Analysis of a multi-wavelength time-resolved observation of a coronal loop

Several items on the diagnostics and interpretation of coronal loop observations are under debate. In this work, we analyze a well-defined loop system detected in a time-resolved observation in several spectral bands. The dataset includes simultaneous images in the TRACE 171 A, 195 A and 284 A bands, and Yohkoh/SXT, and two rasters taken with SoHO/CDS in twelve relevant lines. The loop is initially best visible in the TRACE 195 A filter band, and later in the 171 A filter band, with correspondence with the CDS raster images at log T \~ 6.0-6.1. We have taken as pixel-by-pixel background the latest TRACE, Yohkoh and CDS images where the loop has faded out. We examine the loop morphology evolution, the light curves, the TRACE filter ratio distribution and evolution, the images and emission measure from the CDS spectral lines. Our analysis detects that, after background subtraction, the emission along the loop and its evolution are non-uniform, especially in the 171 A filter band, and that the TRACE 195/171 filter ratio has a moderately non-uniform distribution along the loop and evolves in time. Both the light curves and the filter ratio evolution indicate a globally cooling loop. Relatively hot plasma may be present at the beginning while, during the first CDS raster, the data indicate a rather moderate thermal structuring of the loop. Our data analysis supports a coherent scenario across the different bands and instruments, points out difficulties in diagnostic methods and puts quantitative basis for detailed forward modeling.Comment: 20 pages, 13 figs, refereed, in pres

The Current Sheet Associated with the 2003 November 4 Coronal Mass Ejection: Density, Temperature, Thickness, and Line Width

In the wake of the 2003 November 4 coronal mass ejection associated with the largest solar flare of the last sunspot cycle, a current sheet (CS) was observed by the Ultraviolet Coronagraph Spectrometer (UVCS) as a narrow bright feature in the [Fe XVIII] (106.8 K) line. This is the first UV observation in which the CS evolution is followed from its onset. UV spectra provide diagnostics of electron temperature, emission measure, Doppler shift, line width, and size of the CS as function of time. Since the UVCS slit was inside the Mark IV K-coronameter (MK4) field of view, the combination of UV spectra and MK4 white light data provides estimates of the electron density and depth along the line of sight of the CS. The thickness of the CS in the [Fe XVIII] line is far larger than classical or anomalous resistivity would predict, and it might indicate an effective resistivity much larger than anomalous resistivity, such as that due to hyperdiffusion. The broad [Fe XVIII] line profiles in the CS cannot be explained as thermal widths. They result from a combination of bulk motions and turbulence. The Petschek reconnection mechanism and turbulent reconnection may be consistent with the observations

Three Dimensional Structure and Energy Balance of a Coronal Mass Ejection

The Ultraviolet Coronagraph Spectrometer (UVCS) observed Doppler shifted material of a partial Halo Coronal Mass Ejection (CME) on December 13 2001. The observed ratio of [O V]/O V] is a reliable density diagnostic important for assessing the state of the plasma. Earlier UVCS observations of CMEs found evidence that the ejected plasma is heated long after the eruption. We have investigated the heating rates, which represent a significant fraction of the CME energy budget. The parameterized heating and radiative and adiabatic cooling have been used to evaluate the temperature evolution of the CME material with a time dependent ionization state model. The functional form of a flux rope model for interplanetary magnetic clouds was also used to parameterize the heating. We find that continuous heating is required to match the UVCS observations. To match the O VI-bright knots, a higher heating rate is required such that the heating energy is greater than the kinetic energy. The temperatures for the knots bright in Ly$\alpha$ and C III emission indicate that smaller heating rates are required for those regions. In the context of the flux rope model, about 75% of the magnetic energy must go into heat in order to match the O VI observations. We derive tighter constraints on the heating than earlier analyses, and we show that thermal conduction with the Spitzer conductivity is not sufficient to account for the heating at large heights.Comment: 40 pages, 16 figures, accepted for publication in ApJ For associated mpeg file, please see https://www.cora.nwra.com/~jylee/mpg/f5.mp

The Impact of Social Stereotypes As They Relate to Training Practices of Female Athletes Competing In High-Risk Sports

This study was conducted to investigate if a lack of conditioning and the increased rate of injury among female athletes are due primarily to social stereotypes associated with women\u27s athletics. Ten professional female basketball players and ten high school basketball player were surveyed to determine how strength training is conceptualized and what role strength training had played in injury prevention. The study revealed that the increased rate of injury among female athletes are due to time constraints and/or lack of emphasis on strength and conditioning imposed on the athletes themselves for reasons of not strength training as opposed to social stereotypes associated with women\u27s athletics such as issues in masculinity and as traditionally type casting women as not physically apt. Although young female athletes are being introduced to weight training at a younger age the rate of injury still remains constant among the youth and professional athletes. Female athletes are starting to train physically and emotionally within the same infrastructure as male athletes, however females are unable to perform to the ability of male athletes with little or no deviations in injury rate

DETECTION AND DIAGNOSTICS OF A CORONAL SHOCK WAVE DRIVEN BY A PARTIAL-HALO CORONAL MASS EJECTION ON 2000 JUNE 28

A fast partial-halo coronal mass ejection (CME) was observed on 2000 June 28 by instruments on the SOHO spacecraft. The CME leading edge and filamentary cold core were detected over the northwest limb at 2.32 R? by the SOHO UV Coronagraph Spectrometer (UVCS). The broad profile of the O?VI ?1032 line gives evidence of a shock front at the leading edge, supporting the identification of white-light CME sharp leading edges as fast-mode shocks. Line-of-sight speeds are as high as 1500 km s-1, comparable to the projected speed obtained from LASCO. Pumping of the O?VI ?1032 by Ly? (v = 1810 km s-1) and of O?VI ?1037 by O?VI ?1032 (v = 1648 km s-1) were detected, which provide diagnostics of outflow speed and density. The angle of the ejecta with the plane of the sky is obtained, combining the projected speed from LASCO with the line-of sight-speed, and varies between 7? and 46?. In the latter case the projected height of 2.32 R? was at an actual heliocentric distance of 3.6 R?. An associated solar energetic particle (SEP) event was observed at the L1 point following this CME. The abundance and charge-state data are consistent with a gradual shock-accelerated SEP event. A type II radio burst was observed at the same time the shock front was detected by UVCS

Identification of Super- and Sub-critical Regions in Shocks driven by Coronal Mass Ejections

In this work, we focus on the analysis of a CME-driven shock observed by SOHO/LASCO. We show that white-light coronagraphic images can be employed to estimate the compression ratio X = rho_d / rho_u all along the front of CME-driven shocks. X increases from the shock flanks (where X ~ 1.2) to the shock center (where X ~ 3.0 is maximum). From the estimated X values, we infer the Alfv\'en Mach number for the general case of an oblique shock. It turns out that only a small region around the shock center is supercritical at earlier times, while higher up in the corona the whole shock becomes subcritical. This suggests that CME-driven shocks could be efficient particle accelerators at the initiation phases of the event, while at later times they progressively loose energy, also losing their capability to accelerate high energy particles. This result has important implications on the localization of particle acceleration sites and in the context of predictive space weather studies

Densities and Velocities in Fast Coronal Mass Ejections: Radiative Pumping of the O VI Doublet

In very fast coronal mass ejections (CMEs), it is possible for O VI ions to scatter Lyβ photons that originate in the solar chromosphere and for the λ1037 transition of O VI to scatter λ1032 photons from the solar transition region. This scattering process can be identified by departures of the O VI I1032/I1037 intensity ratio from its collisional value of 2. We report the first detection of this effect in a CME that occurred on 2000 June 28, and we show that this pumping provides a density diagnostic for CMEs faster than 1600 km s-1. At heliocentric distances near 3 R☉, this diagnostic is useful for densities in the 5 × 105-107 cm-3 range