Abstract The remarkable magnetohydrodynamic stability of solar coronal loops has been attributed to the anchoring ends in dense photosphere. However, all previous analyses such line-tying have approximate, sense that they give only upper or lower bounds on critical amount twist (or loop-length) required for breakdown stability. object present paper is remove these approximations and determine exact value twist. When it exceeded magnetic field becomes kink unstable a flare may be initiated. A...

Numerical experiments of the emergence magnetic flux from uppermost layers solar interior to photosphere and its further eruption into low atmosphere corona are carried out. We use idealized models for initial stratification field distribution below similar those used multidimensional in literature. The energy equation is adiabatic except inclusion ohmic viscous dissipation terms, which, however, become important only at interfaces reconnection sites. Three-dimensional both an unmagnetized a...

High cadence, 171 Å, TRACE observations show that outward propagating intensity disturbances are a common feature in large, quiescent coronal loops. These oscillations interpreted as slow magneto-acoustic waves. Using wavelet analysis, we found periods of the order s. However, careful study location footpoints revealed distinct separation between those loops support with smaller than 200 s and larger It was situated above sunspot regions display period s, whereas "non-sunspot" We conclude...

view Abstract Citations (196) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Twisted Flux-Tube Model for Solar Prominences. I. General Properties Priest, E. R. ; Hood, A. W. Anzer, U. It is proposed that a solar prominence consists of cool plasma supported in large-scale curved and twisted magnetic flux tube. As long as the tube untwisted, its curvature concave toward surface, so it cannot support dense against gravity. However, when...

We report on three-dimensional (3D) MHD simulations of the formation jets produced during emergence and eruption solar magnetic fields. The interaction between an emerging ambient field in atmosphere leads to (external) reconnection "standard" with inverse Y-shaped configuration. Eventually, low-atmosphere (internal) sheared fieldlines flux region produces erupting rope a jet underneath it. plasma blows out and, moreover, it unwinds as is ejected into outer atmosphere. fast emission cool...

A theoretical description of slow MHD wave propagation in the solar corona is presented. Two different damping mechanisms, namely thermal conduction and compressive viscosity, are included discussed detail. We revise properties “thermal” mode, which excited when included. The mode purely decaying case standing waves, but oscillatory driven waves. When dominant, waves propagate largely undamped, at slower, isothermal sound speed. This implies that there a minimum time (or length) can be...

Using MHD numerical experiments in three dimensions, we study the emergence of a bipolar magnetic region from solar interior into model corona containing large-scale, horizontal field. An arch-shaped concentrated current sheet is formed at interface between rising magnetized plasma and ambient coronal Three-dimensional reconnection takes place along sheet, so that photosphere become magnetically connected, process repeatedly observed recent satellite missions. We show structure evolution how...

The separation of the cylindrical tearing mode stability problem into a resistive resonant layer calculation and an external marginal ideal magnetohydrodynamic (MHD) (Δ′ calculation) is generalized to axisymmetric toroidal geometry. general structure this analyzed MHD information (the generalization Δ′) required discuss isolated. This can then, in principle, be combined with relevant calculations determine growth rates realistic situations. Two examples are given: first analytic treatment...

Context. The heating of solar coronal plasma to millions degrees is likely be due the superposition many small energy-releasing events, known as nanoflares. Nanoflares dissipate magnetic energy through reconnection.

Aims. We investigate the damping process for propagating transverse velocity oscillations, observed to be ubiquitous in solar corona, due mode coupling.

<i>Context. <i/>The paper is concerned with heating of the solar corona by nanoflares: a superposition small transient events in which stored magnetic energy dissipated reconnection. It proposed that occurs nonlinear phase an ideal kink instability, where reconnection leads to relaxation state minimum energy.<i>Aims. aim investigate aspects on current loop zero net axial current. The dynamical processes leading establishment relaxed are explored. efficiency investigated. <i>Methods. <i/>A 3D...

<i>Aims. <i/>We investigate the emergence of a "sea-serpent" magnetic field into outer solar atmosphere and connection between undulating fieldlines formation Ellerman bombs.<i>Methods. perform 3D numerical experiments solving time-dependent resistive MHD equations.<i>Results. <i/>A sub-photospheric flux sheet develops undulations due to Parker instability. It rises from convectively unstable layer emerges highly stratified through successive reconnection events along system. Brightenings...

Aims. We investigate the spatial damping of propagating kink waves in an inhomogeneous plasma. In limit a thin tube surrounded by transition layer, analytical formulation for driven from bottom boundary corona is presented.

Context. Recent observations of the corona reveal ubiquitous transverse velocity perturbations that undergo strong damping as they propagate. These can be understood in terms propagating kink waves mode coupling inhomogeneous regions.

This paper continues the study of De Moortel & Hood ([CITE]) into propagation slow MHD waves in solar corona. Firstly, damping due to optically thin radiation is investigated and compared effect thermal conduction. In a second stage, gravitational stratification included model it found that this increases length significantly. Finally, different magnetic field geometries on investigated. As first approximation, purely radial considered although amplitudes perturbations decrease divergence...

Aims.We investigate the effects of varying magnetic field strength and twist a flux tube as it rises through solar interior emerges into atmosphere.

Context. This paper extends the models of Craig & McClymont (1991, ApJ, 371, L41) and McLaughlin Hood (2004, A&A, 420, 1129) to include finite β nonlinear effects.

Sigmoids are structures with a forward or inverse S-shape, generally observed in the solar corona soft X-ray emission. It is believed that appearance of sigmoid an active region important factor eruptive activity. The association sigmoids dynamic phenomena such as flares and coronal mass ejections (CMEs) make study important. Recent observations sigmoid, obtained X-Ray Telescope (XRT) on board Hinode, showed formation eruption phase high spatial resolution. These revealed topological...

<i>Context. <i/>Models of flux emergence frequently use a twisted cylindrical loop as the initial starting configuration and ignore coupling between radiation field plasma. In these models, axis original tube never emerges through photosphere. Without emerging, it is very difficult to form realistic sunspot.<i>Aims. <i/>The aim toroidal loop, placed beneath solar photosphere study whether system fully into atmosphere. The curvature means that plasma can drain more effectively than in...