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We report on exceptionally bright bursts (>400 Jy ms) detected from therepeating fast radio burst source FRB 20220912A using the Nan\c{c}ay RadioTelescope (NRT), as part of the ECLAT (Extragalactic Coherent Light fromAstrophysical Transients) monitoring campaign. These bursts exhibit extremelyluminous, broadband, short-duration structures (~ 16 microseconds), which weterm 'microshots' and which can be especially well studied in the NRT datagiven the excellent signal-to-noise and dynamic range (32-bit samples). Theestimated peak flux density of the brightest microshot is 450 Jy. We show thatthe microshots are clustered into dense 'forests', by modelling them as Weibulldistributions and obtaining Weibull shape parameters of approximately 0.5. Ourpolarimetric analysis reveals that the bursts are nearly 100% linearlypolarised; have < 10% circular polarisation fractions; a near-zero averagerotation measure of 0.10(6) rad/m^2; and varying polarisation position anglesover the burst duration. For one of the bursts, we analyse raw voltage datafrom simultaneous observations with the Westerbork RT-1 single 25-m dish. Thesedata allow us to measure the scintillation bandwidth, 0.30(3) MHz, and to probethe bursts on (sub-)microsecond timescales. Some important nuances related todedispersion are also discussed. We propose that the emission mechanism for thebroadband microshots is potentially different from the emission mechanism ofthe broader burst components which still show a residual drift of a few hundredMHz/ms after correcting for dispersion using the microshots. We discuss how theobserved emission is phenomenologically analogous to different types of radiobursts from the Sun.

Dense Forests of Microshots in Bursts from FRB 20220912A