Acceleration of particles in space plasmas by nonlinear magnetosonic waves

An unresolved question of magnetospheric physics concerns the creation of convergent and divergent electric field structures responsible for the acceleration of auroral particles to several kilo-electronvolt. Similarly, an unresolved problem of solar physics concerns the acceleration of particles producing the x-ray coronal emissions. Here we show that both these problems can be explained by electric field structures produced by nonlinear magnetosonic waves. The convergent electric field structures correspond to fast magnetosonic solitons, while divergent electric field structures are produced by slow solitons. Both types of solitons can build potentials of tens of kV in the magnetosphere and hundreds of kV in the solar corona. Such solitons can be created when linear magnetosonic and Alfvén waves propagate through regions of varying Alfvén speed, which occurs on auroral field lines at altitudes of 6000 km, and also above the chromosphere in the solar corona. The initial, linear MHD waves can be produced by bursty bulk flows in the Earth's magnetotail and by chromospheric/photospheric convective flows on the Sun.