Solar cycle and quasi-biennial variations in helioseismic frequencies

Tripathy, S. C.; Jain, Kiran; Simoniello, R.; Hill, F.; Turck‐Chièze, S.

doi:10.1017/s1743921313002263

Cited by 2 publications

(2 citation statements)

References 8 publications

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“…These periods are consistent with those obtained from the analysis of the entire data, suggesting that both cycles have different dominant QBO periods. The QBO period obtained in cycle 23 confirms the single peak in the power spectrum as reported by Tripathy et al (2013b), with a period of about 2 yr (∼700 days). We also obtain an insignificant hump around a period of 1010 days in cycle 23.…”

Section: Resultssupporting

confidence: 84%

“…It is important to mention that the double-peak structure was not identified in earlier studies. For example, Tripathy et al (2013b) reported only a single peak in the global power spectrum by using the oscillation frequencies for cycle 23 and To explore the origin of the two peaks in GWPS, shown in Figure 3, we separated out the frequency shifts for cycles 23 and 24 and calculated the wavelet spectrum and GWPS for both cycles independently. As is evident in Figure 4, the double-peak structure no longer appears in the GWPS; only one peak is obtained in each cycle, but with different QBO period and power; for cycles 23 and 24, the periods are 206 days, respectively.…”

Section: Resultsmentioning

confidence: 99%

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Helioseismic Investigation of Quasi-biennial Oscillation Source Regions

Jain,

Chowdhury,

Tripathy

2023

ApJ

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We studied the temporal evolution of quasi-biennial oscillations (QBOs) using acoustic mode oscillation frequencies from the Global Oscillation Network Group. The data used here span more than 25 yr, covering solar cycles 23 and 24 and the ascending phase of cycle 25. The analysis reveals that QBO-like signals are present in both the cycles, but with different periods. The dominant QBO period in cycle 23 is found to be about 2 yr, while it is about 3 yr in cycle 24. Furthermore, the quasi-biennial oscillatory signals are present only during the ascending and high-activity phases of cycle 23 and quickly weaken around 2005, during the declining phase. In comparison, the QBO signals are present throughout cycle 24, starting from 2009 to 2017. We also explored the depth dependence in QBO signals and obtained a close agreement at all depths, except in the near-surface shear layer. A detailed analysis of the near-surface shear layer suggests that the source region of QBOs is probably within a few thousand kilometers just below the surface.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Helioseismic Investigation of Quasi-biennial Oscillation Source Regions

Jain,

Chowdhury,

Tripathy

2023

ApJ

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Cycle dependence of a quasi-biennial variability in the solar interior

Mehta

Jain

Tripathy

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We investigated the solar cycle dependency on the presence and periodicity of the Quasi-Biennial Oscillation (QBO). Using helioseismic techniques, we used solar oscillation frequencies from the Global Oscillations Network Group (GONG), Michelson Doppler Imager (MDI) and Helioseismic $\&$ Magnetic Imager (HMI) in the intermediate-degree range to investigate the frequency shifts over Cycles 23 and 24. We also examined two solar activity proxies, the F10.7 index and the Mg ii index, for the last four solar cycles to study the associated QBO. The analyses were performed using Empirical Mode Decomposition (EMD) and the Fast Fourier Transform (FFT). We found that the EMD analysis method is susceptible to detecting statistically significant Intrinsic Mode Functions (IMFs) with periodicities that are overtones of the length of the dataset under examination. Statistically significant periodicites, which were not due to overtones, were detected in the QBO range. We see a reduced presence of the QBO in Cycle 24 compared to Cycle 23. The presence of the QBO was not sensitive to the depth to which the p-mode travelled, nor the average frequency of the p-mode. The analysis further suggested that the magnetic field responsible for producing the QBO in frequency shifts of p-modes is anchored above approximately 0.95$\rm R_{\odot }$.

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Solar cycle and quasi-biennial variations in helioseismic frequencies

Cited by 2 publications

References 8 publications

Helioseismic Investigation of Quasi-biennial Oscillation Source Regions

Helioseismic Investigation of Quasi-biennial Oscillation Source Regions

Cycle dependence of a quasi-biennial variability in the solar interior

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