Description
We report the simultaneous observations of quasi-periodic pulsations
(QPPs) in wavelengths of hard X-ray (HXR), microwave, Ly$\alpha$,
and ultraviolet (UV) emissions during the impulsive phase of an X6.4
flare on 2024 February 22 (SOL2024-02-22T22:08). The X6.4 flare
shows three repetitive and successive pulsations in HXR and
microwave wavebands, and they have an extremely-large modulation
depth. The onset of flare QPPs is almost simultaneous with the start
of magnetic cancellation between positive and negative fields. The
wavelet power spectra suggest the presence of double periods, which
are centered at $\sim$200 s and $\sim$95 s, respectively. The
long-period QPP can also be detected in Ly$\alpha$ and UV wavebands
at the flare area, and it could be observed in the adjacent sunspot.
Our observations indicate that the flare QPPs are most likely
triggered by accelerated electrons that are associated with periodic
magnetic reconnections. The long period at $\sim$200 s is probably
modulated by the slow magnetoacoustic wave originating from the
neighboring sunspot, while the short period at $\sim$95 s could be
regarded as its second harmonic mode.
