Sushanta C. Tripathy NSO, Tucson Comparison of Mode Parameters between Velocity and Intensity Acoustic Spectra using MDI data Sushanta C. Tripathy NSO, Tucson

CONTENTS Introduction Results using GONG pipeline: symmetric profiles Problems in 3D asymmetric fitting Results from 2D asymmetric fitting 7/1/2019 LoHCo IX

Introduction Significant differences in central frequencies were found in global spectra obtained simultaneously in V and I (Harvey et al., 1998) Difference depends on ν of the mode and can be as high as 50 μHz above cutoff frequency Shift can not be a property of the mode and must arise from excitation mechanism We use ring diagram techniques to investigate the properties of mode parameters from Velocity (V) and Intensity (I) filtergrams as a function of center to limb 7/1/2019 LoHCo IX

Present study We use MDI Velocity and Intensity full-disk images Taken during 1997, April 19-28 (quiet days) Each region is a 16º square and is tracked for a period of 1664 minutes Processed through GONG ring pipeline Power spectra of individual days are combined to enhance the s/n ratio 7/1/2019 LoHCo IX

Power Spectrum as a function of  V  7/1/2019 LoHCo IX

modes are fitted using the model with symmetric profiles for radial order n  6 200    1100 (resolution of   22) Freq. resolution  10 Hz 7/1/2019 LoHCo IX

 - diagram from fitted spectrum  From Velocity Power spectrum From Intensity Power spectrum   f 7/1/2019 LoHCo IX

Center to Limb frequency differences  Velocity Intensity  7/1/2019 LoHCo IX

Frequency differences as a function of radial order  Velocity Intensity  7/1/2019 LoHCo IX

Differences in frequency (I – V) 7/1/2019 LoHCo IX

Differences in frequency (I – V) 7/1/2019 LoHCo IX

Differences in Frequency as a function of CL 7/1/2019 LoHCo IX

Averaged frequency differences across CL 7/1/2019 LoHCo IX

Summary so far ….  is a function of location on the disk and increases from center to limb among velocity (and intensity)  between V and I is a function of frequency Difference rises rapidly at higher  (and higher )  is a function of location and increases from disk center to limb 7/1/2019 LoHCo IX

3D Asymmetric Fitting We use the model with asymmetric peak profiles of Basu and Antia (1999) 7/1/2019 LoHCo IX

Results from 3D Asymmetric Fitting 7/1/2019 LoHCo IX

And fit 6 parameters, b1,b2,A0,v0,S and w0 2D Asymmetric Fitting We take azimuthal average for each spectra to obtain 2D spectra in k-ω and fit these using asymmetric peak profiles of Antia and Basu (1999) And fit 6 parameters, b1,b2,A0,v0,S and w0 7/1/2019 LoHCo IX

Results from 2D Asymmetric Fitting 7/1/2019 LoHCo IX

Differences in Frequency (V0 – Vp) 7/1/2019 LoHCo IX

Differences in Frequency (I0 – Ip) 7/1/2019 LoHCo IX

Differences in Frequency (Vsy – Vasy) 7/1/2019 LoHCo IX

Differences in Frequency (Isy – Iasy) 7/1/2019 LoHCo IX

Differences in Frequency (V – I) 7/1/2019 LoHCo IX

Differences in Frequency (V – I) 7/1/2019 LoHCo IX

Future Work ….. Better fitting method for 3D power spectra to obtain correct S parameter Compare other parameters e.g. A, U, Γ 7/1/2019 LoHCo IX

THANK YOU Collaborators H. M. Antia Irene Gonzalez-Hernandez Frank Hill Rachel Howe Rudi Komm Cliff Toner THANK YOU 7/1/2019 LoHCo IX