17 research outputs found
Role of the cholinergic nervous system in rheumatoid arthritis: aggravation of arthritis in nicotinic acetylcholine receptor alpha7 subunit gene knockout mice
Investigation of quasi-periodic variations in hard X-rays of solar flares. II. Further investigation of oscillating magnetic traps
In our recent paper (Solar Physics 261, 233) we investigated quasi-periodic
oscillations of hard X-rays during impulsive phase of solar flares. We have
come to conclusion that they are caused by magnetosonic oscillations of
magnetic traps within the volume of hard-X-ray (HXR) loop-top sources. In the
present paper we investigate four flares which show clear quasi-periodic
sequences of HXR pulses. We also describe our phenomenological model of
oscillating magnetic traps to show that it can explain observed properties of
HXR oscillations. Main results are the following: 1. We have found that
low-amplitude quasi-periodic oscillations occur before impulsive phase of some
flares. 2. We have found that quasi-period of the oscillations can change in
some flares. We interpret this as being due to changes of the length of
oscillating magnetic traps. 3. During impulsive phase a significant part of the
energy of accelerated (non-thermal) electrons is deposited within the HXR
loop-top source. 4. Our analysis suggests that quick development of impulsive
phase is due to feedback between pulses of the pressure of accelerated
electrons and the amplitude of magnetic-trap oscillation. 5. We have also
determined electron number density and magnetic filed strength for HXR loop-top
sources of several flares. The values fall within the limits of cm, gauss.Comment: 18 pages, 14 figures, submitted to Solar Physic
High-Energy Aspects of Solar Flares: Overview of the Volume
In this introductory chapter, we provide a brief summary of the successes and
remaining challenges in understanding the solar flare phenomenon and its
attendant implications for particle acceleration mechanisms in astrophysical
plasmas. We also provide a brief overview of the contents of the other chapters
in this volume, with particular reference to the well-observed flare of 2002
July 23Comment: This is the introductory article for a monograph on the physics of
solar flares, inspired by RHESSI observations. The individual articles are to
appear in Space Science Reviews (2011
Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
We review basic theoretical concepts in particle acceleration, with
particular emphasis on processes likely to occur in regions of magnetic
reconnection. Several new developments are discussed, including detailed
studies of reconnection in three-dimensional magnetic field configurations
(e.g., current sheets, collapsing traps, separatrix regions) and stochastic
acceleration in a turbulent environment. Fluid, test-particle, and
particle-in-cell approaches are used and results compared. While these studies
show considerable promise in accounting for the various observational
manifestations of solar flares, they are limited by a number of factors, mostly
relating to available computational power. Not the least of these issues is the
need to explicitly incorporate the electrodynamic feedback of the accelerated
particles themselves on the environment in which they are accelerated. A brief
prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
Measurements of fiducial cross-sections for t\bart production with one or two additional b-jets in pp collisions at √s =8 TeVusing the ATLAS detector
Fiducial cross-sections for production with one or two additional
-jets are reported, using an integrated luminosity of 20.3 fb of
proton--proton collisions at a centre-of-mass energy of 8 TeV at the Large
Hadron Collider, collected with the ATLAS detector. The cross-section times
branching ratio for events with at least one additional -jet is
measured to be 950 70 (stat.) (syst.) fb in the
lepton-plus-jets channel and 50 10 (stat.) (syst.) fb in
the channel. The cross-section times branching ratio for events with at
least two additional -jets is measured to be 19.3 3.5 (stat.)
5.7 (syst.) fb in the dilepton channel (,\,, and \,) using a
method based on tight selection criteria, and 13.5 3.3 (stat.) 3.6
(syst.) fb using a looser selection that allows the background normalisation to
be extracted from data. The latter method also measures a value of 1.30
0.33 (stat.) 0.28 (syst.)\% for the ratio of production with
two additional -jets to production with any two additional jets.
All measurements are in good agreement with recent theory predictions.Comment: 41 pages plus author list + cover page (58 total), 9 Figures, 16
tables, submitted to EPJC, all figures including auxiliary figures are
available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2014-10