Solar cycle variation in the peak asymmetry: solar or artefact?. S. J. Jiménez-Reyes IAC . 13-sept-2004. Blue. Red.
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S. J. Jiménez-Reyes
The convective overshoot in the photosphere makes the asymmetries less negative. It should be stronger in the blue period, when observations are sensitive to variations close to the base of the photosphere.
Our previous studies (Jiménez Reyes et al. 2003) uncovered a clear evidence for a systematic variation over the solar cycle. However, such conclusion ignores any potential contribution from the change in operating configuration through the GOLF lifetime.
Variation of peak asymmetry. It is real?
Blue and red wing measurements artefact?
A one year modulation is visible due to the orbital velocity of the spacecraft.
This is what we can expect if the changes are due to the measurements make at different depths in the solar atmosphere.
Variation of peak asymmetry. It is real? artefact?
Blue Wing (mA)
D1: 129.7 Vmax
Red Wing (mA)
D1: 82.5 Vmax
Given the annual variation of the line-of-sight velocity of the spacecrafts we should see a periodic modulation in the asymmetry variations. Indeed, this modulation should be of the order of height difference between both operating configurations. However, such height-dependent is not found.
Variation of peak asymmetry. How can we proceed?
Cycle 23 artefact?
Note that in terms of level of solar activity, there is not overlapping between blue and red-wing periods.
Nigam & Kosovichev (1998) artefact?
Extraction of the mode parameters
This is a traditional peak fitting in the sense that the asymmetrical frequency shifts of the multiplet is not taken into account.
Frequency shift of low degree artefact?
Using this results it is possible to identify some of the main characteristics of the solar magnetic fields. Thus, differential analysis of the frequency shifts of different low-degree modes can provide information on the distribution of high-latitude fields.
No long-term variations artefact?
Mean change in height and weight
The result found could be explained on the basis of changes in damping affecting both the mode with and the velocity power.
The new data confirms our previous results. artefact?We do not find any dramatic variation between both operating configuration modes.
Variation of peak asymmetry. It is real?
Blue vs Red wing
Time series of 432d long
GOLF vs MDI. 100d and 432d artefact?
We can confirm an asymmetry variation of l=1,3 in both datasets although the peak-to-peak change does not agree. The higher sensitivity found for GOLF might arises from an additional contribution due to the observed depth in the solar atmosphere.
GOLF versus MDI. 100d and 432d
A clear phase difference of around 20 datasets although the peak-to-peak change does not agree. The higher sensitivity found for GOLF might arises from an additional contribution due to the observed depth in the solar atmosphere.º between both operating configurations is found, which coincides with initial estimations (Pallé et al. 1999). However, we did not find any trend of this parameter with time.
In principle, the variation of the asymmetry could be explained as part of a progressive intensity contamination of the velocity measurement. When Ic b
Let suppose first, that the long-term asymmetry variation is due to the observed depth in the solar atmosphere.
Can be explained the short-term variation as part of an intensity contamination?
We compute the phase difference between two simultaneous velocity measurements (GOLF-MDI)
Phase difference V-V
Variation of peak asymmetry.
What about l=4 and 5? simulation:
1. Empirical model of the p-mode simulation:
parameters extracted from previous
2. Empirical model of the p-mode parameter variations normalized to the Radio Flux changes.
3. Relative instrumental sensitivity up to l=5 (theoretical values)
4. Asymmetrical frequency shifts of the multiplets (l=2 and 3).
Artificial data. Results (i) simulation:
Mean asymmetry simulation:
Artificial data. Results (ii)
The leakage from l=4 and 5 might affect the asymmetry determination of l=0,2 since the level of noise cannot be estimated correctly.