Plasma Electrons are free! … A fourth state of matter: Not gas, not liquid, not solid!

PlasmaElectrons are

free! … A fourth state of

matter:Not gas, not

liquid, not solid!

History, Terminology, & Discovery

• First identified by Sir William Crookes (1879)

• Termed by Irving Langmuir

• Ionosphere identified as plasma

• Van Allen Belts (1958)

Types of PlasmaArtificially Induced• Fluorescent lamps• Neon Signs• Plasma televisions• Electric arcs (i.e. those created

by a Marx generator,etc.)• Laser-Produced Plasmas (LPP)• Rocket exhaust• Ion Thrusters

Terrestrial & Astrophysical• Stars (Sun)• Ionosphere• Aurora Borealis• Lightning• Most fires• TLE

Plasma: A Fourth State of Matter

• Ionized “gas”• Most are quasi-neutral• Said: ~99% of matter• Affected by E&M waves

Characteristics

• Electron density: • Temperature: • Molecular Content• Electron Plasma Frequency:• Debye Length:

e

ep m

en

0

22

1 pD m

T

2

3

1vmT

en

Plasma PhysicsStatistics, Mathematics, the Most General Case

• Maxwell-Boltzmann Distribution: particle density distribution

• Fluid Mechanics: Three particle, nonviscous intermingled fluids coupled through their equations of state and collision frequencies

• Maxwell’s Equations:

dAnt

DILdH

t

D

cJH

dAnt

BLdE

t

BE

dAnBB

QdAnDD

;1

;

0;0

;

2

Wave Propagation• Wave propagation

highly dependent on electron plasma frequency: If then the wave

propagates through If then the wave is

deflected

p

• Propagation constant:

Approaches free space value: Turns imaginaryp

2/1

2

2

1

p

ck

ck /

Deflection Case:• Fields vary exponentially • Phase-variation terms decay exponentially (the wave will decay as it propagates)• e.g. Ionosphere reflects E&M radiation with frequency less than its plasma frequency

rki exp

Example: If lightning were to propagate toward the ionosphere would it be deflected? Why or Why not?

• Ionosphere:

17

312

sec106

10

p

e mn

113

324

sec106

10

p

e mn

• Lightning:

Answer: It will not be deflected as its frequency is larger than that of the ionosphere

References• 1909, who valued professional, financial success as well as scientific inquiry, accomplishment, his

summer position stretched into a lifelong career. He became known among his colleagues for his analytical mind, creativity, ambition, and excellent research skills.. "Irving Langmuir." Ziggo. N.p., n.d. Web. 1 July 2010. http://members.home.nl/arjen.boogaard/Irving%20Langmuir.html.

• "Brief History of Plasma Physics." Home Page for Richard Fitzpatrick . N.p., n.d. Web. 1 July 2010.http://farside.ph.utexas.edu/teaching/plasma/lectures/node5.html.

• "Fields & Waves I v2." Plasma Dynamics Lab. N.p., n.d. Web. 1 July 2010. http://hibp.ecse.rpi.edu/~connnor/education/Fields/F09/.

• "Plasma (physics)." 2008/9 Wikipedia Selection for schools. N.p., n.d. Web. 1 July 2010. http://schools-wikipedia.org/wp/p/Plasma_%2528physics%2529.htm.

• "Plasma Physics -- History." NASA Polar, Wind, and Geotail Projects. N.p., n.d. Web. 16 June 2010. http://www-spof.gsfc.nasa.gov/Education/whplasma.html.

• "Plasma Physics." National Ignition Facility & Photon Science. N.p., n.d. Web. 1 July 2010.https://lasers.llnl.gov/programs/science_at_the_extremes/plasma_physics/.

• Riegel, ron. "Irving Langmuir - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. N.p., n.d. Web. 28 June 2010.http://en.wikipedia.org/wiki/Irving_Langmuir.

• Uman, Martin A. Introduction to Plasma Physics. New York: McGraw-Hill, 1964. Print.