E-Print Archive

There are 3977 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
The transition from eruptive to confined flares in the same active region  

Francesco Zuccarello   Submitted: 2017-02-13 03:25

Solar flares are sudden and violent releases of magnetic energy in the solar atmosphere that can be divided in eruptive flares, when plasma is ejected from the solar atmosphere, resulting in a coronal mass ejection (CME), and confined flares when no CME is associated with the flare. We present a case-study showing the evolution of key topological structures, such as spines and fans which may determine the eruptive versus non-eruptive behavior of the series of eruptive flares, followed by confined flares, which are all originating from the same site. To study the connectivity of the different flux domains and their evolution, we compute a potential magnetic field model of the active region. Quasi-separatrix layers are retrieved from the magnetic field extrapolation. The change of behavior of the flares from one day to the next -eruptive to confined- can be attributed to the change of orientation of the magnetic field below the fan with respect to the orientation of the overlaying spine, rather than an overall change in the stability of the large scale field. Flares tend to be more-and-more confined when the field that supports the filament and the overlying field gradually become less-and-less anti-parallel, as a direct result of changes in the photospheric flux distribution, being themselves driven by continuous shearing motions of the different magnetic flux concentrations.

Authors: Zuccarello, Francesco P.; Chandra, Ramesh; Schmieder, Brigitte; Aulanier, Guillaume; Joshi, Reetika
Projects: SDO-AIA,SDO-HMI,SoHO-LASCO

Publication Status: Accepted for publication in Astronomy and Astrophysics
Last Modified: 2017-02-13 12:05
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Vortex and sink flows in eruptive flares as a model for coronal implosions  

Francesco Zuccarello   Submitted: 2017-02-13 03:18

Eruptive flares are sudden releases of magnetic energy that involve many phenomena, several of which can be explained by the standard 2D flare model and its realizations in three-dimensions. We analyze a three-dimensional magnetohydrodynamics simulation in the framework of this model that naturally explains the contraction of coronal loops in the proximity of the flare sites, as well as the inflow towards the region above the cusp-shaped loops. We find that two vorticity arcs located along the flanks of the erupting magnetic flux rope are generated as soon as the eruption begins. The magnetic arcades above the flux-rope legs are then subjected to expansion, rotation or contraction depending on which part of the vortex-flow advects them. In addition to the vortices, an inward-directed magnetic pressure gradient exists in the current sheet below the magnetic flux rope. It results in the formation of a sink that is maintained by reconnection. We conclude that coronal loop apparent implosions observed during eruptive flares are the result of hydro-magnetic effects related to the generation of vortex- and sink-flows when a flux rope moves in a magnetized environment.

Authors: Zuccarello, Francesco P.; Aulanier, Guillaume; Dudík, Jaroslav; Démoulin, Pascal; Schmieder, Brigitte; Gilchrist, Stuart A.
Projects: None

Publication Status: Accepted for publication in The Astrophysical Journal
Last Modified: 2017-02-13 12:05
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

The apparent critical decay index at the onset of solar prominence eruptions  

Francesco Zuccarello   Submitted: 2016-04-28 04:31

A magnetic flux rope (MFR) embedded in a line-tied external magnetic field that decreases with height as z-n is unstable to perturbations if the decay index of the field n is larger than a critical value. The onset of this instability, called torus instability, is one of the main mechanisms that can initiate coronal mass ejections. Since flux ropes often possess magnetic dips that can support prominence plasma, this is also a valuable mechanism to trigger prominence eruptions. Magnetohydrodynamic (MHD) simulations of the formation and/or emergence of MFRs suggest a critical value for the onset of the instability in the range [1.4‑2]. However, detailed observations of prominences suggest a value in the range [0.9‑1.1]. In this Letter, by using a set of MHD simulations, we show why the large discrepancy between models and observations is only apparent. Our simulations indeed show that the critical decay index at the onset of the eruption is n = 1.4 ± 0.1 when computed at the apex of the flux rope axis, while it is n = 1.1 ± 0.1 when it is computed at the altitude of the topmost part of the distribution of magnetic dips. The discrepancy only arises because weakly twisted curved flux ropes do not have dips up to the altitude of their axis.

Authors: Zuccarello F.P., Aulanier G., Gilchrist S.A.
Projects: None

Publication Status: ApJ Letters (published)
Last Modified: 2016-04-29 16:21
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 


Key
Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
The transition from eruptive to confined flares in the same active region
Vortex and sink flows in eruptive flares as a model for coronal implosions
The apparent critical decay index at the onset of solar prominence eruptions

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University