Potential formation triggered by field-aligned electron acceleration due to electron cyclotron Resonance along Diverging Magnetic-Field Lines

Stationary potential drop and ion acceleration along diverging magnetic-Held lines are observed in a fully ionized collisionless plasma flow in the presence of electron cyclotron resonance (ECR) heating (ECRH). Time-resolved measurements for the purpose of clarifying the potential-formation dynamics show that temporal evolutions of the potential profile and electron energy distribution function correlate well with each other. The strong potential drop is found to be caused by a field-aligned electron acceleration due to ECRH, being accompanied by an effective ion acceleration so as to maintain the charge neutrality condition in the downstream region from the ECR point. Index Terms-Diverging magnetic-field lines, electron cyclotron resonance, ion acceleration, stationary potential drop.