Technical Comments

Response to Comment on “Detection of Emerging Sunspot Regions in the Solar Interior”

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Science  20 Apr 2012:
Vol. 336, Issue 6079, pp. 296
DOI: 10.1126/science.1215539
  • Fig. 1

    (A) Mean phase travel-time perturbation map of AR 10488 obtained from an 8-hour data set centered at 03:30 UT, 26 October 2003. The cross-covariances were computed using our method (1), with arcs with a size of 45° and four different orientations. The phase shifts inside the circle, which are caused by the emerging sunspot region, have the maximum amplitude of 16.2 s. (B) Same as (A) except that the cross-covariances, following Braun’s approach, were computed assuming Cartesian geometry (instead of the correct spherical geometry). The maximum amplitude of the phase shifts inside the circle is reduced to 12 s. (C) Same as (B) except that the cross-covariances were computed using a Gaussian phase-speed filter (instead of our specially designed filter). The signal inside the circle was further reduced to 9.7 s. (D) Mean phase travel-time perturbation map made with Braun’s methodology: same as (C) except that the cross-covariances were computed using four Gaussian phase-speed filters at four target depths. The final phase travel-time map shown here is the average of the four individual maps. The strongest signal inside the circle is only 5.9 s, which is not sufficiently high to allow the detection of an emerging sunspot region. The strongest signal in this map, with amplitude of about 7.0 s as in Braun’s comment, is more than 60 Mm away from the location of the emergence. These panels illustrate that only these three differences in Braun’s analysis method can fully explain his negative result. Other factors, discussed in the text, may also be important.

  • Fig. 2

    Schematic representation of the largest ray paths for the smallest and largest focus depths used in our and Braun’s measurement schemes. The largest 1-skip distance in our analysis is about 198 Mm, whereas in Braun’s analysis it is about 334 Mm. The oscillation signals in Braun’s scheme are selected from a much larger region of the solar disc, have much larger horizontal wavelengths and different wave vector orientations at the lower turning point, and they travel much deeper in the solar interior. These waves have also different acoustic power distribution over the frequency. All these factors can significantly affect the phase travel-time shifts.

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  • Response to Comment on “Detection of Emerging Sunspot Regions in the Solar Interior”

    Stathis Ilonidis, Junwei Zhao, Alexander Kosovichev

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