Sushant C. Tripathy, Kiran Jain and Frank Hill

GONG, National Solar Observatory, Tucson, AZ 85719 (email: stripathy@nso.edu)

How to select a quiet region ?

(i) A quiet region at the same heliographic longitude and latitude within the same

Carrington rotation period (commonly used in literature)

(ii) A common quiet region for all the events (neglects temporal variation)

(iii) An ensemble average of quiet regions (fixed at disk center in this analysis)

Aim: Illustrate the variations in properties of oscillation modes between quiet regions

and analyze the effect of different quiet regions on the mode properties of the active region

Technique: Standard ring-diagram technique involving Dopplergrams of about 15˚ x

15˚ in heliographic longitude and latitude. Each region is tracked for 1664 minutes. The

oscillation mode parameters are obtained by fitting a symmetric Lorentzian model to the

power spectrum.

Data: GONG+ Dopplergrams and MDI magnetograms for the period September 2001 to

December 2003. MDI magnetograms are used to calculate Magnetic Activity Index (MAI)

which is a measure of the strength of the strong field component of the associated

magnetic field. We have identified 43 active regions for this study.

(a) Relative frequency differences, (b) ratio of amplitude, and (c) ratio of line widths between

AR NOAA 10244 and the quiet regions Q1 and Q2. The MAI of AR is 16.22G. While the

differences in frequency are similar, there are significant differences between the mode

amplitudes and line widths.

(a) Relative frequency differ-

ences, (b) ratio of amplitude,

and (c) ratio of line width

between the quiet region

located at disk center

corresponding to CR 1979

(DCQ) and the average of 22

quiet region, Q. The error bars

show one standard deviation

from mean Q values.

Changes in (a) mode frequency (ν) , (b) amplitude (A) , and (c) line width (Γ) of oscillation

modes between two quiet regions Q1 and Q2 within CR 1998. Both the regions are located at

S22E25 corresponding to AR NOAA 10244 on 2003 January 07 and have MAI value of 2.06

G and 2.08 G, respectively. The variations between the two regions are larger than expected.

(a) Ratio of amplitude and (b) ratio of line width between the AR

NOAA 10224 and two different quiet regions; quiet region, Q

(open symbols) and average of Q1 and Q2 at the same

heliographic latitude as the active region (filled symbols).

Frequency averaged line widths as a function of the MAI of active

regions. The f-modes have been averaged over modes in the

frequency range of 2500-2750 μHz, p1 and p2 over modes in the

range of 3000-3500 μHz and p3 over modes in the range of 3250-

3750 μHz. The left panel denotes the ratio w.r.t. the disk center

quiet region (QDC) of 2002 May 19 while the right panel shows

the ratio w.r.t. the ensemble average, Q. The active regions are

restricted to 30˚ from the central meridian to minimize the fore-

shortening effect. The changes in line widths are distinctly visible

between the two panels.

Variation of oscillation mode parameters between two quiet regions

Variation of mode parameters between AR NOAA 10244 and

quiet regions, Q1 and Q2

SP41A - 01

Summary:

We have investigated the intrinsic fluctuations associated with mode parameters in quiet

regions and their effect on the active regions

We find a large variation in mode amplitude and line width while the differences in mode

frequencies are within the estimated errors

We conclude that the choice of a single quiet region can misled the result and interpretation.

Acknowledgements: This work utilizes data obtained by the Global OscillationNetwork Group (GONG) program, managed by the National Solar Observatory, whichis operated by AURA, Inc. under a cooperative agreement with the National ScienceFoundation. The data were acquired by instruments operated by the Big Bear SolarObservatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur SolarObservatory, Instituto de Astrofísica de Canarias, and Cerro Tololo InteramericanObservatory. SOHO is a project of international cooperation between ESA and NASA.This work is supported by NASA Grant NNG-05HL41I to National Solar Observatory.

Variations among 22 quiet regions (CR1979-2010)

Comparison of A and Γ between NOAO 10224 and

average quiet regions

Comparison of binned line widths of 43 ARs between

two different quiet regions