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11.
Vršnak B. Roša D. Božić H. Brajša R. Ruždjak V. Schroll A. Wöhl H. 《Solar physics》1999,185(2):207-225
Two large stable solar filaments were used as test tracers to determine the apparent synodic rotation rate as a function of the central meridian distance for several filaments' segments at different heights. An analytic fitting procedure was applied to determine simultaneously the real synodic rotation rate and the height of the traced filament segments. The determined heights were compared with the values obtained from the widths of filament contours on the solar disk and with the values obtained by direct measurements at the solar limb. Furthermore, the obtained rotation rates and heights of the filaments' segments close to the filaments' pivot points were compared with the values obtained using two successive central meridian passages. Finally, sources and scales of errors were investigated and possible implications on the previous studies of the solar differential rotation were considered. 相似文献
12.
Terra rossa and eutric cambisol soils were surveyed in Slovenia. At both sites, 6–13 boreholes were drilled in a regular 24 m × 24 m
square grid. Soil samples from various depths were taken for gamma spectrometric analysis, and radon in soil gas was measured
at a depth of 80 cm using an AlphaGuard instrument. The following ranges of activity concentration (Bq kg−1) were obtained for 238U, 226Ra, 228Ra, 40K and 137Cs: in terra rossa, 64–74, 70–84, 45–49, 293–345, 20–30 and, in eutric cambisol, 55–80, 132–147, 50–57, 473–529, 106–272.
Radon activity concentrations in both soils ranged from about 100 kBq m−3 to 370 kBq m−3. 相似文献
13.
The Julian Alps are located in NW Slovenia and structurally belong to the Julian Nappe where the Southern Alps intersect with
the Dinarides. In the Jurassic, the area was a part of the southern Tethyan continental margin and experienced extensional
faulting and differential subsidence during rifting of the future margin. The Mesozoic succession in the Julian Alps is characterized
by a thick pile of Upper Triassic to Lower Jurassic platform limestones of the Julian Carbonate Platform, unconformably overlain
by Bajocian to Tithonian strongly condensed limestones of the Prehodavci Formation of the Julian High. The Prehodavci Formation
is up to 15 m thick, consists of Rosso Ammonitico type limestone and is subdivided into three members. The Lower Member consists
of a condensed red, well-bedded bioclastic limestone with Fe–Mn nodules, passing into light-grey, faintly nodular limestone.
The Middle Member occurs discontinuously and consists of thin-bedded micritic limestone. The Upper Member unconformably overlies
the Lower or Middle Members. It is represented by red nodular limestone, and by red-marly limestone with abundant Saccocoma sp. The Prehodavci Formation unconformably overlies the Upper Triassic to Lower Jurassic platform limestone of the Julian
Carbonate Platform; the contact is marked by a very irregular unconformity. It is overlain by the upper Tithonian pelagic
Biancone (Maiolica) limestone. The sedimentary evolution of the Julian High is similar to that of Trento Plateau in the west
and records: (1) emergence and karstification of part of the Julian Carbonate Platform in the Pliensbachian, or alternatively
drowning of the platform and development of the surface by sea-floor dissolution; (2) accelerated subsidence and drowning
in the Bajocian, and onset of the condensed pelagic sedimentation (Prehodavci Formation) on the Julian High; (3) beginning
of sedimentation of the Biancone limestone in the late Tithonian. 相似文献
14.
D. Maričić B. Vršnak M. Dumbović T. Žic D. Roša D. Hržina S. Lulić I. Romštajn I. Bušić K. Salamon M. Temmer T. Rollett A. Veronig N. Bostanjyan A. Chilingarian B. Mailyan K. Arakelyan A. Hovhannisyan N. Mujić 《Solar physics》2014,289(1):351-368
We study heliospheric propagation and some space weather aspects of three Earth-directed interplanetary coronal mass ejections (ICMEs), successively launched from the active region AR 11158 in the period 13?–?15 February 2011. From the analysis of the ICME kinematics, morphological evolution, and in situ observations, we infer that the three ICMEs interacted on their way to Earth, arriving together at 1 AU as a single interplanetary disturbance. Detailed analysis of the in situ data reveals complex internal structure of the disturbance, where signatures of the three initially independent ICMEs could be recognized. The analysis also reveals compression and heating of the middle ICME, as well as ongoing magnetic reconnection between the leading and the middle ICME. We present evidence showing that the propagation of these two, initially slower ICMEs, was boosted by the fastest, third ICME. Finally, we employ the ground-based cosmic ray observations, to show that this complex disturbance produced a single cosmic ray event, i.e., a simple Forbush decrease (FD). The results presented provide a better understanding of the ICME interactions and reveal effects that should be taken into account in forecasting of the arrival of such compound structures. 相似文献
15.
Existing methods for conversion between synodic and sidereal rotation velocities of the Sun are tested for validity using state-of-the-art ephemeris data. We found that some of them agree well with ephemeris calculations while others show a discrepancy of almost 0.01° day?1. This discrepancy is attributed to a missing factor and a new corrected relation is given. 相似文献
16.
Brajša R. Wöhl H. Vršnak B. Ruždjak D. Sudar D. Roša D. Hržina D. 《Solar physics》2002,206(2):229-241
Stable recurrent sunspot groups from the Greenwich data set which were identified in at least two subsequent solar rotations were traced. The solar rotation was determined by the period method from the time difference of the two central meridian passages of each of the 327 identified groups. Sidereal rotation periods were calculated from the synodic ones by a seasonal-dependent procedure taking into account the details of the Earth's motion around the Sun. Growing recurrent sunspot groups rotate on the average faster than decaying recurrent sunspot groups, while sunspot groups of all types taken together rotate faster than both growing and decaying recurrent sunspot groups. A north–south rotational asymmetry and a cycle-dependence of rotational velocity of recurrent sunspot groups were analyzed. Positive rotation velocity deviations are larger, but less numerous than the negative ones. Signatures of torsional oscillations were not found analyzing the rotation velocity residual of recurrent sunspot groups as a function of the distance from the average latitude of activity. 相似文献
17.
Venkatesh S. Gong W. Kallaur A. Makar P. A. Moran M. D. Pabla B. Ro C. Vet R. Burrows W. R. Montpetit R. 《Natural Hazards》2000,21(2-3):101-129
Acid rain and photochemical smog are two regionalair-quality issues that have received considerableattention in the last two decades due to their harmfuleffects. Health impacts of particulate matter (PM) inthe atmosphere is another issue of concern.Sulphur dioxide emission controls were introducedin both Canada and the U.S.A. to reduceacid-deposition-related damage. While these emissionreductions have already resulted in reduced sulphatedeposition, based on results from modelling studiesmuch of southeastern Canada is still expected toexperience damaging levels of acid deposition evenafter all currently legislated emission controls arefully implemented. Moreover, there has not been acorresponding reduction in the acidity ofprecipitation. This may be attributable to aconcurrent reduction in base-cation concentration inprecipitation.Models were also developed to understand theformation, transport and diffusion of troposphericozone. The models have been used to provide policyguidance for emission control options to reduceground-level ozone to acceptable limits. In thesummer of 1997 a Canadian pilot project was initiatedto provide real-time forecasts of ground-level ozonein the southeastern part of the province of NewBrunswick in eastern Canada.With the emergence of fine Particulate Matter(PM2.5) as a health concern, efforts are underwayin Canada to develop a unified' regional air-qualitymodel that will address the combined impacts ofvarious pollutants in the atmosphere. In this effortthe atmosphere is viewed as a single entity where theimpacts of multiple pollutants are considered at thesame time. 相似文献
18.
The computation of sparse representations of data on the sphere (e.g. topographical data) is a crucial step for further processing
such as multiple separation, migration, imaging and sparsity promoting data-recovery. The Easy Path Wavelet Transform (EPWT)
is a new tool for sparse data representation that has recently been introduced for image compression. In this paper we consider
the EPWT on spherical triangulations. It is a locally adaptive transform that works along pathways through the array of function
values and exploits the local correlations of the data in a simple appropriate manner. In our approach the usual discrete
one-dimensional orthogonal or biorthogonal wavelet transform can be applied. The EPWT can be used for defining a multiresolution
analysis on the sphere in which the scaling spaces and the wavelet spaces depend adaptively on the data. Issues of implementation
of the EPWT are also considered. 相似文献
19.
We present a statistical analysis of the relationship between the kinematics of the leading edge and the eruptive prominence
in coronal mass ejections (CMEs). We study the acceleration phase of 18 CMEs in which kinematics was measured from the pre-eruption
stage up to the post-acceleration phase. In all CMEs, the three part structure (the leading edge, the cavity, and the prominence)
was clearly recognizable from early stages of the eruption. The data show a distinct correlation between the duration of the
leading edge (LE) acceleration and eruptive prominence (EP) acceleration. In the majority of events (78%) the acceleration
phase onset of the LE is very closely synchronized (within ± 20 min) with the acceleration of EP. However, in two events the
LE acceleration started significantly earlier than the EP acceleration (> 50 min), and in two events the EP acceleration started
earlier than the LE acceleration (> 40 min). The average peak acceleration of LEs (281 m s−2) is about two times larger than the average peak acceleration of EPs (136 m s−2). For the first time, our results quantitatively demonstrate the level of synchronization of the acceleration phase of LE
and EP in a rather large sample of events, i.e., we quantify how often the eruption develops in a “self-similar” manner. 相似文献
20.
The present study tests the usefulness of SoLIM software and GIS techniques for the reconstruction of large vegetation formations from the mid-Holocene period in Romania. We used current reference climate data (temperature, precipitation) and the current extent of ecological regions in Romania to derive climate optimality functions for each vegetation formation. The optimality functions were used to simulate current and past distributions of vegetation. The results showed that the current and mid-Holocene simulated spatial distributions of vegetation are quite similar. Changes were found for about 14% of the Romanian territory (33 946 km2), the most important being the retreat of coniferous forests in favor of mixed forests and of mixed forests in favor of forest steppe. The former is validated by previous pollen-based studies showing the transition from coniferous forests to mixed forests that occurred in several areas of the country after the mid-Holocene. The study demonstrates the potential of this methodological approach to reconstruct past vegetation formations, and at the same time that it is a straightforward and expert knowledge-based method. Although our application uses only climate factors, the results can be further refined by incorporating additional drivers (soil and landform information, site-specific pollen and fossil data, wildfire data) for a more accurate inference of paleovegetation. 相似文献