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.
Highlights
The solar corona continues to intrigue with its million-degree (K) temperature, which is much higher than the sun’s surface temperature of ∼6000 K
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
The only viable alternate option to overcome the limitations of the Imaging Spectrograph of Coronal Electrons (ISCORE) instrument for deployment during a total solar eclipse is to use a polarization camera that is capable of simultaneously measuring the total brightness (K+F), linearly polarized brightness (K), and unpolarized brightness (F) in every single image, which will eliminate the need to turn a linear polarizer through three angles for each of the four filters, which allows us to use all four filters to measure both electron temperature and speed, and allows us to observe up to a coronal height of 4 R⊙ from the sun center
Summary
The solar corona continues to intrigue with its million-degree (K) temperature, which is much higher than the sun’s surface temperature of ∼6000 K. The only viable alternate option to overcome the limitations of the ISCORE instrument for deployment during a total solar eclipse is to use a polarization camera that is capable of simultaneously measuring the total brightness (K+F), linearly polarized brightness (K), and unpolarized brightness (F) in every single image, which will eliminate the need to turn a linear polarizer through three angles for each of the four filters, which allows us to use all four filters to measure both electron temperature and speed, and allows us to observe up to a coronal height of 4 R⊙ from the sun center. In the case of the low solar corona imaged by the ISCORE instrument in the current configuration, each pixel will image an area 0.004 R⊙ × 0.004 R⊙ of the object plane, which is the solar corona and will not cause a significant impact except in localized areas that are subject to coronal brightening
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of Astronomical Telescopes, Instruments, and Systems
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
