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New Infrared Tools to Measure the Solar Coronal Magnetic Field.

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Title:New Infrared Tools to Measure the Solar Coronal Magnetic Field.
Authors:Dima, Gabriel I.
Contributors:Astronomy (department)
Keywords:solar corona
polarimetry
infrared
Hanle effect
Date Issued:Aug 2017
Publisher:University of Hawaiʻi at Mānoa
Abstract:Although the Sun is by far the closest star we can study, we are just beginning to understand more
about the processes taking place both inside and outside its photosphere. Magnetic elds likely
play a signi cant part in many of the dynamic processes observed in the solar corona, but we still
lack the ability to routinely measure the magnetic elds in the corona directly. To address this
problem new diagnostic tools based on coronal emission lines and their polarized properties are
necessary. During my dissertation work I explored a new way to measure weak (<10G) coronal
magnetic elds using linearly polarized infrared emission lines. A theoretical model was developed
to invert linearly polarized measurements of simultaneous forbidden/permitted coronal emission
lines and obtain a solution for the vector magnetic eld. This was complemented by ground-based
measurements using the SOLARC telescope (Haleakal a, Maui) as well as analysis of multi-line
observations obtained during the March 29 2006 total solar eclipse. The main focus was analyzing
linear polarization from three coronal emission lines: FeXIII 1075nm, SiX 1430nm and HeI 1083nm.
These lines were observed both during the March 29 2006 total solar eclipse and using SOLARC.
While the FeXIII1075 is routinely used as a diagnostic tool of the solar corona, the potential for
the SiX1430 and HeI1083 lines as coronal diagnostic tools have not been explored observationally
before. Based on linearly polarized observations of these lines we obtained several important results:
the emission line ratio FeXIII1075/SiX1430 can be used as a temperature diagnostic and as a way
to discriminate between coronal models; discovery of unexpectedly large polarization amplitudes for
the SiX1430 hinting at a need to review our understanding of how this line is formed; con rmation of
the presence of di use polarized HeI1083 emission in the solar corona with polarization orientation
o set from tangential to the solar limb. The results reported here, and hands-on experience with
telescope operation during the project, have shown a decrease in sensitivity of measurements using
SOLARC which needs to be addressed both in terms of upgrading the camera and mirror system
and the data reduction pipeline.
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017.
URI:http://hdl.handle.net/10125/62163
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Astronomy


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