216 research outputs found
Towards improved management of coastal submersion crises - CRISMA-WAVE solution as an example of CRISMA Framework application
Coping with various types of natural or man-made hazards the FP7 SECURITY CRISMA project (http://www.crisrnaprojecteu) has designed and developed an experimental software framework allowing building crisis management simulation application. One of the five pilot applications of CRISMA dealing with preparedness to the coastal submersions was developed and implemented using return of experience of the reference Xynthia storm surge event in the Charente Maritime County in France. The paper addresses the generic CRISMA Framework applicability to simulate mitigation effects of a coastal submersion through CRISMA-Wave implementation of a full modelling cycle. The CRISMA-Wave paradigm reflects user needs for simulation of "what-if" scenarios for short and long-term actions and the paper describes in particular its different components : *Simulation of submersion effects at a range of temporal and spatial scales, *Preparedness Planning, *Assessment of impacts depending on scenarios based on options for managing the inundation risks, *Cascading effects and *Evaluation of damages with comparison of submersion defence scenarios based on cost-benefit and multi criteria analysis
Time delays in quasi-periodic pulsations observed during the X2.2 solar flare on 2011 February 15
We report observations of quasi-periodic pulsations (QPPs) during the X2.2
flare of 2011 February 15, observed simultaneously in several wavebands. We
focus on fluctuations on time scale 1-30 s and find different time lags between
different wavebands. During the impulsive phase, the Reuven Ramaty High Energy
Solar Spectroscopic Imager (RHESSI) channels in the range 25-100 keV lead all
the other channels. They are followed by the Nobeyama RadioPolarimeters at 9
and 17 GHz and the Extreme Ultra-Violet (EUV) channels of the Euv
SpectroPhotometer (ESP) onboard the Solar Dynamic Observatory (SDO). The
Zirconium and Aluminum filter channels of the Large Yield Radiometer (LYRA)
onboard the Project for On-Board Autonomy (PROBA2) satellite and the SXR
channel of ESP follow. The largest lags occur in observations from the
Geostationary Operational Environmental Satellite (GOES), where the channel at
1-8 {\AA} leads the 0.5-4 {\AA} channel by several seconds. The time lags
between the first and last channels is up to 9 s. We identified at least two
distinct time intervals during the flare impulsive phase, during which the QPPs
were associated with two different sources in the Nobeyama RadioHeliograph at
17 GHz. The radio as well as the hard X-ray channels showed different lags
during these two intervals. To our knowledge, this is the first time that time
lags are reported between EUV and SXR fluctuations on these time scales. We
discuss possible emission mechanisms and interpretations, including flare
electron trapping
Numerical simulation of the internal plasma dynamics of post-flare loops
We integrate the MHD ideal equations of a slender flux tube to simulate the
internal plasma dynamics of coronal post-flare loops. We study the onset and
evolution of the internal plasma instability to compare with observations and
to gain insight into physical processes and characteristic parameters
associated with flaring events. The numerical approach uses a finite-volume
Harten-Yee TVD scheme to integrate the 1D1/2 MHD equations specially designed
to capture supersonic flow discontinuities. We could reproduce the
observational sliding down and upwardly propagating of brightening features
along magnetic threads of an event occurred on October 1st, 2001. We show that
high--speed downflow perturbations, usually interpreted as slow magnetoacoustic
waves, could be better interpreted as slow magnetoacoustic shock waves. This
result was obtained considering adiabaticity in the energy balance equation.
However, a time--dependent forcing from the basis is needed to reproduce the
reiteration of the event which resembles observational patterns -commonly known
as quasi--periodic pulsations (QPPs)- which are related with large scale
characteristic longitudes of coherence. This result reinforces the
interpretation that the QPPs are a response to the pulsational flaring
activity.Comment: Accepted MNRAS, 10 pages, 14 figures, 1 tabl
The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV
solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission
launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm
and provides images of the low solar corona over a 54x54 arcmin field-of-view
with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is
designed to monitor all space-weather-relevant events and features in the low
solar corona. Given the limited resources of the PROBA2 microsatellite, the
SWAP telescope is designed with various innovative technologies, including an
off-axis optical design and a CMOS-APS detector. This article provides
reference documentation for users of the SWAP image data.Comment: 26 pages, 9 figures, 1 movi
Mesenteric tissue for the treatment of septic pelvic complications in the absence of greater omentum
Prominence-cavity regions observed using SWAP 174A filtergrams and simultaneous eclipse flash spectra
Images from the SWAP (Proba 2 mission) taken at 174A in the Fe IX/X lines are
compared to simultaneous slitless flash spectra taken during the last solar
total eclipse of July, 11th 2010. Many faint low excitation emission lines
together with the HeI and HeII Paschen Alpha chromospheric lines are recorded
on eclipse spectra where regions of limb prominences are obtained with
space-borne imagers. We consider a deep flash spectrum obtained by summing 80
individual spectra to show the intensity modulations of the continuum.
Intensity depressions are observed around the prominences in both eclipse and
SWAP images. The prominence cavities are interpreted as a relative depression
of plasma density, produced inside the corona surrounding the prominences.
Photometric measurements are shown at different scales and different,
spectrally narrow, intervals for both the prominences and the coronal
background.Comment: 22 pages, 14 figures, accepted to publish in Sol. Phy
Dynamics of Coronal Bright Points as seen by Sun Watcher using Active Pixel System detector and Image Processing (SWAP), Atmospheric Imaging Assembly AIA), and Helioseismic and Magnetic Imager (HMI)
The \textit{Sun Watcher using Active Pixel system detector and Image
Processing}(SWAP) on board the \textit{PRoject for OnBoard Autonomy\todash 2}
(PROBA\todash 2) spacecraft provides images of the solar corona in EUV channel
centered at 174 \AA. These data, together with \textit{Atmospheric Imaging
Assembly} (AIA) and the \textit{Helioseismic and Magnetic Imager} (HMI) on
board \textit{Solar Dynamics Observatory} (SDO), are used to study the dynamics
of coronal bright points. The evolution of the magnetic polarities and
associated changes in morphology are studied using magnetograms and
multi-wavelength imaging. The morphology of the bright points seen in
low-resolution SWAP images and high-resolution AIA images show different
structures, whereas the intensity variations with time show similar trends in
both SWAP 174 and AIA 171 channels. We observe that bright points are seen in
EUV channels corresponding to a magnetic-flux of the order of Mx. We
find that there exists a good correlation between total emission from the
bright point in several UV\todash EUV channels and total unsigned photospheric
magnetic flux above certain thresholds. The bright points also show periodic
brightenings and we have attempted to find the oscillation periods in bright
points and their connection to magnetic flux changes. The observed periods are
generally long (10\todash 25 minutes) and there is an indication that the
intensity oscillations may be generated by repeated magnetic reconnection
Using the unmet obstetric needs indicator to map inequities in life-saving obstetric interventions at the local health care system in Kenya
A virtual appliance as proxy pipeline for the Solar Orbiter/Metis coronagraph
Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted to the study of the Sun that will be launched in October 2018. Metis is designed to perform imaging of the solar corona in the UV at 121.6 nm and in the visible range where it will accomplish polarimetry studies thanks to a variable retarder plate. Due to mission constraints, the telemetry downlink on the spacecraft will be limited and data will be downloaded with delays that could reach, in the worst case, several months. In order to have a quick overview on the ongoing operations and to check the safety of the 10 instruments on board, a high-priority downlink channel has been foreseen to download a restricted amount of data. These so-called Low Latency Data will be downloaded daily and, since they could trigger possible actions, they have to be quickly processed on ground as soon as they are delivered. To do so, a proper processing pipeline has to be developed by each instrument. This tool will then be integrated in a single system at the ESA Science Operation Center that will receive the downloaded data by the Mission Operation Center. This paper will provide a brief overview of the on board processing and data produced by Metis and it will describe the proxy-pipeline currently under development to deal with the Metis low-latency data
On Solving the Coronal Heating Problem
This article assesses the current state of understanding of coronal heating,
outlines the key elements of a comprehensive strategy for solving the problem,
and warns of obstacles that must be overcome along the way.Comment: Accepted by Solar Physics; Published by Solar Physic
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