Beam electrons as a source of Hα flare ribbons

“…H. Ashfield Iv et al 2022). While the velocities we observe are similar to velocities in the M. Druett et al (2017) study on C-class flares, they fall considerably below the velocities expected from X-class flares, as indicated in M. K. Druett & V. V. Zharkova (2018). This discrepancy suggests that the role of the chromosphere might be more substantial than that of the electron beam in influencing the evolution of riblets.…”

“…The best fits produced a close match to both the absorption core and the gradients of the wings. This was achieved by the algorithm in almost every case by using lower but still optically thick τ values coupled with substantial broadening of the Gaussian width parameter σ. Asymmetric profile features resulting from velocity gradients are commonly observed in flares but can also be found in quiet Sun features as well, and have been investigated in numerous studies (e.g., Kuridze et al 2015;Druett et al 2017;Capparelli et al 2017;Druett & Zharkova 2018). For example, in our data we see a "horn" of the Hα profile in the blue wing or a lower gradient away from the central Doppler shifted component in the red wing, which are both visible in the lower panel of Fig.…”

“…The HYDRO2GEN models presented in this paper explain these profiles by the Doppler effect of the plasma macro motion due to hydrodynamic shocks produced by a non-thermal electron beam (Figs.7, 8 & 9). The HYDRO2GEN F10 model produces enhancements in H↵ line profiles that are in excellent agreement with those observed with SST for the C1.5 class flare on June 30, 2013 (Druett et al 2017); this model addresses the concerns raised by Rubio da Costa et al (2016), while interpreting H↵ emission from an X1.0-class flare. Rubio da Costa et al (2016) suggested red asymmetries peaking around 1 Å are to be likely caused by the downflows missing from their simulations.…”

“…H. Ashfield Iv et al 2022). While the velocities we observe are similar to velocities in the M. Druett et al (2017) study on C-class flares, they fall considerably below the velocities expected from X-class flares, as indicated in M. K. Druett & V. V. Zharkova (2018). This discrepancy suggests that the role of the chromosphere might be more substantial than that of the electron beam in influencing the evolution of riblets.…”

“…The best fits produced a close match to both the absorption core and the gradients of the wings. This was achieved by the algorithm in almost every case by using lower but still optically thick τ values coupled with substantial broadening of the Gaussian width parameter σ. Asymmetric profile features resulting from velocity gradients are commonly observed in flares but can also be found in quiet Sun features as well, and have been investigated in numerous studies (e.g., Kuridze et al 2015;Druett et al 2017;Capparelli et al 2017;Druett & Zharkova 2018). For example, in our data we see a "horn" of the Hα profile in the blue wing or a lower gradient away from the central Doppler shifted component in the red wing, which are both visible in the lower panel of Fig.…”

“…The HYDRO2GEN models presented in this paper explain these profiles by the Doppler effect of the plasma macro motion due to hydrodynamic shocks produced by a non-thermal electron beam (Figs.7, 8 & 9). The HYDRO2GEN F10 model produces enhancements in H↵ line profiles that are in excellent agreement with those observed with SST for the C1.5 class flare on June 30, 2013 (Druett et al 2017); this model addresses the concerns raised by Rubio da Costa et al (2016), while interpreting H↵ emission from an X1.0-class flare. Rubio da Costa et al (2016) suggested red asymmetries peaking around 1 Å are to be likely caused by the downflows missing from their simulations.…”

“…H. Ashfield Iv et al 2022). While the velocities we observe are similar to velocities in the M. Druett et al (2017) study on C-class flares, they fall considerably below the velocities expected from X-class flares, as indicated in M. K. Druett & V. V. Zharkova (2018). This discrepancy suggests that the role of the chromosphere might be more substantial than that of the electron beam in influencing the evolution of riblets.…”

“…The best fits produced a close match to both the absorption core and the gradients of the wings. This was achieved by the algorithm in almost every case by using lower but still optically thick τ values coupled with substantial broadening of the Gaussian width parameter σ. Asymmetric profile features resulting from velocity gradients are commonly observed in flares but can also be found in quiet Sun features as well, and have been investigated in numerous studies (e.g., Kuridze et al 2015;Druett et al 2017;Capparelli et al 2017;Druett & Zharkova 2018). For example, in our data we see a "horn" of the Hα profile in the blue wing or a lower gradient away from the central Doppler shifted component in the red wing, which are both visible in the lower panel of Fig.…”

“…The HYDRO2GEN models presented in this paper explain these profiles by the Doppler effect of the plasma macro motion due to hydrodynamic shocks produced by a non-thermal electron beam (Figs.7, 8 & 9). The HYDRO2GEN F10 model produces enhancements in H↵ line profiles that are in excellent agreement with those observed with SST for the C1.5 class flare on June 30, 2013 (Druett et al 2017); this model addresses the concerns raised by Rubio da Costa et al (2016), while interpreting H↵ emission from an X1.0-class flare. Rubio da Costa et al (2016) suggested red asymmetries peaking around 1 Å are to be likely caused by the downflows missing from their simulations.…”