Magnetohydrostatics of a vertical flux tube in the solar atmosphere: Coronal loops, a model of a ring flare filament

Соловьев, А. А.; Kirichek, E. A.

doi:10.1134/s1063773715050072

Cited by 15 publications

(6 citation statements)

References 23 publications

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“…At the periphery of this magnetic structure, the radial component of magnetic field vector approaches zero and the balance of total pressures on either sides of the object is attained as it was demonstrated in the work (Solov'ev & Kirichek, 2015) which studied the equilibrium of vertical magnetic flux tubes in the solar atmosphere. However, as our calculations show, there is no need to attribute an abrupt sideward boundary to the facular knot in our model because the described parameters steadily approach the background values as we move away from the center of the object.…”

Section: Boundary Conditions Of the Problemmentioning

confidence: 84%

Structure of solar faculae

Соловьев

Kirichek

2018

Monthly Notices of the Royal Astronomical Society

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In solar facular regions (plages) three distinct classes of magnetic features are observed: small-scale flux tubes, knots, and pores. Small flux tubes have granular scales; they are in constant motion and can well be simulated numerically according to the concept of magneto-convection. On this dynamic background one observes quite stable, long-lived and bright objects called facular knots, with a diameter of 3-8 Mm and fine (less than 1 Mm) inner filamentary structure. Their magnetic field strength varies in the range from 250 to 1200 G. Our present article considers only these active formations. The stationary MHD problem is solved and analytical formulae are derived for calculation the pressure, density, temperature, and Alfven Mach number in the studied configuration from the corresponding magnetic field structure. The facular knot is modeled in a hydrostatic atmosphere defined by the Avrett & Loeser model (2008) and is surrounded by a weak (2 G) external field corresponding to the average global magnetic field strength on the solar surface. The constructed 3D analytical model presents the facular knot as a magnetic "fountain" with numerous slender fibrils and allows solving the following tasks: 1. Calculation of temperature profiles of the knot at any height of the atmosphere; 2. Description of ring brightening and fine azimuthal fibril structure observed in plages at high spatial resolution; 3. New interpretation of Center-to-Limb Variation problem that fits well with the observational data.

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Section: Boundary Conditions Of the Problemmentioning

confidence: 84%

Structure of solar faculae

Соловьев

Kirichek

2018

Monthly Notices of the Royal Astronomical Society

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“…We apply the following standard BCs which are used by several authors [e.g. Mangalam & Krishan (2000); Solov'ev & Kirichek (2015); Sen & Mangalam (2018)], that [B r (r = 0, z) = 0, B φ (r = 0, z) = 0] which implies that the magnetic field line is vertical at the axis of the flux tube. At the boundary, the radial component vanishes i.e.…”

Section: Grad-shafranov Equation For the Cylindrical Flux Tubementioning

confidence: 99%

Open and Closed Magnetic Configurations of Twisted Flux Tubes

Sen

Mangalam

2019

ApJ

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We construct two classes of magnetohydrostatic (MHS) equilibria for an axisymmetric vertical flux tube spanning from the photosphere to the lower part of the transition region within a realistic stratified solar atmosphere subject to solar gravity. We assume a general quadratic expression of the magnetic flux function for the gas pressure and poloidal current and solve the Grad-Shafranov equation analytically. The solution is a combination of a homogeneous and a particular part where the former is separable by a Coulomb function in r and exponential in z, while the particular part is an open configuration that has no z dependence. We also present another open field solution by using a self-similar formulation with two different profile functions and incorporating stratified solar gravity to maintain the magnetohydrostatic equilibria, which is a modification of earlier self-similar models with a twist. We study the admitted parameter space that is consistent with the conditions in the solar atmosphere and derive magnetic and the thermodynamic structures inside the flux tube that are reasonably consistent with the photospheric magnetic bright points (MBPs) for both open and closed field Coulomb function and self-similar models as estimated from observations and simulations. The obtained open and closed field flux tube solutions can be used as the background conditions for the numerical simulations for the study of the wave propagation through the flux tubes. The solutions can also be used to construct realistic magnetic canopies.

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“…is the average value of the mean effective molar mass from photosphere to transition region given by an empirical formula µ ef f (z) = 1.288 1 − 0.535 z 2.152 3 (Solov'ev and Kirichek, 2015) in the domain of 0 < z < 2.152 Mm. A formulary of the different quantities are listed in Table 1.…”

Section: Boundary Conditions and The Reduced Form Of P And I Pmentioning

confidence: 99%

Model of a fluxtube with a twisted magnetic field in the stratified solar atmosphere

Sen

Mangalam

2018

Advances in Space Research

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We build a single vertical straight magnetic fluxtube spanning the solar photosphere and the transition region which does not expand with height. We assume that the fluxtube containing twisted magnetic fields is in magnetohydrostatic equilibrium within a realistic stratified atmosphere subject to solar gravity. Incorporating specific forms of current density and gas pressure in the Grad-Shafranov equation, we solve the magnetic flux function, and find it to be separable with a Coulomb wave function in radial direction while the vertical part of the solution decreases exponentially. We employ improved fluxtube boundary conditions and take a realistic ambient external pressure for the photosphere to transition region, to derive a family of solutions for reasonable values of the fluxtube radius and magnetic field strength at the base of the axis that are the free parameters in our model. We find that our model estimates are consistent with the magnetic field strength and the radii of Magnetic bright points (MBPs) as estimated from observations. We also derive thermodynamic quantities inside the fluxtube.

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Magnetohydrostatics of a vertical flux tube in the solar atmosphere: Coronal loops, a model of a ring flare filament

Cited by 15 publications

References 23 publications

Structure of solar faculae

Structure of solar faculae

Open and Closed Magnetic Configurations of Twisted Flux Tubes

Model of a fluxtube with a twisted magnetic field in the stratified solar atmosphere

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