Lifetimes of High-[CLC][ITAL]l[/ITAL][/CLC] Solar [CLC][ITAL]p[/ITAL][/CLC]-Modes from Time-Distance Analysis

Chou, Dean‐Yi; Serebryanskiy, A.; Ye, Yi-Jen; Dai, De-Chang; Khalikov, Shukur

doi:10.1086/321713

Cited by 5 publications

(18 citation statements)

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“…The cross-correlation function of the wave packet in a time -distance analysis is computed as the cross-correlation between the signals at a central point and the signals are averaged over an annulus at an angular distance from the central point (Duvall et al, 1993). If f n is the amplitude of the wave packet propagating outward from the central point at distance n , where n is the number of skips, in the absence of dispersion, the change in amplitude of the wave packet can be expressed as…”

Section: Effect Of Dispersionmentioning

confidence: 99%

“…The amplitude of the wavefunction at the central point (f 0 ) is a constant with respect to n. Thus A n is proportional to f n regarding the variable n. With Equation (1), the n dependence of A n can be expressed as (Chou et al, 2001) A n ∝ f 2 0 e −nτ 1 /T .…”

Section: Effect Of Dispersionmentioning

confidence: 99%

“…Recently Chou et al (2001) have used the rate of decrease in amplitude of the crosscorrelation function with the number of skips (equivalent to the travel distance or the travel time) in a time -distance analysis to determine the lifetimes of p modes for mode degrees = 200 − 600 and frequencies ν = 2.5 − 5.5 mHz. The p modes have an important property: p-mode waves bounce back and forth between the surface and a layer in the solar interior.…”

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confidence: 99%

“…Since the lifetime of the wave packet is finite, the amplitude of the cross-correlation decreases with travel distance. Chou et al (2001) have measured the rate of amplitude decrease of the cross-correlation function at different skips for the same wave packet to determine the lifetime of the wave packet. It should be emphasized that the lifetime measured with time -distance analysis is the lifetime of a wave packet, not of an individual mode.…”

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confidence: 99%

“…Dispersion causes the width of the wave packet to increase and the amplitude to decrease. The study of Chou et al (2001) ignored this dispersion effect, which leads to an underestimate for the estimated lifetime. In this study and Burtseva et al (2006), the dispersion effect is taken into account to improve the determination of high-degree p-mode lifetimes.…”

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confidence: 99%

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Effects of Dispersion of Wave Packets in the Determination of Lifetimes of High-Degree Solar p Modes from Time – Distance Analysis: MDI Data

Chou

Ladenkov

2007

Sol Phys

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The cross-correlation function of solar p modes in a time -distance analysis changes with travel distance (or travel time). The exponential decrease in the amplitude of the cross-correlation function with travel distance has been interpreted as the dissipation of solar p-mode power and used to determine the lifetimes of high-degree p modes. It is found that the width of the cross-correlation function increases with travel distance. We interpret the increase in width as the dispersion of the wave packet in a time -distance analysis. The dispersion would also cause a decrease in amplitude and affect the determination of lifetimes. We include the dispersion effect in the determination of lifetimes of high-degree p modes in a time -distance analysis and find that the derived lifetime increases significantly compared with the previous study for degree less than 400.

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Section: Effect Of Dispersionmentioning

confidence: 99%

Section: Effect Of Dispersionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Effects of Dispersion of Wave Packets in the Determination of Lifetimes of High-Degree Solar p Modes from Time – Distance Analysis: MDI Data

Chou

Ladenkov

2007

Sol Phys

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Effects of Dispersion of Wave Packets in the Determination of Lifetimes of High-Degree Solar p Modes from Time – Distance Analysis: TON Data

et al. 2007

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We use the method of time -distance analysis to measure lifetimes of solar p modes in the range = 100 − 600 and ν = 3.0 − 4.5 mHz with data taken with the Taiwan Oscillation Network (TON). The lifetimes of p modes are determined by the changes in the amplitude and width of the cross-correlation function of a wave packet with the number of skips. The amplitude of the cross-correlation function decreases exponentially with the number of skips as in previous work. This decrease has been interpreted as the effect of the finite p-mode lifetime. In this study, we find that the width of the cross-correlation function increases with the number of skips. We interpret this phenomenon as the effect of the dispersion of the wave packet. We include this effect in the determination of the lifetime of the wave packet. The lifetime increases after the dispersion is taken into account. We also study the change in lifetime between solar minimum and maximum.

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Lifetimes of High-Degree p Modes in the Quiet and Active Sun

et al. 2009

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We study variations of the lifetimes of high-ℓ solar p modes in the quiet and active Sun with the solar activity cycle. The lifetimes in the degree range ℓ = 300 -600 and ν = 2.5 -4.5 mHz were computed from SOHO/MDI data in an area including active regions and quiet Sun using the time -distance technique. We applied our analysis to the data in four different phases of solar activity: 1996 (at minimum), 1998 (rising phase), 2000 (at maximum), and 2003 (declining phase). The results from the area with active regions show that the lifetime decreases as activity increases. The maximal lifetime variations are between solar minimum in 1996 and maximum in 2000; the relative variation averaged over all ℓ values and frequencies is a decrease of about 13%. The lifetime reductions relative to 1996 are about 7% in 1998 and about 10% in 2003. The lifetime computed in the quiet region still decreases with solar activity although the decrease is smaller. On average, relative to 1996, the lifetime decrease is about 4% in 1998, 10% in 2000, and 8% in 2003. Thus, measured lifetime increases when regions of high magnetic activity are avoided. Moreover, the lifetime computed in quiet regions also shows variations with the activity cycle.

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Lifetimes of High-[CLC][ITAL]l[/ITAL][/CLC] Solar [CLC][ITAL]p[/ITAL][/CLC]-Modes from Time-Distance Analysis

Cited by 5 publications

References 5 publications

Effects of Dispersion of Wave Packets in the Determination of Lifetimes of High-Degree Solar p Modes from Time – Distance Analysis: MDI Data

Effects of Dispersion of Wave Packets in the Determination of Lifetimes of High-Degree Solar p Modes from Time – Distance Analysis: MDI Data

Effects of Dispersion of Wave Packets in the Determination of Lifetimes of High-Degree Solar p Modes from Time – Distance Analysis: TON Data

Lifetimes of High-Degree p Modes in the Quiet and Active Sun

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