Anti-ExB flow field associated with a vortex formation in a partially   ionized plasma
  A high-density magnetized plasma has been studied for understanding of plasma dynamics in partially ionized plasmas. Ion flow field has been obtained experimentally, and is shown to be associated with a vortex formation. The most remarkable result is that the direction of rotation is opposite to that of the ExB drift. Measurement of neutral density profile reveals that there is a steep density gradient of the neutrals around the vortex, suggesting that the generation of inward momentum of the neutrals due to the density gradient. The momentum is transfered to ion with charge-exchange collision, and cause effective force on the ion. The present experiment shows that this effective force may dominate the ambipolar-electric field and drive the anti-ExB vortical motion of ions. 
Atsushi Okamoto, Kenichi Nagaoka, Shinji Yoshimura, Jovo Vranjes,   Mitsuo Kono, Shinichiro Kado, Masayoshi Y. Tanaka