Observations of Observations of Sunquakes from Sunquakes from GONG and MDIGONG and MDIAlexander KosovichevStanford University

Seismic response to solar flares: Seismic response to solar flares: “Sunquakes”“Sunquakes”

Sunquakes are expanding ring-like waves Sunquakes are expanding ring-like waves excited by solar flares and observed on excited by solar flares and observed on the Sun’s surface.the Sun’s surface.

First sunquake: July 9, 1996First sunquake: July 9, 1996

Kosovichev and Zharkova, 1998

Original unfiltered movieOriginal unfiltered movie

The sequence of events in sunquakesThe sequence of events in sunquakesShock wave hits the photosphere duringthe impulsive phase

Expanding ring wave is observed 20 min later

The expanding waves accelerates with distance because The expanding waves accelerates with distance because acoustic waves propagate through deeper layers for larger distancesacoustic waves propagate through deeper layers for larger distances.

Time-distance analysis of sunquakesTime-distance analysis of sunquakes

These observations suggest that sunquakes are excited by shock wavesThese observations suggest that sunquakes are excited by shock waves propagating downward from the chromosphere into the photosphere, propagating downward from the chromosphere into the photosphere, formed by heating of the chromosphere by high-energy electrons formed by heating of the chromosphere by high-energy electrons – “– “thick-target” model.thick-target” model.

Sunquakes correlate with hard X-ray fluxSunquakes correlate with hard X-ray flux

Anisotropy of July 9, 1996 sunquakeAnisotropy of July 9, 1996 sunquake

Why study sunquakes? Why study sunquakes? Understanding of the physics of the flare Understanding of the physics of the flare

energy release and transportenergy release and transport Interaction between the high-energy particles Interaction between the high-energy particles

and solar plasmaand solar plasma Dynamical processes in solar flares (formation Dynamical processes in solar flares (formation

of shocks, chromospheric evaporation)of shocks, chromospheric evaporation) Magnetic field topologies and reconnections Magnetic field topologies and reconnections

associated with flaresassociated with flares New helioseismic diagnosticsNew helioseismic diagnostics

Direct observations of interaction of acoustic Direct observations of interaction of acoustic waves with magnetic field of sunspots and waves with magnetic field of sunspots and flow fieldsflow fields

Energy release and X-ray sourcesEnergy release and X-ray sources

Energy transport: thick-target modelEnergy transport: thick-target model

High-pressure region

Chromospheric evaporation

Photospheric shock

Ref. Brown, 1971; Kostiuk & Pikelner, 1974

Numerical simulations of the hydrodynamic response to solar flares (thick-target model) (Livshits, Kosovichev et al 1980, Solar Phys.).

Numerical model of the seismic response (1995)Numerical model of the seismic response (1995)

A.-C. Donea & C. Lindsey (2005, ApJ), “egression power”, X17 flare, Oct.28, 2003

After the 1996 event the seismic emission was first noticed in After the 1996 event the seismic emission was first noticed in an integrated acoustic signal – “egression power”an integrated acoustic signal – “egression power”

A.-C. Donea & C. Lindsey, “egression power”, X10 flare, Oct.29, 2003

Seismic radiation from solar flares123

Diana Besliu(1,2), Alina C. Donea(1), Paul Cally(1)

http://www.maths.monash.edu.au/~adonea/DATABASE_SUNQUAKES/DIANA/site_statie/sunquakes.html

New sunquakesNew sunquakes

October 28, 2003, X17 – three eventsOctober 28, 2003, X17 – three events October 29, 2003, X10October 29, 2003, X10 July 16, 2004, X3.6July 16, 2004, X3.6 January 15, 2005, X1.2January 15, 2005, X1.2

No sunquake of comparable magnitude No sunquake of comparable magnitude was observed between 1996 and 2003.was observed between 1996 and 2003.

Sunspot counts and X-flares during Sunspot counts and X-flares during the last three solar cycles. the last three solar cycles.

Graphic courtesy David Hathaway, NASA/NSSTC.Graphic courtesy David Hathaway, NASA/NSSTC.

Sunquakes of Sunquakes of October 28, 2003, X17 flare

Doppler images of the wave fronts Doppler images of the wave fronts of X17 flare of of X17 flare of October 28, 2003

Time-distance diagram of an October 28, 2003, eventTime-distance diagram of an October 28, 2003, event

Sunquake of Sunquake of July 16, 2004, X3.6 flare (MDI)

Sunquake of Sunquake of July 16, 2004, X3.6 flare (GONG)

Sunquake of Sunquake of January 15, 2005, X1.2 flare (MDI)

Sunquake of Sunquake of January 15, 2005, X1.2 flare (GONG)

Extremely narrow directed wave of October 29, 2003, X10 flareExtremely narrow directed wave of October 29, 2003, X10 flare

Can the wave collimation be caused by strong subsurface flows?

Hard X-ray sourcesGamma-ray sources

X-ray, X-ray, -ray and acoustic sources of X17 flare, -ray and acoustic sources of X17 flare, October 28, 2003October 28, 2003

Doppler sources> 1 km/s

Magnetic energy release and Magnetic energy release and subsurface dynamicssubsurface dynamics

X10 and X17 flares of October 28-29, X10 and X17 flares of October 28-29, 20032003

X10 (Halloween) flare, Oct. 29, 2003, 20:37 UT –X10 (Halloween) flare, Oct. 29, 2003, 20:37 UT –MDI magnetogram movieMDI magnetogram movie

20:28 UT

Energy release site

Magnetic field change associated with X10 flare of Magnetic field change associated with X10 flare of Oct. 29, 2003Oct. 29, 2003

Energy release site

Subsurface flow map obtained by time-distance helioseismology during X10 flare

X17.2 flare, Oct. 28, 2003, 9:51 UTX17.2 flare, Oct. 28, 2003, 9:51 UT

Energy release site

X17.2 flare, Oct. 28, 2003, 9:51 UTX17.2 flare, Oct. 28, 2003, 9:51 UT

Energy release site

Subsurface flow map obtained by time-distance helioseismology during X10 flare

The regions of the magnetic energy The regions of the magnetic energy release in solar flares appear to be release in solar flares appear to be related to strong shearing plasma related to strong shearing plasma motions at the depth of 4-6 Mm.motions at the depth of 4-6 Mm.

January 15, 2005, X1.2 flare:January 15, 2005, X1.2 flare:magnetogram (color) and Dopplergram (b/w)magnetogram (color) and Dopplergram (b/w)

Wave front

Location of theinitial impulse

Northward-directed wave

Sourthward-directed wave

Hard X-ray source

January 15, 2005, X1.2 flare:January 15, 2005, X1.2 flare:magnetogram and hard X-ray imagemagnetogram and hard X-ray image

0:41 UT

Hard X-ray source

Soft X-ray source

January 15, 2005, X1.2 flare:January 15, 2005, X1.2 flare:Magnetogram, soft and hard X-ray imagesMagnetogram, soft and hard X-ray images

Hard X-ray sourceVelocity source(shock)

0:41 UT

January 15, 2005, X1.2 flare:January 15, 2005, X1.2 flare:Dopplergram and hard X-ray imageDopplergram and hard X-ray image

Thick-target model explains the Thick-target model explains the sunquakessunquakes

High-pressure region

Chromospheric evaporation

Photospheric shock

Ref. Brown, 1971; Kostiuk & Pikelner, 1974

Initial impulses and seismogramsJanuary 15, 2005

Two shocks generated bytwo beams ofhigh-energy electrons

January 15, 2005, X1.2 flare: Doppler and January 15, 2005, X1.2 flare: Doppler and hard X-ray sourceshard X-ray sources

ConclusionsConclusions Expanding seismic waves (“sunquakes”) excited by solar flares are Expanding seismic waves (“sunquakes”) excited by solar flares are

highly anisotropic having the highest amplitude in the direction of the highly anisotropic having the highest amplitude in the direction of the expansion of the flare ribbons.expansion of the flare ribbons.

The source of sunquakes are downward propagating shocks The source of sunquakes are downward propagating shocks (observed in MDI Dopplergrams); it correlates with hard X-ray (observed in MDI Dopplergrams); it correlates with hard X-ray emission (as in the thick-target flare model).emission (as in the thick-target flare model).

The wave fronts propagate through areas of magnetic field and The wave fronts propagate through areas of magnetic field and sunspots without significant distortion and decay. The time-distance sunspots without significant distortion and decay. The time-distance relations show relatively small variations consistent with the time-relations show relatively small variations consistent with the time-distance helioseismology measurements using the cross-covariance distance helioseismology measurements using the cross-covariance functions.functions.

Sunquakes provide great data for studying the structure of active Sunquakes provide great data for studying the structure of active regions and flare physicsregions and flare physics

It is intriguing that strong sunquakes were observed only in the It is intriguing that strong sunquakes were observed only in the declining phases of the solar cycle. This might be related to declining phases of the solar cycle. This might be related to fundamental changes in the topology of active regions resulting in fundamental changes in the topology of active regions resulting in changes in the energy release properties (e.g. energy release changes in the energy release properties (e.g. energy release height). height).

Need numerical models and new observations with higher spatial and Need numerical models and new observations with higher spatial and temporal resolution, and also spectral data – an excellent target for temporal resolution, and also spectral data – an excellent target for Solar-B observations.Solar-B observations.