bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mediterranean ocean forecasting system: first phase of implementation (1998–2001)
Authors: Pinardi N. , Allen I. , Demirov E. , De Mey P. , Korres G. , Lascaratos A. , Le Traon P.-Y. , Maillard C. , Manzella G. , Tziavos C.
Published: June 2010

Abstract. The Mediterranean Forecasting system Pilot Project has concluded its activities in 2001, achieving the following goals: 1. Realization of the first high-frequency (twice a month) Voluntary Observing Ship (VOS) system for the Mediterranean Sea with XBT profiles for the upper thermocline (0–700 m) and 12 n.m. along track nominal resolution; 2. Realization of the first Mediterranean Multidisciplinary Moored Array (M3A) system for the Near-Real-Time (NRT) acquisition of physical and biochemical observations. The actual observations consists of: air-sea interaction parameters, upper thermocline (0–500 m) temperature, salinity, oxygen and currents, euphotic zone (0–100 m) chlorophyll, nutrients, Photosinthetically Available Radiation (PAR) and turbidity; 3. Analysis and NRT dissemination of high quality along track Sea Level Anomaly (SLA), Sea Surface Temperature (SST) data from satellite sensors to be assimilated into the forecasting model; 4. Assembly and implementation of a multivariate Reduced Order Optimal Interpolation scheme (ROOI) for assimilation in NRT of all available data, in particular, SLA and VOS-XBT profiles; 5. Demonstration of the practical feasibility of NRT ten day forecasts at the Mediterranean basin scale with resolution of 0.125° in latitude and longitude. The analysis or nowcast is done once a week; 6. Development and implementation of nested regional (5 km) and shelf (2–3 km) models to simulate the seasonal variability. Four regional and nine shelf models were implemented successfully, nested within the forecasting model. The implementation exercise was carried out in different region/shelf dynamical regimes and it was demonstrated that one-way nesting is practical and accurate; 7. Validation and calibration of a complex ecosystem model in data reach shelf areas, to prepare for forecasting in a future phase. The same ecosystem model is capable of reproducing the major features of the primary producers’ carbon cycle in different regions and shelf areas. The model simulations were compared with the multidisciplinary M3A buoy observations and assimilation techniques were developed for the biochemical data. This paper overviews the methodological aspects of the research done, from the NRT observing system to the forecasting/modelling components and to the extensive validation/calibration experiments carried out with regional/shelf and ecosystem models. Key words. Oceanography: general (ocean prediction; instruments and techniques) Oceanography: physical (currents)
First results obtained by the Cluster STAFF experiment
Authors: Cornilleau-Wehrlin N. , Chanteur G. , Perraut S. , Rezeau L. , Robert P. , Roux A. , de Villedary C. , Canu P. , Maksimovic M. , de Conchy Y. , Hubert D. , Lacombe C. , Lefeuvre F. , Parrot M. , Pinçon J. L. , Décréau P. M. E. , Harvey C. C. , Louarn Ph. , Santolik O. , Alleyne H. St. C. , Roth M. , Chust T. , Le Contel O. ,   STAFF team
Published: June 2010

Abstract. The Spatio Temporal Analysis of Field Fluctuations (STAFF) experiment is one of the five experiments, which constitute the Cluster Wave Experiment Consortium (WEC). STAFF consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, a waveform unit (up to either 10 Hz or 180 Hz) and a Spectrum Analyser (up to 4 kHz). The Spectrum Analyser combines the 3 magnetic components of the waves with the two electric components measured by the Electric Fields and Waves experiment (EFW) to calculate in real time the 5 × 5 Hermitian cross-spectral matrix at 27 frequencies distributed logarithmically in the frequency range 8 Hz to 4 kHz. The time resolution varies between 0.125 s and 4 s. The first results show the capabilities of the experiment, with examples in different regions of the magnetosphere-solar wind system that were encountered by Cluster at the beginning of its operational phase. First results obtained by the use of some of the tools that have been prepared specifically for the Cluster mission are described. The characterisation of the motion of the bow shock between successive crossings, using the reciprocal vector method, is given. The full characterisation of the waves analysed by the Spectrum Analyser, thanks to a dedicated program called PRASSADCO, is applied to some events; in particular a case of very confined electromagnetic waves in the vicinity of the equatorial region is presented and discussed.Key words. Magnetospheric physics (magnetopause, cusp and boundary layer) – Space plasma physics (waves and instabilities; shock waves)
Improved near real-time data management procedures for the Mediterranean ocean Forecasting System-Voluntary Observing Ship program
Authors: Manzella G. M. R. , Scoccimarro E. , Pinardi N. , Tonani M.
Published: June 2010

Abstract. A "ship of opportunity" program was launched as part of the Mediterranean Forecasting System Pilot Project. During the operational period (September 1999 to May 2000), six tracks covered the Mediterranean from the northern to southern boundaries approximately every 15 days, while a long eastwest track from Haifa to Gibraltar was covered approximately every month. XBT data were collected, sub-sampled at 15 inflection points and transmitted through a satellite communication system to a regional data centre. It was found that this data transmission system has limitations in terms of quality of the temperature profiles and quantity of data successfully transmitted. At the end of the MFSPP operational period, a new strategy for data transmission and management was developed. First of all, VOS-XBT data are transmitted with full resolution. Secondly, a new data management system, called Near Real Time Quality Control for XBT (NRT.QC.XBT), was defined to produce a parallel stream of high quality XBT data for further scientific analysis. The procedure includes: (1) Position control; (2) Elimination of spikes; (3) Re-sampling at a 1 metre vertical interval; (4) Filtering; (5) General malfunctioning check; (6) Comparison with climatology (and distance from this in terms of standard deviations); (7) Visual check; and (8) Data consistency check. The first six steps of the new procedure are completely automated; they are also performed using a new climatology developed as part of the project. The visual checks are finally done with a free-market software that allows NRT final data assessment. Key words. Oceanography: physical (instruments and techniques; general circulation; hydrography)
Mid-latitude ionospheric scintillation anomaly in the Far East
Authors: Hajkowicz L. A. , Minakoshi H.
Published: June 2010

Abstract. A long-term (over 3 years) study has been undertaken to obtain a comprehensive evaluation of VHF ionospheric scintillation morphology in East Asia (at Kokobunji in Japan), using amplitude records from Transit satellites. It is now evident that summer day and night scintillation enhancement in this mid-latitude region is a long-term evidence of a well-known Asian ionospheric disturbance anomaly. The scintillation activity is particularly strong during summer nights (21:00–24:00 LT) and on occasion, all satellite passes recorded on consecutive days are associated with pronounced scintillation activity. A second sub-maximum is observed in the summer pre-noon period (09:00–12:00 LT). The scintillation regions extend latitudinally for a distance of 400–600 km in the F-region and 100–200 km in the E-region, mostly equatorwards of Kokobunji. For comparison similar scintillation data obtained for one year at the same longitudinal sector but in southern mid-latitudes (Brisbane in Australia) were compared with the simultaneous northern scintillation data. The scintillation activity at Brisbane was much less pronounced in the southern summer but was of the same low level during other seasons as that for Kokobunji. This consistent scintillation anomaly, as yet, has not been included in the global scintillation models, which are essential for radio-satellite communications.Key words. Ionosphere (mid-latitude ionosphere; ionospheric irregularities)
Geomagnetic storm effects at F1-layer heights from incoherent scatter observations
Authors: Mikhailov A. V. , Schlegel K.
Published: June 2010

Abstract. Storm effects at F1-layer heights (160–200 km) were analyzed for the first time using Millstone Hill (mid-latitudes) and EISCAT (auroral zone) incoherent scatter (IS) observations. The morphological study has shown both increases (positive effect) and decreases (negative effect) in electron concentration. Negative storm effects prevail for all seasons and show a larger magnitude than positive ones, the magnitude of the effect normally increasing with height. At Millstone Hill the summer storm effects are small compared to other seasons, but they are well detectable. At EISCAT this summer decrease takes place only with respect to the autumnal period and the autumn/spring asymmetry in the storm effects is well pronounced. Direct and significant correlation exists between deviations in electron concentration at the F1-layer heights and in the F2-layer maximum. Unlike the F2-layer the F1-region demonstrates a relatively small reaction to geomagnetic disturbances despite large perturbations in thermospheric parameters. Aeronomic parameters extracted from IS observations are used to explain the revealed morphology. A competition between atomic and molecular ion contributions to Ne variations was found to be the main physical mechanism controlling the F1-layer storm effect. The revealed morphology is shown to be related with neutral composition (O, O2, N2) seasonal and storm-time variations. The present day understanding of the F1-region formation mechanisms is sufficient to explain the observed storm effects.Key words. Atmospheric composition and structure (thermosphere-composition and chemistry); ionosphere (ion chemistry and composition; ionospheric disturbances)
Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations
Authors: Funk O. , Pfeilsticker K.
Published: June 2010

Abstract. This paper addresses the statistics underlying cloudy sky radiative transfer (RT) by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999). Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD). This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate) RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements. Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques)
A note on the ring current in Saturn’s magnetosphere: Comparison of magnetic data obtained during the Pioneer-11 and Voyager-1 and -2 fly-bys
Authors: Bunce E. J. , Cowley S. W. H.
Published: June 2010

Abstract. We examine the residual (measured minus internal) magnetic field vectors observed in Saturn’s magnetosphere during the Pioneer-11 fly-by in 1979, and compare them with those observed during the Voyager-1 and -2 fly-bys in 1980 and 1981. We show for the first time that a ring current system was present within the magnetosphere during the Pioneer-11 encounter, which was qualitatively similar to those present during the Voyager fly-bys. The analysis also shows, however, that the ring current was located closer to the planet during the Pioneer-11 encounter than during the comparable Voyager-1 fly-by, reflecting the more com-pressed nature of the magnetosphere at the time. The residual field vectors have been fit using an adaptation of the current system proposed for Jupiter by Connerney et al. (1981a). A model that provides a reasonably good fit to the Pioneer-11 Saturn data extends radially between 6.5 and 12.5 RS (compared with a noon-sector magnetopause distance of 17 RS), has a north-south extent of 4 RS, and carries a total current of 9.6 MA. A corresponding model that provides a qualitatively similar fit to the Voyager data, determined previously by Connerney et al. (1983), extends radially between 8 and 15.5 RS (compared with a noon-sector magnetopause distance for Voyager-1 of 23–24 RS), has a north-south extent of 6 RS, and carries a total current of 11.5 MA.Key words. Magnetospheric physics (current systems, magnetospheric configuration and dynamics, planetary magnetospheres)
Statistical analysis of nonlinear wave interactions in simulated Langmuir turbulence data
Authors: Soucek J. , Dudok de Wit T. , Krasnoselskikh V. , Volokitin A.
Published: June 2010

Abstract. We present a statistical analysis of strong turbulence of Langmuir and ion-sound waves resulting from beam-plasma interaction. The analysis is carried out on data sets produced by a numerical simulation of one-dimensional Zakharov’s equations. The nonlinear wave interactions are studied using two different approaches: high-order spectra and Volterra models. These methods were applied to identify two and three wave processes in the data, and the Volterra model was furthermore employed to evaluate the direction and magnitude of energy transfer between the wave modes in the case of Langmuir wave decay. We demonstrate that these methods allow one to determine the relative importance of strongly and weakly turbulent processes. The statistical validity of the results was thoroughly tested using surrogated data set analysis.Key words. Space plasma physics (wave-wave interactions; experimental and mathematical techniques; nonlinear phenomena)
Multi-instrument study of the dynamic cusp during dominant IMF By conditions
Authors: Khan H. , Lester M. , Davies J. A. , Milan S. E. , Sandholt P. E.
Published: June 2010

Abstract. We present multi-instrument observations using the meridian scanning photometer (MSP) at NyAlesund, the EISCAT Svalbard radar (ESR) and the CUTLASS Finland HF radar, to investigate the dynamics of the cusp region during pulsed reconnection events. The optical data obtained from the MSP indicate the presence of several poleward-moving auroral forms (PMAFs) which have been previously identified as the auroral signature of pulsed reconnection. Furthermore, the optical green line (557.7 nm) luminosity indicates a loss of emission equatorward of the location of the onset of the PMAFs, characteristic of magnetospheric plasma escaping to the magnetosheath along newly opened field lines. This reduction in green line luminosity creates a "dark region", the equatorward edge of which is found to lie close to the boundary between high and low spectral widths observed by the CUTLASS Finland radar. High spectral widths on the dayside have previously been identified as a good indicator of cusp backscatter. Both of these boundaries have been suggested to provide an accurate representation of the location of the open/closed field line boundary. The ESR observations show enhancements in electron density and electron temperature occurring in conjunction with the optical PMAFs. The observations demonstrate some correspondence with the theoretical predictions of Davis and Lockwood (1996), who used an auroral precipitation model to predict ESR observations in the vicinity of the cusp. However, the limitations of this model are apparent under conditions of large plasma flows in the ionosphere. Finally, convection velocities obtained from the HF radar data illustrate a flow regime similar to that predicted to be driven by strong IMF By, as described by Cowley and Lockwood (1992), demonstrating an initial azimuthal flow followed by a rotation to more poleward directions.Key words. Ionosphere (ionosphere-magnetosphere interactions; particle precipitation) – Magnetospheric physics (magnetopause, cusp and boundary layers)
Rocket-borne investigation of auroral patches in the evening sector during substorm recovery
Authors: Danielides M. A. , Kozlovsky A.
Published: June 2010

Abstract. On 11 February 1997 at 08:36 UT after a substorm onset the Auroral Turbulence 2 sounding rocket was launched from Poker Flat Research Range, Alaska into a moderately active auroral region. This experiment has allowed us to investigate evening (21:00 MLT) auroral forms at the substorm recovery, which were discrete multiple auroral arcs stretched to, the east and southeast from the breakup region, and bright auroral patches propagating westward along the arcs like a luminosity wave, which is a typical feature of the disturbed arc. The rocket crossed an auroral arc of about 40 km width, stretched along southeast direction. Auroral patches and associated electric fields formed a 200 km long periodical structure, which propagated along the arc westward at a velocity of 3 km/s, whereas the ionospheric plasma velocity inside the arc was 300 m/s westward. The spatial periodicity in the rocket data was found from optical ground-based observations, from electric field in situ measurements, as well as from ground-based magnetic observations. The bright patches were co-located with equatorward plasma flow across the arc of the order of 200 m/s in magnitude, whereas the plasma flow tended to be poleward at the intervals between the patches, where the electric field reached the magnitude of up to 20 mV/m, and these maxima were co-located with the peaks in electron precipitations indicated by the electron counter on board the rocket. Pulsations of a 70-s period were observed on the ground in the eastern component of the magnetic field and this is consistent with the moving auroral patches and the north-south plasma flows associated with them. The enhanced patch-associated electric field and fast westward propagation suggest essential differences between evening auroral patches and those occurring in the morning ionosphere. We propose the wave that propagates along the plasma sheet boundary to be a promising mechanism for the evening auroral patches.Key words. Ionosphere (auroral ionosphere; electric fields and currents)
Post midnight spread-F occurrence over Waltair (17.7° N, 83.3° E) during low and ascending phases of solar activity
Authors: Niranjan K. , Brahmanandam P. S. , Ramakrishna Rao P. , Uma G. , Prasad D. S. V. V. D. , Rama Rao P. V. S.
Published: June 2010

Abstract. A study carried out on the occurrence of post midnight spread-F events at a low-latitude station, Waltair (17.7° N, 83.3° E), India revealed that its occurrence is maximum in the summer solstice months of the low solar activity period and decreases with an increase in the sunspot activity. The F-region virtual height variations show that 80% of these spread-F cases are associated with an increase in the F-region altitude. It is suggested with the support of the night airglow 6300 A zenith intensity data obtained with co-located ground-based night airglow photometer and electron temperature data from the Indian SROSS C2 satellite that the seasonal variation of the occurrence and probable onset times of the post midnight spread-F depend on the characteristics of the highly variable semipermanent equatorial Midnight Temperature Maximum (MTM).Key words. Ionosphere (ionospheric irregularities; ionosphere atmosphere interactions) Atmospheric composition and structure (airglow and Aurora)
Long-term trends of foE and geomagnetic activity variations
Authors: Mikhailov A. V. , de la Morena B. A.
Published: June 2010

Abstract. A relationship between foE trends and geomagnetic activity long-term variations has been revealed for the first time. By analogy with earlier obtained results on the foF2 trends it is possible to speak about the geomagnetic control of the foE long-term trends as well. Periods of increasing geomagnetic activity correspond to negative foE trends, while these trends are positive for the decreasing phase of geomagnetic activity. This "natural" relationship breaks down around 1970 (on some stations later) when pronounced positive foE trends have appeared on most of the stations considered. The dependence of foE trends on geomagnetic activity can be related with nitric oxide variations at the E-layer heights. The positive foE trends that appeared after the "break down" effect may also be explained by the [NO] decrease which is not related to geomagnetic activity variations. But negative trends or irregular foE variations on some stations for the same time period require some different mechanism. Chemical pollution of the lower thermosphere due to the anthropogenic activity may be responsible for such abnormal foE behavior after the end of the 1960s.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances)
Multi-frequency observations of E-region HF radar aurora
Authors: Milan S. E. , Lester M. , Sato N.
Published: June 2010

Abstract. Multi-frequency observations of E-region coherent backscatter from decametre waves reveal that auroral echoes tend to comprise two spectral components superimposed, one at low Doppler shifts, below 250 ms-1, and the other Doppler shifted to near the ion-acoustic speed or above, up to 800 ms-1. The low Doppler shift component occurs at all look directions; Doppler shifts near the ion acoustic speed occur when looking at low flow angles along the direction of the electron drift in the electrojet, and Doppler shifts in excess of the ion acoustic speed occur at intermediate flow angles. The latter population appears most commonly at radar frequencies near 10–12 MHz, with its occurrence decreasing dramatically at higher frequencies. The velocity of the high Doppler shift echoes increases with increasing radar frequency, or irregularity wave number k. The velocity of the low Doppler shift population appears to be suppressed significantly below the line-of-sight component of the electron drift. Initial estimates of the altitude from which scatter occurs suggest that the high Doppler shift echoes originate from higher in the E-region than the low Doppler shift echoes, certainly in the eastward electrojet. We discuss these observations with reference to the theories of de/stabilization of two-stream waves by electron density gradients and electrostatic ion cyclotron waves excited by field-parallel electron drifts.Key words. Ionosphere (ionospheric irregularities)
Morphology of the spectral resonance structure of the electromagnetic background noise in the range of 0.1–4 Hz at L = 5.2
Authors: Yahnin A. G. , Semenova N. V. , Ostapenko A. A. , Kangas J. , Manninen J. , Turunen T.
Published: June 2010

Abstract. Continuous observations of fluctuations of the geomagnetic field at Sodankylä Geophysical Observatory (L = 5.2) were used for a comprehensive morphological study of the spectral resonance structure (SRS) seen in the background electromagnetic noise in the frequency range of 0.1–4.0 Hz. It is shown that the occurrence rate of SRS is higher in the nighttime than in the daytime. The occurrence rate is higher in winter than in summer. The SRS frequencies and the difference between neighbouring eigenfrequencies (the frequency scale) increase towards nighttime and decrease towards daytime. Both frequency scale and occurrence rate exhibit a clear tendency to decrease from minimum to maximum of the solar activity cycle. It is found that the occurrence rate of SRS decreases when geomagnetic activity increases. The SRS is believed to be a consequence of a resonator for Alfvén waves, which is suggested to exist in the upper ionosphere. According to the theory of the ionospheric Alfvén resonator (IAR), characteristics of SRS crucially depend on electron density in the F-layer maximum, as well as on the altitudinal scale of the density decay above the maximum.We compared the SRS morphological properties with predictions of the IAR theory. The ionospheric parameters needed for calculation were obtained from the ionosphere model (IRI-95), as well as from measurements made with the ionosonde in Sodankylä. We conclude that, indeed, the main morphological properties of SRS are explained on the basis of the IAR theory. The measured parameters of SRS can be used for improving the ionospheric models.Key words. Ionosphere (auroral ionosphere; wave propagation) – Radio Science (electromagnetic noise and interference)
Periodicities in energy dissipation rates in the auroral mesosphere/lower thermosphere
Authors: Hall C. M. , Nozawa S. , Meek C. E. , Manson A. H. , Luo Y.
Published: June 2010

Abstract. It is possible for medium-frequency (MF) radar systems to estimate kinetic energy dissipation rates by measuring signal fading times. Here, we present approximately 5 years of such results from Tromsø (69° N, 19° E) and in particular, investigate the periodicities present at different altitudes in the regime 80 to 100 km. We detect the known annual variation in the mesosphere and the semiannual variation on the lower thermosphere. In addition, other features are observed including terannual and ~ 27-day components in the lower thermosphere.Key words. Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; turbulence)
Classification of hemispheric monthly mean stratospheric potential vorticity fields
Authors: Huth R. , Canziani P. O.
Published: June 2010

Abstract. Monthly mean NCEP reanalysis potential vorticity fields at the 650 K isentropic level over the Northern and Southern Hemispheres between 1979 and 1997 were studied using multivariate analysis tools. Principal component analysis in the T-mode was applied to demonstrate the validity of such statistical techniques for the study of stratospheric dynamics and climatology. The method, complementarily applied to both the raw and anomaly fields, was useful in determining and classifying the characteristics of winter and summer PV fields on both hemispheres, in particular, the well-known differences in the behaviour and persistence of the polar vortices. It was possible to identify such features as sudden warming events in the Northern Hemisphere and final warming dates in both hemispheres. The stratospheric impact of other atmospheric processes, such as volcanic eruptions, also identified though the results, must be viewed at this stage as tentative. An interesting change in behaviour around 1990 was detected over both hemispheres.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; general circulation; climatology)
Sound speed in the Mediterranean Sea: an analysis from a climatological data set
Authors: Salon S. , Crise A. , Picco P. , de Marinis E. , Gasparini O.
Published: June 2010

Abstract. This paper presents an analysis of sound speed distribution in the Mediterranean Sea based on climatological temperature and salinity data. In the upper layers, propagation is characterised by upward refraction in winter and an acoustic channel in summer. The seasonal cycle of the Mediterranean and the presence of gyres and fronts create a wide range of spatial and temporal variabilities, with relevant differences between the western and eastern basins. It is shown that the analysis of a climatological data set can help in defining regions suitable for successful monitoring by means of acoustic tomography. Empirical Orthogonal Functions (EOF) decomposition on the profiles, performed on the seasonal cycle for some selected areas, demonstrates that two modes account for more than 98% of the variability of the climatological distribution. Reduced order EOF analysis is able to correctly represent sound speed profiles within each zone, thus providing the a priori knowledge for Matched Field Tomography. It is also demonstrated that salinity can affect the tomographic inversion, creating a higher degree of complexity than in the open oceans.Key words. Oceanography: general (marginal and semi-enclosed seas; ocean acoustics)
Reconstructing the long-term cosmic ray intensity: linear relations do not work
Authors: Mursula K. , Usoskin I. G. , Kovaltsov G. A.
Published: June 2010

Abstract. It was recently suggested (Lockwood, 2001) that the cosmic ray intensity in the neutron monitor energy range is linearly related to the coronal source flux, and can be reconstructed for the last 130 years using the long-term coronal flux estimated earlier. Moreover, Lockwood (2001) reconstructed the coronal flux for the last 500 years using a similar linear relation between the flux and the concentration of cosmogenic 10 Be isotopes in polar ice. Here we show that the applied linear relations are oversimplified and lead to unphysical results on long time scales. In particular, the cosmic ray intensity reconstructed by Lockwood (2001) for the last 130 years has a steep trend which is considerably larger than the trend estimated from observations during the last 65 years. Accordingly, the reconstructed cosmic ray intensity reaches or even exceeds the local interstellar cosmic ray flux around 1900. We argue that these unphysical results obtained when using linear relations are due to the oversimplified approach which does not take into account the complex and essentially nonlinear nature of long-term cosmic ray modulation in the heliosphere. We also compare the long-term cosmic ray intensity based on a linear treatment with the reconstruction based on a recent physical model which predicts a considerably lower cosmic ray intensity around 1900.Key words. Interplanetary physics (cosmic rays; heliopause and solar wind termination) – Geomagnetism and paleomagnetism (time variations, secular and long-term)
Substorm-associated large-scale magnetic field changes in the magnetotail: a prerequisite for "magnetotail deflation" events
Authors: Nakai H. , Kamide Y.
Published: June 2010

Abstract. An attempt is made to search for a critical condition in the lobe magnetic field to initiate large-scale magnetic field changes associated with substorm expansions. Using data from ISEE-1 for 1978, sudden decreases in the lobe magnetic field accompanied by magnetic field dipolarizations are identified. In this study, such events are designated as the magnetotail deflation. The magnetic field component parallel to the equatorial plane, BE , is normalized to a fixed geocentric distance, BEN , and is corrected for the compression effect of the solar wind dynamic pres-sure, BENC . It is shown that the BENC value just prior to a magnetotail deflation correlates well with the Dst index; BENC = 37.5 - 0.217 Dst0, where Dst0 denotes the Dst value corrected for the solar wind dynamic pressure. This regression function appears to delineate the upper limit of BENC values, when they are sorted by the Dst0 index. On the basis of this finding it is suggested that a prerequisite condition for magnetotail deflations must exist in the magnetosphere.Key words. Magnetospheric physics (magnetotail; current systems; storms and substorms)
Low frequency geomagnetic field variations at Dome C (Antarctica)
Authors: Lepidi S. , Cafarella L. , Francia P. , Meloni A. , Palangio P. , Schott J. J.
Published: June 2010

Abstract. We conduct an analysis of the geomagnetic field variations recorded at the new Antarctic station Dome C, located very close to the geomagnetic pole, which has been operating for approximately one month during the 1999–2000 campaign. We also perform a comparison with simultaneous measurements at the Italian Antarctic station Terra Nova Bay, in order to investigate the spatial extension of the phenomena observed at very high latitude. Our results show that between the two stations the daily variation is similar and the fluctuations with f ~ 1 mHz are coherent, provided that in both cases the comparison is made between geographically oriented components, suggesting that ionospheric currents related to the geographic position, more than field-aligned currents, are responsible for the lowest frequency variations; conversely, higher frequency (Pc5) fluctuations are substantially decoupled between the two stations. We also found that at Dome C the fluctuation power in the 0.55–6.7 mHz frequency band is well related with the solar wind speed during the whole day and that at Terra Nova Bay the correlation is also high, except around local geomagnetic noon, when the station approaches the polar cusp. These results indicate that the solar wind speed control of the geomagnetic field fluctuation power is very strict in the polar cap and less important close to the polar cusp.Key words. Magnetospheric physics (MHD waves and instabilities; Polar cap phenomena; Solar wind-magnetosphere interactions)
IMF control of cusp proton emission intensity and dayside convection: implications for component and anti-parallel reconnection
Authors: Lockwood M. , Lanchester B. S. , Frey H. U. , Throp K. , Morley S. K. , Milan S. E. , Lester M.
Published: June 2010

Abstract. We study a brightening of the Lyman-a emission in the cusp which occurred in response to a short-lived south-ward turning of the interplanetary magnetic field (IMF) during a period of strongly enhanced solar wind plasma concentration. The cusp proton emission is detected using the SI-12 channel of the FUV imager on the IMAGE spacecraft. Analysis of the IMF observations recorded by the ACE and Wind spacecraft reveals that the assumption of a constant propagation lag from the upstream spacecraft to the Earth is not adequate for these high time-resolution studies. The variations of the southward IMF component observed by ACE and Wind allow for the calculation of the ACE-to-Earth lag as a function of time. Application of the derived propagation delays reveals that the intensity of the cusp emission varied systematically with the IMF clock angle, the relationship being particularly striking when the intensity is normalised to allow for the variation in the upstream solar wind proton concentration. The latitude of the cusp migrated equatorward while the lagged IMF pointed southward, confirming the lag calculation and indicating ongoing magnetopause reconnection. Dayside convection, as monitored by the SuperDARN network of radars, responded rapidly to the IMF changes but lagged behind the cusp proton emission response: this is shown to be as predicted by the model of flow excitation by Cowley and Lockwood (1992). We use the numerical cusp ion precipitation model of Lockwood and Davis (1996), along with modelled Lyman-a emission efficiency and the SI-12 instrument response, to investigate the effect of the sheath field clock angle on the acceleration of ions on crossing the dayside magnetopause. This modelling reveals that the emission commences on each reconnected field line 2–2.5 min after it is opened and peaks 3–5 min after it is opened. We discuss how comparison of the Lyman-a intensities with oxygen emissions observed simultaneously by the SI-13 channel of the FUV instrument offers an opportunity to test whether or not the clock angle dependence is consistent with the "component" or the "anti-parallel" reconnection hypothesis.Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; solar wind-magnetosphere interactions) – Space plasma physics (magnetic reconnection)
Plasma depletion layer: Magnetosheath flow structure and forces
Authors: Wang Y. L. , Raeder J. , Russell C. T.
Published: June 2010

Abstract. The plasma depletion layer (PDL) is a layer on the sunward side of the magnetopause with lower plasma density and higher magnetic field compared to the corresponding upstream magnetosheath values. In a previous study, we have validated the UCLA global (MHD) model in studying the formation of the PDL by comparing model results, using spacecraft solar wind observations as the driver, with in situ PDL observations. In this study, we extend our previous work and examine the detailed MHD forces responsible for the PDL formation. We argue that MHD models, instead of gasdynamic models, should be used to study the PDL, because gasdynamic models cannot produce the PDL on the sunward side of the magnetopause. For northward (IMF), flux tube depletion occurs in almost all the subsolar magnetosheath. However, the streamlines closest to the magnetopause and the stagnation line show the greatest depletion. The relative strength of the various MHD forces changes along these streamlines. Forces along a flux tube at different stages of its depletion in the magnetosheath are analyzed. We find that a strong plasma pressure gradient force along the magnetic field at the bow shock and a pressure gradient force along the flux tube within the magnetosheath usually exist pushing plasma away from the equatorial plane to deplete the flux tube. More complex force structures along the flux tube are found close to the magnetopause. This new, more detailed description of flux tube depletion is compared with the results of Zwan and Wolf (1976) and differences are found. Near the magnetopause, the pressure gradient force along the flux tube either drives plasma away from the equatorial plane or pushes plasma toward the equatorial plane. As a result, a slow mode structure is seen along the flux tube which might be responsible for the observed two-layered slow mode structures. Key words. Magnetospheric physics (magnetosheath; solar wind-magnetosphere interactions). Space plasma physics (numerical simulations studies)
A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere
Authors: Stubbs T. J. , Lockwood M. , Cargill P. , Grande M. , Kellett B. , Perry C.
Published: June 2010

Abstract. We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001) survey of He2+ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992). The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV), we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the tail influence the location and behaviour of the plasma populations in the magnetosphere. Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions; magnetospheric configuration and dynamic)
Multi-instrument observations of the ionospheric counterpart of a bursty bulk flow in the near-Earth plasma sheet
Authors: Grocott A. , Yeoman T. K. , Nakamura R. , Cowley S. W. H. , Frey H. U. , Rème H. , Klecker B.
Published: June 2010

Abstract. On 07 September 2001 the Cluster spacecraft observed a "bursty bulk flow" event in the near-Earth central plasma sheet. This paper presents a detailed study of the coincident ground-based observations and attempts to place them within a simple physical framework. The event in question occurs at ~22:30 UT, some 10min after a southward turning of the IMF. IMAGE and SAMNET magnetometer measurements of the ground magnetic field reveal perturbations of a few tens of nT and small amplitude Pi2 pulsations. CUTLASS radar observations of ionospheric plasma convection show enhanced flows out of the polar cap near midnight, accompanied by an elevated transpolar voltage. Optical data from the IMAGE satellite also show that there is a transient, localised ~1 kR brightening in the UV aurora. These observations are consistent with the earthward transport of plasma in the tail, but also indicate the absence of a typical "large-scale" substorm current wedge. An analysis of the field-aligned current system implied by the radar measurements does suggest the existence of a small-scale current "wedgelet", but one which lacks the global scale and high conductivities observed during substorm expansions. Key words. Ionosphere (auroral ionosphere; ionospheremagnetosphere interactions; plasma convection)
Simultaneous HF measurements of E- and F-region Doppler velocities at large flow angles
Authors: Makarevitch R. A. , Honary F. , Koustov A. V.
Published: June 2010

Abstract. Data collected by the CUTLASS Finland HF radar are used to illustrate the significant difference between the cosine component of the plasma convection in the F-region and the Doppler velocity of the E-region coherent echoes observed at large flow angles. We show that the E-region velocity is ~5 times smaller in magnitude and rotated by ~30° clockwise with respect to convection in the F-region. Also, measurements at flow angles larger than 90° exhibit a completely new feature: Doppler velocity increase with the expected aspect angle and spatial anticorrelation with the backscatter power. By considering DMSP drift-meter measurements we argue that the difference between F- and E-region velocities cannot be interpreted in terms of the convection change with latitude. The observed features in the velocity of the E-region echoes can be explained by taking into account the ion drift contribution to the irregularity phase velocity as predicted by the linear fluid theory. Key words. Ionosphere (auroral ionosphere; ionospheric irregularities; plasma convection)
Acceleration of oxygen ions in the dynamic magnetotail
Authors: Birn J. , Thomsen M. F. , Hesse M.
Published: June 2010

Abstract. The substorm-related acceleration and flux increases of energetic oxygen ions are studied on the basis of test particle orbits in the fields obtained from an MHD simulation of plasmoid formation and ejection and the collapse (dipolarization) of the inner tail. The simulated fluxes show large anisotropies and nongyrotropic effects, phase bunching, and spatially and temporally localized beams. The energy distribution of O+ in the region of an earthward beam in the near tail becomes significantly harder, more pronounced than for protons, in qualitative agreement with observations. The simulation also shows tailward beams of energetic O+ions closely associated with the passage of a plasmoid, both inside the plasma sheet boundary and inside the central plasma sheet, consistent with observations in the far tail. The acceleration at the near-Earth x-type neutral line produces a narrow duskward beam of energetic O+ in the duskward extension of the x-line, which was not found to be as pronounced in proton test particle simulations. Key words. Magnetospheric physics (energetic particles, trapped; magnetotail; storms and substorms)
Long-term evolution of magnetospheric current systems during storms
Authors: Ganushkina N. Yu. , Pulkkinen T. I. , Kubyshkina M. V. , Singer H. J. , Russell C. T.
Published: June 2010

Abstract. We present a method to model the storm-time magnetospheric magnetic field using representations of the magnetic field arising from the various magnetospheric current systems. We incorporate the effects of magnetotail changes during substorms by introducing an additional localized thin current sheet into the Tsyganenko T89 model. To represent the storm-time ring current the T89 ring current is replaced by a bean-shaped current system, which has a cross section that is close to the observed distribution of trapped particles in the inner magnetosphere and has an eastward flowing inner and westward flowing outer components. In addition to the symmetric ring current, an asymmetric partial ring current is taken into account with closing Region 2 sense field-aligned currents. Magnetopause currents are varied in accordance with solar wind dynamic pressure variations. Three moderate geomagnetic storms when Dst reached about –150 nT and one big storm with Dst about –250 nT are modelled. The model free parameters are specified for each time step separately using observations from GOES 8 and 9, Polar, Interball and Geotail satellites and Dst measurements. The model gives a high time-resolution field representation of the large-scale magnetic field, and a very good reproduction of the Dst index. It is shown that the ring current is most important during intense storms, whereas the near-Earth tail currents contribute more to the Dst index than the ring current during moderate storms. Key words. Magnetospheric physics (Current systems; Magnetospheric configuration and dynamics; Storms and substorms)
Spatio-temporal patterns of seasonal rainfall in Spain (1912-2000) using cluster and principal component analysis: comparison
Authors: Muñoz-Díaz D. , Rodrigo F. S.
Published: June 2010

Abstract. In this work, cluster and principal component analysis are used to divide Spain in a limited number of climatically homogeneous zones, based on seasonal rainfall for 32 Spanish localities for the period 1912–2000. Using the hierarchical technique of clustering Ward's method, three clusters have been obtained in winter and spring, and four clusters have been obtained in summer and autumn. Results are similar to those obtained by applying principal component analysis. Centroid series of each cluster and principal component series of each EOF have been compared to analyze the temporal patterns. The comparison of both methods indicates that cluster analysis is suitable to establish spatio-temporal patterns of seasonal rainfall distribution in Spain. Key words. Meteorology and atmospheric dynamics (climatology; precipitation; general or miscellaneous)