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We report quasi-periodic pulsations (QPPs) with double periods during threesolar flares (viz. SOL2011-Feb-15T01:44, SOL2011-Sep-25T04:31,SOL2012-May-17T01:25). The flare QPPs were observed from light curves inLy$\alpha$, hard X-ray (HXR) and microwave emissions, with the Ly$\alpha$emission recorded by the Geostationary Operational Environmental Satellite, theHXR emission recorded by the Reuven Ramaty High-Energy Solar SpectroscopicImager and the Fermi Gamma-ray Burst Monitor, and the microwave emissionrecorded by the Nobeyama Radio Polarimeters and Radioheliograph. By using theMarkov chain Monte Carlo (MCMC) method, QPPs with double periods of about twominutes and one minute were first found in the Ly$\alpha$ emission. Then usingthe same method, a QPP with nearly the same period of about two minutes wasalso found in HXR and microwave emissions. Considering the possible commonorigin (nonthermal electrons) between Ly$\alpha$ and HXR/microwave emission, wesuggest that the two-minute QPP results from the periodic acceleration ofnonthermal electrons during magnetic reconnections. The ratio between thedouble periods in the Ly$\alpha$ emission was found to be close to two, whichis consistent with the theoretical expectation between the fundamental andharmonic modes. However, we cannot rule out other possible driving mechanismsfor the one-minute QPPs in HXR/microwave emissions due to their relativelylarge deviations.

Quasi-Periodic Pulsations Detected in Ly$\alpha$ and Nonthermal Emissions During Solar Flares