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-fie ld lines are observed in a fully ionized collisionless plasma flow in the p resence of electron cyclotron resonance (ECR) heating (ECRH), Time-resolved measurements for the purpose of clarifying the potential-formation dynamic s show that temporal evolutions of the potential profile and electron energ y distribution function correlate well with each other. The strong potentia l drop is found to be caused by a field-aligned electron acceleration due t o ECRH, being accompanied by an effective ion acceleration so as to maintai n the charge neutrality condition in the downstream region from the ECR poi nt.