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-field 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.