Spectroscopic Observations of the Sun
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Helioseismology of the Tachocline
HISTORY OF SOLAR ACTIVITY RECORDED IN POLAR ICE Helioseismology of the Tachocline arkus Roth $iepenheuer-Institut für Sonnen%hysi" History of Solar Acti(ity Reco!)e) in Polar Ice Düben)orf, ,-.,,./0,1 HISTORY OF Theoretical Kno2ledge abo#t SOLAR ACTIVITY RECORDED IN the Solar Interio! POLAR ICE What is the structure of the Sun? Theo!y of the inte!nal st!#ct#!e of the sta!s is *ase) on the f#n)amental %!inci%les of %hysics: Energy conservation, Mass conservation, Momentum conservation P!essu!e an) gra(ity a!e in *alance4 hy)!ostatic e5#ili*!i#m 6 the Sun is stable A theo!etical mo)el of the S#n can *e *#ilt on these %hysical la2s. Is there a possibility to „look inside“ the Sun? HISTORY OF SOLAR ACTIVITY RECORDED IN Oscillations in the Sun and the Sta!s POLAR ICE The Sun and the stars exhibit resonance oscillations! Excitation Mechanism: Small perturbations of the equilibrium lead to oscillations Origin: Granulation (turbulences) that generate sound waves, i.e. pressure perturbations (430.5 nm; courtesy to KIS -) 5 Mm HISTORY OF SOLAR ACTIVITY RECORDED IN Oscillations in the Sun and the Sta!s POLAR ICE The Sun and the stars exhibit resonance oscillations! Excitation Mechanism: Small perturbations of the equilibrium lead to oscillations Origin: Granulation (turbulences) that generate sound waves, i.e. pressure perturbations The superposition of sound waves lead to interferences: amplifications or annihilations. Sun and stars act as resonators ? Fundamental mode and higher harmonics are possible Roth, 2004, SuW 8, 24 10 million10 oscillations, -
On a Transition from Solar-Like Coronae to Rotation-Dominated Jovian-Like
On a transition from solar-like coronae to rotation-dominated jovian-like magnetospheres in ultracool main-sequence stars Carolus J. Schrijver Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, CA 94304 [email protected] ABSTRACT For main-sequence stars beyond spectral type M5 the characteristics of magnetic activity common to warmer solar-like stars change into the brown-dwarf domain: the surface magnetic field becomes more dipolar and the evolution of the field patterns slows, the photospheric plasma is increasingly neutral and decoupled from the magnetic field, chromospheric and coronal emissions weaken markedly, and the efficiency of rotational braking rapidly decreases. Yet, radio emission persists, and has been argued to be dominated by electron-cyclotron maser emission instead of the gyrosynchrotron emission from warmer stars. These properties may signal a transition in the stellar extended atmosphere. Stars warmer than about M5 have a solar-like corona and wind-sustained heliosphere in which the atmospheric activity is powered by convective motions that move the magnetic field. Stars cooler than early-L, in contrast, may have a jovian- like rotation-dominated magnetosphere powered by the star’s rotation in a scaled-up analog of the magnetospheres of Jupiter and Saturn. A dimensional scaling relationship for rotation-dominated magnetospheres by Fan et al. (1982) is consistent with this hypothesis. Subject headings: stars: magnetic fields — stars: low-mass, brown dwarfs — stars: late-type — planets and satellites: general arXiv:0905.1354v1 [astro-ph.SR] 8 May 2009 1. Introduction Main sequence stars have a convective envelope around a radiative core from about spectral type A2 (with an effective temperature of Teff ≈ 9000 K) to about M3 (Teff ≈ 3200 K). -
Perspective Helioseismology
Proc. Natl. Acad. Sci. USA Vol. 96, pp. 5356–5359, May 1999 Perspective Helioseismology: Probing the interior of a star P. Demarque* and D. B. Guenther† *Department of Astronomy, Yale University, New Haven, CT 06520-8101; and †Department of Astronomy and Physics, Saint Mary’s University, Halifax, Nova Scotia, Canada B3H 3C3 Helioseismology offers, for the first time, an opportunity to probe in detail the deep interior of a star (our Sun). The results will have a profound impact on our understanding not only of the solar interior, but also neutrino physics, stellar evolution theory, and stellar population studies in astrophysics. In 1962, Leighton, Noyes and Simon (1) discovered patches of in the radial eigenfunction. In general low-l modes penetrate the Sun’s surface moving up and down, with a velocity of the more deeply inside the Sun: that is, have deeper inner turning order of 15 cmzs21 (in a background noise of 330 mzs21!), with radii than higher l-valued p-modes. It is this property that gives periods near 5 minutes. Termed the ‘‘5-minute oscillation,’’ the p-modes remarkable diagnostic power for probing layers of motions were originally believed to be local in character and different depth in the solar interior. somehow related to turbulent convection in the solar atmo- The cut-away illustration of the solar interior (Fig. 2 Left) sphere. A few years later, Ulrich (2) and, independently, shows the region in which p-modes propagate. Linearized Leibacher and Stein (3) suggested that the phenomenon is theory predicts (2, 4) a characteristic pattern of the depen- global and that the observed oscillations are the manifestation dence of the eigenfrequencies on horizontal wavelength. -
Multi-Spacecraft Analysis of the Solar Coronal Plasma
Multi-spacecraft analysis of the solar coronal plasma Von der Fakultät für Elektrotechnik, Informationstechnik, Physik der Technischen Universität Carolo-Wilhelmina zu Braunschweig zur Erlangung des Grades einer Doktorin der Naturwissenschaften (Dr. rer. nat.) genehmigte Dissertation von Iulia Ana Maria Chifu aus Bukarest, Rumänien eingereicht am: 11.02.2015 Disputation am: 07.05.2015 1. Referent: Prof. Dr. Sami K. Solanki 2. Referent: Prof. Dr. Karl-Heinz Glassmeier Druckjahr: 2016 Bibliografische Information der Deutschen Nationalbibliothek Die Deutsche Nationalbibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.d-nb.de abrufbar. Dissertation an der Technischen Universität Braunschweig, Fakultät für Elektrotechnik, Informationstechnik, Physik ISBN uni-edition GmbH 2016 http://www.uni-edition.de © Iulia Ana Maria Chifu This work is distributed under a Creative Commons Attribution 3.0 License Printed in Germany Vorveröffentlichung der Dissertation Teilergebnisse aus dieser Arbeit wurden mit Genehmigung der Fakultät für Elektrotech- nik, Informationstechnik, Physik, vertreten durch den Mentor der Arbeit, in folgenden Beiträgen vorab veröffentlicht: Publikationen • Mierla, M., Chifu, I., Inhester, B., Rodriguez, L., Zhukov, A., 2011, Low polarised emission from the core of coronal mass ejections, Astronomy and Astrophysics, 530, L1 • Chifu, I., Inhester, B., Mierla, M., Chifu, V., Wiegelmann, T., 2012, First 4D Recon- struction of an Eruptive Prominence -
The Sun and the Solar Corona
SPACE PHYSICS ADVANCED STUDY OPTION HANDOUT The sun and the solar corona Introduction The Sun of our solar system is a typical star of intermediate size and luminosity. Its radius is about 696000 km, and it rotates with a period that increases with latitude from 25 days at the equator to 36 days at poles. For practical reasons, the period is often taken to be 27 days. Its mass is about 2 x 1030 kg, consisting mainly of hydrogen (90%) and helium (10%). The Sun emits radio waves, X-rays, and energetic particles in addition to visible light. The total energy output, solar constant, is about 3.8 x 1033 ergs/sec. For further details (and more accurate figures), see the table below. THE SOLAR INTERIOR VISIBLE SURFACE OF SUN: PHOTOSPHERE CORE: THERMONUCLEAR ENGINE RADIATIVE ZONE CONVECTIVE ZONE SCHEMATIC CONVECTION CELLS Figure 1: Schematic representation of the regions in the interior of the Sun. Physical characteristics Photospheric composition Property Value Element % mass % number Diameter 1,392,530 km Hydrogen 73.46 92.1 Radius 696,265 km Helium 24.85 7.8 Volume 1.41 x 1018 m3 Oxygen 0.77 Mass 1.9891 x 1030 kg Carbon 0.29 Solar radiation (entire Sun) 3.83 x 1023 kW Iron 0.16 Solar radiation per unit area 6.29 x 104 kW m-2 Neon 0.12 0.1 on the photosphere Solar radiation at the top of 1,368 W m-2 Nitrogen 0.09 the Earth's atmosphere Mean distance from Earth 149.60 x 106 km Silicon 0.07 Mean distance from Earth (in 214.86 Magnesium 0.05 units of solar radii) In the interior of the Sun, at the centre, nuclear reactions provide the Sun's energy. -
Dynamics of the Fast Solar Tachocline
A&A 389, 629–640 (2002) Astronomy DOI: 10.1051/0004-6361:20020586 & c ESO 2002 Astrophysics Dynamics of the fast solar tachocline I. Dipolar field E. Forg´acs-Dajka1 and K. Petrovay1,2 1 E¨otv¨os University, Department of Astronomy, Budapest, Pf. 32, 1518 Hungary 2 Instute for Theoretical Physics, University of California, Santa Barbara, CA 93106-4030, USA Received 15 January 2002 / Accepted 16 April 2002 Abstract. One possible scenario for the origin of the solar tachocline, known as the “fast tachocline”, assumes that the turbulent diffusivity exceeds η ∼> 109 cm2 s−1. In this case the dynamics will be governed by the dynamo- generated oscillatory magnetic field on relatively short timescales. Here, for the first time, we present detailed numerical models for the fast solar tachocline with all components of the magnetic field calculated explicitly, assuming axial symmetry and a constant turbulent diffusivity η and viscosity ν. We find that a sufficiently strong oscillatory poloidal field with dipolar latitude dependence at the tachocline–convective zone boundary is able to confine the tachocline. Exploring the three-dimensional parameter space defined by the viscosity in the range log ν = 9–11, the magnetic Prandtl number in the range Prm =0.1−10, and the meridional flow amplitude −1 (−3to+3cms ), we also find that the confining field strength Bconf, necessary to reproduce the observed thickness of the tachocline, increases with viscosity ν, with magnetic Prandtl number ν/η, and with equatorward 3 4 meridional flow speed. Nevertheless, the resulting Bconf values remain quite reasonable, in the range 10 −10 G, for all parameter combinations considered here. -
The Demographics of Massive Black Holes
The fifth element: astronomical evidence for black holes, dark matter, and dark energy A brief history of astrophysics • Greek philosophy contained five “classical” elements: °earth terrestrial; subject to °air change °fire °water °ether heavenly; unchangeable • in Greek astronomy, the universe was geocentric and contained eight spheres, seven holding the known planets and the eighth the stars A brief history of astrophysics • Nicolaus Copernicus (1473 – 1543) • argued that the Sun, not the Earth, was the center of the solar system • the Copernican Principle: We are not located at a special place in the Universe, or at a special time in the history of the Universe Greeks Copernicus A brief history of astrophysics • Isaac Newton (1642-1747) • the law of gravity that makes apples fall to Earth also governs the motions of the Moon and planets (the law of universal gravitation) ° thus the square of the speed of a planet in its orbit varies inversely with its radius ⇒ the laws of physics that can be investigated in the lab also govern the behavior of stars and planets (relative to Earth) A brief history of astrophysics • Joseph von Fraunhofer (1787-1826) • discovered narrow dark features in the spectrum of the Sun • realized these arise in the Sun, not the Earth’s atmosphere • saw some of the same lines in the spectrum of a flame in his lab • each chemical element is associated with a set of spectral lines, and the dark lines in the solar spectrum were caused by absorption by those elements in the upper layers of the sun ⇒ the Sun is made of the same elements as the Earth A brief history of astrophysics ⇒ the Sun is made of the same elements as the Earth • in 1868 Fraunhofer lines not associated with any known element were found: “a very decided bright line...but hitherto not identified with any terrestrial flame. -
Fraunhofer Lines and the Composition of the Sun 1 Summary 2 Papers and Datasets 3 Scientific Background
Fraunhofer lines and the composition of the Sun 1 Summary The purpose of this lab is for you to examine the spectrum of the Sun, to learn about the composition of the Sun (it’s not just hydrogen and helium!), and to understand some basic concepts of spectroscopy. 2 Papers and datasets These documents are all available on the course web page. • Low resolution spectrum of the Sun (from the National Solar Observatory) • Absorption lines of various elements (from laserstars.org and NASA’s Goddard Space Flight Center) • Table of abundances in the Sun 3 Scientific background 3.1 Spectroscopy At its most basic level, spectroscopy is simply splitting light up into different wavelengths. The classic example is a prism: white light goes in, and a rainbow comes out. Spectroscopy for physics and astronomy usually drops the output onto some kind of detector that records the flux at different wavelengths as a “stripe” across the detector. In other words, the output is a data table that lists the measured flux as a function of pixel number. An critical aspect of spectroscopy is wavelength calibration: what wavelength corresponds to which pixel number? Note that that relationship does not have to be — and is often not — linear. That is, the mapping of wavelength to pixel is not a linear relationship, but something more complicated. 3.2 The Sun The Sun is mostly hydrogen and after that mostly helium. You have learned about the fusion processes in the Sun and in other stars that gradually convert hydrogen to helium and then, for some stars, onward to carbon, nitrogen, and oxygen (CNO cycle), and further upward through the periodic table to iron. -
SCIENTIFIC CASE: What Are the Stars Made Of?1
Ages: 15 to 17 years old SCIENTIFIC CASE: What are the stars made of?1 Team members Writer: ____________________________________________________ Computer technician: __________________________________________________ Reader: ____________________________________________________ Spokesperson: ____________________________________________________ Ambassador: ___________________________________________________ Context In 1671, Isaac Newton (1643-1727) described how, when a ray of sunlight goes through a crystal prism with a particular angle, it splits showing different colours.. Fig.1: Newton's Experimentum Crucis (Grusche 2015) -fragment | Fig.2: Prism splitting white light into spectral colours. 1 Educational material manufacturated by “Asociación Planeta Ciencias” under the initiative and coordination of the European Space Agency inside the CESAR program framework. Source: Wikimedia.org . Newton also explained that light coming from stars other than the Sun would also be separated by a prism in a similar fashion. Fig 3. Comparison between a Fig 4. Joseph von Fraunhofer (1787 - 1826) prism and a diffraction grating. Source: Museo Alemán de Munich Source: Wikimedia.org More than a century later, in the first years of the 19th Century, Joseph von Fraunhofer (1787-1826) took a big step – he replaced the prism by a more effective optical component: a diffraction grating. This grating had de ability to separate or diffract light into several, more distinguishable rays. That way, Fraunhofer could split sunlight with a better resolution and, when he did, he found out something extraordinary: light wasn't continuous, but had black lines along the spectrum. Fig 5. Fraunhofer's lines. Source: Wikimedia.org So, what do these black lines mean? The Sun emits light due to its high temperature but, on its way from the inside to space, elements in the star absorb part of that light. -
Radio Emission from Ultra-Cool Dwarfs P
Radio Emission from Ultra-Cool Dwarfs P. K. G. Williams Abstract This is an expanded version of a chapter submitted to the Handbook of Exoplanets, eds. Hans J. Deeg and Juan Antonio Belmonte, to be published by Springer Verlag. The 2001 discovery of radio emission from ultra-cool dwarfs (UCDs), the very low- mass stars and brown dwarfs with spectral types of ∼M7 and later, revealed that these objects can generate and dissipate powerful magnetic fields. Radio observations pro- vide unparalleled insight into UCD magnetism: detections extend to brown dwarfs with temperatures .1000 K, where no other observational probes are effective. The data reveal that UCDs can generate strong (kG) fields, sometimes with a stable dipolar structure; that they can produce and retain nonthermal plasmas with electron accel- eration extending to MeV energies; and that they can drive auroral current systems resulting in significant atmospheric energy deposition and powerful, coherent radio bursts. Still to be understood are the underlying dynamo processes, the precise means by which particles are accelerated around these objects, the observed diversity of mag- netic phenomenologies, and how all of these factors change as the mass of the central object approaches that of Jupiter. The answers to these questions are doubly impor- tant because UCDs are both potential exoplanet hosts, as in the TRAPPIST-1 system, and analogues of extrasolar giant planets themselves. 1. Introduction The process that generates the solar magnetic field is called the dynamo. It is widely believed to depend on the tachocline, the shearing layer between the Sun's radiative inner core and its convective outer envelope (e.g., Charbonneau 2014). -
42879 Fraun.Indd
ANNUAL REPORT 2013 1 Cover photo: Turbine blade demonstrator component built at Fraunhofer Center for Coatings and Laser Applications. See page 11. The background photo appearing on this page and next: Custom tailored boron- doped diamond electrodes developed by Fraunhofer Center for Coatings and Laser Applications. See page 9. About Fraunhofer Fraunhofer USA is a non-profi t research and development organization that performs applied research under contract to government and industry with customers such as federal and state governments, multinational corpora- tions, as well as small to medium-sized companies. Fraunhofer USA is a subsidiary of Fraunhofer-Gesellschaft, a world leading applied R&D organization with 67 institu- ites and research units. Fraunhofer USA is comprised of seven research centers: • Fraunhofer Center for Coatings and Laser Applications (CCL) at Michigan State University • Fraunhofer Center for Energy Innovation (CEI) at the University of Connecticut • Fraunhofer Center for Experimental Software Engineering (CESE) affi liated with the University of Maryland • Fraunhofer Center for Laser Technology (CLT) affi liated with the University of Michigan • Fraunhofer Center for Molecular Biotechnology (CMB) affi liated with the University of Delaware • Fraunhofer Center for Manufacturing Innovation (CMI) at Boston University • Fraunhofer Center for Sustainable Energy Systems (CSE), affi liated with Massachusetts Institute of Technology These partnerships serve as a bridge between academic research and industrial needs. The Fraunhofer USA Digital Media Technologies offi ce and the Fraunhofer Heinrich Hertz Institute, USA offi ce pro- mote and support the products of their respective parent institutes from Germany, namely the Fraunhofer Institute for Integrated Circuits IIS, and the Fraunhofer Heinrich Hertz Institute HHI. -
DIVISION E SOLAR ACTIVITY COMMISSION 2 1. Introduction 2
Transactions IAU, Volume XXXA Reports on Astronomy 2015-2018 c 2018 International Astronomical Union Piero Benvenuti, ed. DOI: 00.0000/X000000000000000X DIVISION E SOLAR ACTIVITY COMMISSION 2 ACTIVITE SOLAIRE PRESIDENT Lyndsay Fletcher VICE-PRESIDENT Paul Cally PAST PRESIDENT Carolus J. Schrijver ORGANIZING COMMITTEE Philippa K. Browning, Jongchul Chae, Manolis Georgoulis, Amy R. Winebarger. TRIENNIAL REPORT 2015-2018 1. Introduction Commission E2 deals with solar activity on all scales, ranging from the nanoflares that may be implicated in coronal heating, to the largest flares and mass ejections, and includes the origin and dynamics of the large-scale magnetic field that is the foundation of this. This report reviews scientific progress in the domain, over the three-year period from mid 2015- early 2018. This period has seen continued exploitation of space-based missions such as Hinode, IRIS, SDO and STEREO, as well as high-resolution ground- based solar observatories such as the SST and the Goode Solar Telescope. The report is divided into the following sections: the solar cycle and dynamo; the large-scale solar magnetic field; coronal heating; solar flares; particle acceleration; flare forecasting; and solar eruptions. Our report aims to be comprehensive in the topics addressed, though to some extent the topics cover reflect the expertise of the commission members, and many important results are omitted due to limited space. 2. Solar Cycle and Dynamo Our understanding of the solar cycle and dynamo, which underpins all magnetic activ- ity, is currently in a state of flux. Modelling and simulation are not sufficiently advanced to robustly reproduce the observables (11-year cycles, butterfly diagram, Sp¨orer’s Law, Hale’s Law, Joy’s Law, magnetic helicity, etc.).