Issue |
A&A
Volume 394, Number 2, November I 2002
|
|
---|---|---|
Page(s) | 701 - 706 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20021063 | |
Published online | 15 October 2002 |
The 1.3-year and 156-day periodicities in sunspot data: Wavelet analysis suggests a common origin
1
Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany e-mail: natalie@linmpi.mpg.de; solanki@linmpi.mpg.de
2
On leave from Astronomical Institute, St. Petersburg University, 198504 St. Petersburg, Russia
Corresponding author: N. A. Krivova, natalie@linmpi.mpg.de
Received:
14
May
2002
Accepted:
11
July
2002
Helioseismic data have revealed a 1.3-year periodicity in
the solar rotation rate near the bottom of the solar convection zone.
In order to test whether these rotation rate variations have a significant
impact on the solar dynamo, we search for such a periodicity in tracers of
relatively freshly emerged flux at the solar surface, namely sunspots.
Sunspot areas and sunspot number time series are studied with the help of
the wavelet transform.
Significant power at this period (1.28 years) is indeed found and is
observed to vary strongly with time.
This provides independent support for the presence of a 1.3 year periodicity
in solar data.
The power at the 154–158-day Rieger period of solar flares is seen to vary
approximately in phase with the 1.28-year period.
Based on this we propose that the Rieger period is the third harmonic
( years) of the 1.3-year period.
If the rotation rate of the Sun does vary with 1.3 years then the enhanced
flaring with the Rieger period may finally be driven by the 1.3 year
periodicity.
However, the power in both periods is also found to
approximately follow the total number of sunspots.
Therefore we cannot rule out that the 1.3-year and 156-day periods are
harmonics of the solar activity cycle.
Finally, our analysis of a calibrated sunspot area record reveals that the
156-day period continues into the most recent cycles, in contrast to earlier
results.
Key words: Sun: interior / Sun: magnetic fields / Sun: sunspots
© ESO, 2002
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