傳統上量測太陽p模式(p-mode)震波生命期的方法是透過能量頻譜(power spectra)上各個p模式的頻寬( spectral line width)分析而得。由於較高階(high-ℓ)的p模式震波與相鄰模式的譜線會有嚴重的重疊(blending)現象發生，導致頻寬分析上的困難。針對高階p模式的震波生命期，有別於傳統的頻譜分析，我們發展了一個新的方法來進行測量。
透過對一特定徑向階次(radial order)的波函數做空間上的傅利葉轉換，我們得到不同的p模式震波之波函數在各個水平波數(horizontal wave number)及時間上的分佈，每個水平波數對應著一組相當接近單一模式(single mode)的波函數。針對這些p模式波函數在時間上的衰減做進一步的分析，我們能夠測得震波能量在時間上的衰減率(decay rate)以及衰減期(decay time)。另一方面，藉由對一特定徑向階次之波函數做時間上的傅利葉轉換，我們也能夠分析p模式震波在空間上的衰減情形，進而估計p模式震波能量的衰減距離(decay length)。由以上方法測量得到的衰減期與衰減距離有良好的一致性。我們使用了HMI (Helioseismic and Magnetic Imager) 的日震觀測數據進行分析，此一方法讓我們能研究最高至ℓ = 1332之高階震波的生命期。

The conventional method to determine the lifetime of solar p modes is via the measurement of the width of the p-mode line profile in power spectra. Nevertheless, this approach can be applied only for low- and intermediate-degree modes. For high-degree modes, mode blending prevents us from using this method. In this study, we develop a new method to measure high-degree p-mode lifetimes.
We adopt a new approach to determine the rate of decay in amplitude of wave function for each mode. The wave function of each p-mode is computed by Fourier decomposing the measured wave function associated with a particular radial order. Fourier decomposing in the spatial domain allows us to study the decay of wave function in the time domain for each wavenumber and radial order, namely, the decay time of each mode. On the other hand, the decay length of each mode can be determined with Fourier decomposition of wave function in the temporal domain. The consistence between the decay time and the decay length serves as a check for this method. This method allows us to study the lifetime of p modes up to ℓ = 1332 using helioseismic data taken with HMI (Helioseismic and Magnetic Imager) onboarded the Solar Dynamical Observatory.

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