Helioseismology and the solar cycle
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Transcript of Helioseismology and the solar cycle
Helioseismology and the Solar Cycle- Rachel Howe - 2006
Mads L. Severinsen, Kristian Jerslev & Lars V. T. Occhionero- d. 18. Maj 2010
Introduktion
Direct observations of Solar Activity → From Photosphere
Activity originates from within the Convective Zone
Measure of solar interior → Helioseismology
Helioseismology 101
Sun oscillates in Spherical Harmonic Oscillations
Y lm ,=−1mc lmP l
mcosei m
Helioseismology 101
l = 1, m = 0 l = 10, m = 5
Helioseismology 101
l = 0 l = 2 l = 20 l = 25 l = 75
Helioseismology 101
gravity modes Surface gravity
modes pressure modes
(acoustic)
Article Data
Sun as a Star l < 4 Whole Sun
Medium Degree l < 300 10''
High Degree l > 200 Very Local
Article Data
Changes in interior dynamics- Torsional oscillation change
Changes in interior dynamics- Phase and amplitude changes
Observations Changes in torsional
oscillation during period Possible changes all way
through convection zone Zonal flows: constrains
dynamo models Changes in meridional
flow oserved through high l oscillations
Changes in mode-parameters- Frequency shifts
Changes in mode-parameters- Frequency shifts
Changes in mode-parameters- Mechanisms
Clear change in frequency as function of activity and time
No clear mechanism
Not only a magnetic effect
Changes in mode-parameters- Amplitude and Width
Changes in mode-parameters- Width and Amplitude
Results:
Damping due to surface activity Width and amplitude inversly related to lifetime
Subsurface structural changes
Subsurface changes still unknown– High l-modes drown in surface variations
– High l-modes hard to observe
Better results with SDO ?
We can only see the outermost part of surface (R=99%)
Conclusion
Chance to look into the Sun's Convection zone Gives experimental data to dynamo-model
confinement See changes in the suns hydrodynamics during
cycles