Energy Cascades in Large-Scale Solar Flare Reconnection

2012 ◽  
pp. 43-48 ◽  
Author(s):  
Miroslav Bárta ◽  
Jan Skála ◽  
Marian Karlický ◽  
Jörg Büchner
Keyword(s):  
Solar Flare ◽  
Large Scale ◽  
Energy Cascades

scholarly journals The frequency of stellar X-ray flares from a large-scale XMM-Newton sample

2015 ◽  
Vol 11 (S320) ◽  
pp. 134-137
Author(s):  
John P. Pye ◽  
Simon R. Rosen
Keyword(s):  
Solar System ◽  
Solar Flare ◽  
Space Weather ◽  
White Light ◽  
Large Scale ◽  
The Sun ◽  
X Ray ◽  
Cool Star ◽  
Exoplanetary Systems ◽  
Solar Type

AbstractWe present estimates of cool-star X-ray flare rates determined from the XMM-Tycho survey (Pyeet al. 2015, A&A, 581, A28), and compare them with previously published values for the Sun and for other stellar EUV and white-light samples. We demonstrate the importance of applying appropriate corrections, especially in regard to the total, effective size of the stellar sample. Our results are broadly consistent with rates reported in the literature for Kepler white-light flares from solar-type stars, and with extrapolations of solar flare rates, indicating the potential of stellar X-ray flare observations to address issues such as ‘space weather’ in exoplanetary systems and our own solar system.

scholarly journals The Contribution of Striations to the Eddy Energy Budget and Mixing: Diagnostic Frameworks and Results in a Quasigeostrophic Barotropic System with Mean Flow

2015 ◽  
Vol 45 (8) ◽  
pp. 2095-2113 ◽  
Author(s):  
Ru Chen ◽  
Glenn R. Flierl
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Ocean Model ◽  
Invariance Property ◽  
Mean Flow ◽  
Eddy Diffusivities ◽  
Energy Cascades ◽  
The Mean ◽  
Flow Theories ◽  
Noise Forcing

AbstractLow-frequency oceanic motions have banded structures termed “striations.” Since these striations embedded in large-scale gyre flows can have large amplitudes, the authors investigated the effect of mean flow on their directions as well as their contribution to energetics and mixing using a β-plane, barotropic, quasigeostrophic ocean model. In spite of the model simplicity, striations are always found to exist regardless of the imposed barotropic mean flow. However, their properties are sensitive to the mean flow. Rhines jets move with the mean flow and are not necessarily striations. If the meridional component of the mean flow is large, Rhines jets become high-frequency motions; low-frequency striations still exist, but they are nonzonal, have small magnitudes, and contribute little to energetics and mixing. Otherwise, striations are zonal, dominated by Rhines jets, and contribute significantly to energetics and mixing. This study extends the theory of β-plane, barotropic turbulence, driven by white noise forcing at small scales, to include the effect of a constant mean flow. Theories developed in this study, based upon the Galilean invariance property, illustrate that the barotropic mean flow has no effect on total mixing rates, but does affect the energy cascades in the frequency domain. Diagnostic frameworks developed here can be useful to quantify the striations’ contribution to energetics and mixing in the ocean and more realistic models. A novel diagnostic formula is applied to estimating eddy diffusivities.

Solar flare activity: Evidence for large-scale changes in the past

Icarus ◽  
1977 ◽  
Vol 32 (1) ◽  
pp. 106-126 ◽  
Author(s):  
Herbert A. Zook ◽  
Jack B. Hartung ◽  
Dieter Storzer
Keyword(s):  
Solar Flare ◽  
Large Scale ◽  
Flare Activity ◽  
The Past

Baroclinic Instability and Loss of Balance

2005 ◽  
Vol 35 (9) ◽  
pp. 1505-1517 ◽  
Author(s):  
M. Jeroen Molemaker ◽  
James C. McWilliams ◽  
Irad Yavneh
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Baroclinic Instability ◽  
Boussinesq Equations ◽  
Approximate Model ◽  
Slow Manifold ◽  
Energy Cascades ◽  
Centrifugal Instability ◽  
Forward Energy ◽  
Balanced Dynamics

Abstract Under the influences of stable density stratification and the earth’s rotation, large-scale flows in the ocean and atmosphere have a mainly balanced dynamics—sometimes called the slow manifold—in the sense that there are diagnostic hydrostatic and gradient-wind momentum balances that constrain the fluid acceleration. The nonlinear balance equations are a widely successful, approximate model for this regime, and mathematically explicit limits of their time integrability have been identified. It is hypothesized that these limits are indicative, at least approximately, of the transition from the larger-scale regime of inverse energy cascades by anisotropic flows to the smaller-scale regime of forward energy cascade to dissipation by more nearly isotropic flows and intermittently breaking inertia–gravity waves. This paper analyzes the particular example of an unbalanced instability of a balanced, horizontally uniform, vertically sheared current, as it occurs within the Boussinesq equations. This ageostrophic, anticyclonic, baroclinic instability is investigated with an emphasis on how it relates to the breakdown of balance in the neighborhood of loss of balanced integrability and on how its properties compare with other examples of ageostrophic anticyclonic instability of rotating, stratified, horizontally sheared currents. It is also compared with the more familiar types of instability for a vertically sheared current: balanced (geostrophic) baroclinic instability, centrifugal instability, and Kelvin–Helmholtz instability.

scholarly journals Witnessing a Large-scale Slipping Magnetic Reconnection along a Dimming Channel during a Solar Flare

2017 ◽  
Vol 842 (2) ◽  
pp. L18 ◽  
Author(s):  
Ju Jing ◽  
Rui Liu ◽  
Mark C. M. Cheung ◽  
Jeongwoo Lee ◽  
Yan Xu ◽  
...  
Keyword(s):  
Solar Flare ◽  
Magnetic Reconnection ◽  
Large Scale

scholarly journals Beyond Kolmogorov cascades

2019 ◽  
Vol 867 ◽  
Author(s):  
Bérengère Dubrulle
Keyword(s):  
Turbulent Flows ◽  
Large Scale ◽  
Scale Space ◽  
Energy Cascade ◽  
Cloud Formation ◽  
Small Scale ◽  
Weak Formulation ◽  
Anisotropic Flow ◽  
Energy Cascades ◽  
Homogeneity Hypothesis

The large-scale structure of many turbulent flows encountered in practical situations such as aeronautics, industry, meteorology is nowadays successfully computed using the Kolmogorov–Kármán–Howarth energy cascade picture. This theory appears increasingly inaccurate when going down the energy cascade that terminates through intermittent spots of energy dissipation, at variance with the assumed homogeneity. This is problematic for the modelling of all processes that depend on small scales of turbulence, such as combustion instabilities or droplet atomization in industrial burners or cloud formation. This paper explores a paradigm shift where the homogeneity hypothesis is replaced by the assumption that turbulence contains singularities, as suggested by Onsager. This paradigm leads to a weak formulation of the Kolmogorov–Kármán–Howarth–Monin equation (WKHE) that allows taking into account explicitly the presence of singularities and their impact on the energy transfer and dissipation. It provides a local in scale, space and time description of energy transfers and dissipation, valid for any inhomogeneous, anisotropic flow, under any type of boundary conditions. The goal of this article is to discuss WKHE as a tool to get a new description of energy cascades and dissipation that goes beyond Kolmogorov and allows the description of small-scale intermittency. It puts the problem of intermittency and dissipation in turbulence into a modern framework, compatible with recent mathematical advances on the proof of Onsager’s conjecture.

scholarly journals Turbulence in the Diffuse Interstellar Medium

2011 ◽  
Vol 7 (S280) ◽  
pp. 187-202
Author(s):  
Edith Falgarone ◽  
Benjamin Godard ◽  
Pierre Hily-Blant
Keyword(s):  
Interstellar Medium ◽  
Large Scale ◽  
Line Emission ◽  
Turbulent Energy ◽  
Velocity Shear ◽  
Rotational Line ◽  
Turbulent Dissipation ◽  
Energy Cascades ◽  
Velocity Increments ◽  
Non Gaussian

AbstractThe diffuse interstellar medium (ISM) hosts the first steps of interstellar chemistry and the seeds of dense structures. Since its turbulent pressure by far exceeds its thermal pressure, turbulence must play a prominent role in its evolution. Fed at galactic scales, turbulent energy cascades down to the dissipation scales, but as in both laboratory and atmospheric turbulence, it does so in an intermittent way : only a tiny fraction of the small-scales is fed by the turbulent cascade, so that dissipation occurs in bursts. In diffuse molecular clouds, where they can be observed, the signatures of intermittency are: (1) the non-Gaussian statistics of velocity increments, and (2) the existence of coherent structures of intense velocity-shear that appear to channel the large-scale turbulent energy down to milliparsec scales. Attempts at modelling the warm chemistry triggered in the diffuse ISM by bursts of turbulent dissipation are promising : in this framework, the so far unexplained molecular richness observed in this medium is naturally understood, in particular its CH+, HCO+ and CO abundances. Turbulent dissipation is also likely at the origin of the H2 rotational line emission of the diffuse ISM and of a significant fraction of its [C II] emission.

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