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Near-IR Solar Coronal Observations with New-Technology Reflecting Coronographs

Published online by Cambridge University Press:  03 August 2017

Raymond N. Smartt ,
Serge Koutchmy  and
Jacques-Clair NoëNs
Raymond N. Smartt
Affiliation:
National Solar Observatory/Sacramento Peak, National Optical Astronomy Observatories,* Sunspot, New Mexico 88349, U.S.A.
Serge Koutchmy
Affiliation:
Institut d'Astrophysique, CNRS, 98 bis, Boulevard Arago, F-75014 Paris, France
Jacques-Clair NoëNs
Affiliation:
Observatoires du Pic-du-midi et de Toulouse, 65200 Bagnères-de-Bigorre, France

Abstract

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Emission-line and K-coronal observations in the IR have the significant advantage of reduced sky brightness compared with the visible, while the effects of seeing are also reduced. Moreover, strong lines are available in the near-IR. Examples of the current capabilities of IR coronal observations using conventional Lyot coronagraphs are discussed briefly. Photometric measurements using the two IR lines of Fe XIII (10,747 Å and 10,798 Å), together with the Fe XIII 3,388 Å line, have provided a valuable electron-density diagnostic, but with low-angular-resolution. The 10,747 Å line has high intrinsic polarization. It has been used for extensive coronal magnetic field measurements, but only the direction of the field, and that with modest angular resolution, has been achieved due basically to flux limitations. Such studies suffer from the lack of high angular resolution and high photon flux. Moreover, the chromatic properties of a singlet objective lens preclude simultaneous observations at widely-differing wavelengths of the important inner coronal region. A coronagraph based on a mirror objective avoids such problems. Further, comparatively high-resolution and high-sensitivity arrays are now available with quantum efficiencies up to 90%. Reflecting coronagraphs with advanced arrays then provide the possibility of obtaining high-resolution images in the infrared to carry out a wide variety of studies crucial to many of the outstanding problems in coronal physics. A program for the development of reflecting coronagraphs is described briefly, with an emphasis on applications to IR coronal studies.

Keywords

infrared: starsSun: coronatelescopes
Type
Part 7: Infrared Technology and the Future
Information
Symposium - International Astronomical Union , Volume 154: Infrared Solar Physics , 1994 , pp. 603 - 608
Copyright
Copyright © Kluwer 1994 

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