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41.
We performed a detailed analysis of 27 slow coronal mass ejections (CMEs) whose heights were measured in at least 30 coronagraphic
images and were characterized by a high quality index (≥4). Our primary aim was to study the radial evolution of these CMEs
and their properties in the range 2 – 30 solar radii. The instantaneous speeds of CMEs were calculated by using successive
height – time data pairs. The obtained speed – distance profiles [v(R)] are fitted by a power law v = a(R−b)
c
. The power-law indices are found to be in the ranges a=30 – 386, b=1.95 – 3.92, and c=0.03 – 0.79. The power-law exponent c is found to be larger for slower and narrower CMEs. With the exception of two events that had approximately constant velocity,
all events were accelerating. The majority of accelerating events shows a v(R) profile very similar to the solar-wind profile deduced by Sheeley et al. (Astrophys. J.
484, 472, 1997). This indicates that the dynamics of most slow CMEs are dominated by the solar wind drag. 相似文献
42.
A. Caporali C. Aichhorn M. Barlik M. Becker I. Fejes L. Gerhatova D. Ghitau G. Grenerczy J. Hefty S. Krauss D. Medak G. Milev M. Mojzes M. Mulic A. Nardo P. Pesec T. Rus J. Simek J. Sledzinski M. Solaric G. Stangl B. Stopar F. Vespe G. Virag 《Tectonophysics》2009,474(1-2):295
The understanding of the intraplate tectonics of Central Europe requires a detailed picture of how stress is transferred from the interaction of the Eurasian, Nubian and Anatolian plates to the Alpine, Carpathian, Pannonian and Dinaric regions. Recent strain distribution is controlled by the Adria horizontal push, by the Vrancea vertical slab pull and associated horizontal displacements, and by the Aegean/Anatolia extension and slab-roll back. We present a horizontal velocity field for the Alpine-Carpathian-Pannonic-Dinaric and Balkan regions resulting from a new combination of seven different GPS networks formed from permanent and campaign stations. Dedicated velocity profiles in two specific regions are studied in detail. One is the Alpine Pannonian region, with a detailed picture of the NS indentation of the Adria microplate into the Southern Alps, in NE Italy, the deformation in the Tauern Window and the eastwards kinematics of a Pannonian plate fragment. The second study region includes Transylvania, the Southern Carpathians up to the Aegean sea and Albania, where a major right lateral shear deformation exists as a consequence of the NE convergence of the Apulia platform towards the Dinarids, and the SSW motion of Macedonia, Western Bulgaria and Rumania, related to the Hellenic arc dynamics in the Eastern Mediterranean. The profiles in the Alpine–Pannonian area indicate that a velocity drop of 2.5 +/− 0.4 mm/yr associated with the Adria indentation concentrates on a segment of some 50 km south of the Periadriatic fault. The deformation becomes extensional by a similar amount just north of the Periadriatic fault, in the Tauern Window, where the updoming of the Tauern Window implies vertical motion which could well be associated with surface extension. In the EW profile, we observe a sudden velocity change of 1.5 +/− 0.2 mm/yr in 20 km, corresponding to the right lateral Lavant fault, which seems to mark the border between dominant indentation kinematics to the West and dominant extrusion kinematics to the East.Three profiles are considered in Southern and Eastern Europe: one across the lower Adriatic sea from Apulia in Italy to the southern Dinarides, which enables it to constrain the velocity drop associated with the subduction of the Adria microplate into the Dinarides to 3.2 +/− 0.5 mm/yr in 140 km. The second profile is longitudinal and constrains the velocity inversion of 7.4 +/− 1.0 mm/yr in 350 km associated with right lateral shear faults in Albania. The third profile crosses the Transylvania region with a shortening of 2.3 +/− 1.0 mm/yr in 220 km, and the Wallachian–Moesian region up to the Chalcidic peninsula in N Greece. This lower part of the profile implies an extensional stretch of the upper crust of 3.2 +/− 0.9 mm/yr in 440 km, culminating in the Hellenic arc. Strain rate maps are presented in this regional scale, showing the excellent agreement between fault plane solutions of crustal earthquakes and the eigenvectors of the GPS derived two dimensional strain rate tensor.Three profiles are considered in the Balkan and SE Carpathians: one across the lower Adriatic sea from Apulia in Italy to the southern Dinarides, which enables to constrain the velocity drop associated to the subduction of the Adria microplate into the Dinarides to 3.2 +/− 0.5 mm/yr in 140 km. The second profile is longitudinal and constrains the velocity inversion of 7.4 +/− 1.0 mm/yr in 350 km associated to right lateral shear faults in Macedonia, a highly seismic region. The third profile crosses the Transylvania with a shortening2.3 +/− 1.0 mm/yr in 220 km, and the Wallachian–Moesian region up to the Chalcidic peninsula in N Greece. This lower part of the profile implies an extensional stretch of the upper crust of 3.2 +/− 0.9 mm/yr in 440 km, culminating in the Hellenic arc. 相似文献
43.
O. Prakash S. Umapathy A. Shanmugaraju P. Pappa kalaivani Bojan Vršnak 《Solar physics》2010,266(1):135-147
Solar coronal holes (CHs) are large regions of the corona magnetically open to interplanetary space. The nearly rigid north?–?south CH boundaries (CHBs) of equatorward extensions of polar CHs are maintained while the underlying photospheric fields rotate differentially, so interchange magnetic reconnection is presumed to be occurring continually at the CHBs. The time and size scales of the required reconnection events at CHBs have not been established from previous observations with soft X-ray images. We use TRACE 195 Å observations on 9 December 2000 of a long-lived equatorial extension of the negative-polarity north polar CH to look for changes of ??5 arcsec to >?20 arcsec at the western CHB. Brightenings and dimmings are observed on both short (≈?5 minutes) and long (≈?7 hours) time scales, but the CHB maintains its quasi-rigid location. The transient CHB changes do not appear associated with either magnetic field enhancements or the changes in those field enhancements observed in magnetograms from the Michelson Doppler Imager (MDI) on SOHO. In seven hours of TRACE observations we find no examples of the energetic jets similar to those observed to occur in magnetic reconnection in polar plumes. The lack of dramatic changes in the diffuse CHB implies that gradual magnetic reconnection occurs high in the corona with large (??10°) loops and/or weak coronal fields. We compare our results with recent observations of active regions at CHBs. We also discuss how the magnetic polarity symmetry surrounding quasi-rigid CHs implies an asymmetry in the interchange reconnection process and a possible asymmetry in the solar wind composition from the eastern and western CHB source regions. 相似文献
44.
During the last decade, several rainfall-induced deep-seated large landslides with volumes of the order of 1 million m3 were triggered in various locations in Slovenia (central Europe), each representing a serious threat to the nearby villages and traffic infrastructure and urging to be mitigated. The Macesnik landslide, triggered in 1989, and the Slano blato landslide, triggered in 2000, were the first two large landslides in Slovenia, where a combination of drainage and retaining works consisting of deep reinforced concrete (RC) shafts/wells was successfully used as a mitigation measure. This paper presents the field conditions and a brief history of the two landslides with emphasis on the design approach and method used for the stability analysis and the design of deep RC shafts/wells. In addition, the paper gives an insight into the problems associated with the execution of works and provides data about the behavior of the two landslides after drainage and retaining works were completed. The monitoring data show that the undertaken mitigation measures were efficient to improve the stability of both landslides and significantly reduce the risk. 相似文献
45.
A. Shanmugaraju S. Prasanna Subramanian Bojan Vrsnak M. Syed Ibrahim 《Solar physics》2014,289(12):4621-4632
We report a detailed analysis of an interaction between two coronal mass ejections (CMEs) that were observed on 14?–?15 February 2011 and the corresponding radio enhancement, which was similar to the “CME cannibalism” reported by Gopalswamy et al. (Astrophys. J. 548, L91, 2001). A primary CME, with a mean field-of-view velocity of 669 km?s?1 in the Solar and Heliospheric Observatory (SOHO)/Large Angle Spectrometric Coronagraph (LASCO), was more than as twice as fast as the slow CME preceding it (326 km?s?1), which indicates that the two CMEs interacted. A radio-enhancement signature (in the frequency range 1 MHz?–?400 kHz) due to the CME interaction was analyzed and interpreted using the CME data from LASCO and from the Solar Terrestrial Relations Observatory (STEREO) HI-1, radio data from Wind/Radio and Plasma Wave Experiment (WAVES), and employing known electron-density models and kinematic modeling. The following results are obtained: i) The CME interaction occurred around 05:00?–?10:00 UT in a height range 20?–?25 R⊙. An unusual radio signature is observed during the time of interaction in the Wind/WAVES dynamic radio spectrum. ii) The enhancement duration shows that the interaction segment might be wider than 5 R⊙. iii) The shock height estimated using density models for the radio enhancement region is 10?–?30 R⊙. iv) Using kinematic modeling and assuming a completely inelastic collision, the decrease of kinetic energy based on speeds from LASCO data is determined to be 0.77×1023 J, and 3.67×1023 J if speeds from STEREO data are considered. vi) The acceleration, momentum, and force are found to be a=?168 m?s?2, I=6.1×1018 kg?m?s?1, and F=1.7×1015 N, respectively, using STEREO data. 相似文献
46.
Djamalddine Boumezerane Smain Belkacemi Bojan Zlender 《Geotechnical and Geological Engineering》2014,32(2):547-559
A fuzzy sets decision support system is proposed for geotechnical site investigation. The system considers parameters such as geology and soil variability that affect the required number of soundings to adequately characterize a site. It permits also to consider vagueness and lack of information. On the basis of available qualitative and quantitative information, the system allows estimating, for common projects, the number of site soundings. Monte Carlo simulations of entry ranges, where each point has a uniform probability distribution, permit to arrange the output in form of histograms fitted with probability functions. The cases presented show that the fuzzy inference system can be used as a systematic decision support for engineers dealing with site characterization. 相似文献
47.
O. Prakash S. Umapathy A. Shanmugaraju P. Pappa kalaivani Bojan Vr?nak 《Astrophysics and Space Science》2012,337(1):47-64
A detailed investigation on DH-type-II radio bursts recorded in Deca-Hectometer (hereinafter DH-type-II) wavelength range
and their associated CMEs observed during the year 1997–2008 is presented. The sample of 212 DH-type-II associated with CMEs
are classified into three populations: (i) Group I (43 events): DH-type-II associated CMEs are accelerating in the LASCO field
view (a>15 m s−2); (ii) Group II (99 events): approximately constant velocity CMEs (−15<a<15 m s−2) and (iii) Group III (70 events): represents decelerating CMEs (a<−15 m s−2). Our study consists of three steps: (i) statistical properties of DH-type-II bursts of Group I, II and III events; (ii)
analysis of time lags between onsets of flares and CMEs associated with DH-type-II bursts and (iii) statistical properties
of flares and CMEs of Group I, II and III events. We found statistically significant differences between the properties of
DH-type-II bursts of Group I, II and III events. The significance (P
a
) is found using the one-way ANOVA-test to examine the differences between means of groups. For example, there is significant
difference in the duration (P
a
=5%), ending frequency (P
a
=4%) and bandwidth (P
a
=4%). The accelerating and decelerating CMEs have more kinetic energy than the constant speed CMEs. There is a significant
difference between the nose height of CMEs at the end time of DH-type-IIs (P
a
≪1%). From the time delay analysis, we found: (i) there is no significant difference in the delay (flare start—DH-type-II
start and flare peak—DH-type-II start); (ii) small differences in the time delay between the CME onset and DH-type-II start,
delay between the flare start and CME onset times. However, there are high significant differences in: flare duration (P
a
=1%), flare rise time (P
a
=0.5%), flare decay time (P
a
=5%) and CMEs speed (P
a
≪1%) of Group I, II and III events. The general LASCO CMEs have lower width and speeds when compared to the DH CMEs. It seems
there is a strong relation between the kinetic energy of CMEs and DH-type-II properties. 相似文献
48.
Vršnak Bojan Warmuth Alexander Maričić Darije Otruba Wolfgang Ruždjak Vladimir 《Solar physics》2003,217(1):187-198
A huge filament eruption of 12 September 2000 associated with a two-ribbon spotless flare is described. During the acceleration phase the shape of the filament changed, and signatures of topological restructuring of large-scale coronal magnetic fields were inferred by tracking changes of nearby coronal holes. At the same time electron beams associated with the flare impulsive phase escaped into interplanetary space. Based on the time–spatial relationships a hypothesis is put forward, according to which the reconnection between the arcade magnetic field and the ambient field provides a temporary link between the open field lines and the flare energy release site, enabling the escape of electron beams into interplanetary space. 相似文献
49.
Statistical analysis of the relationship between type II radio bursts appearing in the metric (m) and decameter-to-hectometer
(DH) wavelength ranges is presented. The associated X-ray flares and coronal mass ejections (CMEs) are also reported. The
sample is divided into two classes using the frequency-drift plots: Class I, representing those events where DH-type-II bursts
are not continuation of m-type-II bursts and Class II, where the DH-type-II bursts are extensions of m-type-II bursts. Our
study consists of three steps: i) comparison of characteristics of the Class I and II events; ii) correlation of m-type-II and DH-type-II burst characteristics with X-ray flare properties and iii) correlation of m-type-II and DH-type-II burst characteristics with CME properties. We have found no clear correlation between
properties of m-type-II bursts and DH-type-II bursts. For example, there is no correlation between drift rates of m-type-II
bursts and DH-type-II bursts. Similarly there is no correlation between their starting frequencies. In Class I events we found
correlations between X-ray flare characteristics and properties of m-type-II bursts and there is no correlation between flare
parameters and DH-type-II bursts. On the other hand, the correlation between CME parameters and m-type-II bursts is very weak,
but it is good for CME parameters and DH-type-II bursts. These results indicate that Class I m-type-II bursts are related
to the energy releases in flares, whereas DH-type-II bursts tend to be related to CMEs. On the contrary, for Class II events
in the case of m-type-II and DH-type-II bursts we have found no clear correlation between both flare and CMEs. 相似文献
50.
Joc Triglav Dušan Petrovič Bojan Stopar 《International Journal of Applied Earth Observation and Geoinformation》2011
The global geospatial community is investing substantial effort in providing tools for geospatial data-quality information analysis and systematizing the criteria for geospatial data quality. The importance of these activities is increasing, especially in the last decade, which has witnessed an enormous expansion of geospatial data use in general and especially among mass users. Although geospatial data producers are striving to define and present data-quality standards to users and users increasingly need to assess the fitness for use of the data, the success of these activities is still far from what is expected or required. As a consequence, neglect or misunderstanding of data quality among users results in misuse or risks. This paper presents an aid in spatio-temporal quality evaluation through the use of spatio-temporal evaluation matrices (STEM) and the index of spatio-temporal anticipations (INSTANT) matrices. With the help of these two simple tools, geospatial data producers can systematically categorize and visualize the granularity of their spatio-temporal data, and users can present their requirements in the same way using business intelligence principles and a Web 2.0 approach. The basic principles and some examples are presented in the paper, and potential further applied research activities are briefly described. 相似文献