Sources of Fluctuating Field on Field-Reversed Configuration Plasma

Fluctuating azimuthal fields, B θ , are detected during a lifetime of a Field-Reversed Configuration plasma. The maximum strength reaches to 70 G which corresponds to about 1.5% of a confining field. Sources of the fields are discussed with relation to such plasma motions as radial shifting and tilting motions, and elliptical deformation of the plasma column triggered by a rotational instability. Analytic formulas of the B θ are derived from disturbance of the confining field due to these motions. Estimated values from the formulas agree well with field profiles obtained from a magnetic probe array.