Modern Solar Mysteries Dr David H Hathaway NASAMSFC

Modern Solar Mysteries Dr. David H. Hathaway NASA/MSFC National Space Science and Technology Center As we learn more, and gain a deeper understanding of things, we uncover even deeper mysteries about he world we live in.

Ancient Solar Mysteries • Why does the sun move across the sky? • Where does the sun go at night? • When will the sun come north again (and can we do something to help it)? • What evil have we done to cause the sun to disappear in the middle of the day?

Recent Solar Mysteries (~100 years ago) • • What is the composition of the sun? How old is the sun? How does the sun produce its energy? What are those spots?

Sunspots and the Sunspot Cycle (Schwabe 1844)

The Latitude Drift of Sunspots (Carrington, 1858)

Solar Flares (First observed by Carrington in September 1859)

A Solar Flare at the Limb

Prominence Eruptions (The “Granddaddy”)

The Sun’s Hot Corona (Edlén 1939) The surface of the sun is at 6000ºC (10, 000ºF) while the corona reaches temperatures greater than 2, 000ºC (3, 000ºF).

The Solar Wind (Parker 1955) Comet tails always point away from the sun. Sunlight itself cannot do this. The solar wind blows off of the sun at a speed of about 1, 000 mph.

Coronal Mass Ejections (OSO 7 1973, Skylab 1974)

Three Major Mysteries 1. What triggers solar flares, prominence eruptions, and coronal mass ejections? 2. What causes the 11 -year cycle of sunspots and solar activity? 3. How is the corona heated and the solar wind accelerated?

Solar Magnetism: THE KEY TO UNDERSTANDING THE SUN Solar Magnetic Fields Modeling Magnetic Fields Measuring Magnetic Fields Predicting Magnetic Behavior

Measuring Magnetic Fields The Solar Spectrum The Zeeman Effect

Magnetic Field Measuring Instruments The Marshall Space Flight Center Magnetograph Facility

Magnetograms and Solar Features

Solar Magnetic Fields Sunspots Coronal Loops Prominences/Filaments Coronal Streamers

Magnetic Fields in Sunspots

Coronal Loops

Coronal Loop Evolution

Post Flare Loops

Magnetic Fields and Solar Eruptions - Theory

Magnetic Fields and Solar Eruptions - Observations Magnetic “Shear” and a Solar Flare

The Sun’s Magnetic Cycle

Hales’s Polarity Law

The Magnetic Butterfly Diagram

The Magnetic Dynamo 1) Differential rotation stretches and amplifies the magnetic field 2) The rising magnetic flux tubes are twisted by the Sun’s rotation 3) Surface flows redistribute the magnetic flux elements

Dynamo Modelling In this model the 11 -year period for the sunspot cycle is set by the speed of the meridional circulation.

Coronal Heating Many small brightenings occur throughout the lower corona These brightening tend to occur where opposite magnetic fields meet

Solar Wind Acceleration The solar wind is held to about half its maximum value in the equatorial regions where coronal streamers form.

Previous Missions Skylab (1973) Spacelab 2 Mission (1985) Solar Maximum Mission (1980 -1989) Yohkoh (Japan/NASA 1991 -2001)

Current Missions Ulysses (ESA/NASA – 1990) TRACE (NASA – 1998) SOHO(ESA/NASA – 1995) RHESSI (NASA – 2002)

Future Missions STEREO (NASA -2005/11) Solar-B (Japan/US/UK – 2005) Solar Dynamics Observatory (NASA -2008/04)

The Bastille Day Event - TRACE

The Bastille Day Event -SOHO

For More Information See: science. nasa. gov