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