Plasma potential formation and particle acceleration due to ECRH in diverging magnetic-field lines

A plasma potential formation is investigated in a fully ionized collisionle ss plasma flow in the presence of electron cyclotron resonance (ECR) heatin g (ECRH) under simple diverging magnetic-field configurations. When ECR tak es place in a diverging region, there appears a strong potential drop along the field lines, which results from a field-aligned electron acceleration, being accompanied by an effective ion acceleration so as to maintain the c harge neutrality condition in the downstream region. Time-resolved measurem ents are performed in order to clarify dynamics of the potential formation.