Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 9 5/6 2002 10.5194/npg-9-463-2002 http://www.nonlin-processes-geophys.net/9/463/2002/ http://www.nonlin-processes-geophys.net/9/463/2002/npg-9-463-2002.html http://www.nonlin-processes-geophys.net/9/463/2002/npg-9-463-2002.pdf 463 475 0000-00-00 Dromion solutions for nonlinear electron acoustic waves in space plasmas S. S. Ghosh A. Sen G. S. Lakhina Indian Institute of Geomagnetism, Dr. Nanabhai Moos Marg, Colaba, Mumbai, 400 005, India Institute for Plasma Research, Bhat, Gandhinagar, 382 428, India Recent high resolution measurements of POLAR and FAST satellites have revealed two-dimensional coherent structures in the polar cap boundary layer (PCBL) region. Since the ion temperature is often observed to be greater than the electron temperature in this region, electron acoustic waves can exist as a normal mode of the plasma system. It is shown that the nonlinear evolution of such waves can be modelled by the coupled Davey-Stewartson I equations. These equations, which are a generalization of the nonlinear Schrödinger equation to two dimensions, admit exponentially localized solutions called dromions. A detailed parametric characterization of the regions of existence of such solutions is presented in the context of the PCBL region.