Replacing the polarizer wheel with a polarization camera to increase the temporal resolution and reduce the overall complexity of a solar coronagraph

Nelson L. Reginald; Natchimuthuk Gopalswamy; Seiji Yashiro; Qian Gong; Madhulika Guhathakurta

doi:10.1117/1.JATIS.3.1.014001

7 February 2017 Replacing the polarizer wheel with a polarization camera to increase the temporal resolution and reduce the overall complexity of a solar coronagraph

Nelson L. Reginald, Natchimuthuk Gopalswamy, Seiji Yashiro, Qian Gong, Madhulika Guhathakurta

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Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 3, Issue 1, 014001 (February 2017). https://doi.org/10.1117/1.JATIS.3.1.014001

Abstract

Experiments that require linearly polarized brightness measurements, traditionally have obtained three successive images through a linear polarizer that is rotated through three well-defined angles and the images are combined to get the linearly polarized brightness. This technique requires a mechanism to hold the linear polarizer in place and to precisely turn it through the three angles. Obviously, the temporal resolution is lost in such a scenario, since the three images that are used to derive the linearly polarized brightness are taken at three different times. Specifically, in a dynamic corona that is in constant reshaping of its structures, the linearly polarized brightness image produced in this manner may not yield true values all around the corona. In this regard, with the advent of the polarization camera, the linearly polarized brightness can be measured from a single image. This also eliminates the need for a linear polarizer and the associated rotator mechanisms and can contribute toward lower weight, size, power requirements, overall risk of the instrument, and most importantly, increase the temporal resolution. We evaluate the capabilities of a selected polarization camera and how these capabilities could be tested in a ground experiment conducted in conjunction with a total solar eclipse. The ground experiment requires the measurement of the linearly polarized brightness, also known as K-corona, in a corona that also contains unpolarized brightness, known as F-corona, in order to measure three important physical properties pertaining to coronal electrons, namely, the electron density, electron temperature, and the electron speed.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Nelson L. Reginald, Natchimuthuk Gopalswamy, Seiji Yashiro, Qian Gong, and Madhulika Guhathakurta "Replacing the polarizer wheel with a polarization camera to increase the temporal resolution and reduce the overall complexity of a solar coronagraph," Journal of Astronomical Telescopes, Instruments, and Systems 3(1), 014001 (7 February 2017). https://doi.org/10.1117/1.JATIS.3.1.014001

Received: 6 May 2016; Accepted: 9 January 2017; Published: 7 February 2017

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