The Radiated Energy Budget of Chromospheric Plasma in a Major Solar Flare Deduced From Multi-Wavelength Observations

This paper presents measurements of the energy radiated by the lower solar atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare (SOL2011-02-15T01:56) in response to an injection of energy assumed to be in the form of nonthermal electrons. Hard X-ray observations from RHESSI were used to track the evolution of the parameters of the nonthermal electron distribution to reveal the total power contained in flare accelerated electrons. By integrating over the duration of the impulsive phase, the total energy contained in the nonthermal electrons was found to be $>2\times10^{31}$ erg. The response of the lower solar atmosphere was measured in the free-bound EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II at 304\AA\ and H I (Ly$\alpha$) at 1216\AA\ by SDO/EVE, the UV continua at 1600\AA\ and 1700\AA\ by SDO/AIA, and the WL continuum at 4504\AA, 5550\AA, and 6684\AA, along with the Ca II H line at 3968\AA\ using Hinode/SOT. The summed energy detected by these instruments amounted to $\sim3\times10^{30}$ erg; about 15% of the total nonthermal energy. The Ly$\alpha$ line was found to dominate the measured radiative losses. Parameters of both the driving electron distribution and the resulting chromospheric response are presented in detail to encourage the numerical modelling of flare heating for this event, to determine the depth of the solar atmosphere at which these line and continuum processes originate, and the mechanism(s) responsible for their generation.Comment: 14 pages, 18 figures. Accepted for publication in Astrophysics Journa

LaRC design analysis report for National Transonic Facility for 304 stainless steel tunnel shell. Volume 4S: Thermal analysis

For abstract, see N76-33552

Bi2Te1.6S1.4 - a Topological Insulator in the Tetradymite Family

We describe the crystal growth, crystal structure, and basic electrical properties of Bi2Te1.6S1.4, which incorporates both S and Te in its Tetradymite quintuple layers in the motif -[Te0.8S0.2]-Bi-S-Bi-[Te0.8S0.2]-. This material differs from other Tetradymites studied as topological insulators due to the increased ionic character that arises from its significant S content. Bi2Te1.6S1.4 forms high quality crystals from the melt and is the S-rich limit of the ternary Bi-Te-S {\gamma}-Tetradymite phase at the melting point. The native material is n-type with a low resistivity; Sb substitution, with adjustment of the Te to S ratio, results in a crossover to p-type and resistive behavior at low temperatures. Angle resolved photoemission study shows that topological surface states are present, with the Dirac point more exposed than it is in Bi2Te3 and similar to that seen in Bi2Te2Se. Single crystal structure determination indicates that the S in the outer chalcogen layers is closer to the Bi than the Te, and therefore that the layers supporting the surface states are corrugated on the atomic scale.Comment: To be published in Physical Review B Rapid Communications 16 douuble spaced pages. 4 figures 1 tabl

LaRC design analysis report for National Transonic Facility for 304 stainless steel tunnel shell. Volume 7S: Special studies

For abstract, see N76-33552

Si IV Resonance Line Emission During Solar Flares: Non-LTE, Non-equilibrium, Radiation Transfer Simulations

The Interface Region Imaging Spectrograph (IRIS) routinely observes the Si IV resonance lines. When analyzing observations of these lines it has typically been assumed they form under optically thin conditions. This is likely valid for the quiescent Sun, but this assumption has also been applied to the more extreme flaring scenario. We used 36 electron beam driven radiation hydrodynamic solar flare simulations, computed using the RADYN code, to probe the validity of this assumption. Using these simulated atmospheres we solved the radiation transfer equations to obtain the non-LTE, non-equilibrium populations, line profiles, and opacities for a model Silicon atom, including charge exchange processes. This was achieved using the `minority species' version of RADYN. The inclusion of charge exchange resulted in a substantial fraction of Si IV at cooler temperatures than those predicted by ionisation equilibrium. All simulations with an injected energy flux $F>5\times10^{10}$ erg cm$^{-2}$ s$^{-1}$ resulted in optical depth effects on the Si IV emission, with differences in both intensity and line shape compared to the optically thin calculation. Weaker flares (down to $F\approx5\times10^{9}$ erg cm$^{-2}$ s$^{-1}$) also resulted in Si IV emission forming under optically thick conditions, depending on the other beam parameters. When opacity was significant, the atmospheres generally had column masses in excess of $5\times10^{-6}$ g cm$^{-2}$ over the temperature range $40$ to $100$ kK, and the Si IV formation temperatures were between $30$ and $60$ kK. We urge caution when analyzing Si IV flare observations, or when computing synthetic emission without performing a full radiation transfer calculation.Comment: Accepted in the Astrophysical Journal, 23 pages (3 appendices, 15 figures

LaRC design analysis report for national transonic facility for 9% nickel tunnel shell. Volume 7: Special studies

For abstract, see N76-33543

LaRC design analysis report for National Transonic Facility for 9% nickel tunnel shell. Volume 3: Finite element analysis of plenum region including side access reinforcement, side access door and angle of attack penetration

For abstract, see N76-33543

An inexpensive economical solar heating system for homes

A low-cost solar home heating system to supplement existing warm-air heating systems is described. The report is written in three parts: (1) a brief background on solar heating, (2) experience with a demonstration system, and (3) information for the homeowner who wishes to construct such a system. Instructions are given for a solar heating installation in which the homeowner supplies all labor necessary to install off-the-shelf components estimated to cost $2,000. These components, which include solar collector, heat exchanger, water pump, storage tank, piping, and controls to make the system completely automatic, are available at local lumber yards, hardware stores, and plumbing supply stores, and are relatively simple to install. Manufacturers and prices of each component used and a rough cost analysis based on these prices are included. This report also gives performance data obtained from a demonstration system which was built and tested at the Langley Research Center

Electron doped Ca10(Pt3As8)(Fe2As2)5 and Ca10(Pt4As8)(Fe2As2)5 - High Tc superconductors with skutterudite intermediary layers

It has been argued that the very high transition temperatures of the highest Tc cuprate superconductors are facilitated by enhanced CuO2 plane coupling through the (Bi,Tl,Hg)-O intermediary layers. Whether enhanced coupling through intermediary layers can also influence Tc in the iron arsenide superconductors has never been tested due the lack of appropriate systems for study. Here we report the crystal structures and properties of two iron arsenide superconductors, Ca10(Pt3As8)(Fe2As2)5 (the 10-3-8 phase) and Ca10(Pt4As8)(Fe2As2)5 (the 10-4-8 phase). Based on -Ca-(PtnAs8)-Ca-Fe2As2- layer stacking, the most important difference in the structures lies in the structural and electronic characters of the intermediary platinum arsenide layers. Electron doping through partial substitution of Pt for Fe in the Fe2As2 layers leads to Tc of 11 K in the 10-3-8 phase and 25 K in the 10-4-8 phase. Using the chemical concepts of Zintl ion electron counting and the stability of Pt in the 5d8 configuration we argue that the dramatic difference in Tc arises because the intermediary layer is semiconducting in the 10-3-8 phase but metallic in the 10-4-8 phase, leading to enhanced interlayer coupling in the 10-4-8 phase. The results suggest that metallic intermediary layers may offer a new road to higher Tc in iron arsenide superconductors