skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube

Abstract

We study the dynamics and topology of an emerging magnetic flux concentration using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board the sunrise balloon-borne solar observatory. We obtain the full vector magnetic field and the line of sight (LOS) velocity through inversions of the Fe i line at 525.02 nm with the SPINOR code. The derived vector magnetic field is used to trace magnetic field lines. Two magnetic flux concentrations with different polarities and LOS velocities are found to be connected by a group of arch-shaped magnetic field lines. The positive polarity footpoint is weaker (1100 G) and displays an upflow, while the negative polarity footpoint is stronger (2200 G) and shows a downflow. This configuration is naturally interpreted as a siphon flow along an arched magnetic flux tube.

Authors:
;  [1]; ;  [2];  [3]; ; ; ; ; ; ;  [4];  [5];  [6];  [7]
  1. Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain)
  2. Instituto de Astrofísica de Andalucía (CSIC), Apdo. de Correos 3004, E-18080 Granada (Spain)
  3. Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain)
  4. Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)
  5. Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany)
  6. National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States)
  7. High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)
Publication Date:
OSTI Identifier:
22661233
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 229; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BALLOONS; CONCENTRATION RATIO; IRON IONS; MAGNETIC FIELDS; MAGNETIC FLUX; PHOTOSPHERE; POLARIMETRY; S CODES; SOLAR FLARES; SPATIAL RESOLUTION; SPINORS; SUN; TOPOLOGY; VELOCITY

Citation Formats

Requerey, Iker S., Cobo, B. Ruiz, Iniesta, J. C. Del Toro, Suárez, D. Orozco, Rodríguez, J. Blanco, Solanki, S. K., Barthol, P., Gandorfer, A., Gizon, L., Hirzberger, J., Riethmüller, T. L., Noort, M. van, Schmidt, W., Pillet, V. Martínez, and Knölker, M., E-mail: iker@iac.es. Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube. United States: N. p., 2017. Web. doi:10.3847/1538-4365/229/1/15.
Requerey, Iker S., Cobo, B. Ruiz, Iniesta, J. C. Del Toro, Suárez, D. Orozco, Rodríguez, J. Blanco, Solanki, S. K., Barthol, P., Gandorfer, A., Gizon, L., Hirzberger, J., Riethmüller, T. L., Noort, M. van, Schmidt, W., Pillet, V. Martínez, & Knölker, M., E-mail: iker@iac.es. Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube. United States. doi:10.3847/1538-4365/229/1/15.
Requerey, Iker S., Cobo, B. Ruiz, Iniesta, J. C. Del Toro, Suárez, D. Orozco, Rodríguez, J. Blanco, Solanki, S. K., Barthol, P., Gandorfer, A., Gizon, L., Hirzberger, J., Riethmüller, T. L., Noort, M. van, Schmidt, W., Pillet, V. Martínez, and Knölker, M., E-mail: iker@iac.es. Wed . "Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube". United States. doi:10.3847/1538-4365/229/1/15.
@article{osti_22661233,
title = {Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube},
author = {Requerey, Iker S. and Cobo, B. Ruiz and Iniesta, J. C. Del Toro and Suárez, D. Orozco and Rodríguez, J. Blanco and Solanki, S. K. and Barthol, P. and Gandorfer, A. and Gizon, L. and Hirzberger, J. and Riethmüller, T. L. and Noort, M. van and Schmidt, W. and Pillet, V. Martínez and Knölker, M., E-mail: iker@iac.es},
abstractNote = {We study the dynamics and topology of an emerging magnetic flux concentration using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board the sunrise balloon-borne solar observatory. We obtain the full vector magnetic field and the line of sight (LOS) velocity through inversions of the Fe i line at 525.02 nm with the SPINOR code. The derived vector magnetic field is used to trace magnetic field lines. Two magnetic flux concentrations with different polarities and LOS velocities are found to be connected by a group of arch-shaped magnetic field lines. The positive polarity footpoint is weaker (1100 G) and displays an upflow, while the negative polarity footpoint is stronger (2200 G) and shows a downflow. This configuration is naturally interpreted as a siphon flow along an arched magnetic flux tube.},
doi = {10.3847/1538-4365/229/1/15},
journal = {Astrophysical Journal, Supplement Series},
number = 1,
volume = 229,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}
  • It is shown how to calculate the equilibrium path of a thin magnetic flux tube in a stratified, nonmagnetic atmosphere when the flux tube contains a steady siphon flow. The equilbrium path of a static thin flux tube in an infinite stratified atmosphere generally takes the form of a symmetric arch of finite width, with the flux tube becoming vertical at either end of the arch. A siphon flow within the flux tube increases the curvature of the arched equilibrium path in order that the net magnetic tension force can balance the inertial force of the flow, which tries tomore » straighten the flux tube. Thus, a siphon flow reduces the width of the arched equilibrium path, with faster flows producing narrower arches. The effect of the siphon flow on the equilibrium path is generally greater for flux tubes of weaker magnetic field strength. Examples of the equilibrium are shown for both isothemal and adiabatic siphon flows in thin flux tubes in an isothermal external atmosphere. 19 refs.« less
  • Critical siphon flows in arched, isolated magnetic flux tubes are studied within the thin flux tube approximation, with a view toward applications to intense magnetic flux concentrations in the solar photosphere. The results of calculations of the strength and position of the standing tube shock in the supercritical downstream branch of a critical siphon flow are presented, as are calculations of the flow variables all along the flux tube and the equilibrium path of the flux tube in the surrounding atmosphere. It is suggested that arched magnetic flux tubes, with magnetic field strength increased by a siphon flow, may bemore » associated with some of the intense, discrete magnetic elements observed in the solar photosphere. 37 refs.« less
  • Within the framework of the assumption of large azimuthal wave numbers, the equations for Alfven and slow magnetosonic waves are obtained using frozen-in material coordinates. These equations are specified for the case of a nonuniform magnetic field with axial symmetry. Assuming a meridional polarization of the magnetic field and velocity perturbations, the effects of Alfven wave propagation are analyzed which are related to geometric characteristics of a nonuniform magnetic field: (a) A finite curvature radius of the magnetic field lines and (b) convergence of magnetic field lines. The interaction between the Alfven and magnetosonic waves is found to be stronglymore » dependent on the curvature radius of the magnetic tube and the local plasma {beta} parameter. The electric field amplitude and the length scale of a wave front are found to increase very strongly in the course of the Alfven wave propagation along a converging magnetic flux tube. Also studied is a temporal decrease of the wave perturbations which is caused by dissipation at the conducting boundary.« less
  • This paper extends the study of steady siphon flows in isolated magnetic flux tubes surrounded by field-free gas to the case of adiabatic flows. The basic equations governing steady adiabatic siphon flows in a thin, isolated magnetic flux tube are summarized, and qualitative features of adiabatic flows in elevated, arched flux tubes are discussed. The equations are then cast in nondimensional form and the results of numerical computations of adiabatic siphon flows in arched flux tubes are presented along with comparisons between isothermal and adiabatic flows. The effects of making the interior of the flux tube hotter or colder thanmore » the surrounding atmosphere at the upstream footpoint of the arch is considered. In this case, is it found that the adiabatic flows are qualitatively similar to the isothermal flows, with adiabatic cooling producing quantitative differences. Critical flows can produce a bulge point in the rising part of the arch and a concentration of magnetic flux above the bulge point. 15 references.« less
  • The arched equilibrium path of a thin magnetic flux tube in a plane-stratified, nonmagnetic atmosphere is calculated for cases in which the flux tube contains a steady siphon flow. The large scale mechanical equilibrium of the flux tube involves a balance among the magnetic buoyancy force, the net magnetic tension force due to the curvature of the flux tube axis, and the inertial (centrifugal) force due to the siphon flow along curved streamlines. The ends of the flux tube are assumed to be pinned down by some other external force. Both isothermal and adiabatic siphon flows are considered for fluxmore » tubes in an isothermal external atmosphere. For the isothermal case, in the absence of a siphon flow the equilibrium path reduces to the static arch calculated by Parker (1975, 1979). The presence of a siphon flow causes the flux tube arch to bend more sharply, so that magnetic tension can overcome the additional straightening effect of the inertial force, and reduces the maximum width of the arch. The curvature of the arch increases as the siphon flow speed increases. For a critical siphon flow, with supercritical flow in the downstream leg, the arch is asymmetric, with greater curvature in the downstream leg of the arch. Adiabatic flow have qualitatively similar effects, except that adiabatic cooling reduces the buoyancy of the flux tube and thus leads to significantly wider arches. In some cases the cooling is strong enough to create negative buoyancy along sections of the flux tube, requiring upward curvature of the flux tube path along these sections and sometimes leading to unusual equilibrium paths of periodic, sinusoidal form.« less