bluuebunny/crossref_metadata_2025 huggingface dataset:
A view of the inner heliosphere during the May 10–11, 1999 low density anomaly
Authors: Usmanov Arcadi V. , Goldstein Melvyn L. , Farrell William M.
Published: February 2004

On May 10 and 11, 1999, near‐Earth spacecraft observed the solar wind density drop to below 0.1 particles cm−3. Using those data, we have mapped solar wind parameters back to the Sun from 1 AU using two techniques. The first assumed constant‐velocity trajectories plus corotation, while the second employed MHD‐derived magnetofluid parameters. This inverse tracing creates a view of the inner heliosphere useful for identifying the source location on the Sun of the density anomaly. We compare the two methods and show that the source location of the anomaly predicted by MHD is mapped ∼20° eastward of the constant‐velocity result. The coronal magnetic field maps indicate that the low density event occurred as the polar coronal magnetic field began reversing. We suggest that the event was initiated by a latitudinal excursion of the low velocity heliospheric current sheet toward the helioequator. The emergence of this slow flow into the preexisting faster wind produced strong rarefaction and anomalously low densities.
GEOTAIL observations of anomalously low density plasma in the magnetosheath
Authors: Terasawa T. , Kasaba Y. , Tsubouchi K. , Mukai T. , Saito Y. , Frank L. A. , Paterson W. R. , Ackerson K. , Matsumoto H. , Kojima H. , Matsui H. , Larson D. , Lin R. , Phan T. , Steinberg J. , McComas D. , Skoug R. , Fujimoto M. , Hoshino M. , Nishida A.
Published: February 2004

During the anomalously low density solar wind interval of May 1999, GEOTAIL was in the magnetosheath for ∼37 hours after making an inbound crossing of the expanding bow shock at ∼8 RE upstream of its nominal position. Comparison among data sets obtained from GEOTAIL (magnetosheath), WIND (near upstream‐bow shock), and ACE (far upstream) reveals several unique features: Firstly, during the interval of 1430–1530 UT on 11 May, we observed both in the solar wind and magnetosheath double‐peaked protons with a peak separation of 250–300 km/s, which was close to the local Alfvén velocity during the event. Secondly, we observed extremely strong strahl electrons both in the solar wind and magnetosheath during the interval of 0600–2100 UT on 11 May 1999. We present an overview of the GEOTAIL observations, and discuss their physical significance.
The distention of the magnetosphere on May 11, 1999: High latitude Antarctic observations and comparisons with low latitude magnetic and geopotential data
Authors: Weatherwax A. T. , Rosenberg T. J. , Lanzerotti L. J. , Maclennan C. G. , Frey H. U. , Mende S. B.
Published: February 2004

We examine the Earth's ionospheric response on May 11, 1999, to an unusually tenuous solar wind, focusing on magnetometer, riometer, and optical data from high geomagnetic latitudes in Antarctica. Comparisons are also made with POLAR satellite data during a perigee pass over Antarctica, and with geomagnetic data collected at low latitudes. It is shown that the southern hemisphere was geophysically active, even though the Kp index on May 11 ranged only from 0 to 0+. Furthermore, despite the fact that the IMF and solar wind conditions favored northern hemisphere polar rain, low energy electron precipitation did occur in the southern polar cap. Geomagnetic power levels at low, cusp, and polar cap latitudes were also lower on May 11 than on surrounding days. Although this might be expected, discrete millihertz peaks in ULF power were still evident, especially at cusp latitudes.
Sensing global Birkeland currents with iridium® engineering magnetometer data
Authors: Anderson Brian J. , Takahashi Kazue , Toth Bruce A.
Published: February 2004

The Iridium system consists of >70 satellites in low altitude, 780km, polar orbits in six equally spaced orbit planes with at least eleven satellites in each plane. Each satellite carries an engineering magnetometer with 48nT resolution. Techniques have been developed at JHU/APL to process Iridium magnetic field data and obtain global maps of magnetic perturbations due to field aligned currents (FACs). The noise level in the processed data is typically 70 to 100 nT and readings above the noise level occur at high magnetic latitudes consistent with an auroral signature. Time series also display well known features characteristic of FACs. Synoptic maps derived using three hours of data from 17 February, 2000, AE ∼100–300nT, show patterns consistent with the Region 1/2 currents previously determined statistically. The Indium data set provides new global measurements of the Birkeland currents in both hemispheres on time scales of a few hours or less.
Energetic electrons downstream of Earth's bow shock: Simulations of acceleration by shock structure
Authors: Lowe R. E. , Burgess D.
Published: February 2004

Energetic electrons have been widely observed downstream of the Earth's bow shock, although the exact electron acceleration mechanism is not completely understood. Using a combination of hybrid shock simulation and electron test particles, we show how trapping by two dimensional structure in the form of ripples can cause electrons to be convected downstream with the magnetic field, despite having magnetic moments which suggest that they should be reflected upstream. These electrons undergo considerable Fermi acceleration during this shock transition and may explain the observed energetic downstream populations.
Self‐consistent injection and acceleration of pickup ions at the solar wind termination shock
Authors: le Roux J. A. , Zank G. P. , Fichtner H. , Ptuskin V. S.
Published: February 2004

A unified description of pickup and anomalous cosmic ray proton transport in the near ecliptic regions of the upwind heliosphere is presented. Multiply reflected ion acceleration theory is used for the injection of pickup protons into the diffusive shock acceleration mechanism, so yielding the anomalous cosmic ray component at the quasi‐perpendicular termination shock. The results show that both the multiply reflected and simultaneously accelerated pickup protons and the anomalous protons significantly modify the termination shock. Although the shock mediation lowers the cut‐off speed of the accelerated pickup protons, a sufficient large population of anomalous protons is accelerated at the termination shock to give a favorable comparison of the modulated anomalous proton spectra up‐stream with observations at large heliocentric distances.
Source regions of the slow solar wind in coronal streamers
Authors: Ofman L.
Published: February 2004

Recent SOHO/UVCS observations of the O5+ ion line emission at 1032Å in coronal streamers indicate that the emission is stronger by an order of magnitude at the edges (legs) of streamers than in the central core of streamers. In contrast, the brightness of the Ly‐α emission peaks in the core of streamers. I have developed the first 2.5D, three‐fluid numerical MHD model of the slow solar wind flow in a coronal streamer. Using the model I find that the enhancement of the oxygen line emission occurs due to the enhanced abundances of O5+ ions in the legs of streamer caused by the Coulomb friction with the outflowing protons. Thus, the enhanced O5+ emission traces the source regions of the slow solar wind in coronal streamers. The identification of these regions helps to understand the origins and the composition of the slow solar wind.
Reconciliation of the substorm onset determined on the ground and at the Polar spacecraft
Authors: Toivanen P. K. , Baker D. N. , Peterson W. K. , Singer H. J. , Turner N. E. , Li X. , Kauristie K. , Syrjäsuo M. , Viljanen A. , Pulkkinen T. I. , Keiling A. , Wygant J. R. , Kletzing C. A.
Published: February 2004

An isolated substorm on Oct. 17, 1997 during a close conjunction of the Polar spacecraft and the ground‐based MIRACLE network is studied in detail. We identify signatures of substorm onset in the plasma sheet midway between the ionosphere and the equatorial plasma sheet, determine their timing relative to the ground signatures, and discuss their counterparts on the ground and in the equatorial plasma sheet. The substorm onset is determined as the negative bay onset at 2040:42(±5 sec) UT coinciding with the onset of auroral precipitation, energization of plasma sheet electrons at Polar, and strong magnetic field variations perpendicular to the ambient field. Such accurate timing coincidence is consistent with the Alfvén transit time between Polar and the ionosphere. Furthermore, the timing of other field and particle signatures at Polar showed clear deviations from the onset time (±2 min). This suggests that the sequence of these signatures around the onset time can be used to validate the signatures predicted by various substorm onset models.
Behavior of the aurora during 10–12 May, 1999 when the solar wind nearly disappeared
Authors: Parks G. , Brittnacher M. , Chua D. , Fillingim M. , Germany G. , Spann J.
Published: February 2004

The aurora was still active with occasional pseudobreakup events when the solar wind density diminished to unusually small densities (0.2 cc−1) during May 10–12, 1999. The aurora was observed at high magnetic latitudes indicating that the electron precipitation source moved northward as the geomagnetic activity decreased. The events we have studied indicate that the solar wind density alone is not the primary parameter that controls the auroral activity. The weak auroral activity was observed with 150 nT magnetic bays and when the interplanetary magnetic field (IMF) Bz was small and positive resulting in small ϵ parameter. A new auroral feature was observed on May 11, 1999, between 0900–2000 UT. The electron precipitation was energetic, uniform, and covered the region commonly identified as the polar cap. This precipitation lasted for more than 10 hours and was stable over time scales of tens of minutes. On May 12, as the solar wind began to recover, a prolonged period of dayside activity occurred and was followed by a typical aurora at 0500 UT.
Propagation property of transient MHD impulses in the Magnetosphere‐Ionosphere System: The 2D model of the Pi2 pulsation
Authors: Fujita S. , Mizuta T. , Itonaga M. , Yoshikawa A. , Nakata H.
Published: February 2004

Propagation property of the 2D‐coupled MHD wave induced from an impulsive current is studied by using a magnetospheric model having the dipole magnetic field, the ionosphere with Pedersen conductivity, and a free outer boundary. This study is the first step toward realistic modeling of Pi2 pulsation generated by the current wedge model. Numerical calculation reveals that the ionosphere controls not only damping of the field‐line resonance oscillation but also its frequency. The field‐line resonance oscillation exhibits the fundamental mode structure along the field line in the plasmasphere. In high latitudes, there are waves bouncing between the ionospheres. This suggests that the waveform in the middle‐ and low‐latitudes is different from that in high‐latitudes.
Ion holes in the slow solar wind: Hybrid simulations
Authors: Buti B. , Goldstein B. E. , Liewer P. C.
Published: February 2004

The spatio‐temporal evolution of large‐amplitude Alfvénic wave packets is investigated using a one‐dimensional hybrid model. For conditions prevailing in the slow solar wind plasma, namely β ∼ 1 (β being the ratio of kinetic pressure to magnetic pressure) and electron temperature Te greater than proton temperature Ti, we observe two branches of ion density holes. One is propagating forward and the other backward in the inertial frame of reference. Kinetic effects as well as strong coupling between density and magnetic field fluctuations are responsible for generating these holes. For the first time, we show the possibility of an Alfvénic wave packet decay into a new and unanticipated nonlinear wave mode that does not exist in the current literature. As T(=Ti/Te) increases, the ion holes disappear because of Landau damping. In the slow solar wind the scale sizes of these ion density cavities are ≤ 2sec. We predict the occurence of such cavites in the slow solar wind; these would be observable when high time resolution plasma data become available.
Magnetic field structure at the diamagnetic cavity boundary (Numerical simulations)
Authors: Israelevich P. L. , Gombosi T. I. , Ershkovich A. I. , DeZeeuw D. L. , Powell K. G.
Published: February 2004

A three‐dimensional adaptive grid MHD simulation of the solar wind interaction with comet Halley shows that the boundary of the diamagnetic cavity is a closed, well defined surface. On this surface magnetic field neutral points should exist, and indeed, two O‐type neutral points were found at the cavity boundary. In addition, the transition from closed magnetic field lines around the diamagnetic cavity to open field lines in the comet tail requires the formation of at least one X‐type neutral point. Such a neutral point was also found in the simulated cometary ionosphere downstream from the cavity. The results of numerical simulations show that the plasma density near the neutral points increases significantly. This increase seems to be indicative of plasma escape from the diamagnetic cavity in the neighborhood of the neutral points, resulting in plasma jets.
Terrestrial magnetosphere as a nonlinear resonator
Authors: Balikhin M. A. , Boaghe O. M. , Billings S. A. , Alleyne H. St C. K.
Published: February 2004

Time domain techniques are used to identify a dynamical model for the evolution of the Dst index under the influence of the solar wind. Frequency domain analysis of this model is used to study spectral properties of the Dst index dynamics. These properties indicate that the dynamics of the Dst index is similar to that of a linear oscillator under the action of an external force. This dynamical system should possess two main properties. Firstly the external driving force should be a nonlinear function of the solar wind parameter VBs and secondly the eigen frequency of the oscillator should be very low in comparison to the temporal characteristics of external force variations. The main process of energy loading in such systems involves nonlinear coupling between different spectral components of the external force with a transfer of their energy to the main resonant frequency.
Initial comparisons of planetary waves in the stratosphere, mesosphere and ionosphere over Antarctica
Authors: Lawrence A. R. , Jarvis M. J.
Published: February 2004

Planetary wave signatures, with periods of approximately 16, 10 and 5 days have been observed at altitudes ranging from 30 km to 220 km over Halley (76°S, 26°W), Antarctica. A comparative analysis of these signatures in the stratosphere, mesosphere and ionosphere has been conducted on a continuous 130‐day data sequence in the austral winter of 1997. This analysis utilises stratospheric European Centre for Medium‐Range Weather Forecasts (ECMWF) operational analyses, mesospheric Imaging Doppler Interferometer (IDI) data and ionospheric sounding data. The development and decay of these planetary waves were characterised as a function of altitude by selecting period ranges corresponding to each of the 16‐day, 10‐day and 5‐day normal mode oscillations from a wavelet analysis. The observations suggest ducting of the quasi 16‐day planetary wave from stratospheric mid‐latitudes to mesospheric high‐latitudes and a strong link between planetary waves in the mesosphere and F2‐region.
A generation mechanism for topside enhanced incoherent backscatter during high frequency modification experiments in Tromsø
Authors: Mishin E. , Hagfors T. , Isham B.
Published: February 2004

Enhanced plasma and ion oscillations on the topside of the ionosphere have been observed during high frequency (HF) ionospheric modification experiments at Tromsø. The topside enhancements occurred when the critical frequency of the F layer was below that of the Z mode reflection. Thus, one can consider Z mode waves as a plausible candidate to produce the enhancements. However, the topside echoes were observed over an angular range of many degrees, apparently not compatible with the prediction of the standard theory of a very narrow coupling window located at the Spitze angle. We propose resonant scatter of the HF pump wave into Z mode waves on small‐scale field‐aligned irregularities to be the cause of the broadening. The irregularities are generated by the HF wave, likely via the resonant instability.
Pc 1 waves and ionospheric Alfvén resonator: Generation or filtration?
Authors: Demekhov A. G. , Trakhtengerts V. Yu. , Bösinger T.
Published: February 2004

We analyze vertical profiles of Pc 1 wave fields produced in the ionosphere by Alfvén waves of magnetospheric origin. We show that the ratio of the electric and magnetic fields varies strongly with frequency due to the influence of the ionospheric Alfvén resonator. The difference is most remarkable for frequencies corresponding to either maximum or minimum ionospheric reflection. Therefore, low‐orbiting satellites detecting Pc 1 emissions in the ionosphere (at the same field line as their magnetospheric source) can provide valuable information regarding the question whether these waves are generated at conditions of maximum or minimum ionospheric reflection and whether this reflection influences significantly their generation in the magnetosphere. Comparison of our theoretical result with recent statistical analysis of Pc 1 pearls recorded onboard DE 2 suggests that these waves correspond to the maximum reflection. This implies that ionospheric reflection played a significant role in formation of these emissions.
Large Alfvén wave power in the plasma sheet boundary layer during the expansion phase of substorms
Authors: Keiling A. , Wygant J. R. , Cattell C. , Temerin M. , Mozer F. S. , Kletzing C. A. , Scudder J. , Russell C. T. , Lotko W. , Streltsov A. V.
Published: February 2004

Observations by the Polar satellite of large Poynting flux in the plasma sheet boundary layer at geocentric distances of 4 to 6 RE and between 22 and 3 hrs magnetic local time were correlated with H‐bay signatures from ground magnetometer records. We provide evidence that large Poynting fluxes occur during the substorm expansion phase. The Poynting fluxes exceeded 1 ergs/cm²s (125 ergs/cm²s when mapped to 100 km), were dominantly directed toward the ionosphere, and were associated with Alfvén waves. These observations demonstrate the importance of Alfvén wave power as a means of energy transport from the distant magnetotail to the ionosphere during the most dynamic phase of substorms.
An injection mechanism for shock waves of arbitrary obliquity
Authors: Rice W. K. M. , Zank G. P. , le Roux J. A.
Published: February 2004

Evidence exists suggesting that not only do heliospheric shocks accelerate particles up to energies as high as a few GeV/nuc. but that the source of these energetic particles are pickup ions or low energy particles present in the suprathermal tail of the solar wind distribution. To be diffusively accelerated at a shock wave a particle needs an energy significantly greater than that of the expected source particles, the so‐called “injection problem”. We present here a model of particle acceleration at shocks of arbitrary obliquity that produces particle energies sufficiently high for diffusive shock acceleration to occur.
The global 11‐year solar signal in July–August
Authors: van Loon Harry , Shea Dennis J.
Published: February 2004

During the past 41 years there has been an observable effect of the 11‐year solar cycle on the temperatures and heights in the levels between the middle troposphere and 10 hPa (the highest level in the data) in July–August. Between 30°S and the North Pole the temperatures and heights were higher at peaks than in valleys of the solar cycle, between 30°S and 70°S they were lower in the peaks, and above Antarctica they were higher. This meridional pattern of differences and the fact that they decrease with decreasing elevation suggest that the solar signal observed below 10 hPa is imposed from above as an indirect, dynamic effect. The pattern of the temperature and height differences indicates that the solar cycle affects the southern winter and northern summer stratospheric vortices. At the earth's surface an 11‐year solar signal is not obvious in the zonally averaged temperatures and pressures in July–August.
Three‐dimensional structure of electron holes driven by an electron beam
Authors: Singh Nagendra , Loo S. M. , Wells B. Earl , Deverapalli C.
Published: February 2004

Using 3‐D particle‐in‐cell (PIC) simulations we studied the structure and temporal behavior of electron holes (e‐holes) in a magnetized plasma driven by an electron beam. When e‐holes are fully evolved from high‐frequency waves in a time of about a few tens of electron plasma periods, most of the wave energy in the plasma resides in them. Parallel to the ambient magnetic field Bo, the potential distribution of an e‐hole is approximately a Gaussian, and the scalelength ℓz is only a few Debye lengths when determined by the effective temperature of the beam‐modified electron distribution function. Transverse to Bo, the potential distribution tends to have a flat top, which makes it difficult to fit a Gaussian distribution, but the scalelengths at which the potential decays in the transverse directions (ℓx and ℓz) are found to be only slightly longer than ℓz. The passages of electron holes monitored at several points in the simulation volume has the signature of bipolar parallel electric field and unipolar perpendicular electric‐field pulses as measured from FAST and POLAR. The eventual decay of e‐holes is accompanied by the generation of lower hybrid (ℓh) waves.
Suprathermal electrons generated by the interaction of powerful radio wave with the ionosphere
Authors: Gurevich A. V. , Carlson H. C. , Milikh G. M. , Zybin K. P. , Djuth F. T. , Groves K.
Published: February 2004

We present two sets of observations of suprathermal electrons, produced by the interaction of powerful radio wave with the ionosphere, as seen using the incoherent scatter radar (ISR) technique. The observational data are compared with the theory of multiple acceleration of electrons in the strongly excited resonance region near the reflection point of the powerful radio wave. The structure of the wide perturbed region filled with energetic (10–20) eV electrons is determined. The size of this region along the Earth magnetic field is shown to be 100 km. The full power going to the accelerated particles is determined: it is 6–8 kW or (4–6)% of the entire HF radiated power. The power carried by the suprathermal electrons flux escaping into magnetosphere is of the order l kW.
Diurnal harmonics in schumann resonance parameters observed on both hemispheres
Authors: Schlegel K. , Füllekrug M.
Published: February 2004

Diurnal harmonics of Schumann resonance parameters have been studied for the first time using data obtained at two sites on opposite hemispheres, Antarctica and Greenland. Signatures of a 24‐h, a 12‐h, and a 8‐h harmonic are clearly discernible in both data sets, but with different strength. The amplitude of the harmonics changes with season as well. The data can partly be explained on the basis of current understanding of Schumann resonances. Their properties are determined by the global lightning activity and by the condition of the upper boundary of the Earth‐ionosphere wave guide. Since atmospheric tides are very important for the dynamics of the D region/mesosphere, some of the results may be explained in terms of these waves.
Interplanetary rotational discontinuities: From the solar wind to the magnetosphere through the magnetosheath
Authors: Hubert D. , Harvey C. C.
Published: February 2004

For the first time the evolution of interplanetary rotational discontinuities (RDs) are observed in the solar wind, in the magnetosheath and in the dayside magnetosphere by the ISEE 1‐2‐3 spacecraft. Interaction of a RD with the bow shock builds up a transient density event (TDE) in the magnetosheath, displaying two density peaks anticorrelated to the magnetic field modulus. TDEs are convected from the bow shock to the dayside magnetopause without spreading. The duration of a TDE is around 15 s and two close TDEs can merge in a single structure. The density in a TDE exceeds the surrounding level by a factor of about 35%, while the field modulus can decrease by a large amount. The interaction of a TDE with the magnetopause is analyzed in terms of impulsive penetration process. The element of plasma injected in the magnetosphere is filamentary, its signature is different from the signature of a flux transfer event or a surface wave.
Seek S310‐25: Quasi‐periodic echoes and polarization electric fields
Authors: Tsunoda Roland T. , Yamamoto Mamoru , Mori Hirotaka , Fukao Shoichiro
Published: February 2004

We have reexamined data collected during the flight of the SEEK S310‐25 sounding rocket, together with a second set of radar measurements, to determine whether a more consistent interpretation could be derived, if we allowed for the possibility that sporadic E (Es) was configured as a sequence of elongated strips in the form of a frontal structure. We show that the features found in the plasma density, electric field ( ) and the so‐called quasi‐periodic (QP) echoes are consistent with a polarization process acting on the Es strips that is driven by a Hall and not a Pedersen current. Specifically, we show that three large
spikes, measured in situ, appeared at intervals of ground distance that were nearly identical to those of the QP echoes. The vector relationship between the spikes and the background was also consistent with this type of polarization process. We also briefly discuss a counterclockwise rotation of
, which could be related with a process responsible for the existence of frontal structures.
Electron beam generated solitary structures in a nonuniform plasma system
Authors: Mandrake L. , Pritchett P. L. , Coroniti F. V.
Published: February 2004

Recent observations by the FAST satellite have identified numerous occurrences in the downward auroral current region of fast solitary structures with a characteristic size of a few local Debye lengths. We utilize a 2.5D electrostatic particle‐in‐cell code to investigate the generation of such structures by the interaction of narrow energetic electron beams with a gravitationally‐bound exponential atmosphere. Cold, narrow electron beams are injected from both the high‐altitude and low‐altitude edges of the simulation domain. Both upward and downward‐going beams experience a strong beam‐plasma instability yielding net positive potential structures. These structures, seen to be holes in electron phase space, then accelerate or decelerate along the density gradient. For the up‐going beams, the potential structures escape from the initial region of intense interaction, after which they propagate surprisingly far. The down‐going structures accelerate but become degraded and break up due to the finer scales present in the increased density region. The gradient‐dependent acceleration therefore selects upward‐going structures as likely to be more robust in the auroral region.
Dawn‐dusk profile of field‐aligned currents on May 11, 1999: A Familiar pattern driven by an unusual cause
Authors: Ohtani S. , Newell P. T. , Takahashi K.
Published: February 2004

On May 11, 1999, when the solar wind almost disappeared, the DMSP‐F13 satellite observed two field‐aligned current (FAC) sheets on both dawn and dusk sides. The dawnside FACs are identified as conventional region 1 (R1) and region 2 (R2) currents. The duskside FACs are collocated with intense polar‐rain precipitation and are identified as midday region 1 and region 0 currents. Whereas the positive IMF BY observed explains the duskward shift/extension of those midday current systems, the extent of the distortion was unusual. It is inferred that the magnetospheric configuration was more axisymmetrical because of extremely low solar‐wind dynamic pressure, and therefore the reconnection took place farther away from the midday sector. Conventional R1 and R2 currents as well as boundary layer‐type precipitation were nearly absent at dusk, suggesting that the viscous interaction did not operate at least observably on the dusk side in the present event.
Interrelation between ELF transients and ionospheric disturbances in association with sprites and elves
Authors: Hobara Yasuhide , Iwasaki N. , Hayashida T. , Hayakawa M. , Ohta K. , Fukunishi H.
Published: February 2004

Red sprites and elves were observed in Japan during the winter of 1998/99 in Hokuriku region by the group of Tohoku Univ. [Fukunishi et al., EOS, 80(46), F217, 1999]. We analyze quantitatively the results from coordinated measurement consisting of ELF transients, VLF subionopheric disturbances and lightning discharges associated with the optical events. We find the clear straightforward relationship between charge transfer of the parent discharge calculated from ELF (f < 15 Hz) and the ionospheric disturbances regardless of the types of optical events indicating significant atmosphere‐mesosphere‐ionosphere coupling. Sprites tend to associate with a large ionospheric disturbance (−13 ∼ + 4.6 dB) with a large charge transfer (52 ∼ 175 C), whereas a large lightning peak current (+223 ∼ + 470 kA) (or slow‐tail amplitude) leading to the strong EMP is necessary to initiate elves, but with rather small ionospheric disturbances.
Energetic trapped electron measurements from the Galileo Jupiter probe
Authors: Mihalov J. D. , Fischer H. M. , Pehlke E. , Lanzerotti L. J.
Published: February 2004

Energetic trapped electrons were measured with the Energetic Particle Instrument (EPI) on the Galileo Jupiter Probe. Samples were taken from inside Io's orbit to just above Jupiter's atmosphere. Under the assumption of simple power law spectra the energetic electron fluxes and spectra agree well with earlier results from the Pioneer spacecraft, at those locations where comparisons can be made. New features from this Galileo data include measurements of the inner boundary of the trappped particles, inside 1.6 RJ, direct observations of the electron pitch angle distributions, and energy spectral softening, both as the atmosphere is approached, and at smaller pitch angles at each measurement location.
parallel electric fields in discrete arcs
Authors: Ergun R. E. , Carlson C. W. , McFadden J. P. , Mozer F. S. , Strangeway R. J.
Published: February 2004

We present a large‐scale model of the parallel electric fields in the upward current region of the aurora. The model, called the “Transition Layer Model”, applies to intense, discrete arcs. It is based on 1‐D spatial, 2‐D velocity static Vlasov simulations and observations from the Fast Auroral Snapshot (FAST) satellite. The model depicts three regions along the magnetic field that are separated by two transition layers which contain parallel electric fields. The current‐voltage properties closely follow the Knight relation.
MU Radar observations of kilometer‐scale waves in the midlatitude lower E‐region
Authors: Rao P. B. , Yamamoto M. , Uchida A. , Hassenpflug I. , Fukao S.
Published: February 2004

The multi‐beam high resolution MU radar experiments, conducted in February 2000, revealed for the first time kilometer‐scale waves in the lower E‐region over Shigaraki, Japan. The waves, occurring over a narrow height range of 92‐97 km, have vertical wavelengths of 0.6 to 1.2 km and periods of 30 to 90 s. The signal intensities associated with these waves, with signal‐to‐noise ratio values less than ∼5 dB, are lower by about 20 dB compared to that of the quasi‐periodic echoes occurring at higher heights. The echoes occur with both negative and positive range rates, changing systematically from one to the other with values of about −25 m s−1and 20 m s−1, respectively. The Doppler velocities, ranging −50 to 25 m s−1, are generally of the same sense as range rates, but somewhat greater in magnitude. The periodicity and wavelength of the waves seem to resemble those revealed in the equatorial electrojet by the high resolution Jicamarca radar observations and also by the nonlocal nonlinear simulations of the gradient‐drift instability. Behavior of the Doppler velocities, however, is found to be different from that reported for the kilometer‐scale waves in the equatorial region.
Io's ultraviolet aurora: Remote sensing of Io's interaction
Authors: Saur Joachim , Neubauer Fritz M. , Strobel Darrell F. , Summers Michael E.
Published: February 2004

With the recent observations of Io's very striking equatorial aurora by Roesler et al. [1999], it is now possible to remotely sense Io's local interaction with the Io plasma torus. Here we present an explanation for the formation of Io's aurora which implies that Io's electron flow is strongly rotated and shielded around Io. The Hall effect close to Io breaks the interaction symmetry to produce a brighter anti‐Jovian radiation spot, and it also results in rotated Alfvén wings. Observations of Io's aurora also impose new constraints on Io's atmosphere. We find, among other things, an atomic oxygen to sulfur dioxide ratio of ∼20%.
Eight‐year climatology of nocturnal temperature and sodium density in the mesopause region (80 to 105 km) over Fort Collins, Co (41°N, 105°W)
Authors: She C. Y. , Chen Songsheng , Hu Zhilin , Sherman James , Vance J. D. , Vasoli Vince , White M. A. , Yu Jirong , Krueger David A.
Published: February 2004

Based on 417 nights of lidar observation between 1990 and 1999 at Fort Collins, CO (41°N, 105°W), we tabulate an eight‐year composite of monthly mean temperatures and Na densities in the mesopause region, and plot the associated altitude/month contours. The maximum and minimum mean mesopause temperatures were 192 K at 101 km and 178 K at 85.5 km on the 294th and 164th days of the year, respectively. The maximum and minimum monthly mean layer temperatures between 83 and 105 km were 205.8 K and 188.8 K, respectively, in November and July. When the episodic warming that peaked in 1993 is removed, the mean temperatures are typically lowered by ∼4 K. Climatology supports a two‐level thermal structure with mesopause occurring at higher altitudes in winter and lower altitudes in summer, and sharp transitions between them taking place in May and August. The maximum and minimum mean peak sodium densities were 4.88 × 109 m−3 at 91 km and 1.49 × 109 m−3 at 90 km on the 310th and 163rd days of the year, respectively.
Causes of global temperature changes during the 19th and 20th centuries
Authors: Andronova Natalia G. , Schlesinger Michael E.
Published: February 2004

During the past two decades there has been considerable discussion about the relative contribution of different factors to the temperature changes observed now over the past 142 years. Among these factors are the “external’ factors of human (anthropogenic) activity, volcanoes and putative variations in the irradiance of the sun, and the “internal” factor of natural variability. Here, by using a simple climate/ocean model to simulate the observed temperature changes for different state‐of‐the‐art radiative‐forcing models, we present strong evidence that while the anthropogenic effect has steadily increased in size during the entire 20th century such that it presently is the dominant external forcing of the climate system, there is a residual factor at work within the climate system, whether a natural oscillation or something else as yet unknown. This has an important implication for our expectation of future temperature changes.
Presence of the Solar de Vries Cycle (∼205 years) during the Last Ice Age
Authors: Wagner Gerhard , Beer Jürg , Masarik Jozef , Muscheler Raimund , Kubik Peter W. , Mende Werner , Laj Carlo , Raisbeck Grant M. , Yiou Francoise
Published: February 2004

Certain characteristic periodicities in the Δ14C record from tree rings, such as the well‐known 11‐yr Schwabe cycle, are known to be of solar origin. The origin of longer‐period cycles, such as the 205‐yr de Vries cycle, in the Δ14C record was less certain, and it was possible to attribute it either to solar or climatic variability. Here, we demonstrate that the de Vries cycle is present in 10Be data from the GRIP ice core during the last ice age (25 to 50 kyr BP). Analysis of the amplitude of variation of this cycle shows it to be modulated by the geomagnetic field, indicating that the de Vries cycle is indeed of solar, rather than climatic, origin.
Global ocean mass variation, continental hydrology and the mass balance of Antarctica Ice Sheet at seasonal time scale
Authors: Cazenave A. , Remy F. , Dominh K. , Douville H.
Published: February 2004

We attempt to quantify the Antarctica annual mass balance by estimating the seasonal water mass exchange among the main surface reservoirs (oceans, atmosphere, continents and ice sheets) using various data sources. These data include Topex‐Poseidon altimetry and in situ ocean temperature data, soil moisture and snow depth data, and atmospheric surface pressure data. We calculate the seasonal (annual) variations of ocean water mass, continental waters and atmospheric water vapor contributions respectively. We find that the observed ∼9 mm annual mean sea level variation caused by water mass exchange with the other reservoirs cannot be totally explained by the combined contributions of snow, soil moisture and atmospheric water vapor. A residual signal, of 3 mm amplitude, maximum at the end of December, is observed that we attribute to the Antarctica annual mass balance. This residue is consistent with existing understanding of Antarctica precipitation.
In situ ion microprobe U‐Pb dating and REE abundances of a carboniferous conodont
Authors: Sano Yuji , Terada Kentaro
Published: February 2004

We report here in situ ion microprobe U‐Pb dating of a conodont micro‐fossil using an ion microprobe method. Thirteen spots on the single fragment of the Carboniferous conodont (size: approximately 800 µm × 100 µm) yield a 238U/206Pb isochron age of 323±36 Ma and a Tera‐Wasserburg concordia intercept age of 332±44 Ma in a three‐dimensional 238U/206Pb‐207Pb/206 Pb‐204Pb/206Pb diagram. These ages are consistent with the depositional and early diagenetic ages of the fossil in its host Mississippian sedimentary sequence within experimental error. The success of the method depends on the chemical fractionation of U from Pb within a hundred‐µm length scale and the consequent variations in Pb isotopic compositions due to radioactive decay. Shale‐normalized rare earth element (REE) abundances of two spots on the same sample show flat patterns from light REE to middle REE and decreases from middle REE to heavy REE with negative anomalies of both Ce and Eu. The REE characteristics are significantly different from those of Devonian conodonts reported by other workers, suggesting discrepant redox states and/or formation environments.
A model of decadal ocean‐atmosphere interaction in the North Pacific Basin
Authors: Jin Fei‐Fei , Kimoto Masahide , Wang Xiaochun
Published: February 2004

From a simple and a global coupled model, we showed that the tropical and extratropical ocean‐atmosphere interactions and the teleconnection between the tropics and extratropics in these interactions are responsible for the co‐variations of the decadal to interdecadal climate fluctuations in the tropical and extratropical Pacific. The subtropical oceanic Rossby waves are found to play an important role in forming the coupled decadal to interdecadal mode. They are responsible for slow exchanges of mass and heat between the tropical and subtropical ocean gyres that serve as an important oceanic linking bridge of the tropical and extratropical decadal to interdecadal ocean‐atmosphere interactions in the Pacific basin.
A stratigraphic link across 1100 km of the Antarctic Ice sheet between the Vostok ice‐core site and Titan Dome (near South Pole)
Authors: Siegert Martin J. , Hodgkins Richard
Published: February 2004

Isochronous internal ice‐sheet layering, measured from airborne 60 MHz radar, was traced between Lake Vostok and the Titan Ice Dome (100 km from South Pole Station), Antarctica. Three layers were selected between Ridge B and Titan Dome, and between Ridge B and Lake Vostok. This layering can be used to correlate the existing Vostok ice core across 1100 km of the ice sheet interior. Our correlation is also matched to the new EPICA ice‐core site, by using an existing radar link between Vostok and Dome C stations. Thus, three East Antarctic ice domes are linked stratigraphically for the first time through internal ice‐sheet radar layering. Our results indicate that the basal layers of ice at Titan Dome are around 165,000 years old suggesting that this location and, by inference, the South Pole Station, are prime sites for a high‐resolution ice core from the last glacial‐interglacial cycle.
Energy balance at the Earth's surface: Heat flux history in eastern Canada
Authors: Beltrami Hugo , Wang Jingfeng , Bras Rafael L.
Published: February 2004

The heat exchange at the air/ground interface is determined by many complex processes making the energy balance at the earth's surface extremely difficult to quantify and model. A new methodology allows heat flux at the Earth's surface to be estimated using ground surface temperature history reconstructed from geothermal data. We found that over a large region in eastern and central Canada, the average heat flux into the ground during the last 1000 years was on the order of 2.8 mWm−2. Our results suggest that significant change in the ground heat flux occurred in the last two centuries. The 200 years averaged heat flux since 1765 is 17.0 mWm−2, while the average heat flux over the latest 100 years is 74.0 mWm−2. The sensitivity of the subsurface to very small energy imbalances makes these type of data and analysis useful complements to the paleoclimatic record; they also provide constrains for general circulation model land‐surface parameterization over a wide range of spatial‐temporal scales.
Using MOMA Broadband Array ScS‐S data to image smaller‐scale structures at the base of the mantle
Authors: Wysession M. E. , Fischer K. M. , Al‐eqabi G. I. , Shore P. J. , Gurari I.
Published: February 2004

ScS‐S residuals obtained at stations of the Missouri‐to‐Massachusetts (MOMA) temporary broadband seismic array are used to delineate variations in seismic velocity structure above the core‐mantle boundary (CMB) at scales smaller than observable with tomographic models. South American earthquakes recorded at MOMA reveal a slow‐velocity anomaly that is at least as small as the limit of the resolution of ScS waves, about 300 km across. This is modeled as being within a region of fast velocities in whole‐mantle models. The slow ScS‐S residuals correlate well with a peak in ScS/S relative amplitudes. The small region of slow shear velocity at the CMB could be a pocket of lower mantle rock trapped beneath the descending Farallon slab, or evidence of chemical boundary layer variations.
Detection of ground subsidence in the city of Paris using radar interferometry: Isolation of deformation from atmospheric artifacts using correlation
Authors: Fruneau Bénédicte , Sarti Francesco
Published: February 2004

This paper presents a new method for the isolation of displacement from atmospheric fringes. This novel approach is based on complex correlation of interferograms. Compared to other methods, this method has the advantage of requiring only a few interferograms (two at least). Its main limitation is the hypothesis of temporally varying atmospheric conditions between acquisitions (not the same heterogeneities on different interferograms). In the city of Paris, this method reveals 2 subsiding zones. Both have the same location as an important underground working site, which took place from 1995 to 1997. The existence of subsidence in the area was known previously from ground truth data. Their spatial extent can now be mapped by interferometry, and the temporal evolution of the subsidence is also examined here.
High‐pressure phase transformation of corundum (α‐Al2O3) observed under shock compression
Authors: Mashimo T. , Tsumoto K. , Nakamura K. , Noguchi Y. , Fukuoka K. , Syono Y.
Published: February 2004

A discontinuous volume change was observed on the Hugoniot curve of corundum (α‐Al2O3) along the  axis by the inclined‐mirror streak photographic technique, probably due to a high‐pressure phase transformation. The transition pressure was measured to be 79 GPa, where shock temparature was estimated to be 860°C, in good agreement with a fully optimized quantum mechanical calculation. The volume change at the transition point was considered to be larger than 3%, which was larger than the theoretically predicted value of the corundum‐Rh2O3 (II) transition, and was consistent with the recent static compression result by using diamond‐anvil cell. The occurence of the phase transformation in alumina under shock compression presents significant implication in earth interior science or ceramic science, and also seriously affects the interpretation of static and shock compresion experiments at ultra‐high pressures.
Topographic analysis of features related to ice on Mars
Authors: Mangold N. , Allemand P.
Published: February 2004

This study analyses the new topographic data from Mars Global Surveyor (MGS) through the lobate debris aprons of Mars. These features are usually interpreted as due to the creep of ground ice. The comparison between measured topographic profiles and profiles calculated from rheological laws demonstrates that these features are due to the solid state deformation of ice. The high volume of such debris aprons can not be explained by rock fall but only by landslides. The ice involved in the flow may then come from the subsurface confirming the presence of large amount of ground ice.
Silicon diffusion in forsterite aggregates: Implications for diffusion accommodated creep
Authors: Farver John R. , Yund Richard A.
Published: February 2004

Silicon diffusion rates were determined in fine‐grained (∼4.5 µm) hot‐pressed forsterite aggregates at 900° to 1200°C and 0.1 MPa using a 30Si‐tracer and standard SIMS analysis. There is no measurable difference in diffusion rates between samples buffered by excess MgO or SiO2, nor samples run in dry N2 or H2/CO2. The results yield the Arrhenius parameters D0, bulk = 5.4 × 10−9 m²/sec and Q = 203±36 kJ/mol. At 1200°C, the grain boundary diffusion rate of 30Si is similar to 26Mg (Si ∼10 times greater), ∼10² less than Fe, and ∼105 less than O. In addition, the 30Si grain boundary diffusion rate is ∼109 greater than the Si volume diffusion rate and indicates that diffusional transport of Si in forsterite aggregates is dominated by grain boundaries.
Thermal tracking of upper crustal fluid flow in the Rhine graben
Authors: Pribnow Daniel , Schellschmidt Rüdiger
Published: February 2004

More than 52,000 temperature values from almost 10,000 boreholes in Germany have been incorporated into a data base since 1977. Due to petroleum‐oriented drilling, a large quantitity of temperature data (both German and French) is available for the Rhine Graben. A horizontal temperature contour map for 800 m depth and a vertical cross section support the concept that thermal anomalies in the Rhine Graben are caused by convection in the upper crust. At the local scale of a borehole, large changes of the temperature gradient to depths of 5 km can roughly be related to different hydraulic conditions of the formations. A better means to qualitatively characterize the convective regime, however, is the observed thermal equilibration in a well after drilling disturbances. The data base is well suitable for an application of temperature as a tracer for fluid flow.