Helio-seismology in 20minHelio-seismology in 20minIntroductionIntroduction

Solar StructureSolar StructurePhysics InvolvedPhysics Involved

Observing NetworksObserving NetworksCurrent ResultsCurrent Results

SummarySummary

David BrandsDavid Brands

Stafford and District Astro. SocStafford and District Astro. Soc.

What is Helio-Seismology?What is Helio-Seismology?

• ““Helios” of the sun (all Greek)Helios” of the sun (all Greek)

• ““Seismos” earthquakeSeismos” earthquake

• ““Logos” knowledgeLogos” knowledge

• Mis-labled because there is almost no Mis-labled because there is almost no shear activity (s wave), only p waves (like shear activity (s wave), only p waves (like sound)sound)

• ““Study of solar p waves to determine Study of solar p waves to determine structure and activity of the sun.”structure and activity of the sun.”

Earthquake PropogationEarthquake Propogation

• P wavesP waves– PressurePressure– FastFast

• S wavesS waves– ShearShear– SlowSlow

• Particle displacement parallel to wave Particle displacement parallel to wave direction direction

• The particles do not move with the wave; The particles do not move with the wave; simply oscillate back and forthsimply oscillate back and forth

• Wave is seen as the motion of the Wave is seen as the motion of the compressed region (ie, a pressure wave)compressed region (ie, a pressure wave)

Pressure “P” Pressure “P” Longitudinal Longitudinal wavewave

• Particle displacement perpendicular to Particle displacement perpendicular to wave direction wave direction

• Particles do not move with the wave; they Particles do not move with the wave; they simply oscillate up and downsimply oscillate up and down

• Wave is seen as the motion of the crests Wave is seen as the motion of the crests and troughsand troughs

Shear “S” Shear “S” Transverse Transverse wavewave

Water Water Waves Waves

• Example of waves that involve a Example of waves that involve a combination of both longitudinal and combination of both longitudinal and transverse motions. transverse motions.

• Particles travel in Particles travel in clockwise circlesclockwise circles. The . The radius of the circles decreases as the radius of the circles decreases as the depth into the water increases. depth into the water increases.

• See two particles in See two particles in blueblue to show that to show that each particle travels in a clockwise circle each particle travels in a clockwise circle as the wave passes. as the wave passes.

Rayleigh Rayleigh surface waves surface waves • In a solidIn a solid• Elliptical pathsElliptical paths

• Rayleigh waves different from water waves in Rayleigh waves different from water waves in one important way.one important way.

• Water wave all particles travel in clockwise Water wave all particles travel in clockwise circles, but in Raleigh solids:circles, but in Raleigh solids:

• Surface particles Surface particles counter-clockwisecounter-clockwise ellipse ellipse• Particles at depth Particles at depth clockwiseclockwise ellispes. ellispes.

HelioseismologyHelioseismology

• Sun – almost no “s” waves, mainly “p”Sun – almost no “s” waves, mainly “p”

• Disturbances generated in convection Disturbances generated in convection zone, near photosphere surfacezone, near photosphere surface

• Propagate to surfacePropagate to surface

• Study of surface effects reveals interiorStudy of surface effects reveals interior

• Resonances make the sun “ring” like a bellResonances make the sun “ring” like a bell

Internal Structure of SunInternal Structure of Sun

ProvenProven

ByBy

HelioHelio

SeizmologySeizmology

2.2M Deg C

170K km 500K km1.6%

170000 Yr

10 Days50Km5mins/0.003 Hz

15.6M Deg C700K km

5000 Deg C

9000 Deg C

2.2M Deg C

0.5 MY

Solar Flare causing QuakeSolar Flare causing Quake

Mathematical models of oscillationsMathematical models of oscillations

•Mirage – light bent by hot airMirage – light bent by hot air

Actually hotter air easier / faster pathActually hotter air easier / faster path

•Sound bent in resonance cavities,Sound bent in resonance cavities,

Temp gradients, adiabatic regionsTemp gradients, adiabatic regions

N no. nodes radially outward

M no. nodes around the equator

L no. nodes around the azimuth

L 20

M 17IN

OUT

Vibration Nodes ExampleVibration Nodes Example

1st Harm1st Harm

2nd harm2nd harm

3rd Harm3rd Harm

4th Harm4th Harm

Mathematical models of oscillationsMathematical models of oscillations

•Mirage – light bent by hot airMirage – light bent by hot air

Actually hotter air easier / faster pathActually hotter air easier / faster path

•Sound bent in resonance cavities,Sound bent in resonance cavities,

Temp gradients, adiabatic regionsTemp gradients, adiabatic regions

N no. nodes radially outward

M no. nodes around the equator

L no. nodes around the azimuth

L 20

M 17IN

OUT

Sounds of the sunSounds of the sun

• Wideband filterWideband filter

• All sounds speeded up 42,000 times to All sounds speeded up 42,000 times to become audiblebecome audible

• 0.003 Hz 0.003 Hz

• Human detection starts at 25HzHuman detection starts at 25Hz

Bison NetworkBison Network((Birmingham Solar Oscillations Network)Birmingham Solar Oscillations Network)

Six-station networkSix-station network– Resonant Scattering SpectrometersResonant Scattering Spectrometers

Gong NetworkGong Network

• Global Oscillation Network Group Global Oscillation Network Group

• Similar to BisonSimilar to Bison

• GONG is:GONG is:– a six-station networka six-station network– extremely sensitive velocity imagersextremely sensitive velocity imagers– located around the Earth located around the Earth – obtain nearly continuous observations of the obtain nearly continuous observations of the

Sun's oscillations. Sun's oscillations.

Gong Instruments (1994)Gong Instruments (1994)

• InterferometerInterferometer

• 6 unit trial6 unit trial

• Before shippingBefore shipping

Data: Schematic MovieData: Schematic Movie

Gong Far Side MappingGong Far Side Mapping

• P wave mappingP wave mapping

• Uses interior modelUses interior model

Network ResultsNetwork Results

• Global results:Global results:– Confirmed / improved model of sun interiorConfirmed / improved model of sun interior– Eliminated model errors in “missing nuetrino”Eliminated model errors in “missing nuetrino”– Maps activity and sunspots on “far” sideMaps activity and sunspots on “far” side– Found “jet stream” in convection layersFound “jet stream” in convection layers– Calculated sun age – agrees with meteoritesCalculated sun age – agrees with meteorites

Helio-SeismologyHelio-Seismology

• Conclusions:Conclusions:– P wave analysis, some S wave, good modelsP wave analysis, some S wave, good models– global detector networksglobal detector networks– Internal structure revealed / refinedInternal structure revealed / refined– ““see” spots and activity on far sidesee” spots and activity on far side– Now looking at nearby stars for similar insightNow looking at nearby stars for similar insight

Helio-seismologyHelio-seismologyin 20 Minutesin 20 Minutes

Questions?Questions?

David BrandsDavid Brands

Stafford and District Astro. SocStafford and District Astro. Soc.