Helicons in Unbounded Plasmas.

Area of Science:

• Plasma Physics
• Astrophysics
• Wave Phenomena

Background:

• Helicons are whistler mode waves characterized by helical phase fronts.
• Previous studies focused on bounded and nonuniform plasma environments like solid-state plasmas and discharge tubes.
• The presence of boundaries and nonuniformities has historically complicated the study of helicons.

Purpose of the Study:

• To demonstrate the existence of helicons in unbounded and uniform plasmas.
• To bridge the gap between laboratory plasma physics and space plasma physics.
• To present the first three-dimensional measurements of helicon field lines.

Main Methods:

• Theoretical analysis of wave propagation in unbounded, uniform plasmas.
• Experimental investigation using plasma devices designed to minimize boundaries and nonuniformities.
• Three-dimensional magnetic field measurements to map helicon field lines.

Main Results:

• Helicons can propagate in unbounded and uniform plasma conditions.
• The study provides the first experimental mapping of helicon field lines in three-dimensional space.
• Helicons with both negative and positive mode numbers were observed to propagate with equal amplitudes.

Conclusions:

• Helicon waves are not limited to bounded or nonuniform plasmas.
• The findings extend the applicability of helicon research to space plasma environments.
• The ability of helicons with opposing mode numbers to propagate equally has implications for wave-particle interactions.