Science Requirements for Helioseismology Frank Hill NSO SPRING
Workshop Nov. 26, 2013
Slide 2
Science drivers Understand dynamics below active regions
vorticity, divergence Continue observations of large-scale zonal
and meridional flows underlying the dynamo and solar activity
Continue measurement of frequency variations during the cycle is
there a near-surface dynamo? Correctly infer the structure below
active regions Improve the precision and accuracy of mode property
measurements to improve inferences of solar interior Further
understand mode excitation and damping Probe solar atmosphere
structure and dynamics are there acoustic cavities? Investigate
magnetic field oscillations magnetoseismology Investigate
relationship between active region magnetic field direction and
subsurface flows Develop space-weather forecasts from
helioseismology
Slide 3
Slide 4
Inversion of meridional flow measurements using 3 years of GONG
data (2007-2009). Top: Flow map as a function of latitude and
depth. Color convention: red poleward flow, blue Equatorward.
Bottom: Average (10 < lat < 30 deg) meridional flow speed as
a function of depth. Deep return meridional flow with amplitude
about 5 m/s is clearly seen. Multi-cell structure in depth is
visible, but requires many more measurements to get robust depth
profile. This result is obtained after systematic East-West travel
time corrections have been subtracted. Deep Meridional Flow
Inversion
Slide 5
Where is Cycle 25??? 2023?- 2034? Cycle 23 (1995-2009)
Equatorward Branch Cycle 24 (2009-2020?) Poleward branch
Equatorward branch Change in differential rotation has hidden weak
Cycle 25 poleward branch
Slide 6
Slide 7
Upper panel: GONG oscillation frequency shifts over solar cycle
23 averaged over 0 120 for two frequency bands: low (green) and
high (red). Lower panel: high-pass filtered data showing ~2 yr
cycles which may be the signature of a near-surface dynamo
(Simoniello et al. 2012)
Slide 8
Coffee Cup Active region subsurface wave speed structure Red
high speed (hot) Blue low speed (cold)
Slide 9
Disagreement between helioseismic methods
Slide 10
Comparison with models (not so good)
Slide 11
P modes and inclined magnetic fields Acoustic modes are
transformed into various MHD modes when they encounter the level at
which the the sound speed and the Alfven speed are equal. The ray
paths and energy partition depends on the strength of the magnetic
field, the inclination of the magnetic field, the acoustic mode
attack angle, and the frequency. This strongly affects the observed
relative phases and thus travel times between observed waves that
are not actually purely acoustic. Cally 2007
Slide 12
Numerical travel time perturbations at 3 (left), 4 (middle) and
5 (right) mHz as functions of field inclination and wave
orientation attack angle
Slide 13
Cross- spectral helioseismology Cross-spectral analysis should
provide more accurate frequencies E.g. simultaneous four- spectra
fitting (P I, P v, C IV, IV ) Phase differences provide information
on excitation & damping Phase differences provide information
on atmospheric structure and possible acoustic cavities Barban,
Hill & Kras, 2004
Slide 14
Magneto-seismology?
Slide 15
Magnetic oscillations at disk center for the period 2008 August
1-28: (Top) Cross-sectional cuts of three- dimensional ring diagram
power spectra at 3.333 mHz. (Bottom) The asymmetry parameter as a
function of frequency obtained from spherical harmonic
decomposition for = 275. But is it the Sun or instrumental
cross-talk?
Slide 16
Vorticity and flares
Slide 17
Validation of GONG Far-Side Helioseismic Maps by comparison
with STEREO observations Liewer, P. C., et al., 2012, Comparison of
Far-Side STEREO Observations of Solar Activity and Active Region
Predictions from GONG, SoPh . we found that for 139 of 157 (89%)
comparisons, STEREO EUVI showed a bright region, indicating
activity, at the location of the GONG predicted far-side active
regions. Only 11% of the predictions showed no significant
brightening in either 195 or 304 images. In this study, we
identified 15 large active regions that appeared on the east limb
(as seen from Earth) between 1 February and 20 July 2011. GONG
successfully predicted eight of these 15 regions (55%) with a
confidence level higher than 70%.
Slide 18
Incorporating Far-Side Observations into ADAPT for Space
Weather Forecasting Diagram of the general data flow and processing
of ADAPT: Modeling / Forecasting Applications Intelligent Front End
Improved Solar Synoptic Maps Coronal & Solar Wind Models Import
& Select Data for Data Assimilator VarianceMagnetic Field
Initial Conditions Analysis Step: combine observations with
forecast Forecast Step: use the WH model to calculate forecast
Assimilation Results ADAPT Solar Magnetogram Data Input Data Data
Assimilator Global Magnetic Field WSA-ENLIL Solar Wind Far-side map
Polarity + Error Estimation Improvements is Solar Wind forecasting
using the far- side data Solar wind speed observations from STEREO
B (black solid lines) vs. 4-day WSA predictions (blue dots) using
daily ADAPT maps without the far-side active region included (a).
The lower time series (b) is the same as (a) except now using ADAPT
maps with the far-side active region from the seismic maps
included. The red vertical bars indicate the range over which WSA
solar wind speed predictions vary over a grid cell. (courtesy of
C.N. Arge) F 10.7 forecasting using ADAP maps with and without
far-side information. Henney, C. et al (26 th NSO Workshop
presentation, May 2012)
Slide 19
Deep focusing travel-time maps of AR 10488. The focus depth
covers 40-70 Mm. Each map is created using 8- hours of MDI data
centered at the emerging AR location. The color scale in the
travel-time maps covers the perturbation range 0 (blue) to -15
(red) sec. Last three panels: magnetic field for time period of the
first panel in the middle row; for time period when AR emerged to
the surface; and intensity map for three days. Only a few active
regions have been detected using this technique. Pre-emergence
active region detection
Slide 20
Science requirements Continue what we do now so solar
cycle-related flows are adequately captured and space weather
forecasts are enabled: Full-disk Doppler velocity Cadence of no
longer than 60 seconds 90% duty cycle 25 year lifetime Sufficient
overlap with current data for cross-calibration Go beyond what we
do now: Multiple heights for mode conversion, cross-spectral
fitting and atmospheric seismology Vector magnetic field for mode
conversion and magnetoseismology Increase spatial resolution to
observe higher latitudes Increase numerical simulation efforts to
understand and guide observations
Slide 21
Multi-wavelength oscillation power, phase, coherence maps from
SDO Data provides info on wave properties as function of height,
needed to provide reliable active region structure inversions. Note
that the high-freq. phase in quiet Sun does not reflect assumed
order of formation heights, as expected for upward- traveling
waves; HMI I L shows a larger phase shift relative to HMI V than
does AIA 1700 . Likely cause is MHD mode conversion.
Slide 22
Technical requirements Observations in multiple spectral lines
e.g.: Ni I 6768 (GONG, MDI) Fe I 6301/2 (magnetic field) CA 8542
(Chromosphere) Fe I 6173 (HMI) Images of 4k 4k pixels (1
resolution) Velocity sensitivity: 1 m/s /pixel /image (?) Magnetic
field sensitivity: 5 G /pixel /image (?) Entrance aperture of at
least 0.5 m Adaptive optics or other image enhancement technology
High-speed image post-processing Instruments located at least six
sites Highly accurate N-S alignment of instruments High-speed
real-time data return via the internet
