We propose a method to regulate numerical dissipation of central numerical fluxes in magnetohydrodynamics,and give a dissipation regulator for central numerical fluxes.We take Local Lax-Friedrichs flux as an example and apply the dissipation regulator in computation.A second order accurate MUSCL data reconstruction is used to extend Local LaxFriedrichs scheme to second-roder.Two test benchmark problems show that the dissipation regulator is effcient.

We study the sonic point glitch of the Burgers' equation, which is formed in a sonic rarefaction fan. The reason of a sonic point glitch and the relation between the sonic point glitch and the entropy condition are discussed. According to these relations, several well-known schemes are classified into two and analyzed. In fact, the sonic point glitch appears only in the case of a transonic rarefaction wave. If the problem to be solved does not include transonic rarefaction waves, the difficulty in computation vanishes. Based on this idea, a new two-step splitting method eliminating the sonic point glitch is proposed. Numerical tests of applying the method to different schemes show that it is good in eliminating the sonic point glitch.