Possible evidence of long-term oscillations in the solar atmosphere

Document Type

Article

Publication Date

12-1-2001

Abstract

We have obtained the temporal correlation function, Q(t), from time sequences of Ca II 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.

Identifier

0035633747 (Scopus)

Publication Title

Solar Physics

External Full Text Location

https://doi.org/10.1023/A:1010312411142

ISSN

00380938

First Page

1

Last Page

11

Issue

1

Volume

199

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