Periodicities in Irradiance and in other Solar Activity Indices During Cycle 23 |
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Authors: | T Ataç A Özgüç J Rybak |
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Institution: | 1. Kandilli Observatory and E.R.I, Bo?azi?i University, ?engelk?y, Istanbul, Turkey 2. Astronomical Institute, Slovak Academy of Sciences, 05960, Tatranska Lomnica, Slovak Republic
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Abstract: | Magnetic fields give rise to distinctive features in different solar atmospheric regimes. To study this, time variations of
the flare index, sunspot number and sunspot area, each index arising from different physical conditions, were compared with
the solar composite irradiance throughout cycle 23. Rieger-type periodicities in these time series were calculated using Fourier
and wavelet transforms (WTs). The peaks of the wavelet power of these periodicities appeared between the years 1999 and 2002.
We found that the solar irradiance oscillations are less significant than those in the other indices during this cycle. The
irradiance shows non-periodic fluctuations during this time interval. The peaks of the flare index, sunspot number and sunspot
total area were seen around 2000.4, 1999.9 and 2001.0, respectively. These periodicities appeared intermittently and were
not simultaneous in different solar activity indices during the three years of the maximum phase of solar cycle 23. |
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