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Our goal is to gain new insights into the physics of wave overreflectionphenomenon in MHD nonuniform/shear flows changing the existing trend/approachof the phenomenon study. The performed analysis allows to separate from eachother different physical processes, grasp their interplay and, by this way,construct the basic physics of the overreflection in incompressible MHD flowswith linear shear of mean velocity, ${\bf U}_0=(Sy,0,0)$, that contain twodifferent types of Alfv${\rm \acute{e}}$n waves. These waves are reduced topseudo- and shear shear-Alfv${\rm \acute{e}}$n waves when wavenumber along$Z$-axis equals zero (i.e., when $k_z=0$). Therefore, for simplicity, welabelled these waves as: P-Alfv${\rm \acute{e}}$n and S-Alfv${\rm \acute{e}}$nwaves (P-AWs and S-AWs). We show that: (1) the linear coupling ofcounter-propagating waves determines the overreflection, (2)counter-propagating P-AWs are coupled with each other, whilecounter-propagating S-AWs are not coupled with each other, but areasymmetrically coupled with P-AWs; S-AWs do not participate in the lineardynamics of P-AWs, (3) the transient growth of S-AWs is somewhat smallercompared with that of P-AWs, (4) the linear transient processes are highlyanisotropic in wave number space, (5) the waves with small streamwisewavenumbers exhibit stronger transient growth and become more balanced, (6)maximal transient growth (and overreflection) of the wave energy occurs in thetwo-dimensional case -- at zero spanwise wavenumber.  To the end, we analyze nonlinear consequences of the described anisotropiclinear dynamics -- they should lead to an anisotropy of nonlinear cascadeprocesses significantly changing their essence, pointing to a need ofrevisiting the existing concepts of cascade processes in MHD shear flows.

Nature and dynamics of overreflection of Alfven waves in MHD shear flows