Temporal changes in the frequencies and widths of the solar p-mode oscillations

Rhodes, E. J.; Reiter, J.; Schou, J.; Larson, T. P.; Scherrer, P. H.; Brooks, Judith; McFaddin, P.; Miller, B. A.; Rodríguez, J.; Yoo, J.

doi:10.1088/1742-6596/271/1/012029

Cited by 11 publications

(8 citation statements)

References 4 publications

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“…Because for degrees l ≫ 1 m-averaging of the originally generated zonal, sectoral, and tesseral power spectra significantly improves the signal-to-noise ratio, the WMLTP method is particularly well suited for the fitting of m-averaged power spectra derived from time series as short as three days, say. This facilitates the detailed investigation of temporal frequency shifts with the phase of the solar activity cycle (see, e.g., Ronan et al 1994;Jefferies 1998;Rhodes et al 2002Rhodes et al , 2003Rose et al 2003;Rabello-Soares et al 2008b;Tripathy et al 2010;Jain et al 2011;Rhodes et al 2011). On the other hand, the generation of m-averaged power spectra requires knowledge of suitable frequency splitting coefficients (cf.…”

Section: Discussionmentioning

confidence: 99%

A METHOD FOR THE ESTIMATION OF $p$-MODE PARAMETERS FROM AVERAGED SOLAR OSCILLATION POWER SPECTRA

Reiter

Rhodes

Kosovichev

et al. 2015

ApJ

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A new fitting methodology is presented which is equally well suited for the estimation of low-, medium-, and high-degree mode parameters from maveraged solar oscillation power spectra of widely differing spectral resolution. This method, which we call the "Windowed, MuLTiple-Peak, averaged spectrum", or WMLTP Method, constructs a theoretical profile by convolving the weighted sum of the profiles of the modes appearing in the fitting box with the power spectrum of the window function of the observing run using weights from

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Section: Discussionmentioning

confidence: 99%

A METHOD FOR THE ESTIMATION OF $p$-MODE PARAMETERS FROM AVERAGED SOLAR OSCILLATION POWER SPECTRA

Reiter

Rhodes

Kosovichev

et al. 2015

ApJ

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“…A similar study, but including more data, demonstrated a quadratic relation between the frequency shifts and activity indices (Rabello-Soares 2011), which was not confirmed by Tripathy et al (2013b). Rhodes et al (2011) also investigated the temporal changes in high-degree pmode frequencies and pointed out that short-duration, high-frequency shifts are more sensitive to changes in solar activity than the shifts measured by long-duration studies consisting only the lower frequencies. Recently, Korzennik et al (2013a) computed high-degree modes for three different epochs from three different instruments and compared the mode parameters.…”

Section: Introductionmentioning

confidence: 99%

Variations in High Degree Acoustic Mode Frequencies of the Sun During Solar Cycles 23 and 24

Tripathy

Jain

Hill

2015

ApJ

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We examine continuous measurements of the high-degree acoustic mode frequencies of the Sun covering the period from 2001 July to June 2014. These are obtained through the ring-diagram technique applied to the full-disk Doppler observations made by the Global Oscillation Network Group (GONG). The frequency shifts in the degree range of 180 ≤ ≤ 1200 are correlated with different proxies of solar activity e.g. 10.7 cm radio flux, the International Sunspot Number and the strength of the local magnetic field. In general, a good agreement is found between the shifts and activity indices, and the correlation coefficients are found to be comparable with intermediate degree mode frequencies.Analyzing the frequency shifts separately for the two cycles, we find that cycle 24 is weaker than cycle 23. Since the magnetic activity is known to be different in the two hemisphere, for the first time, we compute the frequency shifts over the two hemispheres separately and find that the shifts also display hemispheric asymmetry; the amplitude of shifts in the northern hemisphere peaked during late 2011, more than two years earlier than the south. We further correlate the hemispheric frequency shifts with the hemispheric sunspot number and mean magnetic activity index. Since the frequency shifts and the hemispheric activity indices are found to be significantly correlated, we suggest that the shifts be used as an indicator of hemispheric activity since not many indices are measured over the two hemispheres separately. We also investigate the variation at different latitudinal bands and conclude that the shifts in active latitudes correlate well with the local magnetic activity index.

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“…As initially reported by Woodard & Noyes (1985), it is now well established that the frequency of the solar acoustic modes is strong correlated with solar activity. This has been observed for modes with degree up to 3 (e.g., Salabert et al 2004;Chaplin et al 2007), up to about 200 (e.g., Bachmann & Brown 1993;Jain & Bhatnagar 2003;Antia 2003;Dziembowski & Goode 2005;Jain et al 2009) and up to 1000 (e.g., Rhodes et al 2002;Rabello-Soares et al 2006;Rabello-Soares 2011;Rhodes et al 2011). The observed mode frequencies can be inverted to obtain the sound speed in the solar interior where the waves travel through.…”

Section: Introductionmentioning

confidence: 85%

Solar-Cycle Variation of Sound Speed Near the Solar Surface

Rabello-Soares

2012

ApJ

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We present evidence that the sound-speed variation with solar activity has a two-layer configuration, similar to the one observed below an active region, which consists of a negative layer near the solar surface and a positive one in the layer immediately below the first one. Frequency differences between the activity minimum and maximum of solar cycle 23, obtained applying global helioseismology to the Michelson Doppler Imager (MDI) on board SOHO, is used to determine the sound-speed variation from below the base of the convection zone to a few Mm below the solar surface. We find that the sound speed at solar maximum is smaller than at solar minimum at the limit of our determination (5.5 Mm). The min-to-max difference decreases in absolute values until ∼ 7 Mm. At larger depths, the sound speed at solar maximum is larger than at solar minimum and their difference increases with depth until ∼ 10 Mm. At this depth, the relative difference (δc 2 /c 2 ) is less than half of the value observed at the lowest depth determination. At deeper layers, it slowly decreases with depth until there is no difference between maximum and minimum activity.

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Temporal changes in the frequencies and widths of the solar p-mode oscillations

Cited by 11 publications

References 4 publications

A METHOD FOR THE ESTIMATION OF $p$-MODE PARAMETERS FROM AVERAGED SOLAR OSCILLATION POWER SPECTRA

A METHOD FOR THE ESTIMATION OF $p$-MODE PARAMETERS FROM AVERAGED SOLAR OSCILLATION POWER SPECTRA

Variations in High Degree Acoustic Mode Frequencies of the Sun During Solar Cycles 23 and 24

Solar-Cycle Variation of Sound Speed Near the Solar Surface

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