Dr. E.J. Zita, The Evergreen State College, Olympia, WA
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Transcript of Dr. E.J. Zita, The Evergreen State College, Olympia, WA
Sun-Earth Connectionspart of a symposium at the Tacoma campus of
The Evergreen State College14.Sept.2001
The Sun and the Earth are both getting hotter. What does the Sun’s magnetic activity have to do with it? What are the consequences?
We are investigating questions like these in classes and research at Evergreen.
Dr. E.J. Zita, The Evergreen State College, Olympia, WA
http://192.211.16.13/individuals/zita/home.htm
Outline:• Sun radiates Earth• Earth and Sun are warming• Magnetic activity heats the Sun’s atmosphere• Solar magnetism affects the Earth• How do we measure effects on Earth? On Sun?• How do magnetic fields affect the Sun?• How can we predict magnetic storms?• What can we do about it?• Evergreen contributes to understanding the Sun
Sun radiates Earth
Nuclear fusion energetic photons light and heat
Hot gas energetic charged particles solar wind
Diagrams courtesy of NCAR
Sun and Earth are warming
From Friis-Christensen, E., and K. Lassen, "Length of the solar cycle: An indicator of solar activity closely associated with climate," Science, 254, 698-700, 1991. See http://web.dmi.dk/solar-terrestrial/space_weather/
The Sun gets bigger and hotter as it grows older (billions of years).
The Earth is currently warming out of latest ice age (13,000 yrs).
Many factors contribute to (long-term) climate changes and (short-term) temperature variations on Earth.
Earth’s average temperature (blue) tracks solar activity (red).
Magnetic activity heats the Sun’s atmosphere
Diagrams courtesy of
Campfire: hot inside, cooler as you move away
Sun: Hot inside, cool surface, but hotter as you move away!
Solar magnetism affects the Earth
Movies courtesy of
Magnetic field lines snap release hot ions
• aurorae: solar ions trapped in Earth’s magnetic field
• magnetic storms power and satellite outages
How do we measure effects on Earth?
Diagram courtesy of NCAR
Solar observatories: Measure luminosity, count sunspots
Weather stations: Earth temperatures, atmospheric effects
http://mlso.hao.ucar.edu/
How do we measure effects on the Sun?
TRACE: measures fine-scale solar magnetic fields http://vestige.lmsal.com/TRACE/Project/Mission/mission.htm
SOHO: Solar and Heliospheric Observatory: coronal spectra http://nssdc.gsfc.nasa.gov/nmc/tmp/1995-065A.html
YOHKOH: (Japanese for sunbeam) measures high-energy radiation from solar flares (X-rays and neutrons) and quiet structures and pre-flare conditions. http://nssdc.gsfc.nasa.gov/nmc/tmp/1991-062A.html http://www.solar.isas.ac.jp/english/yohkoh_background2.html
How do magnetic fields affect the Sun?
Diagram courtesy of Gregory, Stephen A., and Michael Zeilik. Introductory Astronomy and Astrophysics.
Magnetic field lines rise from inside sun sunspots
Twisted field lines increased magnetic energy
Magnetic reconnection release particles and kinetic energy
Magnetic waves heating
Figure 4
Figure 3
Gregory, p.220
Magnetic waves in Sun’s atmosphere
Created with 3D MHD code by Rosenthal et al., Oslo
Research by Evergreen students at NCAR, Boulder
Sara Petty-Powell and Matt Johnson
How can we predict magnetic storms?
Diagrams courtesy of Montana State University and NCAR
Twisting magnetic fields s-shaped filaments on photosphere
field lines snap and reconnect energy release
Dooling, p. 2(Dooling, Dave. p. 2)
Figure 9
Waves in twisted magnetic fields
Diagrams courtesy of Montana State University
Research by Evergreen faculty at NCAR, BoulderE.J. Zita with Tom Bogdan and B.C. Low
What can we do about it?
• Not a darn thing? the Sun does what it will
• prevention: redesign power circuits and satellites
• understand the Sun better: predict magnetic storms and protect satellites
• enjoy the increased warmth and aurorae
Evergreen contributes understanding
Theory: Zita calculates magnetic waves in Sun’s atmosphere
Modeling: colleagues in Oslo solve equations with computers to generate numerical data (Rosenthal et al.)
Observations: colleagues at NCAR and elsewhere observe Sun with satellites to get real data (Lites et al.)
Analysis: Students help us understand how numerical data connects to theory and real data (Bogdan et al.)
theory
modeling
Observations
analysis
Summary
Diagram courtesy of HAO and WET
Solar magnetic activity greater energy from Sun
greater temperatures, aurorae, magnetic storms on Earth
Multifacted collaboration
better understanding of Sun and Earth
Selected references GONG & NOAO = Global Oscillation Network Group http://www.gong.noao.edu/gonghome.html, http://helios.tuc.noao.edu/
NCAR = National Center for Atmospheric Research, Boulder, CO http://www.hao.ucar.edu/public/education/slides/slides.html
MSU = Montana State University http://solar.physics.montana.edu
Stanford Solar Center http://solar-center.stanford.edu
SOHO: http://sohowww.nascom.nasa.gov/Kaler, James B. Stars . New York: Scientific American Library, 1992. http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/SunLayers.html#BibNASA: http://hesperia.gsfc.nasa.gov/sftheory/index.htmInstitute for Physics and Astronomy, Aarhus University, Denmark http://www.obs.aau.dk/helio_outreach/
Waves in the magnetic solar atmosphere I, Colin Rosenthal and Tom Bogdan, Astrophysical Journal, 2001
Energy transport by waves above the photosphere, Sara Petty-Powell and Matt Johnson, 2001
Wave transformations in a sheared, force-free magnetic field, E.J. Zita, 2001http://192.211.16.13/individuals/zita/research.htm