<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">A reminder of the seminar in 20 min:<div class=""><br class=""></div><div class=""><blockquote type="cite" class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div class=""><span class=""><a href="https://stockholmuniversity.zoom.us/j/67108321819" class="">https://stockholmuniversity.zoom.us/j/67108321819</a></span></div></div></blockquote><br class=""></div><div class="">Arjan and Janet</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 28 Sep 2020, at 12:28, Janet Ting-Wan Chen <<a href="mailto:janet.chen@astro.su.se" class="">janet.chen@astro.su.se</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div class=""><span style="font-size: 14px;" class="">Dear all,</span></div>
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</span></div>
<div class=""><span style="font-size: 14px;" class="">On Friday October 2 at 10:30 we will have the next Astronomy Seminar, remotely via zoom.</span></div>
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<div class=""><span style="font-size: 14px;" class="">Our speaker is Ernest Alsina from Locarno, Switzerland.</span></div>
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<div class=""><span style="font-size: 14px;" class="">Title:</span></div>
<div class=""><span style="font-size: 14px;" class="">Magnetic sensitivity of the H I Lyman-α scattering polarization wings in the solar disk radiation. </span></div>
<div class=""><span style="font-size: 14px;" class=""><br class="">
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<div class=""><span style="font-size: 14px;" class="">Abstract:</span></div>
<div class=""><span style="font-size: 14px;" class="">The linear polarization signals arising from scattering processes in the H I Lyman-α line in the solar disk radiation represent a valuable observable for probing the chromosphere-corona transition region
(TR) and the underlying chromospheric plasma. Whereas the line-center signal encodes information on the magnetic activity and geometry of the TR, the broad large-amplitude scattering polarization signals in the wings, produced through the joint action of partial
frequency redistribution and J-state interference, had generally thought to be insensitive to the influence of magnetic fields. However, our investigations show that such Q/I and U/I wing signals are in fact sensitive to the presence of chromospheric magnetic
fields with a significant longitudinal component. This sensitivity arises from the magneto-optical (MO) effects that introduce a coupling between the transfer equations for Stokes Q and U and it becomes appreciable for field strengths similar to those for
which the Hanle effect operates in the line core (approximately between 5 and 100 gauss), being well below those required for sizable signals to be produced through the familiar Zeeman effect.</span></div>
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<div class=""><span style="font-size: 14px;" class="">In this talk, we begin by giving a primer on the main physical mechanisms that give rise to polarization phenomena in this line. We then show the results of a series of numerical radiative transfer calculations,
highlighting the sensitivity to MO effects both in its wing and frequency-integrated linear polarization signals. The theoretical results presented here further enhance the diagnostic interest of the unprecedented spectropolarimetric and broadband observations
obtained by the Chromospheric Lyman-Alpha Spectropolarimeter (CLASP) sounding rocket mission.</span></div>
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<div class=""><span style="font-size: 14px;" class=""><a href="https://www.albanova.se/event/astronomy-seminar-via-zoom-ernest-alsina/" class="">https://www.albanova.se/event/astronomy-seminar-via-zoom-ernest-alsina/</a></span></div>
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<div class=""><span style="font-size: 14px;" class="">We will have the colloquium using zoom. You will find the invitation at the end of this email.</span></div>
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<div class=""><span style="font-size: 14px;" class="">Some guidelines:</span></div>
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</span></div>
<div class=""><span style="font-size: 14px;" class="">1) Join the session with your microphone muted.</span></div>
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</span></div>
<div class=""><span style="font-size: 14px;" class="">2) When you have a question, press the “raise hand button” and wait till you are asked to ask your question. </span></div>
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<div class=""><span style="font-size: 14px;" class="">3) The session will be online from 10:20, please join at least a few minutes early as we would like to start 10:30 sharp.</span></div>
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<div class=""><span style="font-size: 14px;" class="">We hope to see all of you there!</span></div>
<div class=""><span style="font-size: 14px;" class=""><br class="">
</span></div>
<div class=""><span style="font-size: 14px;" class="">Arjan & Janet</span></div>
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</span></div>
<div class=""><span style="font-size: 14px;" class="">Upcoming events:</span></div>
<div class=""><span style="font-size: 14px;" class="">9/10: Enric Palle (IAC, Spain)</span></div>
<div class=""><span style="font-size: 14px;" class="">16/10: Charlotte Angus (DARK, Denmark)</span></div>
<div class=""><span style="font-size: 14px;" class="">23/10: Anders Jerkstrand (SU)</span></div>
<div class=""><span style="font-size: 14px;" class="">30/10: Höstlov</span></div>
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</span></div>
<div class=""><span style="font-size: 14px;" class="">=========================================</span></div>
<div class=""><span style="font-size: 14px;" class="">Janet Ting-Wan Chen is inviting you to a scheduled Zoom meeting.</span></div>
<div class=""><span style="font-size: 14px;" class=""><br class="">
</span></div>
<div class=""><span style="font-size: 14px;" class="">Topic: Astronomy seminar of Ernest Alsina</span></div>
<div class=""><span style="font-size: 14px;" class="">Time: Oct 2, 2020 10:20 AM Stockholm</span></div>
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</span></div>
<div class=""><span style="font-size: 14px;" class="">Join Zoom Meeting</span></div>
<div class=""><span style="font-size: 14px;" class=""><a href="https://stockholmuniversity.zoom.us/j/67108321819" class="">https://stockholmuniversity.zoom.us/j/67108321819</a></span></div>
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<div class=""><span style="font-size: 14px;" class="">Meeting ID: 671 0832 1819</span></div>
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</span></div>
<div class=""><span style="font-size: 14px;" class="">Dial by your location</span></div>
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<div class=""><span style="font-size: 14px;" class="">Meeting ID: 671 0832 1819</span></div>
<div class=""><span style="font-size: 14px;" class="">Find your local number: <a href="https://stockholmuniversity.zoom.us/u/cb1eUbGvCH" class="">
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<div class=""><span style="font-size: 14px;" class="">Join by SIP</span></div>
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<div class=""><span style="font-size: 14px;" class="">Join by H.323</span></div>
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<div class=""><span style="font-size: 14px;" class="">Meeting ID: 671 0832 1819</span></div>
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<div class=""><span style="font-size: 14px;" class="">Join by Skype for Business</span></div>
<div class=""><span style="font-size: 14px;" class=""><a href="https://stockholmuniversity.zoom.us/skype/67108321819" class="">https://stockholmuniversity.zoom.us/skype/67108321819</a></span></div>
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<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="text-align: start; text-indent: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">-------------------------------------------<br class="">Dr. Arjan Bik<br class="">Stockholm University<br class="">AlbaNova University Center<br class="">Department of Astronomy<br class="">SE-106 91 Stockholm - Sweden<br class="">Tel: +46 (0) 85537 8549<br class=""><a href="https://www.su.se/english/profiles/abik" class="">https://www.su.se/english/profiles/abik</a></div><div style="text-align: start; text-indent: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">-------------------------------------------<br class=""></div></div>
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