Scintillation time-scale measurement of the highly active FRB20201124A

Scintillation of compact radio sources results from the interference between images caused by multipath propagation, and probes intervening scattering plasma velocities emitting source screen. In FRB20201124A, a repeating fast burst (FRB) which entered period extreme activity, we obtained many detections in observations at upgraded Giant Metrewave Radio Telescope (uGMRT) Effelsberg 100\,m Telescope. Bursts nearby time show similar scintillation patterns, measure timescale $14.3\pm1.2$\,min $7\pm2$\,min (1370\,MHz) uGMRT (650\,MHz), respectively, correlating pair spectra. The bandwidth scaled to 1\,GHz is $0.5\pm0.1$\,MHz, inferred velocity $V_{\mathrm{ISS}}\approx (59\pm7) \sqrt{d_{l}/2\,\rm{kpc}}~{\rm km~s}^{-1}$, higher than Earth's for any screen beyond lens distance $d_{l} \gtrsim 400\,$pc. From measured bandwidth, FRB20201124A has comparatively lower pulsars, underscattered factor $\sim 30$ or 1200$ compared NE2001 YMW16 model predictions respectively. This underscattering, together with are consistent more Earth \sim 400\,$pc, rather 2\,kpc spiral arm predicts be dominant scattering. With future measurements, distance, geometry, could through modelling annual variation $V_{\rm ISS}$, inter-station delays interferometric observations. Scintillation/scattering measurements FRBs help improve Galactic electron density models, particularly halo high latitudes.