Heavy Particle Modes and Signature of the I-Regime

The recently discovered properties of the I-confinement Regime are explained as resulting from the excitation of a heavy particle mode. The theoretically predicted mode phase velocity in the direction of the electron diamagnetic velocity and the induced confinement of impurities at the edge of the plasma column have been confirmed by the experiments. The direction of the mode phase velocity is consistent with that (opposite) of the spontaneous rotation in the plasma core. The mode is of the “ion-mixing” type, in that it does not produce any electron transport across the fields and it involves significant poloidal magnetic field fluctuations.United States. Department of Energ

Magnetic Reconnection Driven by Thermal and Non-thermal Particle Energy Densities

Magnetic reconnection is usually associated with conversion of magnetic energy into particle acceleration or thermal energy. However, a specific reconnection process driven by plasma pressure gradients was identified in Ref. [1] with a consistent theory of (non-ideal) MHD m0=1 modes in well confined plasmas. This process, based on an Ohm's law contribution to the electron balance equations, remains the basis for the explanation of the observed sawtooth oscillations of the central plasma pressure and for the inferred magnetic field structures due to fishbone oscillations [2] associated with injected high energy particle populations. A novel process [3] expected to have a wide range of applications concerns magnetic reconnection sustained by a significant gradient of the longitudinal electron temperature and based on the electron thermal energy balance equation rather than on an Ohm's law. A comparison is made with the Biermann Battery concept considering that the growth of reconnection depends on the particle density gradient in addition to that (aligned with it) of the electron temperature

Plasmas and Controlled Nuclear Fusion

Contains report on one research project.U.S. Atomic Energy Commission (Contract AT(30-1)-3980

Analysis of genetic structure of Ranunculus baudotii in a Mediterranean wetland. Implications for selection of seeds and seedlings for conservation

Seed collection and storage of wild species in ex-situ seed banks should be continued as an integrated tool for the conservation of plants in their habitats. Although seed-bank facilities are widely used today, their seed samples often suffer low genetic diversity. Consequently, reintroduced seeds and plant material may not have the resilience to cope with future environmental stress so leading to complete wastage of seeds. Molecular techniques allow the benefit of quantification of the genetic diversity of a seed collection in comparison with that of the natural population. In this study we focus on ex-situ seed bank samples and living collections of Ranunculus peltatus subsp. baudotii. We compare their genetic diversity and structure with that of the natural population before and after undertaking a restoration project on a natural pond in the Tuscan Archipelago National Park. ISSR analyses, carried out on a total of five sampling groups, shows a relatively high level of genetic diversity for the ex-situ cultivated groups. The analysis of molecular variance, in agreement with clustering obtained in the neighbour-joining dendrogram and with the pattern from cluster analysis, suggests dividing the samples analysed into two groups: one formed by individuals sampled before the pond restoration and the other formed by the subsequent pond population. The results highlight the importance of planning mixed propagation lines which can be obtained through the use of a range of germination conditions to exploit a novel source of genetic variability which may otherwise remain hidden within the seed collection

Active black holes: Relevant plasma structures, regimes and processes involving all phase space

The presented theory is motivated by the growing body of experimental information on the characteristics, connected with relevant spectral, time, and space resolutions, of the radiation emission from objects considered as rotating black holes. In the immediate surroundings of these objects, three plasma regions are identified: an innermost Buffer Region, an intermediate Three-regime Region, and a Structured Peripheral Region. In the last region, a Composite Disk Structure made of a sequence of plasma rings corresponding to the formation of closed magnetic surfaces is considered to be present and to allow intermittent accretion flows along the relevant separatrices. The nonlinear “Master Equation” describing composite disk structures is derived and solved in appropriate asymptotic limits. A ring configuration, depending on the state of the plasma at the microscopic level: (i) can be excluded from forming given the strongly nonthermal nature of the electron distribution (in momentum space) within the Three-regime Region allowing the onset of a spiral structure; the observed High Frequency Quasi Periodic Oscillations are associated with these tridimensional structures; (ii) may be allowed to propagate to the outer edge of the Buffer Region where successive rings carrying currents in opposite directions are ejected vertically (in opposite directions) and originate the observed jets; or (iii) penetrates in the Three-regime Region and is dissipated before reaching the outer edge of the Buffer Region. The absence of a coherent composite disk structure guiding accretion in the presence of a significant magnetic field background is suggested to characterize quiescent black holes.United States. Dept. of Energ

Plasmas and Controlled Nuclear Fusion

Contains reports on two research projects.U. S. Atomic Energy Commission (Contract AT(11-1)-3070

Plasmas and Controlled Nuclear Fusion

Contains reports on two research projects.U.S. Atomic Energy Commission (Contract AT(30-1)-3980

Plasma Dynamics

Contains reports on seven research projects.U.S. Air Force - Office of Scientific Research (Grant AFOSR 84-0026)National Science Foundation (Grant ECS 85-14517)U.S. Department of Energy (Contract DE-FGO5-84ER 13272)Lawrence Livermore National Laboratory (Subcontract 6264005)National Science Foundation (Grant ECS 82-13430)U.S. Department of Energy (Contract DE-ACO2-78-ET-51013

Plasmas and Controlled Nuclear Fusion

Contains reports on three research projects.U. S. Atomic Energy Commission (Contract AT(30-1)-3980