Observations of Hα Intensity Oscillations in a Flare Ribbon
Gallagher, Peter T.; Mathioudakis, Mihalis; Bloomfield, D. Shaun; McAteer, R. T. James; Keenan, Francis P.; Williams, David R.; Brown, Daniel S.; Moore, Ruth; Katsiyannis, A.
Australia, United States, United Kingdom, Belgium
Abstract
High-cadence Hα blue wing observations of a C9.6 solar flare obtained at Big Bear Solar Observatory using the Rapid Dual Imager are presented. Wavelet and time-distance methods were used to study oscillatory power along the ribbon, finding periods of 40-80 s during the impulsive phase of the flare. A parametric study found statistically significant intensity oscillations with amplitudes of 3% of the peak flare amplitude, periods of 69 s (14.5 mHz) and oscillation decay times of 500 s. These measured properties are consistent with the existence of flare-induced acoustic waves within the overlying loops.