Possible Evidence of Long-Term Oscillations in the Solar Atmosphere

• Main Author: K.P. Raju;Jagdev Singh;R. Srikanth;Dean-Yi Chou;Ton Team
• Other Authors: 周定一
• Format: Journal/Newspaper
• Language: English
• Published: Springer Verlag 2001
• Subjects: long-term oscillations;solar atmosphere;temporal correlation function;time sequences;Ca II K filtergrams;Dopplergrams;Antarctic observations; 33; Antarctic; Antarc*; Antarctica
• Online Access: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/54797

2010104010023 物理系 We have obtained the temporal correlation function, Q(t), from time sequences of Cathinspii K filtergrams and Dopplergrams from Antarctica, Taiwan Oscillation Network (TON) and Solar and Heliospheric Observatory (SOHO). Q(t) gives the time evolution of the pattern under examination, supergranulation in this case. It has been found that Q(t) shows oscillatory signals of both 5-min and long-term periods. The 5-min oscillations are suppressed by averaging the images over 10 min. An exponential decay curve which represents the lifetime trend of supergranules, is fitted to Q(t) and subtracted out. The Q(t) residuals thus obtained contain the oscillatory component and are then subjected to a periodogram analysis. Significant periodicities in the range of 1.4–10 hours have been noted. The causes of these oscillations are not fully known at present, but the instrumental and atmospheric factors can be ruled out, pointing to solar origin. Various possibilities are discussed. Some of the observed periodicities may be considered as probable candidates for long-term oscillations in the Sun, such as the elusive gravity modes.