation. The convergence of Christmas Island with respect to West Java is 67±7 mm/yr in a direction N11°E ± 4° which is orthogonal to the trench. The magnitude of convergence agrees with the rescaled NUVEL‐1 relative plate model which predicts a value of 71 mm/yr between Australia and Eurasia. The direction of motion matches the direction inferred from earthquake slip vectors at the trench but may be more northerly than the N20°E±3° predicted by NUVEL‐1. On June 2, 1994, almost a year after the last GPS survey, an Mw=7.5 earthquake with slip vector direction N5°E occurred south of central Java.