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