ASTR 1120: Stars & Galaxies Today • Helioseismology – probing inside the Sun with sound waves • How the Sun builds (and destroys) its lovely Magnetic Fields: sunspots, flares, big loops • Homework # 3 due today • Observatory Night 3 on Monday Thurs, Feb 5 -- again by sign-up • Review Sheet available today for in-class Midterm Exam 1 on Fri 11 Feb (review session Wed 9 Feb by Ben Brown) Prof. Juri Toomre TA: Ben Brown • Register on AstronomyPlace by Monday, or you Lecture 11 Fri 4 Feb 05 are out of luck (no more dribbling in!) zeus.colorado.edu/astr1120-toomre
Reading Clicker Q A. Big System View of Sun • What are the solar “layers”, in going from deep inside to outside? core radiative zone • A. core, radiation zone, convection zone, convection zone photosphere, chromosphere, corona - - - - - photosphere • B. core, radiation zone, convection zone, chromosphere corona, chromosphere, photosphere corona • C. core, corona, radiation zone, convection solar wind zone, photosphere, chromosphere
SUN IN Complex PROFILE SURFACE ROTATION SURFACE FEATURES photosphere Vast range SUNSPOTS in temperature and density CORE
chromosphere
PROMINENCES ATMOSPHERE corona ACTIVE REGIONS
1 SOLAR ROTATION as viewed with SOHO
GRANULATION VISIBLE AT SURFACE
Smallest scale of solar convection
``Roiling and boiling’’ at the surface !
Complex Interplay of Convection and Magnetism Granulation: turbulent convection
SUNSPOTS amid field of GRANULES
1 Mm spacing Size: ~ 1 Mm across on ticks
Field of Granules Field of Granules
Berger et al. Berger et al. G-band SwST G-band SwST
2 Convection Zone and Radiative Interior Helioseismology: Millions of sound Just below the waves available to probe solar interior photosphere: REMINDER Deep shell (30%) of very turbulent Some waves noodle convection just below the surface
Drives strong Others almost make it differential rotation to the center
All excited by turbulent But how do granulation visible in we know this? photosphere ACOUSTIC WAVES
Tools of Imaging Helioseismology How Sound Makes A Surface Bounce
• Sound waves inside Sun cause the photosphere to move up and down, with “five-minute oscillations”
• Can detect these with Doppler imaging of gas at solar surface (“see” the sound) Global Oscillation Network Group ( GONG ) gas at solar surface (“see” the sound)
SOHO Spacecraft Michelson Doppler Imager ( MDI )
Doppler movie of solar surface from SOHO SOLAR OSCILLATION MODE
One of millions of modes, each with a different tone!
3 “Power Spectrum” of Solar Oscillations Solar Interior Models Each oscillation Theory vs Helioseismology mode has a FREQUENCY distinctive (measurable) tone
Sensitive to how sound speed varies Temperature Density with depth
Tests models of inside temperature
Observed from SOHO and GONG radius
Interior Differential Rotation Profile Solar Rotation Profiles Variation with radius and Pole Big surprises: latitude Fast equator, TACHOCLINE NEAR-SURFACE slow pole -- Two MAGNETIC SHEAR LAYER over most of DYNAMOS at work: convection zone Global magnetic fields built in Tacholine of tachocline TACHOCLINE strong shear at its base Small-scale fields CZ BOTTOM in near-surface Equator Radiative zone shear zone rotates uniformly RADIUS r/R
SSW in Global View, Apr 2002 Helioseismic Probing of Flows Below Surface
Global Patterns of SOLAR SUBSURFACE WEATHER
Meadering flows like jet streams, interact with active regions
4 SSW Flows Changing as Cycle Progresses
1999 Far-Side Imaging Helioseismology 7 Mm
CR 1948
1997
CR 1923
Diverse Scales of Solar Magnetism SURFACE FEATURES
Now on to GRANULATION & NETWORK SOLAR MAGNETISM
SOFT X-RAY GLOBAL VIEW
Magnetic fields are built in convection zone UV view of solar Convection Zone: magnetism ROTATING SHELL OF TURBULENT chromosphere PLASMA & low corona
Differential Rotation and Magnetic Dynamo go HAND-IN-HAND SOHO EIT 171 A Plasma demo
5 Sunspot in White Light Another UV view of solar magnetism
SOHO EIT Finest close-up 195 A Finest close-up
Zoom-in on evolving sunspot Zoom-in on evolving sunspot Sunspots show “Zeeman splitting”
1000+ Gauss magnetic fields in sunspots
wavelength Æ
B demo
Magnetic Solar Cycle 23 11-year Cycles of Solar Activity
Butterfly Diagram
6 Meanderings of outbound photons Clicker – Energy is how “old” ? E.E. P-P chain makes gamma-ray photons, which “random walk” outwards (getting absorbed, re-emitted), gradually cooling • Light radiated from Sun’s surface reaches us in about 8 minutes, but the energy of REMINDER Takes about that light was released by fusion in the million years solar core about … from creation • A. one year ago to get out • B. ten years ago • C. a hundred years ago So if suddenly turn off • D. a thousand years ago the fusion, what happens? • E. a million years ago
Reading Clicker Q D.D. • What is the composition (by mass) of the Sun ?
• A. 100% hydrogen (H) and helium (He) • B. 50% H, 25% He, 25% other elements • C. 70% He, 28% H, 2% other • D. 70% H, 28% He, 2% other • E. 98% H, 2% He and other
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