Observational Quantification of the Energy Dissipated by Alfv\'en Waves in a Polar Coronal Hole: Evidence that Waves Drive the Fast Solar Wind

We present a measurement of the energy carried and dissipated by Alfv\'en waves in a polar coronal hole. Alfv\'en waves have been proposed as the energy source that heats the corona and drives the solar wind. Previous work has shown that line widths decrease with height in coronal holes, which is a signature of wave damping, but have been unable to quantify the energy lost by the waves. This is because line widths depend on both the non-thermal velocity v_nt and the ion temperature T_i. We have implemented a means to separate the T_i and v_nt contributions using the observation that at low heights the waves are undamped and the ion temperatures do not change with height. This enables us to determine the amount of energy carried by the waves at low heights, which is proportional to v_nt. We find the initial energy flux density present was 6.7 +/- 0.7 x 10^5 erg cm^-2 s^-1, which is sufficient to heat the coronal hole and acccelerate the solar wind during the 2007 - 2009 solar minimum. Additionally, we find that about 85% of this energy is dissipated below 1.5 R_sun, sufficiently low that thermal conduction can transport the energy throughout the coronal hole, heating it and driving the fast solar wind. The remaining energy is roughly consistent with what models show is needed to provide the extended heating above the sonic point for the fast solar wind. We have also studied T_i, which we found to be in the range of 1 - 2 MK, depending on the ion species.Comment: Accepted for the Astrophysical Journa

Evidence for Wave Heating of the Quiet Sun Corona

We have measured the energy and dissipation of Alfvenic waves in the quiet Sun. A magnetic field was used to infer the location and orientation of the magnetic field lines along which the waves are expected to travel. The waves were measured using spectral lines to infer the wave amplitude. The waves cause a non-thermal broadening of the spectral lines, which can be expressed as a non-thermal velocity v_nt. By combining the spectroscopic measurements with this magnetic field model we were able to trace the variation of v_nt along the magnetic field. At the footpoints of the quiet Sun loops we find that waves inject an energy flux in the range of 1.2-5.2 x 10^5 erg cm^-2 s^-1. At the minimum of this range, this amounts to more than 80% of the energy needed to heat the quiet Sun. We also find that these waves are dissipated over a region centered on the top of the loops. The position along the loop where the damping begins is strongly correlated with the length of the loop, implying that the damping mechanism depends on the global loop properties rather than on local collisional dissipation.Comment: Submitted to the Astrophysical Journa

Inferring the Coronal Density Irregularity from EUV Spectra

Understanding the density structure of the solar corona is important for modeling both coronal heating and the solar wind. Direct measurements are difficult because of line-of-sight integration and possible unresolved structures. We present a new method for quantifying such structure using density-sensitive EUV line intensities to derive a density irregularity parameter, a relative measure of the amount of structure along the line of sight. We also present a simple model to relate the inferred irregularities to physical quantities, such as the filling factor and density contrast. For quiet Sun regions and interplume regions of coronal holes, we find a density contrast of at least a factor of three to ten and corresponding filling factors of about 10-20%. Our results are in rough agreement with other estimates of the density structures in these regions. The irregularity diagnostic provides a useful relative measure of unresolved structure in various regions of the corona.Comment: Submitted to the Astrophysical Journa

Evidence of Wave Damping at Low Heights in a Polar Coronal Hole

We have measured the widths of spectral lines from a polar coronal hole using the Extreme Ultraviolet Imaging Spectrometer onboard Hinode. Polar coronal holes are regions of open magnetic field and the source of the fast solar wind. We find that the line widths decrease at relatively low heights. Previous observations have attributed such decreases to systematic effects, but we find that such effects are too small to explain our results. We conclude that the line narrowing is real. The non-thermal line widths are believed to be proportional to the amplitude of Alfven waves propagating along these open field lines. Our results suggest that Alfven waves are damped at unexpectedly low heights in a polar coronal hole. We derive an estimate on the upper limit for the energy dissipated between 1.1 and 1.3 solar radii and find that it is enough to account for up to 70% of that required to heat the polar coronal hole and accelerate the solar wind.Comment: Accepted for publication in the Astrophysical Journal, April 201

Relative Abundance Measurements in Plumes and Interplumes

We present measurements of relative elemental abundances in plumes and interplumes. Plumes are bright, narrow structures in coronal holes that extend along open magnetic field lines far out into the corona. Previous work has found that in some coronal structures the abundances of elements with a low first ionization potential (FIP) < 10 eV are enhanced relative to their photospheric abundances. This coronal-to-photospheric abundance ratio, commonly called the FIP bias, is typically 1 for element with a high-FIP (> 10 eV). We have used EIS spectroscopic observations made on 2007 March 13 and 14 over an ~24 hour period to characterize abundance variations in plumes and interplumes. To assess their elemental composition, we have used a differential emission measure (DEM) analysis, which accounts for the thermal structure of the observed plasma. We have used lines from ions of iron, silicon, and sulfur. From these we have estimated the ratio of the iron and silicon FIP bias relative to that for sulfur. From the results, we have created FIP-bias-ratio maps. We find that the FIP-bias ratio is sometimes higher in plumes than in interplumes and that this enhancement can be time dependent. These results may help to identify whether plumes or interplumes contribute to the fast solar wind observed in situ and may also provides constraints on the formation and heating mechanisms of plumes.Comment: 21 pages; 3 tables; 12 figure

Asymptotic Variance Estimator for Two-Step Semiparametric Estimators

The goal of this paper is to develop techniques to simplify semiparametric inference. We do this by deriving a number of numerical equivalence results. These illustrate that in many cases, one can obtain estimates of semiparametric variances using standard formulas derived in the already-well-known parametric literature. This means that for computational purposes, an empirical researcher can ignore the semiparametric nature of the problem and do all calculations "as if" it were a parametric situation. We hope that this simplicity will promote the use of semiparametric procedures.Two-step semiparametrics

Recurring Characters as Benefits in Applying God’s Word

Hahn Jr., Daniel A., Recurring Characters as Benefits in Applying God’s Word. D.Min. MAP., Concordia Seminary, 2016. 166pp. The purpose of this project was to evaluate the effectiveness of recurring characters in sermon stories as tools for connecting hearers to Biblical concepts. The report tells the story of a six-week series of sermons which were developed for St. John’s Lutheran Church in Millvale, Pennsylvania. The project aimed to determine if the two contemporary characters, created for this series, would become increasingly beneficial over time as hearers became more familiar with them. The report explains the rationale behind the project and its place within the greater field of narrative preaching. It speaks about character creation and storytelling and relates the reception among the hearers. Since stories are widely used in sermons, this project may interest pastors developing a similar serialized story approach in their preaching. The primary component of this study was the series of six storied sermons which were prepared and delivered by the researcher. The subjects in this study were asked to evaluate their hearing experience using criteria that measured their identification with the characters and any resulting connection to the Biblical themes under consideration. The study suggests that recurring characters provide significant benefit to hearers in applying Biblical truths to their lives

Improved Strategies towards Conjugated Oligo Phenylene Ethynylenes

Konjugierte Stäbchenmoleküle stellen eine besondere Klasse von Makromolekülen dar. Aufgrund ihres konjugierten Rückgrats werden sie bezüglich elektronischer Anwendungen diskutiert und ihre Struktur-Eigenschafts-Beziehungen werden untersucht. Mehrere Syntheseverfahren zu derartigen uniformen Oligomeren wurden bereits publiziert, aber nur wenige konzentrieren sich dabei auf Sequenzdefinition. Das etablierte iterative Synthesekonzept basiert auf der Sonogashira Kupplung und anschließender Entschützung einer Dreifachbindung, jedoch ist die Aufreinigung wegen unvermeidbarer Nebenreaktionen erschwert. In dieser Arbeit wurde eine neue, verbesserte Synthesestrategie entwickelt, die sich aus einer decarboxylierenden Kupplung mit anschließender Verseifung zusammensetzt. Dafür wurde zunächst ein Bausteinmolekül, mit einem Bromrest und einer als Ethylester geschützten Alkynylcarbonsäure, synthetisiert. Um die Löslichkeit zu verbessern, wurden zudem Propoxy Seitenketten verwendet. Die Stäbchenmoleküle wurden anschließend über die lineare, iterative Synthesestratgie bestehend aus decarboxylierender Kupplung und Verseifung aufgebaut. Nach zehn Reaktionsschritten wurde ein uniformes Pentamer mit einer Ausbeute von 14% und 73 mg erhalten. Die kupferfreien Bedingungen verhinderten Homokupplung bis zum Trimer und vereinfachten daher die Aufreinigung der Oligomere. Alle finalen Produkte sowie die entsprechenden Intermediate wurden vollständig mit Protonen und Kohlenstoff NMR Spektroskopie, Infrarot Spektroskopie, Massenspektrometrie und Größenausschluss Chromatographie charakterisiert. Außerdem wurden die analytischen Methoden hinsichtlich ihrer Nachweisgrenzen von Verunreinigungen untersucht. Nur eine Kombination verschiedener analytischer Methoden kann die erfolgreiche Synthese sowie eine hohe Reinheit und Uniformität der hier erhaltenen Produkte garantieren. Die Ergebnisse wurden mit der etablierten Strategie basierend auf der Sonogashira Kupplung eingehend verglichen. Mit der neu entwickelten Synthesestrategie können OPEs mit ähnlicher Ausbeute, vereinfachter Aufreinigung und in einem Drittel der Zeit erhalten werden

FORCE-LENGTH PROPERTIES OF LEG EXTENSION AND THEIR IMPLICATIONS FOR STRENGTH DIAGNOSTICS

The aim of this study was to identify the F-l-r of multiarticular leg extension and its relation to muscle function. For that purpose, external forces and kinematics of lower extremity were measured (n = 18) during maximum voluntary isometric contractions in a seated leg press. Range of Motion was 30° - 100° knee flexion and measurements were done in steps of 10°. In addition, net joint moments for hip, knee, and ankle joint were computed by inverse-dynamic modelling. With increasing knee flexion one-legged maximal external force (Fext) decreased significantly from 3369±575 N to 1015±152 N, whereas passive forces only had a minor influence. Moreover, correlations showed that above average Fext at low knee flexion is not necessarily associated with above-average Fext at great knee flexion and vice versa. Similarly, it is not possible to simply deduce high joint moments for all joints from high Fext, just as above-average joint moments in one joint don’t implicitly signify above-average joint moments in another joint. In conclusion, these results show that the diagnosis and interpretation of leg extension strength in terms of muscle function via external forces must be done with extreme caution