To understand the generation and evolution of mafic magmas from Klyuchevskoy volcano in the Kamchatka arc, which is one of the most active arc volcanoes on Earth, a petrological and geochemical study was carried out on time-series samples from the volcano. The eruptive products show significant variations in their whole-rock compositions (52.0–55.5 wt.% SiO2), and they have been divided into high-Mg basalts and high-Al andesites. In the high-Mg basalts, lower-K and higher-K primitive samples (>9 wt.% MgO) are present, and their petrological features indicate that they may represent primary or near-primary magmas. Slab-derived fluids that induced generation of the lower-K basaltic magmas were less enriched in melt component than those associated with the higher-K basaltic magmas, and the fluids are likely to have been released from the subducting slab at shallower levels for the lower-K basaltic magmas than for higher-K basaltic magmas. Analyses using multicomponent thermodynamics indicates that the lower-K primary magma was generated by ~13% melting of a source mantle with ~0.7 wt.% H2O at 1245–1260?°C and ~1.9 GPa. During most of the evolution of the volcano, the lower-K basaltic magmas were dominant; the higher-K primitive magma first appeared in AD 1932. In AD 1937–1938, both the lower-K and higher-K primitive magmas erupted, which implies that the two types of primary magmas were present simultaneously and independently beneath the volcano. The higher-K basaltic magmas evolved progressively into high-Al andesite magmas in a magma chamber in the middle crust from AD 1932 to ~AD 1960. Since then, relatively primitive magma has been injected continuously into the magma chamber, which has resulted in the systematic increase of the MgO contents of erupted materials with ages from ~AD 1960 to present. 相似文献
The transfer of wave energy to plasma energy is a very crucial issue in coronal holes and helmet streamer regions. Mixed mode
Alfvén waves, also known as kinetic Alfvén wave (KAW) can play an important role in the energization of the plasma particles
because of their potential ability to heat and accelerate the plasma particles via Landau damping. This paper presents an
investigation of the growth of a Gaussian perturbation on a non-uniform kinetic Alfvén wave having Gaussian wave front. The
effect of the nonlinear coupling between the main KAW and the perturbation has been studied. The dynamical equations for the
field of the main KAW and the perturbation have been established and their semi-analytical solution has been obtained in the
low (β≪ me/mi≪ 1) and the high (β≫ me/mi≪ 1) β cases. The critical field of the main KAW and the perturbation has been evaluated. Nonlinear evolution of the main
KAW and the perturbation into the filamentary structures and its dependence on various parameters of the solar wind and the
solar corona have been investigated in detail. These filamentary structures can act as a source for the particle acceleration
by wave particle interaction because the KAWs are mixed modes and Landau damping is possible. Especially, in the solar corona,
the low β and the high β cases could correspond to the coronal holes and the helmet streamer. The presence of the primary
and the secondary filaments of the perturbation may change the spectrum of the Alfvénic turbulence in the solar wind. 相似文献
We present a homogeneous X-ray analysis of all 318 gamma-ray bursts detected by the X-ray telescope (XRT) on the Swift satellite up to 2008 July 23; this represents the largest sample of X-ray GRB data published to date. In Sections 2–3 , we detail the methods which the Swift -XRT team has developed to produce the enhanced positions, light curves, hardness ratios and spectra presented in this paper. Software using these methods continues to create such products for all new GRBs observed by the Swift -XRT. We also detail web-based tools allowing users to create these products for any object observed by the XRT, not just GRBs. In Sections 4–6 , we present the results of our analysis of GRBs, including probability distribution functions of the temporal and spectral properties of the sample. We demonstrate evidence for a consistent underlying behaviour which can produce a range of light-curve morphologies, and attempt to interpret this behaviour in the framework of external forward shock emission. We find several difficulties, in particular that reconciliation of our data with the forward shock model requires energy injection to continue for days to weeks. 相似文献
In many circumstances involving heat and mass transfer issues,it is considered impractical to measure the input flux and the resulting state distribution in the domain.Therefore,the need to develop techniques to provide solutions for such problems and estimate the inverse mass flux becomes imperative.Adaptive state estimator(ASE)is increasingly becoming a popular inverse estimation technique which resolves inverse problems by incorporating the semi-Markovian concept into a Bayesian estimation technique,thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters.The ASE is particularly designed for a system that encompasses independent unknowns and/or random switching of input and measurement biases.The present study describes the scheme to estimate the groundwater input contaminant flux and its transient distribution in a conjectural two-dimensional aquifer by means of ASE,which in particular is because of its unique ability to efficiently handle the process noise giving an estimation of keeping the relative error range within 10%in 2-dimensional problems.Numerical simulation results show that the proposed estimator presents decent estimation performance for both smoothly and abruptly varying input flux scenarios.Results also show that ASE enjoys a better estimation performance than its competitor,Recursive Least Square Estimator(RLSE)due to its larger error tolerance in greater process noise regimes.ASE's inherent deficiency of being slower than the RLSE,resulting from the complexity of algorithm,was also noticed.The chosen input scenarios are tested to calculate the effect of input area and both estimators show improved results with an increase in input flux area especially as sensors are moved closer to the assumed input location. 相似文献
Flood relief and rescue form an important basis of disaster management, and the assessment of flood damage is a critical component of flood risk management. In its recent history, Kashmir Valley witnessed the floods in 2014, 2015, 2017, 2019, 2020, and 2021, but the worst flood in the living memory of the people was witnessed in the year 2014, which created widespread loss in economic and societal aspects. The present study discusses the spatial dimension of impact, relief, and rescue of the flood of 2014 in the Kashmir Valley. It analyses the distribution of relief and politics of relief and rescue and highlights the role of the communitarianism and the heroics of the community members in dealing with floods. The study provides the data of relief distribution under different government schemes and reveals that the relief was not distributed equally in various districts of the valley. The study relies on primary and secondary sources of data. Ethnographic approach was used for acquiring primary data because it provides the complex narratives of disasters and the political and social rupture experienced during the disasters. The data have been analysed with the help of Geographic Information System.
Jupiter flux at 327 MHz was monitored using the Ooty radio telescope from July 12th to July 29th during the collision of comet
Shoemaker-Levi 9 with Jupiter. Flux was found to increase steadily from July 17th to July 26th by ∼ 2–5 Jy, after which it
declined to its pre-event value. The comparison of 327 MHz observations with those at 840 MHz and 2240 MHz indicates that
the enhancement was mainly due to the increased synchrotron emission and the contribution of thermal emission was very small
at metric-decimetric frequencies. The enhancement in radio emission was found to be more at 840 MHz than at 327 or 2240 MHz.
The steepening of the spectrum between 327 and 840 MHz as well as between 2240 and 840 MHz was also noted. 相似文献