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931.
E. P. Kontar J. C. Brown A. G. Emslie W. Hajdas G. D. Holman G. J. Hurford J. Ka?parov�� P. C. V. Mallik A. M. Massone M. L. McConnell M. Piana M. Prato E. J. Schmahl E. Suarez-Garcia 《Space Science Reviews》2011,159(1-4):301-355
X-radiation from energetic electrons is the prime diagnostic of flare-accelerated electrons. The observed X-ray flux (and polarization state) is fundamentally a convolution of the cross-section for the hard X-ray emission process(es) in question with the electron distribution function, which is in turn a function of energy, direction, spatial location and time. To address the problems of particle propagation and acceleration one needs to infer as much information as possible on this electron distribution function, through a deconvolution of this fundamental relationship. This review presents recent progress toward this goal using spectroscopic, imaging and polarization measurements, primarily from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Previous conclusions regarding the energy, angular (pitch angle) and spatial distributions of energetic electrons in solar flares are critically reviewed. We discuss the role and the observational evidence of several radiation processes: free-free electron-ion, free-free electron-electron, free-bound electron-ion, photoelectric absorption and Compton backscatter (albedo), using both spectroscopic and imaging techniques. This unprecedented quality of data allows for the first time inference of the angular distributions of the X-ray-emitting electrons and improved model-independent inference of electron energy spectra and emission measures of thermal plasma. Moreover, imaging spectroscopy has revealed hitherto unknown details of solar flare morphology and detailed spectroscopy of coronal, footpoint and extended sources in flaring regions. Additional attempts to measure hard X-ray polarization were not sufficient to put constraints on the degree of anisotropy of electrons, but point to the importance of obtaining good quality polarization data in the future. 相似文献
932.
933.
Hugh S. Hudson 《Space Science Reviews》2011,158(1):5-41
This article broadly reviews our knowledge of solar flares. There is a particular focus on their global properties, as opposed
to the microphysics such as that needed for magnetic reconnection or particle acceleration as such. Indeed solar flares will
always remain in the domain of remote sensing, so we cannot observe the microscales directly and must understand the basic
physics entirely via the global properties plus theoretical inference. The global observables include the general energetics—radiation
in flares and mass loss in coronal mass ejections (CMEs)—and the formation of different kinds of ejection and global wave
disturbance: the type II radio-burst exciter, the Moreton wave, the EIT “wave”, and the “sunquake” acoustic waves in the solar
interior. Flare radiation and CME kinetic energy can have comparable magnitudes, of order 1032 erg each for an X-class event, with the bulk of the radiant energy in the visible-UV continuum. We argue that the impulsive
phase of the flare dominates the energetics of all of these manifestations, and also point out that energy and momentum in
this phase largely reside in the electromagnetic field, not in the observable plasma. 相似文献
934.
In this paper, one of the most possible methods for calculations of ejector devices equipped with the cylindrical mixing chambers
is considered; the method is based on averaging the flow parameters at the chamber inlet. We present the calculation results
and their comparison with the earlier published data, as well as the quantitative assessment of this method and feasibilities
of its use for different technical devices embodying the concept of ejection. 相似文献
935.
Some methods of optimizing a cutting tool kit by the minimum labour content criterion in milling of an article are considered.
Their advantages and disadvantages are given. 相似文献
936.
The scheme variants of implementing the thermal protection against heat flows being generated by the body of a high-temperature
stationary gas turbine engine (GTE) are presented. The scheme of the experimental bench with a working section is given. Methodical
approaches to the heat transfer calculation at different variants of forced and natural convection organization and under
various operating conditions are described. The generalized results of the experiments carried out using a heat curtain being
generated by porous injection are presented. 相似文献
937.
N.A. Tikhomirova S.A. Ushakova Yu.A. Kudenko I.V. Gribovskaya E.S. Shklavtsova Yu.V. Balnokin L.G. Popova N.A. Myasoedov J.-B. Gros Ch. Lasseur 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
This study addresses the possibility of growing different halophytic plants on mineralized human urine as a way to recycle NaCl from human wastes in a bioregenerative life support system (BLSS). Two halophytic plant species were studied: the salt-accumulating Salicornia europaea and the salt-secreting Limonium gmelinii. During the first two weeks, plants were grown on Knop’s solution, then an average daily amount of urine produced by one human, which had been preliminarily mineralized, was gradually added to the experimental solutions. Nutrient solutions simulating urine mineral composition were gradually added to control solutions. NaCl concentrations in the stock solutions added to the experimental and control solutions were 9 g/L in the first treatment and 20 g/L in the second treatment. The mineralized human urine showed some inhibitory effects on S. europaea and L. gmelinii. The biomass yield of experimental plants was lower than that of control ones. If calculated for the same time period (120 d) and area (1 m2), the amount of sodium chloride taken up by S. europaea plants would be 11.7 times larger than the amount taken up by L. gmelinii plants (486 g/m2 vs. 41 g/m2). Thus, S. europaea is the better choice of halophyte for recycling sodium chloride from human wastes in BLSS. 相似文献
938.
A.S. Polyakova N.P. Perevalova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Ionospheric response to tropical cyclones (TCs) was estimated experimentally on the example of three powerful cyclones – KATRINA (23–31 August 2005), RITA (18–26 September 2005), and WILMA (15–25 October 2005). These TCs were active near the USA Atlantic coast. Investigation was based on Total Electron Content (TEC) data from the international network of two-frequency ground-based GPS receivers and the NCEP/NCAR Reanalysis data. We studied the spatial–temporal dynamics of wave TEC disturbances over two periods of ranges (02–20 min and 20–60 min). To select the ionospheric disturbances which were most likely to be associated with the cyclones, maps of TEC disturbances were compared with those of meteorological parameters. 相似文献
939.
B.G. Ayantunji P.N. Okeke J.O. Urama 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The seasonal variation of surface refractivity over Nigeria was studied using two years in-situ meteorological data from eight locations over Nigeria. The result shows that the surface refractivity generally has higher value during rainy season than dry season at all location studied. The results also show that the value of surface refractivity increases from arid region in the north to the coastal area in south. The results also show that local meteorology plays a very important role in refractivity variation. 相似文献
940.
K. Durga Prasad S.V.S. Murty 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A Wireless Sensor Network for in situ probing of lunar water/ice is proposed. The mission scenario in single and multi-tier architectures for probing water in a permanently shadowed region of the Moon and different scenarios of exploration are discussed. The ideas presented in the paper are a positive assertion of feasibility for the sensor node hardware, given current levels of technological advancements. 相似文献