排序方式: 共有32条查询结果,搜索用时 156 毫秒
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Chaston CC Wilber M Mozer FS Fujimoto M Goldstein ML Acuna M Reme H Fazakerley A 《Physical review letters》2007,99(17):175004
Observations at the Earth's magnetopause identify mode conversion from surface to kinetic Alfvén waves at the Alfvén resonance. Kinetic Alfvén waves radiate into the magnetosphere from the resonance with parallel scales up to the order of the geomagnetic field-line length and spectral energy densities obeying a k(perpendicular)(-2.4) power law. Amplitudes at the Alfvén resonance are sufficient to both demagnetize ions across the magnetopause and provide field-aligned electron bursts. These waves provide diffusive transport across the magnetopause sufficient for boundary layer formation. 相似文献
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Measurements of synchrotron radiation emitted by 30-MeV runaway electrons in the TEXTOR-94 tokamak show that the runaway population decays after switching on neutral beam injection (NBI). The decay starts only with a significant delay, which decreases with increasing NBI heating power. This delay provides direct evidence of the energy dependence of runaway confinement, which is expected if magnetic modes govern the loss of runaways. Application of the theory by Mynick and Strachan [Phys. Fluids 24, 695 (1981)] yields estimates for the "mode width" (delta) of magnetic perturbations: delta<0.5 cm in Ohmic discharges, increasing to delta = 4.4 cm for 0. 6 MW NBI. 相似文献
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Dunlop MW Zhang QH Bogdanova YV Lockwood M Pu Z Hasegawa H Wang J Taylor MG Berchem J Lavraud B Eastwood J Volwerk M Shen C Shi JK Constantinescu D Frey H Fazakerley AN Sibeck D Escoubet P Wild JA Liu ZX 《Physical review letters》2011,107(2):025004
The extent of where magnetic reconnection (MR), the dominant process responsible for energy and plasma transport into the magnetosphere, operates across Earth's dayside magnetopause has previously been only indirectly shown by observations. We report the first direct evidence of X-line structure resulting from the operation of MR at each of two widely separated locations along the tilted, subsolar line of maximum current on Earth's magnetopause, confirming the operation of MR at two or more sites across the extended region where MR is expected to occur. The evidence results from in-situ observations of the associated ion and electron plasma distributions, present within each magnetic X-line structure, taken by two spacecraft passing through the active MR regions simultaneously. 相似文献
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Parks GK Lee E Lin N Mozer F Wilber M Dandouras I Rème H Lucek E Fazakerley A Goldstein M Gurgiolo C Canu P Cornilleau-Wehrlin N Décréau P 《Physical review letters》2007,98(26):265001
Solitary nonlinear (deltaB/B>1) electromagnetic pulses have been detected in Earth's geomagnetic tail accompanying plasmas flowing at super-Alfvénic speeds. The pulses in the current sheet had durations of approximately 5 s, were left-hand circularly polarized, and had phase speeds of approximately the Alfvén speed in the plasma frame. These pulses were associated with a field-aligned current J(parallel) and observed in low density (approximately 0.3 cm(-3)), high temperature (T(e) approximately T(i) approximately 3x10(7) K), and beta approximately 10 plasma that included electron and ion beams streaming along B. The wave activity was enhanced from below the ion cyclotron frequency to electron cyclotron and upper hybrid frequencies. The detailed properties suggest the pulses are nonlinearly steepened ion cyclotron or Alfvén waves. 相似文献
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Rory Campbell Dr. Martin F. Davis Mathew Fazakerley Dr. Peter Portius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18690-18698
The first charge‐neutral Lewis base adducts of tin(IV) tetraazide, [Sn(N3)4(bpy)], [Sn(N3)4(phen)] and [Sn(N3)4(py)2], and the salt bis{bis(triphenylphosphine)iminium} hexa(azido)stannate [(PPN)2Sn(N3)6] (bpy = 2,2′‐bipyridine; phen = 1,10‐phenanthroline; py = pyridine; PPN = N(PPh3)2) have been prepared using covalent or ionic azide‐transfer reagents and ligand‐exchange reactions. The azides were isolated on the 0.3 to 1 g scale and characterized by IR and NMR spectroscopies, microanalytical and thermal methods and their molecular structures determined by single‐crystal XRD. All complexes have a distorted octahedral Sn[N]6 coordination geometry and possess greater thermal stability than their Si and Ge homologues. The nitrogen content of the adducts of up to 44 % exceed any SnIV compound known hitherto. 相似文献
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Szostak M Collins KD Fazakerley NJ Spain M Procter DJ 《Organic & biomolecular chemistry》2012,10(30):5820-5824
Herein we describe a strategy for the selective, electron transfer reduction of lactones of all ring sizes and topologies using SmI(2)-H(2)O and a Lewis base to tune the redox properties of the complex. The current protocol permits instantaneous reduction of lactones to the corresponding diols in excellent yields, under mild reaction conditions and with useful chemoselectivity. We demonstrate the broad utility of this transformation through the reduction of complex lactones and sensitive drug-like molecules. Sequential electron transfer reactions and syntheses of deuterated diols are also described. 相似文献
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Chaston CC Phan TD Bonnell JW Mozer FS Acuńa M Goldstein ML Balogh A Andre M Reme H Fazakerley A 《Physical review letters》2005,95(6):065002
We identify drift-kinetic Alfvén waves in the vicinity of a reconnection X line on the Earth's magnetopause. The dispersive properties of these waves have been determined using wavelet interferometric techniques applied to multipoint observations from the Cluster spacecraft. Comparison of the observed wave dispersion with that expected for drift-kinetic Alfvén waves shows close agreement. The waves propagate outwards from the X line suggesting that reconnection is a kinetic Alfvén wave source. Energetic O+ ions observed in these waves indicate that reconnection is a driver of auroral ion outflow. 相似文献
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Neal J. Fazakerley Dr. Matthew D. Helm Prof. David J. Procter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6718-6723
The first enantiospecific total synthesis of the antibacterial natural product (+)‐pleuromutilin has been achieved. The approach includes the synthesis of a non‐racemic cyclisation substrate from (+)‐trans‐dihydrocarvone, a highly selective SmI2‐mediated cyclisation cascade, an electron transfer reduction of a hindered ester, and the first efficient conversion of (+)‐mutilin to the target. 相似文献