Hostname: page-component-586b7cd67f-tf8b9 Total loading time: 0 Render date: 2024-11-22T15:27:37.497Z Has data issue: false hasContentIssue false
  • English
  • Français

A new look at sunspot formation using theory and observations

Published online by Cambridge University Press:  12 September 2017

I. R. Losada ,
J. Warnecke ,
K. Glogowski ,
M. Roth ,
A. Brandenburg ,
N. Kleeorin  and
I. Rogachevskii
I. R. Losada
Affiliation:
Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden, email: illa.rivero.losada@gmail.com Department of Astronomy, Stockholm University, SE-10691 Stockholm, Sweden Nordic Optical Telescope, Apartado 474, E-38700 Santa Cruz de La Palma, Spain Kiepenheuer-Institut für Sonnenphysik, Schöneckstraße 6, D-79104, Freiburg, Germany
J. Warnecke
Affiliation:
Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany
K. Glogowski
Affiliation:
Kiepenheuer-Institut für Sonnenphysik, Schöneckstraße 6, D-79104, Freiburg, Germany
M. Roth
Affiliation:
Kiepenheuer-Institut für Sonnenphysik, Schöneckstraße 6, D-79104, Freiburg, Germany
A. Brandenburg
Affiliation:
Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden, email: illa.rivero.losada@gmail.com Department of Astronomy, Stockholm University, SE-10691 Stockholm, Sweden Laboratory for Atmospheric and Space Physics, JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80303, USA
N. Kleeorin
Affiliation:
Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden, email: illa.rivero.losada@gmail.com Department of Mechanical Engineering, Ben-Gurion University of the Negev, POB 653, Beer-Sheva 84105, Israel
I. Rogachevskii
Affiliation:
Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden, email: illa.rivero.losada@gmail.com Department of Mechanical Engineering, Ben-Gurion University of the Negev, POB 653, Beer-Sheva 84105, Israel
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Sunspots are of basic interest in the study of the Sun. Their relevance ranges from them being an activity indicator of magnetic fields to being the place where coronal mass ejections and flares erupt. They are therefore also an important ingredient of space weather. Their formation, however, is still an unresolved problem in solar physics. Observations utilize just 2D surface information near the spot, but it is debatable how to infer deep structures and properties from local helioseismology. For a long time, it was believed that flux tubes rising from the bottom of the convection zone are the origin of the bipolar sunspot structure seen on the solar surface. However, this theory has been challenged, in particular recently by new surface observation, helioseismic inversions, and numerical models of convective dynamos. In this article we discuss another theoretical approach to the formation of sunspots: the negative effective magnetic pressure instability. This is a large-scale instability, in which the total (kinetic plus magnetic) turbulent pressure can be suppressed in the presence of a weak large-scale magnetic field, leading to a converging downflow, which eventually concentrates the magnetic field within it. Numerical simulations of forced stratified turbulence have been able to produce strong super-equipartition flux concentrations, similar to sunspots at the solar surface. In this framework, sunspots would only form close to the surface due to the instability constraints on stratification and rotation. Additionally, we present some ideas from local helioseismology, where we plan to use the Hankel analysis to study the pre-emergence phase of a sunspot and to constrain its deep structure and formation mechanism.

Keywords

Sun: sunspotsSun: magnetic fieldsturbulencehelioseismology
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S327: Fine Structure and Dynamics of the Solar Atmosphere , October 2016 , pp. 46 - 59
Copyright
Copyright © International Astronomical Union 2017 

References

Babcock, H. W. (1961). The Topology of the Sun's Magnetic Field and the 22-Year Cycle. ApJ, 133:572.Google Scholar
Barnes, G., Birch, A. C., Leka, K. D., & Braun, D. C. (2014). Helioseismology of Pre-emerging Active Regions. III. Statistical Analysis. ApJ, 786:19.Google Scholar
Birch, A. C., Braun, D. C., Leka, K. D., Barnes, G., & Javornik, B. (2013). Helioseismology of Pre-emerging Active Regions. II. Average Emergence Properties. ApJ, 762:131.Google Scholar
Birch, A. C., Schunker, H., Braun, D. C., Cameron, R., Gizon, L., Löptien, B., & Rempel, M. (2016). A low upper limit on the subsurface rise speed of solar active regions. Science Advances, 2 (7).Google Scholar
Bogdan, T. J., Brown, T. M., Lites, B. W., & Thomas, J. H. (1993). The absorption of p-modes by sunspots - Variations with degree and order. ApJ, 406:723–734.Google Scholar
Brandenburg, A., Kemel, K., Kleeorin, N., Mitra, D., & Rogachevskii, I. (2011). Detection of Negative Effective Magnetic Pressure Instability in Turbulence Simulations. ApJL, 740:L50.Google Scholar
Brandenburg, A., Kemel, K., Kleeorin, N., & Rogachevskii, I. (2012). The Negative Effective Magnetic Pressure in Stratified Forced Turbulence. ApJ, 749:179.Google Scholar
Brandenburg, A., Kleeorin, N., & Rogachevskii, I. (2013). Self-assembly of Shallow Magnetic Spots through Strongly Stratified Turbulence. ApJL, 776:L23.Google Scholar
Brandenburg, A., Rogachevskii, I., & Kleeorin, N. (2016). Magnetic concentrations in stratified turbulence: the negative effective magnetic pressure instability. New Journal of Physics, 18 (12):125011.Google Scholar
Brandenburg, A. & Subramanian, K. (2005). Astrophysical magnetic fields and nonlinear dynamo theory. Phys. Rep., 417:1–209.Google Scholar
Braun, D. C. (1995). Scattering of p-Modes by Sunspots. I. Observations. ApJ, 451:859.Google Scholar
Braun, D. C. (2012). Comment on “Detection of Emerging Sunspot Regions in the Solar Interior”. Science, 336:296.Google Scholar
Braun, D. C., Duvall, T. L. Jr., & Labonte, B. J. (1987). Acoustic absorption by sunspots. ApJL, 319:L27–L31.Google Scholar
Braun, D. C., Duvall, T. L. Jr., & Labonte, B. J. (1988). The absorption of high-degree p-mode oscillations in and around sunspots. ApJ, 335:1015–1025.Google Scholar
Braun, D. C., Duvall, T. L. Jr., Labonte, B. J., Jefferies, S. M., Harvey, J. W., & Pomerantz, M. A. (1992). Scattering of p-modes by a sunspot. ApJL, 391:L113–L116.Google Scholar
Braun, D. C. & Fan, Y. (1998). Helioseismic Measurements of the Subsurface Meridional Flow. ApJL, 508:L105–L108.Google Scholar
Caligari, P., Moreno-Insertis, F., & Schussler, M. (1995). Emerging flux tubes in the solar convection zone. 1: Asymmetry, tilt, and emergence latitude. ApJ, 441:886–902.Google Scholar
Cheung, M. C. M. & Isobe, H. (2014). Flux Emergence (Theory). Living Reviews in Solar Physics, 11:3.Google Scholar
Clette, F., Svalgaard, L., Vaquero, J. M., & Cliver, E. W. (2014). Revisiting the Sunspot Number. A 400-Year Perspective on the Solar Cycle. Space Sci. Rev., 186:35–103.CrossRefGoogle Scholar
Couvidat, S. (2013). Oscillation Power in Sunspots and Quiet Sun from Hankel Analysis Performed on SDO/HMI and SDO/AIA Data. Sol. Phys., 282:15–38.Google Scholar
Crouch, A. D., Cally, P. S., Charbonneau, P., Braun, D. C., & Desjardins, M. (2005). Genetic magnetohelioseismology with Hankel analysis data. MNRAS, 363:1188–1204.CrossRefGoogle Scholar
DeGrave, K., Jackiewicz, J., & Rempel, M. (2014). Time-distance Helioseismology of Two Realistic Sunspot Simulations. ApJ, 794:18.Google Scholar
Dikpati, M. & Gilman, P. A. (2001). Flux-Transport Dynamos with α-Effect from Global Instability of Tachocline Differential Rotation: A Solution for Magnetic Parity Selection in the Sun. ApJ, 559:428–442.Google Scholar
Doerr, H.-P., Roth, M., Zaatri, A., Krieger, L., & Thompson, M. J. (2010). A new code for Fourier-Legendre analysis of large datasets: First results and a comparison with ring-diagram analysis. Astron. Nachr., 331:911.Google Scholar
Gizon, L. & Birch, A. C. (2005). Local Helioseismology. Living Reviews in Solar Physics, 2:6.CrossRefGoogle Scholar
Ilonidis, S., Zhao, J., & Kosovichev, A. (2011). Detection of Emerging Sunspot Regions in the Solar Interior. Science, 333:993.Google Scholar
Jabbari, S., Brandenburg, A., Losada, I. R., Kleeorin, N., & Rogachevskii, I. (2014). Magnetic flux concentrations from dynamo-generated fields. A&A, 568:A112.Google Scholar
Jensen, J. M., Duvall, T. L. Jr., Jacobsen, B. H., & Christensen-Dalsgaard, J. (2001). Imaging an Emerging Active Region with Helioseismic Tomography. ApJL, 553:L193–L196.Google Scholar
Käpylä, P. J., Brandenburg, A., Kleeorin, N., Käpylä, M. J., & Rogachevskii, I. (2016). Magnetic flux concentrations from turbulent stratified convection. A&A, 588:A150.Google Scholar
Kemel, K., Brandenburg, A., Kleeorin, N., Mitra, D., & Rogachevskii, I. (2012a). Spontaneous Formation of Magnetic Flux Concentrations in Stratified Turbulence. Sol. Phys., 280:321–333.Google Scholar
Kemel, K., Brandenburg, A., Kleeorin, N., Mitra, D., & Rogachevskii, I. (2013). Active Region Formation through the Negative Effective Magnetic Pressure Instability. Sol. Phys., 287:293–313.Google Scholar
Kemel, K., Brandenburg, A., Kleeorin, N., & Rogachevskii, I. (2012b). Properties of the negative effective magnetic pressure instability. Astron. Nachr., 333:95.Google Scholar
Kitchatinov, L. L. & Mazur, M. V. (2000). Stability and equilibrium of emerged magnetic flux. Sol. Phys., 191:325–340.Google Scholar
Kitiashvili, I. N., Kosovichev, A. G., Wray, A. A., & Mansour, N. N. (2010). Mechanism of Spontaneous Formation of Stable Magnetic Structures on the Sun. ApJ, 719:307–312.Google Scholar
Kleeorin, N., Mond, M., & Rogachevskii, I. (1993). Magnetohydrodynamic instabilities in developed small-scale turbulence. Physics of Fluids B, 5:4128–4134.Google Scholar
Kleeorin, N., Mond, M., & Rogachevskii, I. (1996). Magnetohydrodynamic turbulence in the solar convective zone as a source of oscillations and sunspots formation. A&A, 307:293.Google Scholar
Kleeorin, N. & Rogachevskii, I. (1994). Effective Ampère force in developed magnetohydrodynamic turbulence. Phys. Rev. E, 50:2716–2730.Google Scholar
Kleeorin, N., Rogachevskii, I., & Ruzmaikin, A. (1990). Magnetic force reversal and instability in a plasma with developed magnetohydrodynamic turbulence. JETP, 70:878–883.Google Scholar
Kleeorin, N. I., Rogachevskii, I. V., & Ruzmaikin, A. A. (1989). The effect of negative magnetic pressure and the large-scale magnetic field instability in the solar convective zone. Pisma v Astronomicheskii Zhurnal, 15:639–645.Google Scholar
Komm, R., Morita, S., Howe, R., & Hill, F. (2008). Emerging Active Regions Studied with Ring-Diagram Analysis. ApJ, 672:1254–1265.Google Scholar
Kosovichev, A. G. (2012). Local Helioseismology of Sunspots: Current Status and Perspectives. Sol. Phys., 279:323–348.Google Scholar
Kosovichev, A. G., Basu, S., Bogart, R., Duvall, T. L. Jr., Gonzalez-Hernandez, I., Haber, D., Hartlep, T., Howe, R., Komm, R., Kholikov, S., Parchevsky, K. V., Tripathy, S., & Zhao, J. (2011). Local helioseismology of sunspot regions: Comparison of ring-diagram and time-distance results. In Journal of Physics Conference Series, volume 271 of Journal of Physics Conference Series, page 012005.Google Scholar
Kosovichev, A. G., Zhao, J., & Ilonidis, S. (2016). Local Helioseismology of Emerging Active Regions: A Case Study. ArXiv e-prints.Google Scholar
Krause, F. & Rädler, K.-H. (1980). Mean-field magnetohydrodynamics and dynamo theory.Google Scholar
Leighton, R. B. (1964). Transport of Magnetic Fields on the Sun. ApJ, 140:1547.Google Scholar
Leighton, R. B. (1969). A Magneto-Kinematic Model of the Solar Cycle. ApJ, 156:1.Google Scholar
Leka, K. D., Barnes, G., Birch, A. C., Gonzalez-Hernandez, I., Dunn, T., Javornik, B., & Braun, D. C. (2013). Helioseismology of Pre-emerging Active Regions. I. Overview, Data, and Target Selection Criteria. ApJ, 762:130.CrossRefGoogle Scholar
Losada, I. R., Brandenburg, A., Kleeorin, N., Mitra, D., & Rogachevskii, I. (2012). Rotational effects on the negative magnetic pressure instability. A&A, 548:A49.Google Scholar
Losada, I. R., Brandenburg, A., Kleeorin, N., & Rogachevskii, I. (2013). Competition of rotation and stratification in flux concentrations. A&A, 556:A83.Google Scholar
Masada, Y. & Sano, T. (2016). Spontaneous Formation of Surface Magnetic Structure from Large-scale Dynamo in Strongly Stratified Convection. ApJL, 822:L22.Google Scholar
Moffatt, H. K. (1978). Magnetic Field Generation in Electrically Conducting Fluids. Cambridge University Press, Cambridge.Google Scholar
Parker, E. N. (1955). The Formation of Sunspots from the Solar Toroidal Field. ApJ, 121:491.Google Scholar
Parker, E. N. (1975). The generation of magnetic fields in astrophysical bodies. X - Magnetic buoyancy and the solar dynamo. ApJ, 198:205–209.Google Scholar
Rempel, M. & Cheung, M. C. M. (2014). Numerical Simulations of Active Region Scale Flux Emergence: From Spot Formation to Decay. ApJ, 785:90.Google Scholar
Rogachevskii, I. & Kleeorin, N. (2007). Magnetic fluctuations and formation of large-scale inhomogeneous magnetic structures in a turbulent convection. Phys. Rev. E, 76 (5):056307.Google Scholar
Schunker, H., Braun, D. C., Birch, A. C., Burston, R. B., & Gizon, L. (2016). SDO/HMI survey of emerging active regions for helioseismology. A&A, 595:A107.Google Scholar
Singh, N. K., Brandenburg, A., & Rheinhardt, M. (2014). Fanning Out of the Solar f-mode in the Presence of Non-uniform Magnetic Fields? ApJL, 795:L8.Google Scholar
Singh, N. K., Raichur, H., & Brandenburg, A. (2016). High-wavenumber Solar f-mode Strengthening Prior to Active Region Formation. ApJ, 832:120.Google Scholar
Spruit, H. C. (1974). A model of the solar convection zone. Sol. Phys., 34:277–290.Google Scholar
Steenbeck, M., Krause, F., & Rädler, K.-H. (1966). Berechnung der mittleren Lorentz-Feldstärke v × b für ein elektrisch leitendes Medium in turbulenter, durch Coriolis-Kräfte beeinflußter Bewegung. Z. Naturforsch. A, 21:369.Google Scholar
Stein, R. & Nordlund, A. (2012a). Spontaneous Pore Formation in Magneto-Convection Simulations. In Golub, L., De Moortel, I., & Shimizu, T., editors, Fifth Hinode Science Meeting, volume 456 of Astronomical Society of the Pacific Conference Series, page 39.Google Scholar
Stein, R. F. & Nordlund, Å. (2012b). On the Formation of Active Regions. ApJL, 753:L13.Google Scholar
Stix, M. (1976). Differential rotation and the solar dynamo. A&A, 47:243–254.Google Scholar
Warnecke, J. & Brandenburg, A. (2010). Surface appearance of dynamo-generated large-scale fields. A&A, 523:A19.Google Scholar
Warnecke, J., Brandenburg, A., & Mitra, D. (2011). Dynamo-driven plasmoid ejections above a spherical surface. A&A, 534:A11.Google Scholar
Warnecke, J., Käpylä, P. J., Käpylä, M. J., & Brandenburg, A. (2016a). Influence of a coronal envelope as a free boundary to global convective dynamo simulations. A&A, 596:A115.Google Scholar
Warnecke, J., Käpylä, P. J., Mantere, M. J., & Brandenburg, A. (2012). Ejections of Magnetic Structures Above a Spherical Wedge Driven by a Convective Dynamo with Differential Rotation. Sol. Phys., 280:299–319.Google Scholar
Warnecke, J., Käpylä, P. J., Mantere, M. J., & Brandenburg, A. (2013a). Spoke-like Differential Rotation in a Convective Dynamo with a Coronal Envelope. ApJ, 778:141.Google Scholar
Warnecke, J., Losada, I. R., Brandenburg, A., Kleeorin, N., & Rogachevskii, I. (2013b). Bipolar magnetic structures driven by stratified turbulence with a coronal envelope. ApJL, 777:L37.Google Scholar
Warnecke, J., Losada, I. R., Brandenburg, A., Kleeorin, N., & Rogachevskii, I. (2016b). Bipolar region formation in stratified two-layer turbulence. A&A, 589:A125.Google Scholar
Zhao, J., Kosovichev, A. G., & Sekii, T. (2010). High-Resolution Helioseismic Imaging of Subsurface Structures and Flows of a Solar Active Region Observed by Hinode. ApJ, 708:304–313.Google Scholar
Zharkov, S. & Thompson, M. J. (2008). Time Distance Analysis of the Emerging Active Region NOAA 10790. Sol. Phys., 251:369–380.Google Scholar