865 research outputs found
Electrical stimulation with non-implanted devices for stress urinary incontinence in women
The authors would like to thank Luke Vale, Imran Omar, Sheila Wallace and Suzanne MacDonald at the Cochrane Incontinence Group for their support. We would also like to thank Mette Frahm Olsen, Gavin Stewart, Miriam Brazelli, Anna Sierawska, and Beatriz Gualeo for help with translations.Peer reviewedPublisher PD
Automated LASCO CME catalog for solar cycle 23: are CMEs scale invariant?
In this paper we present the first automatically constructed LASCO CME
catalog, a result of the application of the Computer Aided CME Tracking
software (CACTus) on the LASCO archive during the interval September 1997 -
January 2007. We have studied the CME characteristics and have compared them
with similar results obtained by manual detection (CDAW CME catalog). On
average CACTus detects less than 2 events per day during solar minimum up to 8
events during maximum, nearly half of them being narrow (< 20 degrees).
Assuming a correction factor, we find that the CACTus CME rate is surprisingly
consistent with CME rates found during the past 30 years. The CACTus statistics
show that small scale outflow is ubiquitously observed in the outer corona. The
majority of CACTus-only events are narrow transients related to previous CME
activity or to intensity variations in the slow solar wind, reflecting its
turbulent nature. A significant fraction (about 15%) of CACTus-{\it only}
events were identified as independent events, thus not related to other CME
activity. The CACTus CME width distribution is essentially scale invariant in
angular span over a range of scales from 20 to 120 degrees while previous
catalogues present a broad maximum around 30 degrees. The possibility that the
size of coronal mass outflows follow a power law distribution could indicate
that no typical CME size exists, i.e. that the narrow transients are not
different from the larger well-defined CMEs.Comment: 13 pages. ApJ, accepte
Etude Des Contraintes Residuelles Engendrees Par le Procede de Soudage Vertical Montant. EUR 2801. = Study of Residual Constraints Caused by the Vertical Welding Process. EUR 2801.
Coexistence of Self-Organized Criticality and Intermittent Turbulence in the Solar Corona
An extended data set of extreme ultraviolet images of the solar corona
provided by the SOHO spacecraft are analyzed using statistical methods common
to studies of self-organized criticality (SOC) and intermittent turbulence
(IT). The data exhibits simultaneous hallmarks of both regimes, namely power
law avalanche statistics as well as multiscaling of structure functions for
spatial activity. This implies that both SOC and IT may be manifestations of a
single complex dynamical process entangling avalanches of magnetic energy
dissipation with turbulent particle flows.Comment: 4 pages, 4 figure
The detection of ultra-relativistic electrons in low Earth orbit
Aims. To better understand the radiation environment in low Earth orbit
(LEO), the analysis of in-situ observations of a variety of particles, at
different atmospheric heights, and in a wide range of energies, is needed.
Methods. We present an analysis of energetic particles, indirectly detected by
the Large Yield RAdiometer (LYRA) instrument on board ESA's Project for
On-board Autonomy 2 (PROBA2) satellite as background signal. Combining
Energetic Particle Telescope (EPT) observations with LYRA data for an
overlapping period of time, we identified these particles as electrons with an
energy range of 2 to 8 MeV. Results. The observed events are strongly
correlated to geo-magnetic activity and appear even during modest disturbances.
They are also well confined geographically within the L=4-6 McIlwain zone,
which makes it possible to identify their source. Conclusions. Although highly
energetic particles are commonly perturbing data acquisition of space
instruments, we show in this work that ultra-relativistic electrons with
energies in the range of 2-8 MeV are detected only at high latitudes, while not
present in the South Atlantic Anomaly region.Comment: Topical Issue: Flares, CMEs and SEPs and their space weather impacts;
20 pages; 7 figures; Presented during 13th European Space Weather Week, 201
A nanoflare heating model for the quiet solar corona
The energy input into the lower solar corona by flare evaporation events has
been modeled according to the available observations for quiet regions. The
question is addressed whether such heating events can provide the observed
average level of the coronal emission measure and thus of the observed flux of
extreme ultraviolet (EUV) and X-ray emission without contradicting the observed
average power spectrum of the emission measure, the typical emission measure
variations observed for individual pixels and the observed flare energy
distribution. As the assumed flare height influences the derived flare energy,
the mathematical foundations of nanoflare distributions and their conversion to
different height assumptions are studied first. This also allows a comparison
with various published energy distributions differing in height assumptions and
to relate the observations to the input parameters of the heating model. An
analytic evaluation of the power spectrum yields the relationship between the
average time profile of nanoflares (or microflares), assumed to be self-similar
in energy, and the power spectrum. We find that the power spectrum is very
sensitive to the chosen time profile of the flares. Models are found by
numerical simulation that fit all available observations. They are not unique
but severely constrained. We concentrate on a model with a flare height
proportional to the square root of the flare area. The existence of a fitting
model demonstrates that nanoflare heating of the corona is a viable and
attractive mechanism.Comment: 11 pages, 7 figures, updated spelling of 1st autor's nam
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
Energy Distribution of Micro-events in the Quiet Solar Corona
Recent imaging observations of EUV line emissions have shown evidence for
frequent flare-like events in a majority of the pixels in quiet regions of the
solar corona. The changes in coronal emission measure indicate impulsive
heating of new material to coronal temperatures. These heating or evaporation
events are candidate signatures of "nanoflares" or "microflares" proposed to
interpret the high temperature and the very existence of the corona. The energy
distribution of these micro-events reported in the literature differ widely,
and so do the estimates of their total energy input into the corona. Here we
analyze the assumptions of the different methods, compare them by using the
same data set and discuss their results.
We also estimate the different forms of energy input and output, keeping in
mind that the observed brightenings are most likely secondary phenomena. A
rough estimate of the energy input observed by EIT on the SoHO satellite is of
the order of 10% of the total radiative output in the same region. It is
considerably smaller for the two reported TRACE observations. The discrepancy
can be explained partially by different thresholds for flare detection. There
is agreement on the slope and the absolute value of the distribution if the
same method were used and a numerical error corrected. The extrapolation of the
power law to unobserved energies that are many orders of magnitude smaller
remains questionable. Nevertheless, these micro-events and unresolved smaller
events are currently the best source of information on the heating process of
the corona
Invasive mechanical ventilation in cancer patients: prior non-invasive ventilation is a poor prognostic factor
info:eu-repo/semantics/publishe
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