tailieunhanh - Astrophysics and Space Science Proceedings Phần 8

Khu vực đăng nhập Sửa đổi tần số dao động? Để ước tính tốt như thế nào chúng ta có thể liên kết các địa điểm của khu vực hoạt động như là địa điểm của những thay đổi tần số, chúng tôi tính toán hệ số tương quan Pearson (rp) giữa các thay đổi và MAI cho mỗi ba vòng ngày. | Do Active Regions Modify Oscillation Frequencies 377 few tiles with positive frequency shifts that have no counterparts in the MAI image implying a weaker agreement. To estimate how well we can associate the locations of active regions as locations of frequency shifts we calculate the Pearson s correlation coefficient rp between the shifts and MAI for each of the three ring-days. These are found to be and and and for CR 2009 and 2058 respectively and confirms that the correlation between shifts and the surface magnetic activity during the two activity periods are significantly different. This result is consistent with the recent findings inferred from global modes Jain et al. 2009 . Thus the argument that the solar-cycle variations in the global mode frequencies are due to global averaging of the local effect of active regions Hindman et al. 2001 is only partially supported by our analysis. We believe that the weak component of the magnetic field for example ubiquitous horizontal field or turbulent field must be taken into account to fully explain the frequency shifts particularly during the minimal-activity phase of the solar cycle. Acknowledgment We thank John Leibacher for a critical reading of the manuscript. This research was supported in part by NASA grants NNG 05HL41I and NNG 08EI54I. This work utilizes data obtained by the Global Oscillation Network Group program managed by the National Solar Observatory which is operated by AURA Inc. under a cooperative agreement with the National Science Foundation. The data were acquired by instruments operated by the Big Bear Solar Observatory High Altitude Observatory Learmonth Solar Observatory Udaipur Solar Observatory Instituto de Astrofisica de Canarias and Cerro Tololo Interamerican Observatory. This work also utilizes 96min magnetograms from SOI MDI on board Solar and Heliospheric Observatory SOHO . SOHO is a project of international cooperation between ESA and NASA. References .