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Opening Remarks

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- Why the details?
- Not everything I said is included in the slides.
- Please pay attention to the lectures and catch the most essential points.
- Form your own opinions and thoughts.
- Should ask questions.
- Try to attend classes as much as you can.

- Turn off your cell phone during the class.
- Do not conduct private conversation.
- If you have questions, you may directly ask me.
- If you have urgent need to leave the room, you are excused. Otherwise do not leave the classroom frequently.
- After several classes we should have a review session. Druing the meeting let us exchange ideas about the teaching.

- Most of the stuff I discuss during the class may not be found in standard textbooks.
- The Universiy gives me this teaching task and responsibility. Personally I take it seriously.
- I sincerely wish that you can learn something new from this course. Let us work ogether and optimize the result.

- Normal and regular courses
Designed for basic education and training.

- Special topic courses
Expectations are very different. My responsibility is to introduce some new and special stuff. My duty is to promote kinetic theory and space plasma physics.

- “Nonlinear processes in space plasmas”
- “Space plasma physics and kinetic instabilities”

- Basic and general theory
- Theories of plasma instabilities
- Discussion of several important phenomena in space physics

Introducing Plasma Physics

- Plasma physics was initially advanced for controlled thermonuclear fusion research.
- There are special processes that mainly occur in space plasmas. Space plasma physics is a field basically developed for understnading space ans astrophysical plasmas.

- Plasma is an ionized gas.
- Charged particles can be affected by electric and magnetic fields.
- It was thought that plasma may be studied in a similar way as we dealt with a neutral gas which is generally treated as a fluid.
- Since a neutral gas may be studied with hydrodynamics, plasma may be considered as a conducting fluid.

- As a result, magnetohydrodynamics was born.
- MHD theory was unsuccessful in fusion experiments in mid 1950s.
- Kinetic theory began to attract attention.
- Discovery of numerous new instabilities
that pushes the birh of modern plasma

physics.

Scientists gradually realize that the basic physical property of plasmas is critically different from that of a neutral gas.

- In a neutral gas inter-particle collisions dominate but in a plasma wave-particle interactions prevail.
- There exist many instabilities in plasmas while very few instabilities occur in gases.
- Plasma turbulence can greatly modify the physics of a plasma. As a result, many new physical processes can take place in plasmas that are not possible in gases.

- In plasmas there are many wave modes.
- Instabilities imply that these wave modes can be amplified. The enhanced waves can result in nonlinear processes that can change the fundamental property.
- Particle-particle interactions are much less important than the interactions of waves with particles.
- There are many other reasons.
Consequently we must recognize plasma physics is a new branch of physics, and in general plasmas should not be treated as a gas.

- A paper by L. D. Landau was published in 1946.
- In this paper Landau showed that Langmuir wave may be damped while there are no collisions.
- Later on this paper led to the realization of wave-particle resonance.
- It also led to the discovery of kinetic instabilities in plasmas.

The reason is simple:

In stellar and solar atmosphere, in interstellar or interplanetary space plasma is everywhere. How can one understand the physics in these regions without the knowledge of plasma physics?

- Single particle dynamics
- MHD and fluid theories
- Kinetic theory

- Many physical processes in plasmas depend on microscopic particle motion.
- However, fluid dynamics considers only averaged particle motion.
- And single particle dynamics cannot represent an ensemble of particles.
- Kinetic theory seems to be the best tool available to study plasma physics.

- Gravitational field
- Electric and magnetic fields
- Ambient or background field
- Fields associated with waves
- Self-consistent fields

- Density, velocity and pressure are all functions of coordinates space that is dimensional.
- All physical quantities and the force fields are statistically averaged.
- As a result, the theory does not and cannot describe microscopic particle motion.

- Phase space
- Distribution function
- Probability density
- Kinetic equation
- Fokker-Planck equation
- Lenard-Balescu equation
- Vlasov equation

- Fluid theory may be useful if we only want to study dynamic issues.
- However, if we want to explain some important phenomena and understand the underlying physics, fluid dynamics theory is not sufficient.
- Remember: plasma is very different from an ordinary gas.

- In real space particles move randomly.
- Microscopic fields and density fluctuate in time and space.
- Concept of phase space is important.
- Only statistical averaged quantities are of interest.
- Kinetic theory is developed for this goal.

- In a real plasma fields and particle density are random microscopic quantities.
- All particles are moving stochastically.
- However, each particle is governed by the equation of motion which is controlled by microscopic fields are .
- Each particle moves continuously in phase space.