bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluxes and fluences of SEP events derived from SOLPENCO
Authors: Aran A. , Sanahuja B. , Lario D. 
Published: June 2010

Abstract. We have developed aran04 a tool for rapid predictions of proton flux and fluence profiles observed during gradual solar energetic particle (SEP) events and upstream of the associated traveling interplanetary shocks. This code, named SOLPENCO (for SOLar Particle ENgineering COde), contains a data base with a large set of interplanetary scenarios under which SEP events develop. These scenarios are basically defined by the solar longitude of the parent solar activity, ranging from E75 to W90, and by the position of the observer, located at 0.4 AU or at 1.0 AU, from the Sun. We are now analyzing the performance and reliability of SOLPENCO. We address here two features of SEP events especially relevant to space weather purposes: the peak flux and the fluence. We analyze how the peak flux and the fluence of the synthetic profiles generated by SOLPENCO vary as a function of the strength of the CME-driven shock, the heliolongitude of the solar parent activity and the particle energy considered. In particular, we comment on the dependence of the fluence on the radial distance of the observer (which does not follow an inverse square law), and we draw conclusions about the influence of the shock as a particle accelerator in terms of its evolving strength and the heliolongitude of the solar site where the SEP event originated.
Numerical simulation of the Adriatic Sea principal tidal constituents
Authors: Janeković I. , Kuzmić M. 
Published: June 2010

Abstract. The primary goal of this study was to incorporate data-derived harmonic constants into a complex dynamic model using a form of variational data assimilation, with a view to improve the prediction of 7 dominant tidal constituents in the Adriatic Sea. Firstly, harmonic-constant data for 6 Adriatic stations were fed into a steady-state, 3-D, forward/inverse model to furnish optimal boundary conditions (OBCs). Calculated OBCs were then used to derive individual constituent responses, as well as to synthesise seven-constituent boundary conditions for the time stepping, 3-D model. A separate set of 25 stations provided control harmonic constant data. In validating the model output particular attention has been given to the often-ignored tidal currents. To that end 14 current meter data records were processed into tidal current ellipse parameters and used to examine the comparable model output. Comparison to gauge data has shown that the present solution is better than our own previous one, and shows an improvement over recent solutions by other authors. The model accurately reproduces available data with individual station amplitude differences rarely exceeding 1cm, and with the phase error commonly staying well below 10°. For all tidal constituents individual station differences result in RMSE in the 0.33-0.71-cm range for amplitude, and the 5.6°-19.2° range for phase. Semidiurnal currents appear to be modelled better than the diurnal ones (generally over-predicted). High eccentricity of both data and model-derived ellipses often impaired calculating the proper sense of rotation; inclination of the ellipses proved to be the most robust parameter, successfully predicted for most constituents at all depths.
The importance of solar illumination for discrete and diffuse aurora
Authors: Hamrin M. , Norqvist P. , Rönnmark K. , Fellgård D. 
Published: June 2010

Abstract. We present a comprehensive overview of the occurrence of discrete and diffuse aurora in the nightside Northern Hemisphere at invariant latitudes 55°-75°. Twenty-one months of Freja observations (1 January 1993 to 30 September 1994) from the Northern Hemisphere, obtained at altitude, are included in this investigation. We investigate the importance of seasonal effects, solar illumination and geomagnetic activity for the auroral precipitation. The seasonal variations in the occurrence of discrete aurora are separated from the dependence on solar illumination of the ionosphere. When the effects of sunlight are eliminated, aurora is found to be more common during the summer. The occurrence of diffuse, as well as discrete aurora, is suppressed by solar illumination of the ionosphere. This dependence of diffuse auroral precipitation on ionospheric conditions is not predicted by theories that attribute diffuse aurora to equatorial pitch-angle diffusion of hot magnetospheric electrons.
Solar eclipse effect on geomagnetic induction parameters
Authors: Ádám A. , Verõ J. , Szendrõi J. 
Published: June 2010

Abstract. The 11 August 1999 total solar eclipse had been studied using a large array of stations in Central Europe (Bencze et al., 2005). According to the result of this study, the amplitudes of the field line resonance (FLR)-type pulsations decreased in and around the dark spot by about a factor of 2, and this decrease moved with the velocity of the dark spot in the same direction. This decrease was interpreted as a switch-off of the FLR-type pulsations, due to a change in the eigenperiod of the field line as a consequence of a change in the charged particle distribution along the field line. An effect was also found in the phase of the (magnetic or electric) perpendicular components. At the Nagycenk (NCK) observatory lying in the zone of totality, both magnetic and electric records were available. The magnetotelluric (MT) sounding curve computed by the usual method for the eclipse interval (08:00-14:00 UT) fits the previously known standard curve extremely well. During the eclipse, however, impedance values in the FLR period range were highly scattered. The scatter remained as long as the eclipse lasted. Coherence values between magnetic and electric components decreased significantly. In contrast, an earlier similar switch-off of the FLR-type activity on the same day did not cause a similar scatter, in spite of a comparably low coherence. Thus, the lack of FLR-type activity disturbed the usual MT connection between the magnetic and electric components during the eclipse. The induction vector (tipper), especially its real part, shows a clear effect of the eclipse in the FLR period range (24-29 s), too. Both at NCK and at Bad Bergzabern (BBZ, westernmost station and longest FLR period), a definite decrease in the real tipper was ascertained during the totality. The average direction of the tipper did not change. Concerning both parameters, a random effect cannot fully explain the observed phenomena. The scatter of the EM induction parameters is most likely due to the switch-off of the FLR activity. The possibility of such an effect should be considered in induction studies. Pilipenko and Fedotov (1993) supposed an opposite effect and emphasised lower quality data, if resulting from FLR-type pulsations, while we claim high quality data just from such an activity.
Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate
Authors: Lockwood M. , Davies J. A. , Moen J. , van Eyken A. P. , Oksavik K. , McCrea I. W. , Lester M. 
Published: June 2010

Abstract. Using data from the EISCAT (European Incoherent Scatter) VHF and CUTLASS (Co-operative UK Twin-Located Auroral Sounding System) HF radars, we study the formation of ionospheric polar cap patches and their relationship to the magnetopause reconnection pulses identified in the companion paper by Lockwood et al. (2005). It is shown that the poleward-moving, high-concentration plasma patches observed in the ionosphere by EISCAT on 23 November 1999, as reported by Davies et al. (2002), were often associated with corresponding reconnection rate pulses. However, not all such pulses generated a patch and only within a limited MLT range (11:00-12:00 MLT) did a patch result from a reconnection pulse. Three proposed mechanisms for the production of patches, and of the concentration minima that separate them, are analysed and evaluated: (1) concentration enhancement within the patches by cusp/cleft precipitation; (2) plasma depletion in the minima between the patches by fast plasma flows; and (3) intermittent injection of photoionisation-enhanced plasma into the polar cap. We devise a test to distinguish between the effects of these mechanisms. Some of the events repeat too frequently to apply the test. Others have sufficiently long repeat periods and mechanism (3) is shown to be the only explanation of three of the longer-lived patches seen on this day. However, effect (2) also appears to contribute to some events. We conclude that plasma concentration gradients on the edges of the larger patches arise mainly from local time variations in the subauroral plasma, via the mechanism proposed by Lockwood et al. (2000).
Remote sensing of aerosols over the oceans using MSG/SEVIRI imagery
Authors: Thieuleux F. , Moulin C. , Bréon F. M. , Maignan F. , Poitou J. , Tanré D. 
Published: June 2010

Abstract. The SEVIRI instrument on board Meteosat Second Generation (MSG) offers new capabilities to monitor aerosol transport over the Atlantic and the Mediterranean at high temporal and spatial resolutions, in particular, Saharan dust from North Africa, biomass-burning aerosols from subtropical Africa and pollution from Europe. An inversion technique was developed to estimate both aerosol optical thickness and Angström coefficients from SEVIRI measurements at 0.63 and 0.81 µm. This method relies on an optimized set of aerosol models to ensure a fast processing of full-resolution MSG images and to allow the processing of long time series. SEVIRI images for slots 45, 49 and 53 (11:15, 12:15, 13:15 UT) were processed for June 2003. The retrieved optical thicknesses and Angström coefficients are in good agreement with AERONET in-situ measurements in the Atlantic and in the Mediterranean. Monthly mean maps of both parameters are compared to that obtained with the polar orbiting sensor POLDER for June 2003. There is a good consistency between the two monthly means in terms of optical thickness, but the Angström coefficients show significant differences in the Atlantic zone which is affected by dust transport. These differences may be explained by the lack of specific non-spherical dust models within the inversion. The preliminary results presented in this paper demonstrate, nevertheless, the potential of MSG/SEVIRI for the monitoring of aerosol optical properties at high frequencies over the Atlantic and the Mediterranean.
Statistical characteristics of the total ion density in the topside ionosphere during the period 1996-2004 using empirical orthogonal function (EOF) analysis
Authors: Zhao B. , Wan W. , Liu L. , Yue X. , Venkatraman S. 
Published: June 2010

Abstract. We have applied the empirical orthogonal function (EOF) analysis to examine the climatology of the total ion density Ni at 840 km during the period 1996-2004, obtained from the Defense Meteorological Satellite Program (DMSP) spacecraft. The data set for each of the local time (09:30 LT and 21:30 LT) is decomposed into a time mean plus the sum of EOF bases Ei of space, multiplied by time-varying EOF coefficients Ai. Physical explanations are made on the first three EOFs, which together can capture more than 95% of the total variance of the original data set. Results show that the dominant mode that controls the Ni variability is the solar EUV flux, which is consistent with the results of Rich et al. (2003). The second EOF, associated with the solar declination, presents an annual (summer to winter) asymmetry that is caused by the transequatorial winds. The semiannual variation that appears in the third EOF for the evening sector is interpreted as both the effects of the equatorial electric fields and the wind patterns. Both the annual and semiannual variations are modulated by the solar flux, which has a close relationship with the O+ composition. The quick convergence of the EOF expansion makes it very convenient to construct an empirical model for the original data set. The modeled results show that the accuracy of the prediction depends mainly on the first principal component which has a close relationship with the solar EUV flux.
The climatology of ionospheric plasma bubbles and irregularities over Brazil
Authors: Chu F. D. , Liu J. Y. , Takahashi H. , Sobral J. H. A. , Taylor M. J. , Medeiros A. F. 
Published: June 2010

Abstract. In this paper, we examine ionospheric plasma depletions (or bubbles) and irregularities observed by photometers and a ground-based receiver of the global positioning system (GPS) both located in Brazil, South America. A simultaneous observation reveals that when the ionospheric plasma becomes depleted, the GPS total electron content decreases and the associated phase fluctuations grow. Statistical results show that the plasma bubbles and the significant GPS phase fluctuations generally occur during October-March. The solar activity variation is not obvious in either observation except during the equinoctial months. The GPS phase fluctuations suggest that the most pronounced ionospheric irregularities appear between 20:00 and 01:00 LT, which generally agree with previous ionospheric bubble observations.
Unusual heavy ion injection events observed by Freja
Authors: Yamauchi M. , Eliasson L. , Lundin R. , Norberg O. 
Published: June 2010

Abstract. Heavy ion injection events (registered in the C+/N+/O+ mass channel) into the ionosphere at 1700km height are surveyed using the Swedish-German Freja satellite data. Heavy ion injections from the inner magnetosphere are mostly found in the nightside sector with a few exceptions that occur on the dayside. We report on these exceptional cases, particularly two specific events which seem to have a different generation/transport mechanism of heavy ions from the majority of cases: 1) mono-energetic heavy ion injection near local noon with oxygen first and protons later; and 2) a multiple heavy ion dispersion event at 9 MLT. Both events are unique without any similar events in terms of dispersion pattern during the more than 2 years of the entire Freja operation, and these events are found during the main phase of major magnetic storms (peak Dst is -144nT and -105nT). The first event is probably of dayside origin but the exact mechanism to make both energy filter and mass filter is unknown. The second event can be traced back to one localized energization of dense oxygen with strong pitch-angle anisotropy within 1000km distance from the spacecraft.
Localized fast flow disturbance observed in the plasma sheet and in the ionosphere
Authors: Nakamura R. , Amm O. , Laakso H. , Draper N. C. , Lester M. , Grocott A. , Klecker B. , McCrea I. W. , Balogh A. , Rème H. , André M. 
Published: June 2010

Abstract. An isolated plasma sheet flow burst took place at 22:02 UT, 1 September 2002, when the Cluster footpoint was located within the area covered by the Magnetometers-Ionospheric Radars-All-sky Cameras Large Experiment (MIRACLE). The event was associated with a clear but weak ionospheric disturbance and took place during a steady southward IMF interval, about 1h preceding a major substorm onset. Multipoint observations, both in space and from the ground, allow us to discuss the temporal and spatial scale of the disturbance both in the magnetosphere and ionosphere. Based on measurements from four Cluster spacecraft it is inferred that Cluster observed the dusk side part of a localized flow channel in the plasma sheet with a flow shear at the front, suggesting a field-aligned current out from the ionosphere. In the ionosphere the equivalent current pattern and possible field-aligned current location show a pattern similar to the auroral streamers previously obtained during an active period, except for its spatial scale and amplitude. It is inferred that the footpoint of Cluster was located in the region of an upward field-aligned current, consistent with the magnetospheric observations. The entire disturbance in the ionosphere lasted about 10min, consistent with the time scale of the current sheet disturbance in the magnetosphere. The plasma sheet bulk flow, on the other hand, had a time scale of about 2min, corresponding to the time scale of an equatorward excursion of the enhanced electrojet. These observations confirm that localized enhanced convection in the magnetosphere and associated changes in the current sheet structure produce a signature with consistent temporal and spatial scale at the conjugate ionosphere.
A statistical study of gravity waves from radiosonde observations at Wuhan (30° N, 114° E) China
Authors: Zhang S. D. , Yi F. 
Published: June 2010

Abstract. Several works concerning the dynamical and thermal structures and inertial gravity wave activities in the troposphere and lower stratosphere (TLS) from the radiosonde observation have been reported before, but these works were concentrated on either equatorial or polar regions. In this paper, background atmosphere and gravity wave activities in the TLS over Wuhan (30° N, 114° E) (a medium latitudinal region) were statistically studied by using the data from radiosonde observations on a twice daily basis at 08:00 and 20:00 LT in the period between 2000 and 2002. The monthly-averaged temperature and horizontal winds exhibit the essential dynamic and thermal structures of the background atmosphere. For avoiding the extreme values of background winds and temperature in the height range of 11-18km, we studied gravity waves, respectively, in two separate height regions, one is from ground surface to 10km (lower part), and the other is within 18-25km (upper part). In total, 791 and 1165 quasi-monochromatic inertial gravity waves were extracted from our data set for the lower and upper parts, respectively. The gravity wave parameters (intrinsic frequencies, amplitudes, wavelengths, intrinsic phase velocities and wave energies) are calculated and statistically studied. The statistical results revealed that in the lower part, there were 49.4% of gravity waves propagating upward, and the percentage was 76.4% in the upper part. Moreover, the average wave amplitudes and energies are less than those at the lower latitudinal regions, which indicates that the gravity wave parameters have a latitudinal dependence. The correlated temporal evolution of the monthly-averaged wave energies in the lower and upper parts and a subsequent quantitative analysis strongly suggested that at the observation site, dynamical instability (strong wind shear) induced by the tropospheric jet is the main excitation source of inertial gravity waves in the TLS.
Ionosphere dynamics over the Southern Hemisphere during the 31 March 2001 severe magnetic storm using multi-instrument measurement data
Authors: Yizengaw E. , Dyson P. L. , Essex E. A. , Moldwin M. B. 
Published: June 2010

Abstract. The effects of the 31 March 2001 severe magnetic storm on the Southern Hemisphere ionosphere have been studied using ground-based and satellite measurements. The prime goal of this comprehensive study is to track the ionospheric response from high-to-low latitude to obtain a clear understanding of storm-time ionospheric change. The study uses a combination of ionospheric Total Electron Content (TEC) obtained from GPS signal group delay and phase advance measurements, ionosonde data, and data from satellite in-situ measurements, such as the Defense Metrological Satellite Program (DMSP), TOPographic EXplorer (TOPEX), and solar wind data from the Advanced Composition Explorer (ACE). A chain of Global Positioning System (GPS) stations near the 150° E meridian has been used to give comprehensive latitude coverage extending from the cusp to the equatorial region. A tomographic inversion algorithm has been applied to the GPS TEC measurements to obtain maps of the latitudinal structure of the ionospheric during this severe magnetic storm period, enabling both the spatial and temporal response of the ionosphere to be studied. Analysis of data from several of the instruments indicates that a strong density enhancement occurred at mid-latitudes at 11:00 UT on 31 March 2001 and was followed by equatorward propagating large-scale Travelling Ionospheric Disturbances (TIDs). The tomographic reconstruction revealed important features in ionospheric structure, such as quasi-wave formations extending finger-like to higher altitudes. The most pronounced ionospheric effects of the storm occurred at high- and mid-latitudes, where strong positive disturbances occurred during the storm main phase, followed by a long lasting negative storm effect during the recovery phase. Relatively minor storm effects occurred in the equatorial region.
Origin of the turbulent spectra in the high-altitude cusp: Cluster spacecraft observations
Authors: Nykyri K. , Grison B. , Cargill P. J. , Lavraud B. , Lucek E. , Dandouras I. , Balogh A. , Cornilleau-Wehrlin N. , Rème H. 
Published: June 2010

Abstract. High-resolution magnetic field data from Cluster Flux Gate Magnetometer (FGM) and the Spatio-Temporal Analysis of Field Fluctuations (STAFF) instruments are used to study turbulent magnetic field fluctuations during the high-altitude cusp crossing on 17 March 2001. Despite the quiet solar wind conditions, the cusp was filled with magnetic field turbulence whose power correlates with the field-aligned ion plasma flux. The magnetic field wave spectra shows power law behavior with both double and single slopes with break in the spectra usually occurring in the vicinity of the local ion cyclotron frequency. Strong peaks in the wave power close to local ion cyclotron frequency were sometimes observed, with secondary peaks at higher harmonics indicative of resonant processes between protons and the waves. We show that the observed spectral break point may be caused partly by damping of obliquely propagating kinetic Alfvén (KAW) waves and partly by cyclotron damping of ion cyclotron waves.
Observing the north polar ionosphere on 30 October 2003 by GPS imaging and IS radars
Authors: Stolle C. , Lilensten J. , Schlüter S. , Jacobi Ch. , Rietveld M. , Lühr H. 
Published: June 2010

Abstract. The evening of 30 October 2003 was subject to a major storm main phase. For this time, we combine large-scale electron content maps from GPS imaging with time series of electron density and temperature of two EISCAT radars in Tromsø and Svalbard and the Sondrestrom radar, for observing the north polar ionosphere. The GPS assimilations resulted in the image of the electron content trace of an anti-sunward polar Tongue Of Ionisation (TOI) consecutively to 20:00 UT. In combination with the radar observations we concluded that the TOI persisted during the whole period of continuous southward IMF Bz until about 22:40 UT while its largest extension toward the nightside auroral region was found between 21:00-22:00 UT. A typical F region electron temperature of ~2000 K and the plasma velocity of ~800 ms-1 support its convective origin from the dayside mid-latitudes. Due to the structured appearance of the electron content distribution and the radar electron density time series we believe that discrete plasma patches formed inside the anti-sunward drift pattern. After two large oscillations of the IMF Bz the nightside plasma density was observed to re-enhance after 23:00 UT along a longitudinal band below 70 N. Coinciding electron temperatures of ~2000 K suggest again the convective nature of the plasma, while a modified convection pattern is expected.