Aerospace EnvironmentASEN-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

• 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

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.

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.

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)

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

Sun-Earth Connections

Follow the Sun:The Naked Eye Perspective

. Eclipses

. Comet

. Sunspot

. Auroras

We observethe Sun at differentwavelengths

Solar Cycle

Our ever changing Sunover its 11 year cycle - seen here in X-rays

Solar Minimum – 1996/7 Solar Maximum – 2000/1

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Cme

SOHO/EIT Observes Prominence Eruption & Flare

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Size of Earth Relative to Solar CME Structure

Earth

CME

• 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.

These protons reach Earth inless than 30 minutes

Less than 1 hour afterthe initial proton arrivalthe POLAR/VIS imageris saturated and remainsso for almost a day

Vis-proton-bastille

During violent solar events,the Sun can accelerate

electrons and protons toalmost the speed of lightwhich gives them huge

amounts of energy. Protonsand electrons at these

high energies can be verydangerous to living cells

Lethal Dosages of Radiation

R a d ia tio n D an g ers to A s tro n a u ts

B etw e en A p o llo 1 6 an d 1 7 ,o n e o f th e la rg es t so la r p ro to nev e n ts ev e r re co rd e d a rr iv eda t E a rth . T h e rad ia tio n le v e lsan a s tro n au t in s id e a sa te llitew o u ld e x p e rie n ce d u r in g th isev e n t w ere s im u la ted . E v e nin s id e a sp a ce c ra ft, a s tro n a u tsw o u ld h a v e ab so rb ed le th a ld o ses o f rad ia tio n w ith in 1 0 h rsa f te r th e s ta rt o f th e e v en t(4 0 0 0 m S v ).

• 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

PARTICLE ENERGIES OF CONCERN

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.

The Earth’s Magnetosphere

recon

Producing the Aurora

Auroras are produced by electrons andprotons striking Earth’s atmosphere.When oxygen and nitrogen atoms arehit by these energetic particles, theybecome excited or ionized. As theyrelax to their original state, they emitlight of a characteristic color

Green = OxygenRed = Oxygen (lower energy electrons)

Blue = NitrogenAlso emitted in UV and X-ray

The Phases of the Aurora

Quiet Growth Onset

Expansion Maximum Area Recovery

January 10, 1997

October 22, 1999

July 16, 2000

C o n fu se d H o m in g P ig e o n s

C erta in an im a l sp ec ie s o n E a rtha re a b le to d e tec t th e m ag n e ticfie ld a n d u se it fo r n av ig a tio n a lp u rp o se s .

D u rin g sp ace w ea th e r d is tu rb an ce s , th e in ten se e lec tr ic cu rre n tsflo w in g in n e a r-E a r th sp a ce p ro d u c e n o n -s te ad y m ag n e tic fie ld sth a t a re fe lt a t th e E a rth 's su rface . H o m in g p ig eo n s h a v e b e eno b se rv ed to b e co m e c o n fu se d d u rin g su ch d is tu rb a n ce s an d c anev e n b e lo s t.