Observations of Flare Induced Doppler Shifts in the Si~{iii} 1206\,Å line

Doppler shifts in chromospheric and transition-region lines during solar flares are often interpreted as chromospheric condensation or evaporation. However, alternative sources of Doppler-shifted emission have been suggested, such as filament eruptions, jets or chromospheric bubbles. We analyse high-cadence scans from SORCE/SOLSTICE, which provide one-minute resolution profiles of the transition-region Si~{iii} (1206\,Å, T = 104.6\,K) line. 11 X-, M-, and C-class events observed during these scans with clear impulsive phase Si~{iii} enhancements were identified. By subtracting a quiet-Sun profile and fitting Gaussian profiles to the Si~{iii} line, measurements of flare-induced Doppler shifts were made. After correcting for a systematic trend in these shifts with solar longitude, two of the 11 events were found to exhibit a significant Doppler shift, {}one with a 201.36±21.94\;km\,s⁻¹ redshift and the other with a -39.75±11.00\;km\,s⁻¹ blueshift{}. Intriguingly, SDO/AIA 304\,Å and 1600\,Å imaging revealed a bright eruption coincident with the event that exhibited a blueshift, suggesting the shift may have resulted from the eruption rather than evaporation alone. Our results highlight Si~{iii} as a useful diagnostic of flaring dynamics at a temperature that has received limited attention to date. Future comparisons of these observations with radiative hydrodynamic simulations, along with new observations from state-of-the-art spectrometers such as SOLAR-C/EUVST and MUSE, should clarify the mechanisms behind the observed shifts in this study.