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Observations of Sunquakes from GONG and MDI. Alexander Kosovichev Stanford University. Seismic response to solar flares: “Sunquakes”. Sunquakes are expanding ring-like waves excited by solar flares and observed on the Sun’s surface. First sunquake: July 9, 1996. Kosovichev and Zharkova, 1998.

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Observations of sunquakes from gong and mdi

Observations of Sunquakes from GONG and MDI

Alexander Kosovichev

Stanford University


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

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


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

Kosovichev and Zharkova, 1998



The sequence of events in sunquakes
The sequence of events in sunquakes

Shock wave hits the photosphere during

the impulsive phase

Expanding ring wave is observed

20 min later


Time distance analysis of sunquakes
Time-distance analysis of sunquakes

The expanding waves accelerates with distance because

acoustic waves propagate through deeper layers for larger distances.


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

These observations suggest that sunquakes are excited by shock waves

propagating downward from the chromosphere into the photosphere,

formed by heating of the chromosphere by high-energy electrons

– “thick-target” model.



Why study sunquakes
Why study sunquakes?

  • Understanding of the physics of the flare energy release and transport

    • Interaction between the high-energy particles and solar plasma

    • Dynamical processes in solar flares (formation of shocks, chromospheric evaporation)

    • Magnetic field topologies and reconnections associated with flares

  • New helioseismic diagnostics

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



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

Chromospheric evaporation

High-pressure region

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.).



After the 1996 event the seismic emission was first noticed in

an integrated acoustic signal – “egression power”

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



Seismic radiation from solar flares123 Oct.29, 2003

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 sunquakes
New sunquakes Oct.29, 2003

  • October 28, 2003, X17 – three events

  • October 29, 2003, X10

  • July 16, 2004, X3.6

  • January 15, 2005, X1.2

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


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

Graphic courtesy David Hathaway, NASA/NSSTC.


Sunquakes of october 28 2003 x17 flare
Sunquakes of cycles. October 28, 2003, X17 flare




Sunquake of july 16 2004 x3 6 flare mdi
Sunquake of cycles. July 16, 2004, X3.6 flare (MDI)


Sunquake of july 16 2004 x3 6 flare gong
Sunquake of cycles. July 16, 2004, X3.6 flare (GONG)


Sunquake of january 15 2005 x1 2 flare mdi
Sunquake of cycles. January 15, 2005, X1.2 flare (MDI)


Sunquake of january 15 2005 x1 2 flare gong
Sunquake of cycles. January 15, 2005, X1.2 flare (GONG)


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

Can the wave collimation be caused by strong subsurface flows?


X ray g ray and acoustic sources of x17 flare october 28 2003
X-ray, flareg-ray and acoustic sources of X17 flare, October 28, 2003

Doppler sources

> 1 km/s

Hard X-ray sources

Gamma-ray sources


Magnetic energy release and subsurface dynamics
Magnetic energy release and subsurface dynamics flare

  • X10 and X17 flares of October 28-29, 2003



Magnetic field change associated with x10 flare of oct 29 2003

Energy release site flare

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

20:28 UT


Energy flarerelease site

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



Energy release site flare

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


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

Energy release site



January 15 2005 x1 2 flare magnetogram color and dopplergram b w
January 15, 2005, X1.2 flare: appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.magnetogram (color) and Dopplergram (b/w)

Wave front


Location of the appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.

initial impulse


Northward- appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.

directed wave


Sourthward- appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.

directed wave


January 15, 2005, X1.2 flare: appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.magnetogram and hard X-ray image

0:41 UT

Hard X-ray source


January 15, 2005, X1.2 flare: appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.Magnetogram, soft and hard X-ray images

Soft X-ray source

Hard X-ray source


January 15, 2005, X1.2 flare: appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.Dopplergram and hard X-ray image

0:41 UT

Velocity source

(shock)

Hard X-ray source


Thick target model explains the sunquakes
Thick-target model explains the sunquakes appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.

Chromospheric evaporation

High-pressure region

Photospheric shock

Ref. Brown, 1971; Kostiuk & Pikelner, 1974


Initial impulses and seismograms appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.

January 15, 2005


January 15, 2005, X1.2 flare: Doppler and hard X-ray sources appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.

Two shocks

generated by

two beams of

high-energy

electrons


Conclusions
Conclusions appear to be related to strong shearing plasma motions at the depth of 4-6 Mm.

  • Expanding seismic waves (“sunquakes”) excited by solar flares are highly anisotropic having the highest amplitude in the direction of the expansion of the flare ribbons.

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

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

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

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

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


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