In situ Observations of CIRs on STEREO,Wind, and ACE During 2007 – 2008     

Mason  G. M.  Desai  M. I.  Mall  U.  Korth  A.  Bucik  R.  von Rosenvinge  T. T.  Simunac  K. D. 《Solar physics》2009,256(1-2):393-408

During the 2007 and 2008 solar minimum period, STEREO, Wind, and ACE observed numerous Corotating Interaction Regions (CIRs) over spatial separations that began with all the spacecraft close to Earth, through STEREO separation angles of ～?80 degrees in the fall of 2008. Over 35 CIR events were of sufficient intensity to allow measurement of He and heavy ion spectra using the IMPACT/SIT, EPACT/STEP and ACE/ULEIS instruments on STEREO, Wind, and ACE, respectively. In addition to differences between the spacecraft expected on the basis of simple corotation, we observed several events where there were markedly different time-intensity profiles from one spacecraft to the next. By comparing the energetic particle intensities and spectral shapes along with solar wind speed we examine the extent to which these differences are due to temporal evolution of the CIR or due to variations in connection to a relatively stable interaction region. Comparing CIRs in the 1996?–?1997 solar minimum period vs. 2007?–?2008, we find that the 2007?–?2008 period had many more CIRs, reflecting the presence of more high-speed solar wind streams, whereas 1997 had almost no CIR activity.

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STEREO Observations of Energetic Ions in Corotating Interaction Regions During the May 2007 Solar Events     

Bučík  R.  Mall  U.  Gómez-Herrero  R.  Korth  A.  Mason  G. M. 《Solar physics》2009,259(1-2):361-380

Solar Physics - Elemental composition and energy spectra of ～?0.1?–?1.0 MeV/n heavy ions were analyzed in two corotating interaction region (CIR) events...  相似文献   

Novae ejecta as colliding shells     

Robert Williams  Elena Mason 《Astrophysics and Space Science》2010,327(2):207-217

Following on our initial absorption-line analysis of fifteen novae spectra we present additional evidence for the existence of two distinct components of novae ejecta having different origins. As argued in Paper I one component is the rapidly expanding gas ejected from the outer layers of the white dwarf by the outburst. The second component is pre-existing outer, more slowly expanding circumbinary gas that represents ejecta from the secondary star or accretion disk. We present measurements of the emission-line widths that show them to be significantly narrower than the broad P Cygni profiles that immediately precede them. The emission profiles of novae in the nebular phase are distinctly rectangular, i.e., strongly suggestive of emission from a relatively thin, roughly spherical shell. We thus interpret novae spectral evolution in terms of the collision between the two components of ejecta, which converts the early absorption spectrum to an emission-line spectrum within weeks of the outburst. The narrow emission widths require the outer circumbinary gas to be much more massive than the white dwarf ejecta, thereby slowing the latter’s expansion upon collision. The presence of a large reservoir of circumbinary gas at the time of outburst is suggestive that novae outbursts may sometime be triggered by collapse of gas onto the white dwarf, as occurs for dwarf novae, rather than steady mass transfer through the inner Lagrangian point.  相似文献   

China University of Geosciences enters the twenty-first century     

Ge Yafei  & Roger Mason 《Geology Today》1999,15(5):194-196

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The Canary Eddy Corridor: A major pathway for long-lived eddies in the subtropical North Atlantic     

Pablo Sangrà  Ananda Pascual  Ángel Rodríguez-Santana  Francisco Machín  Evan Mason  James C. McWilliams  Josep L. Pelegrí  Changming Dong  Anna Rubio  Javier Arístegui  Ángeles Marrero-Díaz  Alonso Hernández-Guerra  Antonio Martínez-Marrero  Maricel Auladell 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2100-2114

We report, from remote sensing and in situ observations, a new type of permanent structure in the eastern subtropical Atlantic Ocean, that we call the “Canary Eddy Corridor”. The phenomenon, is a zonal long-lived (>3 months) mesoscale eddy corridor, whose source is the flow perturbation of the Canary Current and the Trade Winds at the Canary Islands. The latitudinal range of the corridor spans 22°N–29°N and extends from the Canaries to at least 32ºW, near the mid-Atlantic. This is the main region of long-lived westward-propagating eddies in the subtropical northeast Atlantic. From a age-distribution study we observe that at least 10% of mesoscale eddies in this region are long-lived, with a dominance of anticyclones over cyclones. Another four westward-propagating eddy corridors were also detected: two small corridors north and south of the Azores Front; a small zonal corridor located near 31ºN, south of the island of Madeira; and a small corridor located near the Cape Blanc giant filament. The existence of these corridors may change, at least for the northeastern subtropical Atlantic, the general idea that mesoscale eddies are disorganized, ubiquitous structures in the ocean. The Canary Eddy Corridor constitutes a direct zonal pathway that conveys water mass- and biogeochemical properties offshore from the Canary Island/Northwest Africa upwelling system, and may be seen as a recurrent offshore pump of organic matter and carbon to the oligotrophic ocean interior. Estimates of volume and mass transport indicate that Canary Eddy Corridor westward transport is more than one-fourth of the southward transport of the Canary Current. The westward transport of kinetic energy by the eddies of the Canary Corridor is as important as the southward transport by the Canary Current. The total primary production related to the Corridor may be as high as the total primary production of the northwest Africa upwelling system for the same latitude range.  相似文献   

Atmospheric boundary layer flows: Their structure and measurement     

P. Mason 《Boundary-Layer Meteorology》1995,72(1-2):213-214

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The sensitivity of large-eddy simulation of turbulent shear flow to subgrid models     

P. J. Mason  A. R. Brown 《Boundary-Layer Meteorology》1994,70(1-2):133-150

Previous large-eddy simulations of turbulent shear flows have shown significant sensitivity to some aspects of the subgrid-scale turbulence models. In particular, Mason and Thomson (1992) demonstrated a marked improvement in simulations through the inclusion of stochastic stress variations in the subgrid model. Here a series of simulations is presented with a view to exploring the general sensitivity to such a subgrid model and in particular to the size and nature of the stochastic stress variations. The model proposed by Mason and Thomson is found to be fairly satisfactory but some quantitative uncertainty remains.  相似文献   

Instances of premonitory crustal velocity ratio changes in Iran     

A. Hedayati  J.L. Brander  R.G. Mason 《Tectonophysics》1978,44(1-4)

Anomalous compressional to shear wave velocity ratios seem to have occurred shortly before microearthquakes recorded during a survey of the region of Teheran, Iran. Furthermore, the time durations of these changes have the same dependence on the subsequent magnitude as similar changes found elsewhere in the world.  相似文献   

The oceans as source of cloud-forming nuclei     

Dr. B. J. Mason 《Pure and Applied Geophysics》1957,36(1):148-155

Summary The number and size of salt particles produced by the bursting of air bubbles in sea water has been measured. Bubbles of diameters varying between 1/2 and 2 mm each produced about 300 nuclei the sizes of which, under the electron microscope, were mainly between 0.1 and 0.5 diameter. They appeared to consist mainly of sodium chloride, the smallest ones containing only 10^–15 g of salt.These results, together with measurements of the size distribution of salt nuclei collected over the oceans in areas of spray formation, indicate that the total concentrations of salt nuclei over the oceans in winds of up to 15 m sec^–1 probably do not exceed 100 cm^–3. The corresponding rate of production of salt nuclei at the sea surface is estimated to be 1000 cm^–2 sec^–1. It is therefore inferred that sea spray contributes perhaps only one-fifth of the nuclei involved in cloud formation, the majority being the products of combustion, either natural or man-made.  相似文献   

Progress in cloud physics research     

B. J. Mason 《Meteorology and Atmospheric Physics》1953,6(1):1-52

Summary This progress report summarises the researches of the cloud physics group at Imperial College during the last four years 1949–1952. It describes work carried out on the following topics: 1. the spontaneous condensation of water vapour; 2. measurements on the concentration and size distribution of sea-salt nuclei over the N. Atlantic and their contribution to atmospheric opacity; 3. laboratory and theoretical studies on the supercooling and freezing of water and aqueous solutions; 4. experimental and theoretical researches on ice crystal growth from the vapour; 5. theoretical computations on the growth of water drops and ice particles in both layer and shower type clouds; 6. studies of the form, structure and development of high-level ice clouds and their formation relative to orographic features; 7. the construction of instruments for precipitation studies.

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Zusammenfassung Der vorliegende Bericht gibt einen Überblick über die Forschungen der Arbeitsgruppe für Wolkenphysik am Imperial College in London während der vier Jahre 1949 bis 1952. Es werden Untersuchungen über folgende Probleme beschrieben: 1. Spontane Wasserdampfkondensation; 2. Messungen über die Konzentration und die Größenverteilung von Meersalzkernen über dem Nordatlantik und über ihren Anteil an der atmosphärischen Trübung; 3. theoretische und Laboratoriumsuntersuchungen über Unterkühlung und Gefrieren von Wasser und wässerigen Lösungen; 4. experimentelle und theoretische Untersuchungen über das Wachstum von Eiskristallen aus der dampfförmigen Phase; 5. theoretische Berechnungen über das Wachstum von Wassertropfen und Eispartikeln sowohl in Schicht- wie in Quellbewölkung; 6. Untersuchungen über Form, Aufbau und Entwicklung von hohen Eiswolken und über die Abhängigkeit ihrer Bildung von den orographischen Verhältnissen; 7. Konstruktion von Instrumenten für Niederschlagsuntersuchungen.

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Résumé Le présent rapport résume les recherches effectuées par le groupe d'étude de la physique des nuages de l'«Imperial College» au cours des quatre années 1949–1952, et qui ont concerné les domaines suivants: 1. condensation spontanée de la vapeur d'eau; 2. mesure de la concentration et de la distribution de grosseur des noyaux de sel marin au-dessus de l'Atlantique et leur rôle dans le trouble atmosphérique; 3. recherches théoriques et expérimentales sur la surfusion et la solidification de l'eau et de solutions aqueuses; 4. recherches théoriques et expérimentales sur la croissance de cristaux de glace à partir de la phase gazeuse; 5. essais de calcul de l'accroissement de gouttes d'eau et de particules de glace à l'intérieur de nuages stratifiés ou cumuliformes; 6. recherches sur la forme, la structure et le développement des nuages glacés à haute altitude, ainsi que sur le rôle du relief terrestre sur leur formation; 7. construction d'instruments utiles aux recherches pluviométriques.

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With 26 Figures  相似文献