Aerospace Environment ASEN-5335

1. AerospaceEnvironmentASEN-5335 • Instructor: Prof. Xinlin Li (pronounce: Shinlyn Lee) • Contact info: e-mail: lix@lasp.colorado.edu (preferred) phone: 2-3514, or 5-0523, fax: 2-6444, website: http://lasp.colorado.edu/~lix • Office hours: 9:00-11:00 pm Wed at ECOT 534, Tue & Thu, after class. • Grader’s office hours: 3:30-5:30 pm Wed at TA’s office

2. • Required Texts: Introduction to the Space Environment, T. F. Tascione, Krieger, second edition, paperback 1994. • Recommended Reference:Handbook of Geophysics and the Space Environment, Air Force Geophysics Laboratory, 1985, available from National Technical Information Service and Physics of the Space Environment by Tamas I. Gombosi, CAMBRIDGE University Press, 1998. •Grading: Grades will be based upon two exams (middle: 30% and final: 35%) , homework sets (25%), and quizzes in class (10%, best 5 out of 7). No late homework will be accepted. • Bring a calculator, it may be needed for in-class exercise or quiz

3. Sun-Earth Connections & Aerospace Environment • An Understanding of the general properties and characteristics of the aerospace environment including the underlying physics • An exposure and practical experience with existing models and codes which are used to provide numerical estimates of the various environmental parameters. • An introduction to the environmental hazards to both silicon based and carbon based bodies.

4. The Sun • The Sun is located in a spiral arm of our Galaxy, in the so-called Orions arm, some 30,000 light-years from the center. • The Sun orbits the center of the Milky Way in about 225 million years. The solar system has a velocity of 220 km/s • Our galaxy consists of about 2 billion other stars and there are about 100 billion other galaxies • The Sun is 333,000 times more massive than the Earth . • It consists of 90% Hydrogen, 9% Helium and 1% of other elements • Total energy radiated: 100 billion tons of TNT per second • The Sun has inspired mythology in many cultures including the ancient Egyptians, the Aztecs, the Native Americans, and the Chinese.

6. Principal Features of the Sun - High-latitude solar wind (from coronal holes) is high-speed (600-800 km/s) - Typical low-latitude solar wind is high-density and low-speed (300-500 km/s)

7. Sun-Earth Connections The Sun is dynamic The Earth responds to the changing Sun This response is known as Space Weather Our Aerospace Environment is part of the nature resulted from the Sun

8. Follow the Sun:The Naked Eye Perspective . Eclipses . Comet . Sunspot . Auroras

11. We observe the Sun at different wavelengths

12. Solar Cycle Our ever changing Sun over its 11 year cycle - seen here in X-rays

14. Solar Minimum – 1996/7 Solar Maximum – 2000/1 eitcompare

16. Cme

17. SOHO/EIT Observes Prominence Eruption & Flare eit714

18. Size of Earth Relative to Solar CME Structure • The Earth is small compared to the size of the plasma “blob” from a Coronal Mass Ejection (CME). • The image shows the size of a CME region shortly after “lift off” from the solar corona. • The CME continues to expand, as it propagates away from the Sun, until its internal pressure is just balanced by the magnetic and plasma pressure of the surrounding medium. CME Earth

19. These protons reach Earth in less than 30 minutes Less than 1 hour after the initial proton arrival the POLAR/VIS imager is saturated and remains so for almost a day Vis-proton-bastille

20. Lethal Dosages of Radiation During violent solar events, the Sun can accelerate electrons and protons to almost the speed of light which gives them huge amounts of energy. Protons and electrons at these high energies can be very dangerous to living cells

24. Legal and moral reasons require NASA limit astronaut radiation exposures • U.S. Occupational Safety and Health Administration officially classifies astronauts as “radiation workers” • Adherence to ALARA (As Low As Reasonably Achievable) is recognized throughout NASA’s manned space flight requirements documents • Radiation protection philosophy--any radiation exposure results in some risk • ISS astronaut exposures will be much higher than typical ground-based radiation worker • Astronaut legal dose limits (50 REM/yr and 30 REM/mon) are 10 times that allowed ground based radiation workers • Space radiation more damaging than radiation typically encountered by ground-based workers

25. PARTICLE ENERGIES OF CONCERN

26. The Earth’s Magnetosphere Energetic electrons and protons are not able to penetrate down to the Earth’s surface directly. Particles gain entry through the cusps that are shaped like funnels over the polar regions or they enter far downstream from the Earth. Particles that enter downstream can be transported toward the Earth and accelerated to high energies, producing auroras and radiation belts.

27. recon

28. Producing the Aurora Auroras are produced by electrons and protons striking Earth’s atmosphere. When oxygen and nitrogen atoms are hit by these energetic particles, they become excited or ionized. As they relax to their original state, they emit light of a characteristic color Green = Oxygen Red = Oxygen (lower energy electrons) Blue = Nitrogen Also emitted in UV and X-ray

29. The Phases of the Aurora Quiet Growth Onset Expansion Maximum Area Recovery

30. January 10, 1997

31. October 22, 1999

32. July 16, 2000