Driving sudden current and voltage in expanding and compressing plasma

Area of Science:

• Plasma physics
• Magnetohydrodynamics
• Wave-particle interactions

Background:

• Langmuir waves are fundamental plasma oscillations.
• Collisionless damping occurs when wave-particle interactions dominate over collisions.
• Plasma expansion can alter its properties, including collisionality.

Purpose of the Study:

• To investigate the transition of a magnetized plasma from a collisionless damping regime to one with induced electrical currents.
• To analyze the factors influencing current drive efficiency during plasma expansion and recompression.
• To explore the generation of dc voltage via anisotropic fast-particle distributions.

Main Methods:

• Simulating a magnetized plasma with an initial Langmuir wave.
• Modeling plasma expansion perpendicular to the magnetic field.
• Analyzing the resulting anisotropic fast-particle distributions and induced electrical currents/voltages.
• Investigating the impact of plasma collisionality and L/R time on current drive efficiency.

Main Results:

• A sudden transition to collisionless damping was observed during plasma expansion.
• Anisotropic fast-particle distributions led to induced electrical currents and dc voltage.
• Current drive efficiency depended on expansion rate, collisionality, and plasma L/R time.
• Plasma recompression further enhanced current drive by reducing electron collision rates.

Conclusions:

• Plasma expansion perpendicular to a magnetic field can nonlinearly generate electrical currents and voltage.
• The observed phenomenon offers a mechanism for current drive in nonstationary plasmas.
• Controlling plasma dynamics, such as expansion and recompression, can optimize current drive efficiency.