HELIOSEISMOLOGY
Maria Pia Di Mauro
INAF- Istituto di Astrofisica Spaziale e Fisica Cosmica
Rome (Italy)
IHY Conference “The Sun, the Heliosphere, and the Earth” Bad Honnef, May 14-18 2007
The story.....
Periodic Motions P  5 min
of the absorption lines of the photospheric spectrum
(Leighton et al. 1962)
PULSATIONS OF THE PHOTOSPHERE!!!
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Normal Modes
Acoustic waves trapped
in resonant cavities  p modes
(Ulrich 1971, Leibacher & Stein 1972)
Normal modes
n radial order
l harmonic degree
mazimuthal order
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
The proof
Deubner 1975
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Patches of the solar surface oscillate up and down
These data from the
SOI/MDI
instrument
on board the SOHO
satellite
1024x1024 points
over visible disk
1-minute cadence
or better
One Million of indipendent modes excited.
Each mode with a different tone!!
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Mode trapping
Eigenfunction oscillates as function of r when
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Helioseismology
Study of the solar oscillations observed at the surface
to probe the structure and the dynamics of the Sun
Study of oscillations in the Sun in a similar way as
geoseismology is the study of earthquakes
The technique is very similar to trying to determine the
shape of musical instruments from the sound they
make.
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Why helioseismology?
Frequencies
depend on the structure of the star
r(r) , p(r) , G1(r) , c(r)
but only 2 independent functions: e.g.r(r) and c(r)
Frequencies can be measured with accuracy (10-5)
Basic physics addressed
-Equation of state, opacities, neutrinos, general relativity, fluid
dynamics
 Stellar physics addressed
-Stellar evolution, differential rotation, origin of solar magnetism,
nature of spatial and temporal inhomogeneitities
Solar-terrestrial physics addressed
-Origin of magnetic storms
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Helioseismic Methods
Global Helioseismology
Local Helioseismology
•Structure and dynamics of pieces
• Structure & dynamics of the of the solar interior & changes with
longitudinally averaged
solar time
interior & changes with time
•Travel time of running sound waves
• Frequencies of p modes
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Notable Successes of Helioseismology
Depth of the solar convection zone (Christensen-Dalsgaard 1985)
Opacity
Neutrino Problem
Diffusion of helium and heavy elements (Basu et al. 1996)
Helium abundance
Relativistic effect in the core (Elliot & Kosovichev 1998)
Internal Dynamics
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
HELIOSEISMIC APPROACHES
Forward approach
Model
Observables
Inverse approach
Aim of inversion: to make inferences about
localized properties of the solar interior
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
ACTUAL SOUND-SPEED DIFFERENCE
SUN-MODEL S
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Turbulent diffusion
Christensen-Dalsgaard & Di Mauro 2007 in press
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
New solar surface abundances
Asplund et al. (2004 A&A 417, 751)
 Grevesse &
Noels 1993
Improvements:
Non-LTE analysis
3D atmosphere models
Unfortunately this model has a too small
CZ and lower He abundance than
inferred one!!
Montalban et al. 2004
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
RELATIVE DENSITY DIFFERENCES
SUN-MODEL S
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
EQUATION OF STATE
First adiabatic exponent
G1 5/3 in the interior
  ln p 
G 
except in the H and He 1   ln r 

 ad
ionization zones
 MHD (Mihalas, Däppen & Hummer 1990)- chemical picture
• Pressure ionization (Partition equation)
•NonRelativistic Electron degeneracy
•Excited states
•Coulomb correction in the Debye-Hückel approximation
OPAL (Rogers, Swenson & Iglesias 1996) - physical picture
•Pressure ionization
•Relativistic Electron degeneracy(OPAL2001)
•Excited states Partition equation and degree of ionization
•Coulomb correction (many-body quantum physics)
•Electron exchange
•Quantum diffraction
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
EOS in the surface
Difference between SUN and Model S
MDI data l<1000
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
HELIUM ABUNDANCE IN CZ
Y cannot be directly obtained by spectroscopy
Y by solar Models matching L Y  0.27-0.28
Now: Helioseismic inversions
REFERENCE
DATA
Y MHD
Y OPAL
HLH 100l 1200
0.24560.007
0.24890.0028
BBSO 4 l140
0.2320.006
0.2480.006
Richard et al.
(1998)
MDI
0 l140
0.2420.002
0.2480.002
Basu (1998)
MDI
l194
Basu & Antia
(1995)
Kosovichev
(1996)
Di Mauro et
al. (2002)
MDI
l1000
0.25240.0001 0.24880.0001
0.24570.0005 0.25390.0005
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Internal Rotation
simmetry
of the
Di Mauro etRotation
al. 1998 breaks sphericalHowe
et al. 2000
Sun and splits the frequency of oscillations
tachocline
rc/R = 0.67 +/- 0.05 (Di Mauro et al 1997)
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
The Solar Cycle
 Activity grows and
decays over 11 years
 Zones of magnetic
activity move towards
the equator
 Bands of slower and
faster rotation also
migrate, ahead of the
magnetic bands
Deviations from the mean rotation
profile as a function of latitude and time
Howe et al. 2000
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
TORSIONAL OSCILLATIONS
0.99 R
0.95 R
MDI
OLA
0.90 R
0.84 R
Differences between inversions of data taken at
successive times reveal the “torsional oscillation”
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Torsional oscillations of whole CZ
Differencing rotation inversions at successive 72-day epochs
relative to solar minimum (1996) shows equatorward and
poleward migration of torsional oscillations
Vorontsov et al. 2002 Science
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Tachocline Oscillations
Howe 2006
The rotation rate appears to show quasi-periodic
oscillations of 1.3 year period near the base of the
convection zone at mid-latitudes
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
ROTATION IN THE CORE
MDI l < 100 (Schou et al. 1998)+
IRIS l=1-3 (Lazreck et al. 1996; Gizon et
al 1997, Fossat 1998)
GONG l=1-3 (Gavryuseva &
Gavryuseva 1998)
Di Mauro et al. 1998
BISON +LOWL l=1-4
(Chaplin et al. 1999)
GOLF l=1-2
(Corbard et al. 1998)
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
News!!!
Solar Gravity Modes detected with GOLF!!!
Garcia et al. 2007 on Science last week
10 years of
observations
from GOLF
Observed g mode is consistent with a model with a
rotation rate 3 or 5 times higher than radiative interior
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
Conclusion
Improve model
Observations
•Diffusion
•Non adiabatic effects
•Convection
•Rotation
•Magnetic fields
•EOS
•2D model
•
•
Longer series of
oscillations data
g modes
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
The future…
SDO Solar Dynamics Observatory, HMI (local helioseismology)
NASA launch: 2008 to understand variation of magnetic fields
dynamical processes and solar structure and its impact on
Earth
PICARD CNES Launch: 2009 PREMOS (low l and
g modes) to study of the Earth climate and Sun
variability relationship
SO Solar Orbiter ESA Launch: 2013 VIM (local
helioseismology at high latitude) to study, by approaching
as close as 45 solar radii, the polar regions and the side of
the Sun not visible from Earth
DYNAMICS Dynamics and Magnetism from the Internal
core to the Chromosphere of the Sun,
Turck-Chieze et al. Saclay, (France) Launch:???
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007
European Helio and
Asteroseismology Network
Co-ordinated Action funded by FP6
the 6th Framework Programme of the European Union
Objective:
Bringing together the European research groups active in
helio- & asteroseismology.
Start date: April 1, 2006
Duration: 48 months
Coordinator:
Oskar von der Lühe,
Kiepenheuer-Institut für Sonnenphysik, Freiburg
More information http://www.helas-eu.org
Maria Pia Di Mauro - IHY Conference Bad Honnef, May 14-18 2007