Quasi-periodic pulsation detected in Lyman-alpha emission during solar flares (2003.01877v1)

Abstract: We investigated the quasi-periodic pulsation (QPP) in Lyman-alpha, X-ray and extreme-ultraviolet (EUV) emissions during two solar flares, i.e., an X-class (SOL2012-01-27T) and a C-class (SOL2016-02-08T). The full-disk Lyman-alpha and X-Ray flux during these solar flares were recorded by the EUV Sensor and X-Ray Sensor on board the Geostationary Operational Environmental Satellite. The {\deg}are regions were located from the EUV images measured by the Atmospheric Imaging Assembly. The QPP could be identified as a series of regular and periodic peaks in the light curves, and its quasi-periodicity was determined from the global wavelet and Fourier power spectra. A quasi-periodicity at about 3 minutes is detected during the impulsive phase of the X-class flare, which could be explained as the acoustic wave in the chromosphere (e.g., Milligan et al. 2017). Interestingly, a quasi-periodicity at roughly 1 minute is discovered during the entire evolutionary phases of solar flares, including the precursor, impulsive, and gradual phases. This is the first report of 1-minute QPP in the Lyman-alpha emission during solar flares, in particular during the flare precursor. It may be interpreted as a self-oscillatory regime of the magnetic reconnection, such as magnetic dripping.

• The paper detects and characterizes quasi-periodic pulsations (QPPs) in Lyman-alpha (Ly-α) emission during solar flares, focusing on X-class and C-class events using satellite data.
• Using Fourier, wavelet, and statistical analyses, researchers found consistent 1-minute QPPs across all flare phases and 3-minute QPPs specifically in the impulsive phase of an X-class flare.
• These findings provide constraints for flare emission models and highlight the potential of QPPs as diagnostic tools for understanding coronal parameters and predicting space weather.

Quasi-periodic Pulsation in Lyman-alpha Emission During Solar Flares

In a focused investigation on solar flare emissions, the work examines quasi-periodic pulsations (QPPs) with particular attention to Lyman-alpha (Ly-α) emissions. Authors Dong Li et al. have meticulously analyzed data from two solar flares: an X-class (SOL2012-01-27T) and a C-class (SOL2016-02-08T). Using data recorded by the Environmental Satellite's EUV and X-Ray Sensors and supplemented by extreme-ultraviolet (EUV) images from the Solar Dynamics Observatory's Atmospheric Imaging Assembly, the researchers detailed structured analyses revealing significant periodic emissions.

The presence of QPPs as periodic fluctuations of electromagnetic radiation in solar flares is well-documented. However, this paper identifies and characterizes previously unreported 1-minute and 3-minute quasi-periodicities in Ly-α emissions across different flare phases — a crucial advancement in understanding solar flare mechanisms.

Methodology and Results

The paper employed Fourier and wavelet analysis to conclusively detect QPPs both in full-disk Ly-α and SXR emissions recorded by the Geostationary Operational Environmental Satellite (GOES). A 1-minute QPP was observed consistently across all phases of the solar flare, from precursor through impulsive to gradual phases. In contrast, the 3-minute QPP was limited to the impulsive phase of the X-class flare, aligning with previously theorized acoustic wave origins within the chromosphere. The use of detrended light curve and global wavelet power analysis provided essential insights into the behavior and persistence of QPPs.

The detection and verification of these QPPs were further substantiated by examining the local EUV flux within AIA 304 Å data, consistent with the global observations from Ly-α and SXR channels. Notably, these observational insights were cross-verified through ARIMA and SARIMA models, lending credence to the periodic nature of the data collected.

Discussion

The discovery of 1-minute QPPs is significant in understanding flare dynamics, providing potential constraints for existing models of flare emissions. This periodicity, detected both in Ly-α and other channels, suggests an inherent oscillatory mechanism possibly driven by a self-oscillatory regime of magnetic reconnection processes or MHD wave interactions. The persistence of such QPPs regardless of flare phase points towards intrinsic modulation within the solar atmosphere, likely linked to magnetic dripping or magnetosonic wave phenomena.

The implications for solar physics are profound. The ability to discern phase-dependent periodicities in QPPs could revolutionize diagnostic techniques for examining coronal parameters, improving predictive capabilities regarding flare-induced solar weather impacts. Understanding the complementary or distinct mechanisms driving 1-minute versus multi-minute QPPs may also elucidate nuances in flare-triggering processes and energy dissipation in the solar corona.

Future Directions

The paper's findings pave the way for comprehensive models accounting for various QPP-driven phenomena. Future solar missions equipped with advanced Ly-α observational instruments can harness these insights for real-time flare monitoring and analysis. The planned instruments such as the Extreme Ultraviolet Imager on the Solar Orbiter or the Lyman-alpha Solar Telescope onboard the Advanced Space-based Solar Observatory promise significant advances in resolving ambiguities regarding the precise origin and propagation mechanisms of QPPs.

Ultimately, this research contributes significantly to the field of solar physics, emphasizing the need for integrated observational and theoretical studies in understanding the complexities of solar flare dynamics and their broader implications within heliophysics.