Bibcode
DOI
Jiménez-Reyes, S. J.; García, R. A.; Jiménez, A.; Chaplin, W. J.
Referencia bibliográfica
The Astrophysical Journal, Volume 595, Issue 1, pp. 446-457.
Fecha de publicación:
9
2003
Revista
Número de citas
63
Número de citas referidas
38
Descripción
We have used observations made by the Global Oscillations at Low
Frequency (GOLF) and the Variability of Irradiance and Gravity
Oscillations Sun Photometer (VIRGO/SPM) instruments on board the
ESA/NASA Solar and Heliospheric Observatory satellite to study
variations in the excitation and damping of low angular degree (low-l)
solar p-modes on the rising phase of activity cycle 23. Our analysis
includes a correction procedure that for the first time allows GOLF data
to be ``treated'' as a single homogeneous set, thereby compensating for
the change of operational configuration partway through the mission.
Over the range 2.5<=ν<=3.5mHz, we uncover an increase in
damping and decrease in mode power that is consistent with previous
findings. Furthermore, an excellent level of agreement is found between
the variations extracted from the GOLF and VIRGO/SPM data. We find no
net long-term changes to the modal energy supply rate. However, an
analysis of the residuals uncovers the presence of a quasi-periodic
signature of period ~1.5 yr (most pronounced for SPM). While it is true
that several workers claim to have uncovered similar periodicities in
other phenomena related to the near-surface layers of the Sun here, we
are at present more inclined to attribute our finding to an artifact of
the mode-fitting procedure. We also uncover a significant change in the
asymmetry of mode peaks in the GOLF data, as found in previous studies
of much longer data sets. These assumed that the dominant contribution
to this arose from the switch in operating configuration partway through
the mission (which altered the depth in the solar atmosphere sampled by
the instrument). However, our preliminary analysis of data collected
over the 100 day period beginning 2002 November 19-when the instrument
switched back to its original configuration-suggests that this change
may have a solar cycle component.