Origins of the Ambient Solar Wind: Implications for Space Weather

The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress -- in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue connected with a 2016 ISSI workshop on "The Scientific Foundations of Space Weather." 44 pages, 9 figure

Effect of Chemically Inert Particles on Thermodynamic Characteristics and Detonation of a Combustible Gas

[[abstract]]An approximate model of chemical equilibrium in heterogeneous mixtures of a combustible gas with chemically inert solid or liquid particles has been suggested. It includes explicit algebraic formulas for the calculation of the molar mass of the gas, internal energy, and heat capacities of gas-particles mixture, and ordinary differential equations for the description of isentropic compression and adiabatic index of the system. The model can be also useful for the rough estimations of thermodynamic parameters of gaseous mixtures with particles of soot. As an example of a possible application of the suggested model of chemical equilibrium, parameters of stationary one-dimensional detonation wave in gas-particles mixtures are calculated. The algorithm of estimation of detonation cell size in such heterogeneous mixtures is presented. Detonation wave parameters and cell size in the stoichiometric hydrogen-oxygen mixture with particles of W, Al2O3, and SiO2 have been calculated. The results of the calculations of detonation parameters and cell sizes are used for analysis of the method of multi-front detonation wave suppression by particles injection before the leading shock front of the wave. The minimal total mass of the particles and characteristic size of the cloud, which are necessary for detonation suppression, have been calculated. It is shown that such suppression is more effective if the particles have high heat capacity, low melting point, and high heat of melting. Among the particles under consideration, the particles of Al2O3 are the best for the detonation wave suppression