M. A. AllenG. RowlandsMahidol UniversityThe University of Warwick2018-09-072018-09-072000-01-01Journal of Plasma Physics. Vol.64, No.4 (2000), 475-480002237782-s2.0-0034289236https://repository.li.mahidol.ac.th/handle/123456789/26367We derive the approximate form and speed of a solitary-wave solution to a perturbed KdV equation. Using a conventional perturbation expansion, one can derive a first-order correction to the solitary-wave speed, but at the next order, algebraically secular terms appear, which produce divergences that render the solution unphysical. These terms must be treated by a regrouping procedure developed by us previously. In this way, higher-order corrections to the speed are obtained, along with a form of solution that is bounded in space. For this particular perturbed KdV equation, it is found that there is only one possible solitary wave that has a form similar to the unperturbed soliton solution.Mahidol UniversityPhysics and AstronomyArticleSCOPUS10.1017/S0022377800008813