Numerical simulation of Numerical simulation of effects of reduced effects of reduced

excitationof 5-min.solar excitationof 5-min.solar oscillations in sunspotsoscillations in sunspots

Konstantin Parchevsky,Konstantin Parchevsky,Alexander KosovichevAlexander Kosovichev

Stanford University, HEPLStanford University, HEPL

MotivationMotivation

The amplitude of 5-min. oscillations is The amplitude of 5-min. oscillations is significantly smaller in sunspots than in the significantly smaller in sunspots than in the quiet Sun.quiet Sun. Lack of wave sources inside sunspots where Lack of wave sources inside sunspots where

convection is suppressed by strong magnetic convection is suppressed by strong magnetic field.field.

Interaction of incoming waves with magnetic Interaction of incoming waves with magnetic field and perturbations of pressure and field and perturbations of pressure and density inside sunspots.density inside sunspots.

k- k- diagram diagram

l

, m

Hz

Source depth 0.34 , Slice depth = 0 Mm

0 500 1000 1500 2000 25000

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l

, m

Hz

0 500 1000 15000

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simulations observations

Artificial maskArtificial mask

x, Mm

y M

m

0 10 20 30 40 50

0

5

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500 10 20 30 40 50

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x, Mm

rela

tive

ampl

itude

Amplitude mapsAmplitude mapsobservations simulations

= 3.65 ± 0.6 mHz

amplitude ratio: 4.0 ± 0.9 4.6 ± 1.0

MDI continuum

120 120 50 Mm3

Amplitude ratio vs.Amplitude ratio vs.sunspot diametersunspot diameter

5 6 7 8 9 10 11 121.5

2

2.5

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Sunspot diameter, Mm

Am

plitu

de r

atio

ConclusionConclusion

1.1. The suppression of acoustic sources The suppression of acoustic sources inside sunspots can almost entirely inside sunspots can almost entirely explain the reduced oscillation amplitude explain the reduced oscillation amplitude observed in sunspots.observed in sunspots.

2.2. Amplitude ratio of acoustic waves inside Amplitude ratio of acoustic waves inside and outside sunspots depends on and outside sunspots depends on sunspots radii. The bigger radius, the sunspots radii. The bigger radius, the bigger suppression.bigger suppression.