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Transverse MHD waves permeate the solar atmosphere and are a candidate forcoronal heating. However, the origin of these waves is still unclear. In thiswork, we analyse coordinated observations from \textit{Hinode}/SOT and\textit{IRIS} of a prominence/coronal rain loop-like structure at the limb ofthe Sun. Cool and dense downflows and upflows are observed along the structure.A collision between a downward and an upward flow with an estimated energy fluxof $10^{7}-10^{8}$~erg~cm$^{-2}$~s$^{-1}$ is observed to generate oscillatorytransverse perturbations of the strands with an estimated$\approx40~$km~s$^{-1}$ total amplitude, and a short-lived brightening eventwith the plasma temperature increasing to at least $10^{5}~$K. We interpretthis response as sausage and kink transverse MHD waves based on 2D MHDsimulations of plasma flow collision. The lengths, density and velocitydifferences between the colliding clumps and the strength of the magnetic fieldare major parameters defining the response to the collision. The presence ofasymmetry between the clumps (angle of impact surface and/or offset of flowingaxis) is crucial to generate a kink mode. Using the observed values wesuccessfully reproduce the observed transverse perturbations and brightening,and show adiabatic heating to coronal temperatures. The numerical modellingindicates that the plasma $\beta$ in this loop-like structure is confinedbetween $0.09$ and $0.36$. These results suggest that such collisions fromcounter-streaming flows can be a source of in-situ transverse MHD waves, andthat for cool and dense prominence conditions such waves could have significantamplitudes.

In-situ generation of transverse MHD waves from colliding flows in the solar corona