Long-Period Oscillations in Polar Plumes as Observed by cds on Soho     

D. Banerjee  E. O'Shea  J.G. Doyle 《Solar physics》2000,196(1):63-78

We examine spectral time series of the transition region line Ov 629Å, observed with the Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft in July 1997. Both Fourier and wavelet transforms have been applied independently to the analysis of plume oscillations in order to find the most reliable periods. The wavelet analysis allows us to derive the duration as well as the periods of the oscillations. Our observations indicate the presence of compressional waves with periods of 10–25 min. We have also detected a 11±1 min periodicity in the network regions of the north polar coronal hole. The waves are produced in short bursts with coherence times of about 30 min. We interpret these oscillations as outward propagating slow magneto-acoustic waves, which may contribute significantly to the heating of the lower corona by compressive dissipation and which may also provide enough energy flux for the acceleration of the fast solar wind. The data support the idea that the same driver is responsible for the network and plume oscillations with the network providing the magnetic channel through which the waves propagate upwards from the lower atmosphere to the plumes.  相似文献   

Polar Plumes and Inter-plume regions as observed by SUMER on SOHO     

Banerjee  D.  Teriaca  L.  Doyle  J.G.  Lemaire  P. 《Solar physics》2000,194(1):43-58

We present observations of Ovi 1032 Å line profiles obtained with the SUMER instrument on SOHO extending from the solar disk to 1.5 R above the limb in the north polar coronal hole. Variations of the intensity and linewidth in the polar plume and inter-plume regions are investigated. We find an anti-correlation between the intensity and the linewidth in the plume and inter-plume regions with detailed plume structures been seen out to 1.5 R . Possible implications regarding the magnetic topologies of these two regions and related heating mechanisms are discussed. The Ovi linewidth measurements are combined with UVCS output to provide an overview of its variations with height extending up to 3.5 R . We find a linear increase of the linewidth from 1 to 1.2 R , then a plateau followed by a sharp increase around 1.5 R .  相似文献   

PLANETARY HABITABILlTY STUDIES GO UNDERGROUND     

Martin J. Heath  L.R. Doyle 《地学学报》1996,8(3):301-302

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Impulsive phase of flares in soft X-ray emission     

E. Antonucci  A. H. Gabriel  L. W. Acton  J. L. Culhane  J. G. Doyle  J. W. Leibacher  M. E. Machado  L. E. Orwig  C. G. Rapley 《Solar physics》1982,78(1):107-123

Observations using the Bent Crystal Spectrometer instrument on the Solar Maximum Mission show that turbulence and blue-shifted motions are characteristic of the soft X-ray plasma during the impulsive phase of flares, and are coincident with the hard X-ray bursts observed by the Hard X-ray Burst Spectrometer. A method for analysing the Ca xix and Fe xxv spectra characteristic of the impulsive phase is presented. Non-thermal widths and blue-shifted components in the spectral lines of Ca xix and Fe xxv indicate the presence of turbulent velocities exceeding 100 km s^-1 and upward motions of 300–400 km s^-1.The April 10, May 9, and June 29, 1980 flares are studied. Detailed study of the geometry of the region, inferred from the Flat Crystal Spectrometer measurements and the image of the flare detected by the Hard X-ray Imaging Spectrometer, shows that the April 10 flare has two separated footpoints bright in hard X-rays. Plasma heated to temperatures greater than 10⁷ K rises from the footpoints. During the three minutes in which the evaporation process occurs an energy of 3.7 × 10³⁰ ergs is deposited in the loop. At the end of the evaporation process, the total energy observed in the loop reaches its maximum value of 3 × 10³⁰ ergs. This is consistent with the above figures, allowing for loss by radiation and conduction. Thus the energy input due to the blue-shifted plasma flowing into the flaring loop through the footpoints can account for the thermal and turbulent energy accumulated in this region during the impulsive phase.On leave from Torino University, Italy.  相似文献   

Experiments using new initial soil moisture conditions and soil map in the Eta model over La Plata Basin     

Moira E. Doyle  Javier Tomasella  Daniel A. Rodriguez  Sin Chan Chou 《Meteorology and Atmospheric Physics》2013,121(3-4):119-136

An effort towards a more accurate representation of soil moisture and its impact on the modeling of weather systems is presented. Sensitivity tests of precipitation to soil type and soil moisture changes are carried out using the atmospheric Eta model for the numerical simulation of the development of a mesoscale convective system over northern Argentina. Modified initial soil moisture conditions were obtained from a hydrological balance model developed and running operationally at INPE. A new soil map was elaborated using the available soil profile information from Brazil, Paraguay, Uruguay, and Argentina and depicts 18 different soil types. Results indicate that more accurate initial soil moisture conditions and incorporating a new soil map with hydraulic parameters, more representative of South American soils, improve daily total precipitation forecasts both in quantitative and spatial representations.  相似文献   

Corrosion of metal roof materials related to volcanic ash interactions     

Christopher Oze  Jim Cole  Allan Scott  Thomas Wilson  Grant Wilson  Sally Gaw  Samuel Hampton  Colin Doyle  Zhengwei Li 《Natural Hazards》2014,71(1):785-802

Metal roofing material is commonly used for residential and industrial roofs in volcanically active areas. Increased corrosion of metal roofing from chemically reactive volcanic ash following ash deposition post-eruption is a major concern due to decreasing the function and stability of roofs. Currently, assessment of ash-induced corrosion is anecdotal, and quantitative data are lacking. Here, we systematically evaluate the corrosive effects of volcanic ash, specifically ash leachates, on a variety of metal roofing materials (i.e. weathered steel, zinc, galvanized steel, and Colorsteel©) utilizing weathering chamber experiments and direct acid treatments. Weathering chamber tests were carried out for up to 30 days, and visual, chemical, and surface analyses did not definitively identify significant corrosion in any of the test roofing metal samples. Direct concentrated acid treatments with hydrochloric (HCl), sulphuric (H₂SO₄), and hydrofluoric (HF) acids demonstrate that roofing materials are chemically resilient. Our experimental results suggest that ash-leachate-related corrosion is a longer-term process (>1 month), potentially related to a multitude of factors including increased ash leachate concentrations, the dissolution of the glass matrix of the ash, moisture retention at the ash-surface boundary, and potential reactions involving photo-oxidation. Overall, corrosion is not a simple process related to the short-term release of acid and/or salt leachates from the ash surface, but a product of dynamic interactions involving ash and water at the surface of metal roofing material for extended periods.  相似文献   

The Big Issue:¹ empowering homeless women through academic research?     

Lisa Doyle 《Area》1999,31(3):239-246

Summary This paper discusses academic research as a means of empowerment for people in marginalized groups, using the example of homeless women. Issues connected to the position of the researcher in relation to both the agencies dealing with homeless people and the homeless women themselves are discussed. Many agencies have underlying ideologies and overt practices that reinforce hierarchical relations and certain gendered expectations. The paper considers the difficulties this creates when working with and presenting findings to agencies whose principles are in conflict with one's own, and also discusses the social relations of conducting empowering doctoral research.  相似文献