27 research outputs found
Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter
The Coronal Multichannel Polarimeter (CoMP) measures not only the
polarization of coronal emission, but also the full radiance profiles of
coronal emission lines. For the first time, CoMP observations provide
high-cadence image sequences of the coronal line intensity, Doppler shift and
line width simultaneously in a large field of view. By studying the Doppler
shift and line width we may explore more of the physical processes of CME
initiation and propagation. Here we identify a list of CMEs observed by CoMP
and present the first results of these observations. Our preliminary analysis
shows that CMEs are usually associated with greatly increased Doppler shift and
enhanced line width. These new observations provide not only valuable
information to constrain CME models and probe various processes during the
initial propagation of CMEs in the low corona, but also offer a possible
cost-effective and low-risk means of space weather monitoring.Comment: 6 figures. Will appear in the special issue of Coronal Magnetism,
Sol. Phy
Review article: MHD wave propagation near coronal null points of magnetic fields
We present a comprehensive review of MHD wave behaviour in the neighbourhood
of coronal null points: locations where the magnetic field, and hence the local
Alfven speed, is zero. The behaviour of all three MHD wave modes, i.e. the
Alfven wave and the fast and slow magnetoacoustic waves, has been investigated
in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null
points, for a variety of assumptions, configurations and geometries. In
general, it is found that the fast magnetoacoustic wave behaviour is dictated
by the Alfven-speed profile. In a plasma, the fast wave is focused
towards the null point by a refraction effect and all the wave energy, and thus
current density, accumulates close to the null point. Thus, null points will be
locations for preferential heating by fast waves. Independently, the Alfven
wave is found to propagate along magnetic fieldlines and is confined to the
fieldlines it is generated on. As the wave approaches the null point, it
spreads out due to the diverging fieldlines. Eventually, the Alfven wave
accumulates along the separatrices (in 2D) or along the spine or fan-plane (in
3D). Hence, Alfven wave energy will be preferentially dissipated at these
locations. It is clear that the magnetic field plays a fundamental role in the
propagation and properties of MHD waves in the neighbourhood of coronal null
points. This topic is a fundamental plasma process and results so far have also
lead to critical insights into reconnection, mode-coupling, quasi-periodic
pulsations and phase-mixing.Comment: 34 pages, 5 figures, invited review in Space Science Reviews => Note
this is a 2011 paper, not a 2010 pape
Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results
The chromosphere is a thin layer of the solar atmosphere that bridges the
relatively cool photosphere and the intensely heated transition region and
corona. Compressible and incompressible waves propagating through the
chromosphere can supply significant amounts of energy to the interface region
and corona. In recent years an abundance of high-resolution observations from
state-of-the-art facilities have provided new and exciting ways of
disentangling the characteristics of oscillatory phenomena propagating through
the dynamic chromosphere. Coupled with rapid advancements in
magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly
investigate the role waves play in supplying energy to sustain chromospheric
and coronal heating. Here, we review the recent progress made in
characterising, categorising and interpreting oscillations manifesting in the
solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review
Propagating Disturbances in Coronal Loops: A Detailed Analysis of Propagation Speeds
Quasi-periodic disturbances have been observed in the outer solar atmosphere
for many years now. Although first interpreted as upflows (Schrijver et al.
(1999)), they have been widely regarded as slow magnetoacoustic waves, due to
observed velocities and periods. However, recent observations have questioned
this interpretation, as periodic disturbances in Doppler velocity, line width
and profile asymmetry were found to be in phase with the intensity oscillations
(De Pontieu et al. (2010),Tian1 et al. (2011))}, suggesting the disturbances
could be quasi-periodic upflows. Here we conduct a detailed analysis of the
velocities of these disturbances across several wavelengths using the
Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory
(SDO). We analysed 41 examples, including both sunspot and non sunspot regions
of the Sun. We found that the velocities of propagating disturbances (PDs)
located at sunspots are more likely to be temperature dependent, whereas the
velocities of PDs at non sunspot locations do not show a clear temperature
dependence. We also considered on what scale the underlying driver is affecting
the properties of the PDs. Finally, we found that removing the contribution due
to the cooler ions in the 193 A wavelength suggests that a substantial part of
the 193 emission of sunspot PDs can be contributed to the cool component of
193\AA.Comment: 26 Papges, 15 Figure
Limb Spicules from the Ground and from Space
We amassed statistics for quiet-sun chromosphere spicules at the limb using
ground-based observations from the Swedish 1-m Solar Telescope on La Palma and
simultaneously from NASA's Transition Region and Coronal Explorer (TRACE)
spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond
resolution obtained after maximizing the ground-based resolution with the
Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained
specific statistics for sizes and motions of over two dozen individual
spicules, based on movies compiled at 50-second cadence for the series of five
wavelengths observed in a very narrow band at H-alpha, on-band and in the red
and blue wings at 0.035 nm and 0.070 nm (10 s at each wavelength) using the
SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from
TRACE. The MOMFBD restoration also automatically aligned the images,
facilitating the making of Dopplergrams at each off-band pair. We studied 40
H-alpha spicules, and 14 EUV spicules that overlapped H-alpha spicules; we
found that their dynamical and morphological properties fit into the framework
of several previous studies. From a preliminary comparison with spicule
theories, our observations are consistent with a reconnection mechanism for
spicule generation, and with UV spicules being a sheath region surrounding the
H-alpha spicules
Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations
Magnetohydrodynamic Oscillations in the Solar Corona and Earth’s Magnetosphere: Towards Consolidated Understanding
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1995 Solid Waste 30-year volume summary
This document, prepared by Pacific Northwest Laboratory (PNL) under the direction of Westinghouse Hanford Company (WHC), provides a description of the annual low-level mixed waste (LLMW) and transuranic/transuranic mixed solid waste (TRU-TRUM) volumes expected to be managed by Hanford`s Solid Waste Central Waste Complex (CWC) over the next 30 years. The waste generation sources and waste categories are also described. This document is intended to be used as a reference for short- and long-term planning of the Hanford treatment, storage, and disposal (TSD) activities over the next several decades. By estimating the waste volumes that will be generated in the future, facility planners can determine the timing of key waste management activities, evaluate alternative treatment strategies, and plan storage and disposal capacities. In addition, this document can be used by other waste sites and the general public to gain a better understanding of the types and volumes of waste that will be managed at Hanford
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1995 solid waste 30-year container volume summary
This report describes a 30-year forecast of the solid waste volumes by container category. The volumes described are low-level mixed waste (LLMW) and transuranic/transuranic mixed (TRU-TRUM) waste. These volumes and their associated container categories will be generated or received at the US Department of Energy Hanford Site for storage, treatment, and disposal at Westinghouse Hanford Company`s Solid Waste Operations Complex (SWOC) during a 30-year period from FY 1995 through FY 2024. The data presented in this report establish a baseline for solid waste management both in the present and future. With knowledge of the volumes by container type, decisions on the facility handling and storage requirements can be adequately made. It is recognized that the forecast estimates will vary as facility planning and missions continue to change and become better defined; however, the data presented in this report still provide useful insight into Hanford`s future solid waste management requirements