UofA/NSO Summer SchoolIntroduction to the Sun 6/17/06 Welcome to the The First Joint Arizona/NSO...
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Transcript of UofA/NSO Summer SchoolIntroduction to the Sun 6/17/06 Welcome to the The First Joint Arizona/NSO...
UofA/NSO Summer School Introduction to the Sun6/17/06
Welcome to the The First Joint Arizona/NSO Summer SchoolJune 11-16, NSO Sac Peak Observatory, NM
UofA/NSO Summer School Introduction to the Sun6/17/06
List of Topics and Lecturers• Helioseismology
– Rachel Howe, NSO, Tucson– Rudi Komm, NSO, Tucson
• Solar Interior– Gordon Petrie, NSO, Tucson
• Radiative Transfer– Han Uitenbroek, NSO, Sac Peak
• Solar Magnetohydrodynamics– Randy Jokipii, UofA, Tucson
• Photospheric and Chromospheric Magnetic Fields– K.S. Balasubramanian (Bala), NSO, Sac Peak
• Solar-Energetic Particles– Joe Giacalone, UofA, Tucson
• Space Weather– Tom Bogan, NCAR, Boulder
UofA/NSO Summer School Introduction to the Sun6/17/06
List of Activities
• Computer software programs– RASL/DASL CDs and workbooks– xsolar (Chris Russell, UCLA)
• Solar wind, interplanetary magnetic fields
– Helioseismology application widget (Rachel Howe)
• Solar viewing through Hα telescopes– Outside of visitor center
• Poster viewing/discussion
UofA/NSO Summer School Introduction to the Sun6/17/06
List of Other Activities
• Monday – reception at the director’s house• Tuesday – White Sands picnic• Wednesday –
– Tour of NSO facilities, – Community BBQ
• Thursday – Pizza Night / Star Party
UofA/NSO Summer School Introduction to the Sun6/17/06
The Physics of the Sun
UofA/NSO Summer School Introduction to the Sun6/17/06
Why Study the Sun ?
• Influence on Earth
• Important for Astronomy– Only star that we can see closely
• The source of many interesting and important physics problems
• For Me?– Many basic properties are a mystery!
• dynamo, coronal heating, source of high-energy particles, etc.
– Space radiation environment, space weather, acceleration of high-energy charged particles
UofA/NSO Summer School Introduction to the Sun6/17/06
UofA/NSO Summer School Introduction to the Sun6/17/06
Source of the Sun’s Internal Energy:p-p chain is dominate for the Sun; also CNO chain
UofA/NSO Summer School Introduction to the Sun6/17/06
Solar Structure: The Standard Solar
Model
• Theoretical model used to determine the physical properties of the Sun’s interior
• Hydrostatic and thermal equilibrium– A big ball of gas held together by
gravity + radiative diffusion
• Can add convection, but this is difficult (simple approach – mixing-length theory)
• Nuclear reaction rates and opacities are needed
• Boundary conditions are tricky – need to use an iterative approach
UofA/NSO Summer School Introduction to the Sun6/17/06
Solar Oscillations
• Waves can propagate through the Sun causing a variety of vibrations– Like sound waves
• These are used to infer pressures, densities, chemical compositions, and rotation rates within the Sun – Constraints on solar
models
• Helioseismology
UofA/NSO Summer School Introduction to the Sun6/17/06
• Turbulent convective motions cause overturning (bubbling) motions inside the Sun. – These are responsible for
the granulation pattern seen on the Sun’s surface.
– Rayleigh-Bénard convection
UofA/NSO Summer School Introduction to the Sun6/17/06
Recent High-resolution Images of
granulation
UofA/NSO Summer School Introduction to the Sun6/17/06
The photosphere
• About 5700K– Coolest region of the
Sun (coldest in sunspots)
• Sunspots (usually in pairs)
• Variety of convection cells (granulation, supergranulation, etc.)
• Limb Darkening
UofA/NSO Summer School Introduction to the Sun6/17/06
UofA/NSO Summer School Introduction to the Sun6/17/06
UofA/NSO Summer School Introduction to the Sun6/17/06
UofA/NSO Summer School Introduction to the Sun6/17/06
The Chromosphere
• Above the photosphere is a layer of less dense but higher temperature gases called the chromosphere
“Color Sphere”
• characterized by spikesof rising gas
• Spicules extend upward from the photosphere into the chromosphere along the boundaries of supergranules
UofA/NSO Summer School Introduction to the Sun6/17/06
UofA/NSO Summer School Introduction to the Sun6/17/06
The Corona
• The outermost layer of the solar atmosphere, the corona, is made of very high-temperature gases at extremely low density
• The solar corona blends into the solar wind at great distances from the Sun
• Because the corona is very hot, it is best viewed in the x-ray part of the spectrum
• What heats the corona remains an open question!
UofA/NSO Summer School Introduction to the Sun6/17/06
Emission Spectra in the UV
Far UV
To the far rightof this plot is theextreme UV (soft X-ray)
Near UV
Dupree et al., ApJ, 1973
UofA/NSO Summer School Introduction to the Sun6/17/06
SOHO/EIT image at 195 Angstroms (FeXII)
UofA/NSO Summer School Introduction to the Sun6/17/06
Sunspots
• Existence known since 350 BC (Greece), 28 BC (China)
• Lower temperature
• Umbra and penumbra
• Associated with Intense magnetic fields– Zeeman effect
UofA/NSO Summer School Introduction to the Sun6/17/06
The Babcock model andSolar Dynamo
UofA/NSO Summer School Introduction to the Sun6/17/06
The 11-year Sunspot Cycle
Number of Sunspots versus time – they come and go every 11 years
Number of Sunspots versus latitude – forms a “butterfly pattern”
UofA/NSO Summer School Introduction to the Sun6/17/06
The Sun and Earth’s Climate:The Maunder Minimum
• Complete absence of sunspots for 50 years corresponds to a mini ice age
• There is a loose correlation between global man temperature and sunspots
UofA/NSO Summer School Introduction to the Sun6/17/06
Magnetism is the Key to Understanding the Sun
UofA/NSO Summer School Introduction to the Sun6/17/06
UofA/NSO Summer School Introduction to the Sun6/17/06
Coronal loops expand from the surface of the Sun following a solar explosion (solar flare) on April 21, 2002
TRACE movie
UofA/NSO Summer School Introduction to the Sun6/17/06
The Buildup and release of magnetic field energy
• CMEs and Flares– A solar flare is a brief
eruption of hot, ionized gases from a sunspot group
– A coronal mass ejection (CME) is much larger
• Geomagnetic storms
• High-Energy Particles (Space Radiation)
Halloween 2003 storms
UofA/NSO Summer School Introduction to the Sun6/17/06
The Sun is the Most Important Particle Accelerator in the Solar System
UofA/NSO Summer School Introduction to the Sun6/17/06
UofA/NSO Summer School Introduction to the Sun6/17/06
Aurora in Tucson
UofA/NSO Summer School Introduction to the Sun6/17/06
SOHO/LASCO (C3) Coronagraph
“Halloween” solar storms of 2003
UofA/NSO Summer School Introduction to the Sun6/17/06
Propagating Shocks
• Analogy with sonic booms
• Efficient particle accelerators
• Radiation Environment and Space Weather
UofA/NSO Summer School Introduction to the Sun6/17/06
My research has shown that the angle between the shock propagation direction and the magnetic field determines the maximum energy in the particle events
Perpendicular shocks high-energy particles
UofA/NSO Summer School Introduction to the Sun6/17/06
Perpendicular Shocks in the solar atmosphere
UofA/NSO Summer School Introduction to the Sun6/17/06
Analogy to Cosmic Rays and Supernove remants:Supernova Remnant 1006 – Chandra image
UofA/NSO Summer School Introduction to the Sun6/17/06
To Finish