bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative measurements of total ozone amount and aerosol optical depth during a campaign at El Arenosillo, Huelva, Spain
Authors: de La Casinière A. , Cachorro V. , Smolskaia I. , Lenoble J. , Sorribas M. , Houët M. , Massot O. , Antón M. , Vilaplana J. M. 
Published: June 2010

Abstract. A one week field campaign took place in September 2002 at El Arenosillo, Spain. The objective was to compare total ozone column (TOC) and aerosol optical depth (AOD) from near ultraviolet to near infrared, measured by several Spanish and French instruments. Three spectroradiometers, Brewer, SPUV02, and LICOR, and a CIMEL photometer, have been used simultaneously and the results are presented for four clear days. TOC values are given by the Brewer instrument, and by SPUV02, using two different methods. The ground instruments compare satisfactorily (within 5 DU) and the values are consistent with TOMS data (within 10 DU). AOD from the various instruments are compared at seven different wavelengths between 320 nm and 1020 nm: the agreement is very good at 350, 380, and 870 nm; at the four other wavelengths the difference is smaller than 0.03, which can be explained by a relative difference of 4% only between the calibrations of the various instruments. Larger AOD diurnal variations were observed at short wavelengths than in the visible and near infrared; this is most likely due to changes in aerosol size along the day, during the campaign.
Motion of the dayside polar cap boundary during substorm cycles: I. Observations of pulses in the magnetopause reconnection rate
Authors: Lockwood M. , Moen J. , van Eyken A. P. , Davies J. A. , Oksavik K. , McCrea I. W. 
Published: June 2010

Abstract. Using data from the EISCAT (European Incoherent Scatter) VHF radar and DMSP (Defense Meteorological Satellite Program) spacecraft passes, we study the motion of the dayside open-closed field line boundary during two substorm cycles. The satellite data show that the motions of ion and electron temperature boundaries in EISCAT data, as reported by Moen et al. (2004), are not localised around the radar; rather, they reflect motions of the open-closed field line boundary at all MLT throughout the dayside auroral ionosphere. The boundary is shown to erode equatorward when the IMF points southward, consistent with the effect of magnetopause reconnection. During the substorm expansion and recovery phases, the dayside boundary returns poleward, whether the IMF points northward or southward. However, the poleward retreat was much faster during the substorm for which the IMF had returned to northward than for the substorm for which the IMF remained southward - even though the former substorm is much the weaker of the two. These poleward retreats are consistent with the destruction of open flux at the tail current sheet. Application of a new analysis of the peak ion energies at the equatorward edge of the cleft/cusp/mantle dispersion seen by the DMSP satellites identifies the dayside reconnection merging gap to extend in MLT from about 9.5 to 15.5 h for most of the interval. Analysis of the boundary motion, and of the convection velocities seen near the boundary by EISCAT, allows calculation of the reconnection rate (mapped down to the ionosphere) from the flow component normal to the boundary in its own rest frame. This reconnection rate is not, in general, significantly different from zero before 06:45 UT (MLT<9.5 h) - indicating that the X line footprint expands over the EISCAT field-of-view to earlier MLT only occasionally and briefly. Between 06:45 UT and 12:45 UT (9.5<MLT<15.5 h) reconnection is continuously observed by EISCAT, confirming the (large) MLT extent of the reconnection footprint deduced from the DMSP passes. As well as direct control by the IMF on longer timescales, the derived reconnection rate variation shows considerable pulsing on timescales of 2-20 min during periods of steady southward IMF.
Simultaneous in-situ observations of the signatures of dayside reconnection at the high- and low-latitude magnetopause
Authors: Wild J. A. , Milan S. E. , Cowley S. W. H. , Bosqued J. M. , Rème H. , Nagai T. , Kokubun S. , Saito Y. , Mukai T. , Davies J. A. , Cooling B. M. A. , Balogh A. , Daly P. W. 
Published: June 2010

Abstract. We present magnetic field and particle data recorded by the Cluster and Geotail satellites in the vicinity of the high- and low-latitude dayside magnetopause, respectively, on 17 February 2003. A favourable conjunction of these spacecraft culminated in the observation of a series of flux transfer events (FTEs), characterised by bipolar perturbations in the component of the magnetic field normal to the magnetopause, an enhancement in the overall magnetic field strength, and field tilting effects in the plane of the magnetopause whilst the satellites were located on the magnetosheath side of the boundary. Whilst a subset of the FTE signatures observed could be identified as being either normal or reverse polarity, the rapid succession of events observed made it difficult to classify some of the signatures unambiguously. Nevertheless, by considering the source region and motion of flux tubes opened by magnetic reconnection at low latitudes (i.e. between Cluster and Geotail), we demonstrate that the observations are consistent with the motion of northward (southward) and tailward moving flux tubes anchored in the Northern (Southern) Hemisphere passing in close proximity to the Cluster (Geotail) satellites. We are able to demonstrate that a multi-spacecraft approach, coupled with a realistic model of flux tube motion in the magnetosheath, enables us to infer the approximate position of the reconnection site, which in this case was located at near-equatorial latitudes.
Definition of Saturn's magnetospheric model parameters for the Pioneer 11 flyby
Authors: Belenkaya E. S. , Alexeev I. I. , Kalegaev V. V. , Blokhina M. S. 
Published: June 2010

Abstract. This paper presents a description of a method for selection parameters for a global paraboloid model of Saturn's magnetosphere. The model is based on the preexisting paraboloid terrestrial and Jovian models of the magnetospheric field. Interaction of the solar wind with the magnetosphere, i.e. the magnetotail current system, and the magnetopause currents screening all magnetospheric field sources, is taken into account. The input model parameters are determined from observations of the Pioneer 11 inbound flyby.
Enhanced gravity-wave activity and interhemispheric coupling during the MaCWAVE/MIDAS northern summer program 2002
Authors: Becker E. , Fritts D. C. 
Published: June 2010

Abstract. We present new sensitivity experiments that link observed anomalies of the mesosphere and lower thermosphere at high latitudes during the MaCWAVE/MIDAS summer program 2002 to enhanced planetary Rossby-wave activity in the austral winter troposphere. We employ the same general concept of a GCM having simplified representations of radiative and latent heating as in a previous study by Becker et al. (2004). In the present version, however, the model includes no gravity wave (GW) parameterization. Instead we employ a high vertical and a moderate horizontal resolution in order to describe GW effects explicitly. This is supported by advanced, nonlinear momentum diffusion schemes that allow for a self-consistent generation of inertia and mid-frequency GWs in the lower atmosphere, their vertical propagation into the mesosphere and lower thermosphere, and their subsequent dissipation which is induced by prescribed horizontal and vertical mixing lengths as functions of height. The main anomalies in northern summer 2002 consist of higher temperatures than usual above 82 km, an anomalous eastward mean zonal wind between 70 and 90 km, an altered meridional flow, enhanced turbulent dissipation below 80 km, and enhanced temperature variations associated with GWs. These signals are all reasonably described by differences between two long-integration perpetual model runs, one with normal July conditions, and another run with modified latent heating in the tropics and Southern Hemisphere to mimic conditions that correspond to the unusual austral winter 2002. The model response to the enhanced winter hemisphere Rossby-wave activity has resulted in both an interhemispheric coupling through a downward shift of the GW-driven branch of the residual circulation and an increased GW activity at high summer latitudes. Thus a quantitative explanation of the dynamical state of the northern mesosphere and lower thermosphere during June-August 2002 requires an enhanced Lorenz energy cycle and correspondingly enhanced GW sources in the troposphere, which in the model show up in both hemispheres.
The atmospheric background situation in northern Scandinavia during January/February 2003 in the context of the MaCWAVE campaign
Authors: Blum U. , Baumgarten G. , Schöch A. , Kirkwood S. , Naujokat B. , Fricke K. H. 
Published: June 2010

Abstract. The atmosphere background wind field controls the propagation of gravity waves from the troposphere through the stratosphere into the mesosphere. During January 2003 the MaCWAVE campaign took place at Esrange, with the purpose of observing vertically ascending waves induced by orography. Temperature data from the U. Bonn lidar at Esrange (68° N/21° E) and the ALOMAR RMR lidar (69° N/16° E), wind data from Esrange MST radar ESRAD, as well as wind data from the ECMWF T106 model, are used to analyse the atmospheric background situation and its effect on mountain wave propagation during January/February 2003. Critical levels lead to dissipation of vertically ascending waves, thus mountain waves are not observable above those levels. In the first half of January a minor as well as a major stratospheric warming dominated the meteorological background situation. These warmings led to a wind reversal, thus to critical level filtering and consequently prevented gravity waves from propagating to high altitudes. While the troposphere was not transparent for stationary gravity waves most of the time, there was a period of eight days following the major warming with a transparent stratosphere, with conditions allowing gravity waves generated in the lower troposphere to penetrate the stratosphere up to the stratopause and sometimes even into the lower mesosphere. In the middle of February a minor stratospheric warming occurred, which again led to critical levels such that gravity waves were not able to ascend above the middle stratosphere. Due to the unfavourable troposphere and lower stratosphere conditions for gravity wave excitation and propagation, the source of the observed waves in the middle atmosphere is probably different from orography.
Sporadic sodium and E layers observed during the summer 2002 MaCWAVE/MIDAS rocket campaign
Authors: Williams B. P. , Croskey C. L. , She C. Y. , Mitchell J. D. , Goldberg R. A. 
Published: June 2010

Abstract. On 5 July 2002, a MaCWAVE (Mountain and Convective Waves Ascending VErtically) payload launched from Andøya Rocket Range, Norway, observed narrow enhanced layers of electron density that were nearly coincident with sporadic sodium layers measured by the Weber sodium lidar at the nearby ALOMAR Observatory. We investigate the formation mechanism of these layers using the neutral wind and temperature profiles measured directly by the lidar and the vertical motion deduced from the sodium mixing ratio. Through comparisons of the lidar data to the sporadic E in situ data, we find support for the concentration and downward motion of ions to an altitude where chemical models predict the rapid conversion of sodium ions to neutral sodium.
In-situ electron and ion measurements and observed gravity wave effects in the polar mesosphere during the MaCWAVE program
Authors: Croskey C. L. , Mitchell J. D. , Friedrich M. , Schmidlin F. J. , Goldberg R. A. 
Published: June 2010

Abstract. Langmuir probe electron and ion measurements from four instrumented rockets flown during the MaCWAVE (Mountain and Convective Waves Ascending VErtically) program are reported. Two of the rockets were launched from Andøya Rocket Range, Norway, in the summer of 2002. Electron scavenging by ice particulates produced reductions of the electron density in both sharp narrow (≈1–2 km) layers and as a broad (≈13 km) depletion. Small-scale irregularities were observed in the altitude regions of both types of electron depletion. The scale of the irregularities extended to wavelengths comparable to those used by ground-based radars in observing PMSE. In regions where ice particles were not present, analysis of the spectral signatures provided reasonable estimates of the energy deposition from breaking gravity waves. Two more instrumented rockets were flown from Esrange, Sweden, in January 2003. Little turbulence or energy deposition was observed during one flight, but relatively large values were observed during the other flight. The altitude distribution of the observed turbulence was consistent with observations of a semidiurnal tide and gravity wave instability effects as determined by ground-based lidar and radar measurements and by falling sphere measurements of the winds and temperatures (Goldberg et al., 2006; Williams et al., 2006).
Statistics of 150-km echoes over Jicamarca based on low-power VHF observations
Authors: Chau J. L. , Kudeki E. 
Published: June 2010

Abstract. In this work we summarize the statistics of the so-called 150-km echoes obtained with a low-power VHF radar operation at the Jicamarca Radio Observatory (11.97 S, 76.87 W, and 1.3 dip angle at 150-km altitude) in Peru. Our results are based on almost four years of observations between August 2001 and July 2005 (approximately 150 days per year). The majority of the observations have been conducted between 08:00 and 17:00 LT. We present the statistics of occurrence of the echoes for each of the four seasons as a function of time of day and altitude. The occurrence frequency of the echoes is ~75% around noon and start decreasing after 15:00 LT and disappear after 17:00 LT in all seasons. As shown in previous campaign observations, the 150-echoes appear at a higher altitude (>150 km) in narrow layers in the morning, reaching lower altitudes (~135 km) around noon, and disappear at higher altitudes (>150 km) after 17:00 LT. We show that although 150-km echoes are observed all year long, they exhibit a clear seasonal variability on altitudinal coverage and the percentage of occurrence around noon and early in the morning. We also show that there is a strong day-to-day variability, and no correlation with magnetic activity. Although our results do not solve the 150-km riddle, they should be taken into account when a reasonable theory is proposed.
Long-term behavior of the Kelvin waves revealed by CHAMP/GPS RO measurements and their effects on the tropopause structure
Authors: Venkat Ratnam M. , Tsuda T. , Kozu T. , Mori S. 
Published: June 2010

Abstract. The vertical and temporal variations of Kelvin waves and the associated effects on the tropical tropopause were studied using long-term (from May 2001 to October 2005) CHAMP/GPS (CHAllenging Mini satellite Payload/Global Positioning System) radio occultation (RO) measurements. The periods of these waves were found to be varying in between 10 and 15 days, with vertical wavelengths 5–8 km. These variations clearly show eastward phase propagation in the time-longitude section and eastward phase tilts with height in altitude-longitude, displaying the characteristics of Kelvin waves. The peak variance in the temperature is found over the Indian Ocean and into the western Pacific within the broad region of the equator. Kelvin wave amplitudes were found significantly enhanced in the eastward shear of the quasi-biennial oscillation (QBO) and are confined in and around the tropopause during westward phase of QBO, where it extends between 17 and 25 km during the eastward phase of QBO and is damped away above, consistent with earlier reported results. The amplitudes are increasing during the months of Northern Hemisphere winter and sometimes they are highly sporadic in nature. Seasonal and inter-annual variations in the Kelvin wave amplitudes near the tropical tropopause coincide exactly with the tropopause height and temperature, with a sharp tropopause during maximum Kelvin wave activity. A clear annual oscillation, along with a month-to-month coincidence is evident most of the time in both the tropopause height and Kelvin wave activity, with maximum and minimum Kelvin wave amplitudes during the Northern Hemisphere winter and summer, respectively. In addition, a signature of quasi-biennial oscillation (QBO) in the tropopause structure is also seen in long-term tropopause variations, although the amplitudes are less when compared to the annual oscillation. In the westward phase of QBO (during strong Kelvin wave activity) at 20km (in 2001–2002 winter and 2003–2004 winter), the tropopause height was slightly larger with a sharp tropopause and low temperature. The process behind these observed features has been discussed.
Top-side ionosphere response to extreme solar events
Authors: Dmitriev A. V. , Yeh H.-C. , Chao J.-K. , Veselovsky I. S. , Su S.-Y. , Fu C. C. 
Published: June 2010

Abstract. Strong X-flares and solar energetic particle (SEP) fluxes are considered as sources of topside ionospheric disturbances observed by the ROCSAT-1/IPEI instrument during the Bastille Day event on 14 July 2000 and the Halloween event on 28 October–4 November 2003. It was found that within a prestorm period in the dayside ionosphere at altitudes of ~600 km the ion density increased up to ~80% in response to flare-associated enhancements of the solar X-ray emission. Ionospheric response to the SEP events was revealed both at sunlit and nightside hemispheres, where the ion density increased up to ~40% and 100%, respectively. We did not find any prominent response of the ion temperature to the X-ray and SEP enhancements. The largest X-ray and SEP impacts were found for the X17 solar flare on 28 October 2003, which was characterized by the most intense fluxes of solar EUV (Tsurutani et al., 2005) and relativistic solar particles (Veselovsky et al., 2004). Solar events on 14 July 2000 and 29 October 2003 demonstrate weaker impacts with respect to their X-ray and SEP intensities. The weakest ionospheric response is observed for the limb X28 solar flare on 4 November 2003. The topside ionosphere response to the extreme solar events is interpreted in terms of the short-duration impact of the solar electromagnetic radiation and the long-lasting impact of the SEP.
Thermally driven circulation in a region of complex topography: comparison of wind-profiling radar measurements and MM5 numerical predictions
Authors: Bianco L. , Tomassetti B. , Coppola E. , Fracassi A. , Verdecchia M. , Visconti G. 
Published: June 2010

Abstract. The diurnal variation of regional wind patterns in the complex terrain of Central Italy was investigated for summer fair-weather conditions and winter time periods using a radar wind profiler. The profiler is located on a site where interaction between the complex topography and land-surface produces a variety of thermally and dynamically driven wind systems. The observational data set, collected for a period of one year, was used first to describe the diurnal evolution of thermal driven winds, second to validate the Mesoscale Model 5 (MM5) that is a three-dimensional numerical model. This type of analysis was focused on the near-surface wind observation, since thermally driven winds occur in the lower atmosphere. According to the valley wind theory expectations, the site – located on the left sidewall of the valley (looking up valley) – experiences a clockwise turning with time. Same characteristics in the behavior were established in both the experimental and numerical results. Because the thermally driven flows can have some depth and may be influenced mainly by model errors, as a third step the analysis focuses on a subset of cases to explore four different MM5 Planetary Boundary Layer (PBL) parameterizations. The reason is to test how the results are sensitive to the selected PBL parameterization, and to identify the better parameterization if it is possible. For this purpose we analysed the MM5 output for the whole PBL levels. The chosen PBL parameterizations are: 1) Gayno-Seaman; 2) Medium-Range Forecast; 3) Mellor-Yamada scheme as used in the ETA model; and 4) Blackadar.
A global climatology for equatorial plasma bubbles in the topside ionosphere
Authors: Gentile L. C. , Burke W. J. , Rich F. J. 
Published: June 2010

Abstract. We have developed a global climatology of equatorial plasma bubble (EPB) occurrence based on evening sector plasma density measurements from polar-orbiting Defense Meteorological Satellite Program (DMSP) spacecraft during 1989-2004. EPBs are irregular plasma density depletions in the post-sunset ionosphere that degrade communication and navigation signals. More than 14400 EPBs were identified in ~134000 DMSP orbits. DMSP observations basically agree with Tsunoda's (1985) hypothesis that EPB rates peak when the terminator is aligned with the Earth's magnetic field, but there are also unpredicted offsets in many longitude sectors. We present an updated climatology for the full database from 1989-2004 along with new plots for specific phases of the solar cycle: maximum 1989-1992 and 1999-2002, minimum 1994-1997, and transition years 1993, 1998, and 2003. As expected, there are significant differences between the climatologies for solar maximum and minimum and between the two solar maximum phases as well. We also compare DMSP F12, F14, F15, and F16 observations at slightly different local times during 2000-2004 to examine local time effects on EPB rates. The global climatologies developed using the DMSP EPB database provide an environmental context for the long-range prediction tools under development for the Communication/Navigation Outage Forecasting System (C/NOFS) mission.
Alternating bursts of low energy ions and electrons near the substorm onset
Authors: Kozelova T. V. , Lazutin L. L. , Kozelov B. V. , Meredith N. , Danielides M. A. 
Published: June 2010

Abstract. The substorm associated behavior of the low energy particles (30 eV–28.5 keV) near the earthward edge of the plasma sheet is examined using data from CRRES during the late growth and early expansion phases of a substorm on 12 March 1991 and their significance for the substorm onset mechanism is discussed. In this substorm, the CRRES was located on L ~6.3 and ~20° westward of the substorm onset and observed the sequence of the alternating bursts of the low energy ions and electrons. The bursts of the 0.633–9.6 keV ions occurred 1–2 min before the (7.31–21.7 keV) electron bursts. The first ion burst happened 2min before the substorm onset, at the moment of weak brightening of the most equatorial pre-breakup arc near the latitude ~62°. The alternation of the ion and electron bursts may be a signature of a drift-Alfvén ballooning instability on the inner edge of the plasma sheet near substorm onset.