Double Coronal Hard and Soft X-ray Source Observed by RHESSI: Evidence for Magnetic Reconnection and Particle Acceleration in Solar Flares

We present data analysis and interpretation of an M1.4-class flare observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) on April 30, 2002. This event, with its footpoints occulted by the solar limb, exhibits a rarely observed, but theoretically expected, double-source structure in the corona. The two coronal sources, observed over the 6-30 keV range, appear at different altitudes and show energy-dependent structures with the higher-energy emission being closer together. Spectral analysis implies that the emission at higher energies in the inner region between the two sources is mainly nonthermal, while the emission at lower energies in the outer region is primarily thermal. The two sources are both visible for about 12 minutes and have similar light curves and power-law spectra above about 20 keV. These observations suggest that the magnetic reconnection site lies between the two sources. Bi-directional outflows of the released energy in the form of turbulence and/or particles from the reconnection site can be the source of the observed radiation. The spatially resolved thermal emission below about 15 keV, on the other hand, indicates that the lower source has a larger emission measure but a lower temperature than the upper source. This is likely the result of the differences in the magnetic field and plasma density of the two sources.Comment: Accepted by ApJ (12/06/2007), scheduled for the 03/20/2008 Vol. 676 No. 1 Issue, 13 pages, 9 figure

Collaborative Funding to Facilitate Airport Ground Access, Research Report 11-27

This report presents the findings and conclusions from a research study that has examined the challenges of funding airport ground access projects and the role of collaborative funding strategies between the different agencies that typically become involved in such projects. The report reviews the recent literature on funding airport ground access projects, as well as funding transportation projects more generally. This is followed by a detailed review of current federal transportation funding programs relevant to airport ground access projects, as well as a discussion of state and local funding programs and potential opportunities for private-sector funding. A major component of the research described in the report consists of detailed case studies of seven selected airport ground access projects, including a major intermodal center, two automated people-mover projects, two airport access highway projects, and two airport rail links. These case studies examine the history of each project, the costs involved, and the funding programs and mechanisms used to finance the projects. Based on the literature review, the review of current funding programs, and the case study findings, the report identifies potential funding strategies for intermodal airport ground access projects, requirements for effective implementation of these strategies, and a recommended approach to facilitate successful project development and implementation. The report also presents recommended changes to transportation funding program rules and regulations that could facilitate and simplify development of intermodal solutions to future airport ground access needs