Space Science Reviews

, Volume 210, Issue 1–4, pp 37–76 | Cite as

Measurements of Photospheric and Chromospheric Magnetic Fields

  • Andreas Lagg
  • Bruce Lites
  • Jack Harvey
  • Sanjay Gosain
  • Rebecca Centeno
Article

Abstract

The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space.

Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution.

Keywords

Sun Magnetic field Chromosphere Photosphere Measurement Observations Spectro-polarimetry 

Notes

Acknowledgements

Hinode is a Japanese mission developed and launched by ISAS/JAXA, collaborating with NAOJ as a domestic partner, NASA and STFC (UK) as international partners. Scientific operation of the Hinode mission is conducted by the Hinode science team organized at ISAS/JAXA. This team mainly consists of scientists from institutes in the partner countries. Support for the post-launch operation is provided by JAXA and NAOJ (Japan), STFC (UK), NASA, ESA, and NSC (Norway). B. Lites was supported in part by the FPP project at LMSAL and HAO under NASA contract NNM07AA01C. The National Center for Atmospheric Research is sponsored by the National Science Foundation. The National Solar Observatory is operated by the Association of Universities for Research in Astronomy (AURA, Inc.) under a cooperative agreement with the National Science Foundation. The 1.5-meter GREGOR solar telescope was built by a German consortium under the leadership of the Kiepenheuer-Institut für Sonnenphysik in Freiburg with the Leibniz-Institut für Astrophysik Potsdam, the Institut für Astrophysik Göttingen, and the Max-Planck-Institut für Sonnensystemforschung in Göttingen as partners, and with contributions by the Instituto de Astrofìsica de Canarias and the Astronomical Institute of the Academy of Sciences of the Czech Republic. This study is supported by the European Commission’s FP7 Capacities Programme under the Grant Agreement number 312495.

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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Andreas Lagg
    • 1
  • Bruce Lites
    • 2
  • Jack Harvey
    • 3
  • Sanjay Gosain
    • 3
  • Rebecca Centeno
    • 2
  1. 1.Max Planck Institute for Solar System ResearchGöttingenGermany
  2. 2.High Altitude ObservatoryNational Center for Atmospheric ResearchBoulderUSA
  3. 3.National Solar ObservatoryTucsonUSA

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