bluuebunny/crossref_metadata_2025 huggingface dataset:
Sind selbst- und fremdbezogene Kausalüberzeugungen austauschbar?
Authors: Buff Alex
Published: January 2004

Zusammenfassung. Skinner, Chapman und Baltes (1988) machen darauf aufmerksam, dass in selbstbezogenen Überzeugungen hinsichtlich Ursache-Wirkungs-Zusammenhängen Kausal- und Kapazitätsüberzeugungen vermischt sein können. Um diese Konfundierung zu vermeiden, ersetzen sie in ihrem Modell wahrgenommener Kontrolle selbstbezogene Kausalüberzeugungen durch solche allgemeiner Art. Die vorliegende Studie beschäftigt sich mit der Frage der Äquivalenz der beiden Formen. Verglichen werden selbst- und fremdbezogene Kausalüberzeugungen für gute und schlechte Mathematiknoten von Schülerinnen und Schülern der 8. Klassenstufe. In verschiedener Hinsicht ergeben sich Hinweise auf substanzielle Unterschiede. U.a. sind Korrelationen thematisch gleicher Facetten und unterschiedlicher Referenz in den meisten Fällen relativ gering, Mittelwertsunterschiede eher die Regel als die Ausnahme, und selbstbezogene Kausalüberzeugungen erweisen sich auch als deutlich bessere Prädiktoren hinsichtlich des Kriteriums Kontrollüberzeugung als fremdbezogene. Die Ergebnisse legen den Schluss nahe, dass das globale Ersetzen von selbst- durch fremdbezogene Kausalüberzeugungen eher kritisch betrachtet werden muss.
Fördert Gruppendiskussion die Perspektiven-Koordination?
Authors: Mischo Christoph
Published: January 2004

Zusammenfassung. Eine entscheidende Bedingung für sozial kompetentes Handeln sind die beteiligten sozialen Kognitionen. Diese werden im Rahmen des Ansatzes interpersonaler Aushandlungs-Strategien von Selman hinsichtlich des Niveaus der Perspektiven-Koordination und hinsichtlich der Schritte der Informationsverarbeitung spezifiziert. Zur Förderung der Perspektiven-Koordination wird in dieser Studie die in der Moralförderung bewährte Methode der Dilemma-Diskussion eingesetzt. In einem Prä-Post Kontrollgruppen-Design wird der Frage nachgegangen, ob die Diskussion über soziale Dilemmata zwischen Gleichaltrigen (6. und 7. Klasse) zu einer höheren Stufe der Perspektive-Koordination führt als die ausschließlich individuelle Bearbeitung dieser Dilemmata. Unabhängig von der Intelligenz führt die kooperative Bearbeitung gegenüber der individuellen Bearbeitung der Konfliktepisoden zu einer höheren Perspektiven-Übernahme hinsichtlich zwei der insgesamt vier Schritte der Informationsverarbeitung. Zusammenhänge zwischen Fremdbeurteilung des Sozialverhaltens und der Stufe der Perspektiven-Koordination bestehen zum ersten Messzeitpunkt bei drei der vier Informationsverarbeitungs-Schritte. Abschließend werden weitere Forschungsfragen und Anwendungsperspektiven diskutiert.
Nuclear reactions in the uppermost Earth atmosphere as a source of the magnetospheric positron radiation belt
Authors: Gusev A. A. , Jayanthi U. B. , Martin I. M. , Pugacheva G. I. , Spjeldvik W. N.
Published: January 2004

A physical mechanism for the formation of a natural positron belt in the Earth's magnetosphere is considered. It is assumed that a natural source of energetic positrons as well as electrons can be created owing to the decay of charged pions π± → μ± → e±, which have their origin in nuclear collisions between energetic trapped inner zone protons and heavier atoms (He and O) in the upper atmosphere of the Earth. Simulations of these processes demonstrate that there is a predominant production of positive pions over negative pions, and consequently the decays result in a substantial excess of positrons over electrons at energies greater than tens of MeV. This positron excess is found to be energy‐dependent and to decrease with increasing incident proton energy; this excess is essentially absent at proton energies corresponding to cosmic ray primaries of ≥8 GeV. Our numerical computations for the resulting e+/e− fluxes provide ratio values of ∼4 at multi‐MeV energies and at L = 1.2 ± 0.1. The simulation results presented herein are compared to the existing and recent experimental evidence.
Electric conductivity and electric field in the stratosphere: Middle‐latitude balloon flight results
Authors: Curto J. J. , Alberca L. F. , Holzworth R. H. , de la Morena B. , Batlló J. , Solé J. G. , Altadill D.
Published: January 2004

Electric field and conductivity measurements were obtained for two high‐altitude balloon flights between Italy and Spain in 1989 and 1990. The high altitudes of these flights, 35 and 38 km, allowed us an opportunity to explore the electrical parameters of the upper stratosphere at midlatitudes and to extend the validity of earlier models to nearly 40 km. These new electric field and conductivity data are compared to similar data collected by many other groups. Our data are shown to be best represented by an extrapolation of the empirical model of Holzworth [1991] and therefore can be seen as extending the region of validity for his model from its upper altitude of 28 km by an additional 10 km to 38 km altitude. The possible influence of photoelectric emissions in the results is also discussed.
A test of real‐time prediction of magnetic cloud topology and geomagnetic storm occurrence from solar signatures
Authors: McAllister A. H. , Martin S. F. , Crooker N. U. , Lepping R. P. , Fitzenreiter R. J.
Published: January 2004

On the basis of the location, orientation, and surrounding magnetic field configuration of an erupting filament observed on September 27, 1997, an Earth‐encounter with a magnetic cloud having specific topological properties and an ensuing geomagnetic storm were predicted for September 30, assuming an average Sun‐Earth transit time. A subsequent comparison with solar wind and geomagnetic data surrounding September 30 yielded a mixed level of success. Although a geomagnetic storm occurred on October 1, ironically, the strong southward magnetic field responsible for it was not encountered at the leading edge of the cloud, as predicted, but rather in the preceding sheath. In retrospect, the most likely sources of the southward field in the sheath were either a preceding CME or magnetic flux from high in the corona, not draped or turbulent flux from the ambient solar wind as is often supposed. With the aid of a flux rope model, we show that the elevation and polarity of the cloud axis and the chirality of the cloud were predicted correctly but that the trajectory of the spacecraft (and Earth) through what was deduced to be the leg of a flux rope loop precluded encounter with its leading southward field. The storm began with a sudden commencement near 0100 UT on October 1, corresponding to passage of a shock‐like discontinuity, and the Dst storm index reached a minimum of −108 nT 14 hours later at 1500 UT. The leading edge of the cloud, however, coincident with the onset of counterstreaming electrons confirming its identification, was not encountered until 1700 UT. The disagreement between the predicted and actual arrival time reflects not only the lack of speed prediction capabilities but also the inability to predict whether encounter will be head‐on with the apex of a flux rope loop or, as deduced in this case, passage through one of its legs.
Global hybrid simulation of the dayside reconnection layer and associated field‐aligned currents
Authors: Lin Y.
Published: January 2004

A two‐dimensional global hybrid simulation is carried out to study the structure of the magnetopause boundary layer in the noon‐midnight meridian plane associated with the dayside reconnection. In the simulation the bow shock, magnetosheath, and magnetopause are formed self‐consistently by supersonic solar wind passing the geomagnetic field. The dayside reconnection is triggered by imposing a current‐dependent resistivity at the subsolar magnetopause. A large‐amplitude rotational discontinuity is formed in the quasi‐steady reconnection layer in the northern and southern hemispheres. The rotational discontinuity possesses an electron sense, or right‐hand polarization in the magnetic field as the discontinuity is formed from the X line, and the magnetic structures in the magnetopause northward and southward of the X line are asymmetric in the cases with a nonzero By component of the interplanetary magnetic field (IMF). However, later the rotational discontinuity tends to evolve to a structure with a smallest field rotational angle and thus may reverse its sense of the field rotation. The Walen relation is tested for electron and ion flows in the magnetopause rotational discontinuities with left‐hand and right‐hand polarizations. Field‐aligned currents are generated in the magnetopause rotational discontinuity during the reconneetion, and nearly 5% of the magnetopause currents propagate with Alfvén waves along the field lines into the polar ionosphere. In addition, a weak secondary rotational discontinuity or Alfvén wave pulse propagates from the reconnection site into the magnetosphere. The sense of the field‐aligned currents is investigated for various values of the IMF By. The Hall effects on the structure of the magnetopause boundary layer and the field‐aligned currents are discussed.
Predicting the mean Bz magnitude
Authors: Keating C. F. , Lawrence T. L. , Prebble R. C.
Published: January 2004

When a “boxcar” average of the Bz magnitude is plotted, a clear cyclic pattern is apparent with an approximate correlation with the sunspot cycle. The Bz cycle minima are seen to occur at nearly the same time as the sunspot cycle minima. The cyclic maxima appear to be characterized by a double peak, with the second peak occurring in the descending phase of the sunspot cycle. This cyclical nature makes it possible to apply the McNish‐Lincoln technique to make predictions concerning the future level of Bz magnitude. This method leads to a prediction of the maximum average magnitude in Bz occurring in the year 2003 time frame.
Radial profile of the magnetospheric plasma pressure extracted from magnetic field data
Authors: Feshchenko E. Y. , Maltsev Y. P.
Published: January 2004

We have solved the equation for magnetostatic equilibrium for an anisotropic plasma pressure; this equation allows us to determine the pressure profile from a given magnetic field. We have used the magnetic field model of Ostapenko and Maltsev [1997], which is a valid representation of the magnetospheric field for distances ranging from 3 to 10 RE (Earth radii). This model has as parameters the Dst and Kp indices, the vertical component of the interplanetary magnetic field, and the solar wind dynamic pressure. The radial profile of the magnetospheric plasma pressure computed for quiet conditions is close to that obtained from direct measurements. The effect of each model parameter on the profile has been studied. The total energy content for distances from 3 to 10 RE appears to be controlled primarily by the solar wind dynamic pressure.
Specification of geomagnetically induced electric fields and currents in pipelines
Authors: Trichtchenko L. , Boteler D. H.
Published: January 2004

Variations of the Earth's magnetic field induce electric fields in pipelines. These induced electric fields drive electric currents along the pipelines that can interfere with the cathodic protection systems installed to prevent corrosion of the pipelines. For design of systems to counteract these effects it is necessary to be able to calculate the size of the currents that will be produced by different geomagnetic conditions. In this study we present the results of numerical modeling of the induced electric fields and currents produced in a long, coated pipeline buried in the Earth. We investigate the effects of the frequency dependence for the electric field and current in the pipe. Calculations are made for different frequencies of the source fields in two extremum cases, E and H polarizations of the incident geoelectromagnetic field. It is shown that at low frequencies (<0.01 Hz) the effects of frequency dependence on electric fields and currents in the pipe are negligible but that they should be taken into account at higher frequencies (1 Hz).
A real‐time model‐observation comparison of F2 peak electron densities during the Upper Atmospheric Research Collaboratory campaign of October 1997
Authors: Wang W. , Killeen T. L. , Burns A. G. , Reinisch B. W.
Published: January 2004

The first‐principles, time‐dependent Thermosphere‐Ionosphere Nested Grid (TING) Model has been run automatically in real time to support the Upper Atmospheric Research Collaboratory (UARC) campaigns. This real‐time modeling capability is the first published description of the running of a comprehensive model of the coupled thermosphere‐ionosphere system that successfully performs real‐time nowcasts and short‐term forecasts of the upper atmosphere. These nowcasts and forecasts use observed real‐time geophysical parameters as model input. Real‐time modeling also provides an opportunity to evaluate rigorously the accuracy of the model for space weather purposes by comparing model outputs with observations. Digisonde‐derived F2 peak electron densities from three sites (Millstone Hill, Tromsø, and Sondre Stromfjord) were compared with the corresponding TING model outputs during the October 14–29, 1997, UARC campaign. It is found that under solar minimum, equinox, geomagnetically quiet conditions, the F2 peak electron densities simulated by the model were in good agreement with those observed by the Digisondes. At both midlatitudes and high latitudes the TING Model almost reproduced the observed diurnal variations of F2 peak electron densities. There were, however, short‐period variations of F2 peak electron densities during both day and night that were not simulated by the model.
Fast ejecta during the ascending phase of solar cycle 23: ACE observations, 1998–1999
Authors: Burlaga L. F. , Skoug R. M. , Smith C. W. , Webb D. F. , Zurbuchen T. H. , Reinard Alysha
Published: January 2004

We discuss fast ejecta observed at 1 AU during a period of increasing solar activity from February 5, 1998, to November 29, 1999. “Fast ejecta” are transient, noncorotating flows that move past the Earth during a day or more, with a maximum speed >600 km s−1. We identify two classes of fast ejecta at 1 AU: (1) magnetic clouds, whose local magnetic structure is that of a flux rope; and (2) “complex ejecta,” which are not flux ropes and have disordered magnetic fields. Nearly equal numbers of magnetic clouds and complex ejecta were found: four and five, respectively. The complex ejecta had weaker magnetic fields and higher proton temperatures than the magnetic clouds on average. The average β for the complex ejecta (0.25 ± 0.09) was larger than that for the magnetic clouds (0.06 ± 0.04). The complex ejecta and magnetic clouds had comparable speeds on average, namely, 558 ± 80 and 500 ± 63 km s−1, respectively. Using the duration of the stream and that of the counterstreaming electrons to measure the ejecta, the average time for the complex ejecta to move past ACE was 3 days, which is more than twice that for the magnetic clouds. All of the magnetic clouds contain some material with a high a/proton density ratio (>8%) and a density ratio of O7+/O6+> 1. However, three of the five complex ejecta did not contain material with O7+/O6+> 1, although four of the complex ejecta contained material with O7+/O6+> 1. All of the magnetic clouds caused geomagnetic storms. Three complex ejecta produced no geomagnetic storms. The other two complex ejecta produced geomagnetic storms indirectly: one by driving a shock into the rear of a magnetic cloud and the other by amplifying southward fields in its leading edge and interaction region. Most of the magnetic clouds were associated with a single solar source, but nearly all of the complex ejecta could have had multiple sources. We find evidence in the solar observations that some of the complex ejecta could have been produced by the interaction of two or more coronal mass ejections (CMEs). At least three CMEs might have interacted to produce a large complex ejection that arrived at 1 AU on May 4, 1998. This complex ejection was overtaking and interacting with a magnetic cloud. We discuss several hypotheses concerning the structures and origins of complex ejecta, including the likely possibility that some complex ejecta are formed by a series of interacting CMEs of various sizes.
Prospects for an ionospheric index of neutral thermospheric composition, with space‐weather applications
Authors: Wright J. W. , Conkright R. O.
Published: January 2004

We address the need for an easily observable indicator of thermospheric state, and particularly one sensitive to the neutral concentration ratio, [O]/[N2]. Accepting foF2 as the observable of choice, several options for a derived thermospheric daily index are considered; these include midday and nighttime mean values of foF22, and others based on the rate of change of foF22 during sunrise, which might serve as indicators of [O]/[N2]. We show the global morphology of a promising sunrise index over more than three solar cycles, derived from data in the National Geophysical Data Center Ionospheric Digital Database (NGDC/IDD) and similar databases. There are well‐defined dependencies on solar activity, season, geography, and storm‐disturbance level. We compare the indices to ESRO4 satellite global observations of [O]/[N2] and find correlation coefficients as low as 0.3 (southern winter) and as high as 0.8 (close passes, all data), depending upon hemisphere and season, satellite/ground‐site proximity, satellite altitude, etc. Using median foF22 to compare our sunrise index to the Mass Spectrometer‐Incoherent Scatter (MSIS‐90) model atmosphere at a constant pressure level, we find similar latitude variations in three longitude sectors and two solar cycle extremes. A successful index of [O]/[N2], available daily from monitoring ionosondes (and perhaps from Global Positioning System. Total Electron Content (GPS/TEC) monitors, derived similarly), would have important applications in aeronomy, space weather, and telecommunications forecasting.
Forecasting the arrival of shock‐accelerated solar energetic particles at Earth
Authors: Cohen C. M. S. , Mewaldt R. A. , Cummings A. C. , Leske R. A. , Stone E. C. , Slocum P. L. , Wiedenbeck M. E. , Christian E. R. , von Rosenvinge T. T.
Published: January 2004

Energetic particles accelerated at interplanetary shocks can result in an increased radiation dose for astronauts as well as an increased risk to satellite hardware. These shocks are known to occasionally accelerate protons to energies greater than 100 MeV and can result in very high fluxes. Advanced warning of the arrival of strong interplanetary shocks can enable steps to be taken to minimize the potential risks. In an effort to monitor and assess the radiation risk to astronauts, two real‐time count rate monitors were implemented in the Solar Isotope Spectrometer (SIS) on the ACE spacecraft. These rates measure protons with energies >10 and >30 MeV. Since ACE is located at the L1 Lagrangian point, these rates provide information and warning up to 1 hour before an interplanetary shock reaches Earth. Using ACE and GOES, data we have examined examples of shocks and associated energetic particles that have been detected at ACE and were later observed near Earth in an effort to develop more fully the forecasting capability of ACE. Because of the limited amount of solar activity during 1997–1999, this current work is primarily a proof of concept.
Solar cosmic ray events for the period 1561–1994: 1. Identification in polar ice, 1561–1950
Authors: McCracken K. G. , Dreschhoff G. A. M. , Zeller E. J. , Smart D. F. , Shea M. A.
Published: January 2004

The geophysical significance of the thin nitrate‐rich layers that have been found in both Arctic and Antarctic firn and ice cores, dating from the period 1561–1991, is examined in detail. It is shown that variations of meteorological origin dominate the record until the snow has consolidated to high‐density firn some 30 years after deposition. The thin nitrate layers have a characteristic short timescale (<6 weeks) and are highly correlated with periods of major solar‐terrestrial disturbance, the probability of chance correlation being less than 10−9. A one‐to‐one correlation is demonstrated between the seven largest solar proton fluence events that have been observed since continuous recording of the cosmic radiation started in 1936, and the corresponding thin nitrate layers for the event date. The probability of this occurring by chance is <10−6. This high degree of statistical correlation, together with the modeling studies of Jackman, Vitt, and coworkers, is interpreted as establishing that the impulsive nitrate events are causally related to the generation of energetic particles by solar activity. The timescale of the nitrate events is too short to be understood in terms of transport mechanisms in the gaseous phase and indicates that the nitrate must be precipitated to the polar caps by the gravitational sedimentation of stratospheric solid particles. A conversion factor is established between the impulsive transient nitrate concentrations and the >30 MeV solar proton fluence. The proton fluences (omnidirectional fluence cm−2) derived from the 70 largest impulsive nitrate events between 1561 and 1950 are tabulated. The proton fluence probability distribution derived from these large impulsive nitrate events are in good agreement with earlier studies of the cumulative probabilities of solar proton events and with the observation of cosmogenic isotopes in moon rocks. The cumulative probability curve derived from the impulsive nitrate events indicates a rapidly decreasing probability of occurrence of >30 MeV solar proton events having an omnidirectional fluence exceeding 6 × 109 cm−2. It is concluded that the impulsive nitrate events are reliable indicators of the occurrence of large fluence solar proton events and that they provide a quantitative measure of these events. It is further concluded that the impulsive nitrate events will permit the study of solar activity for many thousands of years into the past.
Ground disturbances of the ring, magnetopause, and tail currents on the day the solar wind almost disappeared
Authors: Jordanova V. K. , Farrugia C. J. , Fennell J. F. , Scudder J. D.
Published: January 2004

We study ring current dynamics on a day of exceptionally low solar wind density (of ∼0.1 cm−3). Inner magnetospheric measurements of geomagnetic activity show geomagnetic quiet par excellence. On May 11, 1999, the values were |Dst| < 10 nT and Kp = 0+. The field at geostationary orbit was very close to dipolar. We simulate the global evolution of the ring current ion population during this period and compare the effect of the magnetopause, ring, magnetotail, and field‐aligned currents on the Dst index. Measured H+, He+, and O+ energy and pitch angle distributions by the Magnetospheric Ion Composition Spectrometer (MICS) and HYDRA instruments on Polar on May 9 are used as initial conditions for our kinetic model. Comparing model results with Polar data on May 11, we find remarkable agreement, proving the applicability of our model for these magnetospheric conditions. We compare modeled H+ and He+ ion distributions with quiet time ring current distributions inferred from statistical studies, and we find that as a general trend, the simulation results have lower values than the statistical patterns. The ground magnetic field disturbances due to the ring and the magnetopause currents decrease quasi‐monotonically on May 11, reaching limiting magnitudes of ∼5 and ∼3 nT, respectively. These values are substantially smaller than the ∼20 nT quiet time values obtained from statistical studies.
Interplanetary scintillation observations for the solar wind disappearance event of May 1999
Authors: Vats Hari Om , Sawant H. S. , Oza Rupal , Iyer K. N. , Jadhav Ravi
Published: January 2004

In this article we present ground‐based interplanetary scintillation (IPS) measurements at 103 and 327 MHz for the period of the solar wind disappearance event of May 1999 as seen by various space probes. The solar wind velocity measurements at 327 MHz showed a variable solar wind velocity during this period at a distance of ∼0.5 AU from the Sun. The average solar wind velocity from three radio sources varied in the range of 200–300 km s−1. The scintillation index measurements at 103 MHz indicate that plasma density was very low in the interplanetary medium closer to the Earth and that the density was normal away from it during May 11–13. The scintillation index was enhanced significantly on May 14 after the disappearance event. The comparison with the in situ observations shows that the effect is dramatic in IPS observations. IPS and in situ measurements show that a large, tenuous, and slow plasma cloud engulfed our planet around this time, which could be because of a corotating low‐density narrow stream. From the source (Sun) point of view, this was mostly a normal plasma flow in most of the interplanetary medium.
Tracing shock waves from the corona to 1 AU: Type II radio emission and relationship with CMEs
Authors: Leblanc Yolande , Dulk George A. , Vourlidas Angelos , Bougeret Jean‐Louis
Published: January 2004

We report on 10 type II bursts observed with ground‐based spectrographs in the meter‐decameter range, and with the Radio and Plasma Wave Investigation on the Wind spacecraft from 13.8 to 0.01 MHz. We have selected events with contemporaneous observations of flares and of coronal mass ejections (CMEs) by Large‐Angle and Spectrometric Coronagraph (LASCO) telescopes. We trace the history of each event from the time of the impulsive phase of the flare, the CME liftoff time, and the start time of the radio bursts. We derive the speed of the type II shock by using a coronal/solar wind density model, and the height‐time progression is compared with that of the CME as observed in the plane of the sky and then converted into the radial direction. For most events a shock at 1 AU was observed in situ. The results show the following: (1) All type II bursts occurred within 2 or 3 min of the impulsive phase of a flare. (2) The speeds of the disturbances from the time of the flares to the time of the shocks at 1 AU were very similar to the speeds of the type II‐emitting shocks; they were in the range of 600 to 1300 km s−1. (3) When the type II burst was observed far out in the solar wind, the progression of the type II source had about the same speed in the solar wind as in the corona. (4) The CME liftoffs were before the flares and the type II bursts by 1–24 min for most of the selected events. As a consequence, in the corona, the type II bursts, being behind the fronts of the CMEs, are usually blast waves. (5) When a shock and CME material are observed at 1 AU, the time of arrival implies a deceleration of the CME in the solar wind, as is observed in the LASCO data. (6) Somewhere in the solar wind the shocks very likely become piston‐driven, related to the CME.
Auroral emission generated by a trimethyl aluminum release
Authors: Gelinas L. J. , Kelley M. C. , Sia C. , Larsen M. F.
Published: January 2004

A trimethyl aluminum (TMA) release rocket launched during the 1998 Coqui II sounding rocket campaign in Puerto Rico produced what appeared to be an artificially generated aurora. This phenomenon has been observed on several other occasions but has heretofore not been reported. In this paper we discuss the observation of artificially generated auroral light in relation to a kerosene‐doped TMA release and propose an auroral generation mechanism involving motion of charged particulates associated with the TMA trail.
Three‐dimensional magnetopause and tail current model of the magnetosphere of Ganymede
Authors: Stone Shawn M. , Armstrong Thomas P.
Published: January 2004

The encounters of Ganymede by the Galileo spacecraft have shown the existence of an intrinsic magnetic field as well as a magnetosphere for Ganymede [Kivelson et al., 1996, 1997, 1998; Kurth et al., 1997; Volwerk et al., 1999; Williams et al., 1997a, 1997b]. The magnetic field in the region of Ganymede was first modeled by Kivelson et al. [1996] as a simple dipole, excluding external field sources (namely, a field due to magnetopause and magnetotail currents), superposed on the Jovian background magnetic field. We call this model M1 herein. This paper presents an alternative model with magnetopause and tail field current contributions, along with an internal multipole model for Ganymede, that has been derived by refitting the internal and external source model coefficients to the magnetic field data local to the Galileo spacecraft using the methods of Choe and Beard [1974a, 1974b]. For brevity we will refer to this model as the Stone‐Choe‐Beard (SCB) model. Both models are then compared to the original magnetic field data for the G2 and G7 encounters. The SCB model represents the magnetic field and its variations at the spacecraft, especially at the magnetopause crossings, more accurately than M1. A method that tests both models throughout the magnetosphere of Ganymede utilizing particle absorption signatures will be presented in a manuscript in progress.
Magnetic impulse event: A detailed case study of extended ground and space observations
Authors: Kataoka R. , Fukunishi H. , Lanzerotti L. J. , Maclennan C. G. , Frey H. U. , Mende S. B. , Doolittle J. H. , Rosenberg T. J. , Weatherwax A. T.
Published: January 2004

Analysis of conjugate data from extended magnetometer networks in northern and southern high latitudes is used to elucidate the initiation and the evolution of a magnetic impulse event (MIE) on June 6, 1997. In addition, data from all‐sky imagers, imaging riometers, and Super Dual Auroral Radar Network radars in Antarctica are investigated to confirm the energy content, motion, and electrical current structure of the MIE. The MIE was accompanied by traveling convection vortices (TCVs) that began at ∼10 MLT and moved eastward (toward dusk) and slightly equatorward at 1–3 km/s across the noon meridian with north‐south conjugacy. The MIE had upward field‐aligned currents with soft electron precipitation that was located near the trailing edge of the Hall current loop. During the MIE interval the interplanetary magnetic field (IMF) was directed strongly outward from the Sun (Bx = −5 nT), with a slightly positive (1–2 nT) Bz, and a nearly zero By. Since abrupt solar wind pressure changes are unlikely under this IMF orientation (and none was, in fact, observed), classical mechanisms for MIE generation, such as a pressure pulse or dayside reconnection, are excluded. It is speculated that an abrupt IMF cone angle change from 60° to 20°, ∼30 min prior to the MIE onset, may have been an indirect trigger of this event via the interaction between the solar wind and the bow shock.
ELF/VLF waves correlated with transversely accelerated ions in the auroral region observed by Akebono
Authors: Kasahara Yoshiya , Hosoda Tomohisa , Mukai Toshifumi , Watanabe Shigeto , Kimura Iwane , Kojima Hirotsugu , Niitsu Ryotaro
Published: January 2004

Plasma waves observed by the Akebono satellite in the region of ion heating/acceleration transverse to the geomagnetic field line are studied. Especially, electrostatic, broadband low‐frequency noise is closely correlated with transversely accelerated ions. Simultaneous electron precipitation in the energy ranges from a few tens to hundreds eV is also usually observed. Our waveform analysis revealed that the electrostatic broadband noise is classified into two types of noise: one is continuous noise with upper cutoff around a few kilohertz, and the other is an intermittent impulsive waveform extended more than 10 kHz. A possible explanation to the dominant part of continuous broadband noise is that they are ion acoustic waves generated by precipitating electrons (approximately a few hundreds eV) and that the wave is the possible main energy source of ion heating/acceleration. The other mechanisms may, however, be sometimes important for generating the broadband noise. Using long‐period observation data sets of Akebono, which is orbiting in the altitude range between 270 and 10,000 km, statistical studies on the spatial and temporal distribution of the continuous broadband noise are made. Several kinds of statistical features are clarified: (1) The occurrence region is distributed in the cusp and along the auroral oval, (2) the region is extended toward the lower latitude while the geomagnetic activity is higher, (3) the intensity is larger in the cusp than it is in the nightside, and (4) it is largest in winter and weakest in summer.
Retrieval and validation of mesospheric temperatures from Wind Imaging Interferometer observations
Authors: Shepherd Marianna G. , Reid Boedijanti , Zhang Shengpan , Solheim Brian H. , Shepherd Gordon G. , Wickwar Vincent B. , Herron Joshua P.
Published: January 2004

A method has been developed for the retrieval of mesospheric temperatures in the 65–90 km altitude range from satellite observations made by the Wind Imaging Interferometer (WINDII) aboard the Upper Atmosphere Research Satellite (UARS). Retrieved temperatures are derived from Rayleigh scattered sunlight observed in a wavelength band centered at 553 nm. Integrated line‐of‐sight radiance observations are inverted to tangent height volume scattering profiles, which are proportional to atmospheric density. From these, absolute temperature profiles are calculated using a technique derived from established Rayleigh lidar retrieval methods assuming that the atmosphere is in hydrostatic equilibrium and that it obeys the ideal gas law. Sources of error have been identified and typical temperature uncertainty values for individual profiles are determined to be < 2.5%, 5.5%, and 13% for altitudes of 70 km, 80 km, and 90 km, respectively. A thorough comparison of the derived WINDII temperatures is performed against a number of ground‐based and satellite measurements, including ground‐based lidar, falling spheres, the High Resolution Doppler Imager observations aboard UARS, and against common atmospheric models. The data consist of spring equinox observations in March and April 1992/1993, summer solstice data in July/August 1992/1993, fall equinox data in September/October 1992, and winter solstice data in December 1992/1993 and January 1993/1994. The results of the comparisons show that WINDII temperatures are in reasonable to excellent agreement with a number of established temperature studies. In particular, July Northern Hemisphere monthly averaged temperatures show that characteristics of the mesopause obtained by WINDII are in very good agreement with other measurements. This good agreement with other established data sets and a determination of the error bounds of our recovered temperatures have shown that WINDII data can be used to confidently derive near‐global temperatures of the upper mesosphere between 65 and 90 km. Above 90 km the errors increase, and systematic differences may arise with other measurements.
An investigation into the influence of tidal forcing on F region equatorial vertical ion drift using a global ionosphere‐thermosphere model with coupled electrodynamics
Authors: Millward G. H. , Müller‐Wodarg I. C. F. , Aylward A. D. , Fuller‐Rowell T. J. , Richmond A. D. , Moffett R. J.
Published: January 2004

A recent development of the coupled thermosphere‐ionosphere‐plasmasphere model (CTIP) has been the inclusion of the electrodynamic coupling between the equatorial ionosphere and thermosphere. The vertical ion drifts which result are shown to be largely in agreement with empirical data, on the basis of measurements made at the Jicamarca radar and other equatorial sites [Scherliess and Fejer, 1999]. Of particular importance, the CTIP model clearly reproduces the “prereversal enhancement” in vertical ion drift, a key feature of the observational data. Inacurracies in the modeled daytime upward ion motion have been investigated with regard to changing the magnitude and phase of components of the lower thermospheric tidal forcing. The results show that daytime vertical ion motion is highly dependent upon both the magnitude and phase of the semidiurnal tidal component. In addition, the CTIP model shows the prereversal enhancement to be unaffected by changes in tidal forcing, but only for conditions of high solar activity. During periods of low solar activity the form of the prereversal enhancement is clearly dependant upon the magnitude and phase of the semidiurnal tide.
On the similarity features of normalized frequency spectrograms of magnetospherically reflected whistlers
Authors: Lundin B. , Krafft C.
Published: January 2004

A modified electron whistler dispersion law is derived to be used for analytical and numerical investigation of magnetospherically reflected (MR) whistlers' propagation for finite ratio ωc/ωp of electron gyrofrequencies to plasma frequencies if the wave frequency is much less than ωp. The contribution of ions is included in the value of the lower hybrid resonance frequency only. Ray‐tracing simulations are carried out in order to reproduce MR whistler spectrograms typical of those observed on high‐altitude equatorial and low‐altitude satellites. It is found that spectrograms of MR whistlers with frequencies normalized to the equatorial electron gyrofrequency at the L shell of wave observation are close to each other when satellites are located on the equator at different altitudes (or at low altitude and different latitudes). Moreover, normalized frequencies corresponding to flattening of traces on spectrograms at large group delay times can be obtained by following me path of a single extreme quasi‐resonant whistler ray starting downward at the equator with a group velocity direction corresponding to the resonance cone. On the basis of obtained results, a possible interpretation of the origin and spectral characteristics of discrete plasmaspheric emissions is discussed.
Global electrodynamics observed during the initial and main phases of the July 1991 magnetic storm
Authors: Wilson G. R. , Burke W. J. , Maynard N. C. , Huang C. Y. , Singer H. J.
Published: January 2004

Data acquired by seven fortuitously positioned satellites in the interplanetary medium, the magnetosphere, and the topside ionosphere, as well as from numerous ground magnetometers have allowed us to follow the evolution of global currents and electric fields during the geomagnetic storm on July 8–9, 1991. An interplanetary disturbance collided with the magnetosphere at ∼1636 UT on July 8th, compressing the magnetopause inside of geostationary orbit for about 3 hours, as observed by magnetometers on two GOES satellites. The resulting storm developed in four segments with a 7 hour lull separating the initial and main phases. The initial phase was characterized by (1) an extensive, DP 2 current system that produced an AE perturbation of ∼3500 nT, with reporting stations on the dayside, (2) a twenty‐fold increase in auroral electron fluxes, and (3) the immediate appearance of electric fields in the inner magnetosphere. The main phase intensification and earthward movement of the ring current are associated with southward turnings of the interplanetary magnetic field (IMF) and a polar cap potential increase above 200 kV. A significant fraction of the ring current growth was observed prior to the first of several substorms that occurred during the main and recovery phases. The beginning of recovery was characterized by a diminution of the southward IMF component, the cross polar cap potential and magnetospheric electric fields. It was also marked by a substorm onset. Considering the timing of Dst modulations relative to substorm occurrence, we conclude that during this magnetic storm, the electric fields responsible for ring current transport/energization were mostly associated with the DP 2 current system. Finally, in the evening‐sector penetration electric fields of the initial and main phases led to the formation of upward moving equatorial plasma bubbles that were detected by two DMSP satellites in the topside ionosphere.
Influence of solar wind on Jupiter's magnetosphere deduced from currents in the equatorial plane
Authors: Khurana Krishan K.
Published: January 2004

Galileo is the sixth spacecraft to have visited Jupiter's magnetosphere. Among them the six spacecraft have sampled a fairly large expanse of magnetospheric local times and latitudes under varying solar wind conditions. An adequate (though not optimum) database of field and particles now exists that makes it possible to map the current circuits at a global scale. We have used the magnetic field observations from all six of the spacecraft to compute the electric current density in the equatorial plane of Jupiter's magnetosphere by making certain appropriate assumptions. We show that in the middle magnetosphere the azimuthal currents are much stronger on the nightside (∼ 144 MA between the radial distances of 10 and 50 RJ) than they are on the dayside (∼ 88 MA in the same distance range). From current continuity considerations we conclude that the nightside partial ring current is fed and emptied by field‐aligned currents in the dusk and the dawn sectors, respectively. These currents are similar (but opposite in polarity) to Region 2 field‐aligned currents observed in the Earth's magnetosphere. Because the presence of Region 1 or 2 sense field‐aligned currents in a magnetosphere indicates the presence of solar wind driven convection in a magnetosphere, a surprising conclusion of the present analysis is that the solar wind influence reaches deep into the heart of Jupiter's magnetosphere. Other findings of this study are that (1) the equatorial field strength is remarkably constant over all local times, (2) the equatorial source of the outward field‐aligned currents required for the generation of aurorae is located between the radial distances of 10 and 30 RJ with a peak near 20 RJ, and (3) the Jovian magnetosphere displays a magnetic field configuration intermediate to a Parker spiral and a magnetosphere driven by solar wind.
Semiannual variation of the geomagnetic Dst index: Evidence for a dominant nonstorm component
Authors: Cliver Edward W. , Kamide Y. , Ling A. G. , Yokoyama N.
Published: January 2004

The geomagnetic Dst index exhibits a strong semiannual variation with amplitude of 5.3 nT (on an average baseline of −16.4 nT) for 1957–1997. If we consider the five quietest Dst days for each month during this interval, we find that while the average Dst baseline shifts from −16.4 to +4.0 nT, the amplitude of the 6‐month wave remains relatively strong at 2.5 nT. Thus ∼50% (2.5 nT/5.3 nT) of the seasonal variation of the Dst index results from modulation of its quiet time baseline. The seasonal modulation of Dst appears to consist of both a storm component, resulting from rapid variations of the ring current and other currents, and a slowly varying, nonstorm component. We estimate that the storm component accounts for only ∼30–50% of the amplitude of the 6‐month wave in Dst versus ∼50–70% for the nonstorm component. The classic equinoctial effect appears to dominate the storm component, accounting for 20–40% of the amplitude of the 6‐month wave in Dst versps ∼10% for the combined axial/Russell‐McPherron mechanisms. Candidate mechanisms for the nonstorm component of the 6‐month wave in Dst include the Malin‐Isikara effect (the seasonal displacement of ring/tail currents by solar wind compression) and a semiannual variation of magnetopause currents.
Tidal influence on the oxygen and hydroxyl nightglows: Wind Imaging Interferometer observations and thermosphere/ionosphere/mesosphere electrodynamics general circulation model
Authors: Zhang Shengpan P. , Roble Raymond G. , Shepherd Gordon G.
Published: January 2004

Longitudinal zonally averaged Wind Imaging Interferometer (WINDII) (on UARS) night‐time oxygen (O(1S)) and hydroxyl (P(3) line in the OH(8,3) Meinel band) volume emission rates exhibit dramatic spatial and temporal variations. The recently improved thermosphere/ionosphere/mesosphere electrodynamics general circulation model (TIME‐GCM) produces simulations for the two airglows through the input of (1,1) upward propagating diurnal tides. The model simulations show excellent agreement with WINDII observations in both the local tune domain and the latitudinal domain between 40°S and 40°N. The influence of diurnal tides on the two airglows in strongest in the tropical region. In the local solar time domain the emission rate and peak altitude at the equator show large tidal perturbations, but they are fairly stable at midlatitude. In the latitudinal domain there is an equatorial trough in the oxygen emission rate which exists regardless of local time and season. The hydroxyl emission rate is more dependent on local time and season. At equinox it has a prominent equatorial maximum which disappears at dawn, whereas at solstice it has a very weak equatorial maximum at dusk, changing soon after midnight to an equatorial minimum. These features of emission rates are also compared to TIME‐GCM simulations for meridional wind, temperature, and atomic oxygen density, [O], with and without upward propagating diurnal tides. The results are as follows: (1) The large oscillations of the two nightglows as well the atomic oxygen density in the tropical region are driven by the diurnal propagating tides. In altitude the mesosphere and lower thermosphere is divided into two type of cells, one with meridional winds converging at the equator, higher temperature, and enhanced [O] and airglow emission rates, and the other with meridional winds diverging from the equator, lower temperature, and depleted [O] and airglow emission rates; all these are essentially related to the wavelength and phase of the diurnal tides. (2) The relatively stable airglow emission rates at around 20° are related to the minimum fluctuation of temperature and stable meridional wind directions in spite of the maximized wind speed in this region. (3) The year‐around equatorial depletion in the oxygen airglow and the double‐peaked profile in the hydroxyl airglow are most likely produced by the diurnal tides. Further investigation is needed particularly for the absolute value of the oxygen emission rate, the interhemispheric comparison of the oxygen emission rate, why WINDII observes maximum summer emissions whereas the TIME‐GCM gives maximum winter emission, and the effects of waves in addition to the diurnal tides.
Climatology of middle‐ and low‐latitude daytime F region disturbance neutral winds measured by Wind Imaging Interferometer (WINDII)
Authors: Emmert J. T. , Fejer B. G. , Fesen C. G. , Shepherd G. G. , Solheim B. H.
Published: January 2004

We have modeled the global climatology of middle‐ and low‐latitude F region daytime disturbance neutral winds using extensive measurements by the Wind Imaging Interferometer (WINDII) instrument on board the UARS. The perturbation winds were obtained by subtracting the quiet time values from the disturbed winds along the satellite orbit, which effectively removes average measurement bias. The zonal disturbance winds are mostly westward (except in the early morning sector), increase with latitude, and have largest values in the late afternoon sector. In general, the meridional perturbation winds are equatorward, increase linearly with latitude, and decrease from early morning to afternoon hours. The zonal and meridional perturbations increase roughly linearly with Kp and expand to lower latitudes with increasing magnetic activity. The meridional disturbance winds are largest for low solar flux conditions. We present empirical analytical models for longitudinally averaged disturbance winds from 60° to the equator. Our model winds are in poor agreement with results from the empirical wind model Horizontal Wind Model‐93 during the entire daytime period. There are also important discrepancies between the average perturbations winds from WINDII and the National Center for Atmospheric Research thermosphere‐ionosphere electrodynamic general circulation model, particularly at midlatitudes. These differences could be explained in part by the storm time dependence of the disturbance winds and by the variability of the high‐latitude electric fields.