NONLINEAR MAGNETOSONIC WAVES AND MIRROR MODE STRUCTURES IN THE MARCH 1991 ULYSSES INTERPLANETARY EVENT

In examining the March 23-25, 1991 Ulysses (2.2 AU) high speed solar wind events, we find two distinct plasma wave modes: steepened magnetosonic waves with whistler precursors and mirror mode structures. These two modes are locally generated by plasma instabilities, presumably associated with anisotropies existing in the energetic shock particles and solar wind plasma, respectively. The magnetosonic waves are generated by a righthand resonant instability associated with a approximately 40 keV ion beam. By an extrapolation of the results presented here, assuming microflares and nanoflares at the Sun generate shocks in the lower corona and these shocks accelerate energetic ions, we suggest that the ions, via the right-hand resonant instability, generate magnetosonic waves which steepened to form "microshocks" (such as shown here). These shocks could, in tum, accelerate more energetic ions, leading to a shock/energetic ion/magnetosonic wave cascade. These newly formed magnetosonic waves and shocks presumably could propagate in a broad range of directions, leading to energy dissipation over a large region of the outer corona.