Homology tutorial

Hugh Hudson Solar MURI 21-Nov-03

Definition:

Homology is the tendency for event morphology torepeat precisely.

Comment:

Here morphology means anything at all: image, timeseries, spectrum, location…

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Trevisan et al., RMA&A 21, 557, 1990

H

Cliver & Wefer, Solar Phys. 71, 39, 1981

Microwaves

TRACE

24 October 2003 15:17 24 October 2003 22:02

K. Schrijver, 20-Nov-03

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Yohkoh spiky arcades

Morita et al., Solar Phys. 200, 137, 2001

Yohkoh “candle flame”

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Bastille Day?

Processes in which the entropy of an isolated system would decrease do not occur, or, in every process taking place in an isolated system, the entropy of the system either increases or remains constant

Second law of thermodynamics

Solar application

An eruption (e.g., a CME) proceeds irreversibly becauseOf energy dissipation (e.g., through reconnection or shockwaves

Common knowledgeRanns et al., A&A 360, 1173 (2000)Nitta & Hudson, GRL 28, 3801 (2001)

Emerging flux leads to near-homology

Comment

This explanation for homologous flares implies some persistence in the flux emergence, ie a coherence over timescales of the interval of homology

Heyvaerts, Priest & Rust, ApJ 216, 123, 1977

Standard emerging-flux cartoon

Note the poor cartoonsmanship -the panels show different field lines

• The flow associated with flux emergenceimplies changes in the footpoint geometry.• Successive events would have differentcoronal null geometries.• The separatrix current in this geometrycirculates only in the corona.

Nitta & Hudson, GRL 28, 3801 (2001)

Soft X-rays, hard X-rays

Magnetism (MDI), hard X-rays (HXT), soft X-rays (SXT)

Emerging flux time-history

Chertok et al., JGR to be published (2003? 2004?)

Homologous dimmings

Dimmings at various wavelengths

Conclusions

• Homologous flares might be explainable by persistent flux emergence, even in a reconnection model

• Homologous CMEs might be explained similarly, if they are basically derived from small spatial scales in ARs

• Chertok et al dash that hope, though, because the homology extends to the quiet corona on large scales, with dissipation