177,096 research outputs found
Solar Wind MHD Turbulence for Different Phases of the Solar Cycle
No full textRecent results have shown that solar wind MHD turbulence can be described not only as a mixture of inward and outward stochastic Alfvénic fluctuations but includes also advected coherent structures, partially dominated by an excess of magnetic energy. The present study analyzes the role played by these two contributions for different phases of the solar cycle, comparing also different solar cycles. In addition, we show a study on the radial evolution of solar wind turbulence between 1 and 1.4 AU, obtained from a recent alignment between Earth and Ulysses occurred at the end of August 2007. This unusual event gave us the opportunity to analyze the same plasma sample at different observational points
Waiting time distributions of B_s and AE extreme events.
No full textWe present a preliminary statistical study on the intermittency of B_s and AE, focusing in particular on the distributions of their respective extreme events, for different phases of the solar cycle. In order to recognize the extreme events affecting our statistics, we use a technique, called local intermittency measure (LIM), based on wavelet decomposition. Once we have selected all the extreme events we can measure the waiting time between consecutive events and build the relative distribution. Our analysis shows that these distributions are characterized by well defined power laws which would suggest the existence of long term correlations typical of turbulent processes. Moreover, we find that these distributions do not depend on the particular phase of the solar cycle considered
Alfvenic turbulence in "newborn" polar flows
No full textThe three-dimensional structure of the solar wind is strongly dependent upon the Sun's activity cycle. At low solar activity a bimodal structure is dominant, with a fast and uniform flow at the high latitudes and slow and variable flows at low latitudes. Around solar maximum, in sharp contrast, variable flows are observed at all latitudes. This last kind of pattern, however, is a relatively short-living feature, and quite soon after solar maximum the polar wind tends to regain its role. The plasma parameter distributions for these newborn polar flows appear very similar to those typically observed in polar wind at low solar activity. The point addressed here is about turbulence, known to be able of playing a key role in space plasma heating. A ubiquitous presence of a turbulence of Alfvenic type is a well established feature for low-solar-activity polar wind. Does this hold for the new polar flows seen near solar maximum? An answer is given here through a comparative statistical analysis on parameters as total energy, cross helicity, and residual energy, that well describe the Alfvenic character of fluctuations. Our results indicate that the main features of the Alfvenic turbulence observed in low-solar-activity polar wind are quickly recovered in the new polar flows developed shortly after solax maximum
Observing Small Scale Alfvénic Turbulence Around 0.2 AU
No full textRecent results obtained from the analysis of interplane- tary observations recorded by Helios 2 within the inner heliosphere showed, for the first time, that the Probability Distribution Function (PDF) of magnetic field vector fluctuations, within the MHD frequency range of turbulence, can be remarkably well fitted by a double log- normal. These two components of the total PDF have been ascribed to Alfvénic fluctuations and advected struc- e tures. Since this analysis was carried on using only magnetic field data because of low time resolution of plasma measurements, we lack of a sure proof of the Alfvénic nature of those fluctuations that we believe contribute to one of the two lognormals. Moreover, we still don't know whether the advected structures forming the second log- normal are locally generated by the turbulent evolution of the fluctuations or they rather come from the source re- gions of the wind where they reflect the complicate topology of the magnetic field. Remote sensing and high time resolution in-situ observations performed by Solar Orbiter at the perihelion, during the corotation phase, would certainly amplify the results already reached by Helios and would eventually give an answer to these problems
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Observing MHD turbulence in the solar wind.
No full textSolar wind MHD turbulence can be described as a mixture of inward and outward stochastic Alfvénic fluctuations, including also convected structures, dominated by an excess of magnetic energy. This study focuses on the role that magnetically dominated fluctuations have within the solar wind turbulence. This kind of fluctuations can be interpreted as non-propagating structures, advected by the wind during its expansion. In particular, observations performed in the ecliptic revealed a clear radial dependence of these magnetic structures within fast wind, but not within slow wind. At short heliocentric distances (0.3AU), the turbulent population is largely dominated by Alfvénic fluctuations characterised by high values of normalised cross-helicity and a remarkable level of energy equipartition. However, as the wind expands, another population, characterised by lower values of Alfvénicity and a clear imbalance in favour of magnetic energy becomes visible and clearly distinguishable from the Alfvénic population
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
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