Solar Oscillation Frequency Changes on Time Scales of Nine Days

Tripathy, S. C.; Hill, F.; Jain, Kiran; Leibacher, J. W.

doi:10.1007/s11207-007-9000-z

Cited by 25 publications

(34 citation statements)

References 19 publications

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“…The mean frequency shifts normalized with mode inertia are determined as the difference between the frequencies of corresponding modes observed on different epochs and the average frequency over the entire period using Eq. (2) of Tripathy et al (2007). The frequency shifts in the frequency range of 2000 μHz ν 3500 μHz are shown in Fig.…”

Section: Analysis and Resultsmentioning

confidence: 94%

Solar cycle and quasi-biennial variations in helioseismic frequencies

Tripathy¹,

Jain²,

Simoniello

et al. 2012

Proc. IAU

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The prolonged period of solar minimum between cycles 23 and 24 has invoked a great deal of interest to understand the origin of the unusually low solar activity. Even though the origin of solar activity is believed to lie in the shear layer at the base of the convection zone, the analysis of helioseismic data seem to orientate us toward the near surface. In this context, we analyze the signature of the quasi-biennial periodicity seen in the oscillation frequencies which may provide additional constraints on the solar dynamo models.

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Section: Analysis and Resultsmentioning

confidence: 94%

Solar cycle and quasi-biennial variations in helioseismic frequencies

Tripathy¹,

Jain²,

Simoniello

et al. 2012

Proc. IAU

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show abstract

“…It may thus be surprising if there is anything new to learn in this area, but recent work using very short nine-day time series has revealed a more complex relationship between the mode frequencies and the surface field. Tripathy et al (2007) have shown that the slope of the linear relationship between ν and various activity indices varies with time and the phase of the solar cycle, as seen in Fig. 7.…”

Section: The Futurementioning

confidence: 87%

Helioseismology and the solar cycle: Past, present and future

Hill

2008

J Astrophys Astron

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A major goal of helioseismology is to understand the mechanism of the solar cycle. In this paper, some results of helioseismic observations relevant to the cycle are briefly reviewed, the current stateof-the-art is discussed, and near-term future directions are sketched out. Topics covered include the internal rotation rate; activity-related parameter variations; the tachocline; far-side imaging; the torsional oscillation; and meridional flows.

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“…The acoustic frequencies can be affected by different phenomena associated to both weak and strong components of the magnetic field [e.g. [7][8][9][10]. Those may contribute to the observed frequency shifts through indirect (thermal and structural) effects and direct (via Lorentz force) effects.…”

Section: Introductionmentioning

confidence: 99%

On the relation between activity-related frequency shifts and the sunspot distribution over the solar cycle 23

et al. 2017

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Abstract. The activity-related variations in the solar acoustic frequencies have been known for 30 years. However, the importance of the different contributions is still not well established. With this in mind, we developed an empirical model to estimate the spot-induced frequency shifts, which takes into account the sunspot properties, such as area and latitude. The comparison between the model frequency shifts obtained from the daily sunspot records and those observed suggests that the contribution from a stochastic component to the total frequency shifts is about 30%. The remaining 70% is related to a global, long-term variation. We also propose a new observable to investigate the short-and mid-term variations of the frequency shifts, which is insensitive to the long-term variations contained in the data. On the shortest time scales the variations in the frequency shifts are strongly correlated with the variations in the total area covered by sunspots. However, a significant loss of correlation is still found, which cannot be fully explained by ignoring the invisible side of the Sun when accounting for the total sunspot area. We also verify that the times when the frequency shifts and the sunspot areas do not vary in a similar way tend to coincide with the times of the maximum amplitude of the quasi-biennial variations found in the seismic data.

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Solar Oscillation Frequency Changes on Time Scales of Nine Days

Cited by 25 publications

References 19 publications

Solar cycle and quasi-biennial variations in helioseismic frequencies

Solar cycle and quasi-biennial variations in helioseismic frequencies

Helioseismology and the solar cycle: Past, present and future

On the relation between activity-related frequency shifts and the sunspot distribution over the solar cycle 23

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