ION-ACOUSTIC SHOCKS FORMED IN A COLLISIONLESS PLASMA WITH NEGATIVE-IONS

Ion acoustic shocks are formed in a plasma with negative ions, where T -e greater than or equal to T+ much greater than T- (T-e, T+, T-: temp eratures of electrons, positive ions, and negative ions, respectively) . Depending on the ratio epsilon of negative to positive density, a st eepening of positive or negative density jumps is observed. For epsilo n < epsilon(c) (approximate to 0.65, critical value), positive density jumps evolve into compressive shocks. For epsilon > epsilon(c), howev er, negative density jumps evolve into rarefactive shocks. The ratio e psilon(c) observed is well explained on the basis of Korteweg-de Vries equation.