Observations of sunquakes from gong and mdi
This presentation is the property of its rightful owner.
Sponsored Links
1 / 47

Observations of Sunquakes from GONG and MDI PowerPoint PPT Presentation


  • 73 Views
  • Uploaded on
  • Presentation posted in: General

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.

Download Presentation

Observations of Sunquakes from GONG and MDI

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


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


Original unfiltered movie


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

The expanding waves accelerates with distance because

acoustic waves propagate through deeper layers for larger distances.


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.


Anisotropy of July 9, 1996 sunquake


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 release and X-ray sources


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.).


Numerical model of the seismic response (1995)


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


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 sunquakes

  • 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.

Graphic courtesy David Hathaway, NASA/NSSTC.


Sunquakes of October 28, 2003, X17 flare


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


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


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


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


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


Sunquake of 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

Doppler sources

> 1 km/s

Hard X-ray sources

Gamma-ray sources


Magnetic energy release and subsurface dynamics

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


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


Energy release site

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

20:28 UT


Energyrelease site

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


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


Energy release site

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


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

Energy release site


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


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

Wave front


Location of the

initial impulse


Northward-

directed wave


Sourthward-

directed wave


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

0:41 UT

Hard X-ray source


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

Soft X-ray source

Hard X-ray source


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

0:41 UT

Velocity source

(shock)

Hard X-ray source


Thick-target model explains the sunquakes

Chromospheric evaporation

High-pressure region

Photospheric shock

Ref. Brown, 1971; Kostiuk & Pikelner, 1974


Initial impulses and seismograms

January 15, 2005


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

Two shocks

generated by

two beams of

high-energy

electrons


Conclusions

  • 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.


  • Login