Bibcode
Simoniello, R.; Finsterle, W.; García, R. A.; Salabert, D.; Jiménez, A.; Elsworth, Y.; Schunker, H.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 516, id.A30
Advertised on:
6
2010
Revista
Número de citas
11
Número de citas referidas
9
Descripción
We used long duration, high quality, unresolved (Sun-as-a star)
observations collected by the ground based network BiSON and by the
instruments GOLF and VIRGO on board the ESA/NASA SOHO satellite to
search for solar-cycle-related changes in mode characteristics in
velocity and continuum intensity for the frequency range between 2.5 mHz
<ν< 6.8 mHz. Over the ascending phase of solar cycle 23 we
found a suppression in the p-mode amplitudes both in the velocity and
intensity data between 2.5 mHz <ν< 4.5 mHz with a maximum
suppression for frequencies in the range between 2.5 mHz <ν<
3.5 mHz. The size of the amplitude suppression is 13 ± 2 per cent
for the velocity and 9 ± 2 per cent for the intensity
observations. Over the range of 4.5 mHz <ν< 5.5 mHz the
findings hint within the errors to a null change both in the velocity
and intensity amplitudes. At still higher frequencies, in the so called
High-frequency Interference Peaks (HIPs) between 5.8 mHz <ν<
6.8 mHz, we found an enhancement in the velocity amplitudes with the
maximum 36 ± 7 per cent occurring for 6.3 mHz <ν< 6.8
mHz. However, in intensity observations we found a rather smaller
enhancement of about 5 ± 2 per cent in the same interval. There
is evidence that the frequency dependence of solar-cycle velocity
amplitude changes is consistent with the theory behind the mode
conversion of acoustic waves in a non-vertical magnetic field, but there
are some problems with the intensity data, which may be due to the
height in the solar atmosphere at which the VIRGO data are taken.
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