Magnetic Dissipation in the Magnetic Dissipation in the Photosphere and Heating of Photosphere and Heating of

the Coronathe Corona

Valentyna AbramenkoValentyna AbramenkoBig Bear Solar ObservatoryBig Bear Solar Observatory

andandAlexei PevtsovAlexei Pevtsov

National Solar ObservatoryNational Solar Observatory

Soft X-ray luminosity of the Soft X-ray luminosity of the corona corona

Data: Yohkoh/SXT Data: Al 0.1 μm channel AlMgMn-sandwich channel

Data: SOHO/MDI high resolution magnetograms

Objects: Active regions near the center of the solar disk

Objects: Active regions near the center of the solar disk

Analyzed Quantities: •Averaged (over an area) flux in each channel•Temperature•Emission Measure

Analyzed Quantitiy: •Averaged (over an area)

magnetic energy dissipation rate

CORONACORONA PHOTOSPHEREPHOTOSPHERE

?

Magnetic energy dissipationMagnetic energy dissipation

Structure of Magnetic Energy Structure of Magnetic Energy DissipationDissipation

Line-of-sight Magnetic Field, BzMagnetic energy dissipation, ε/η

Magnetic dissipation versus averaged Magnetic dissipation versus averaged flux in Al.1 and AlMgMn channelsflux in Al.1 and AlMgMn channels

Flux d

ensi

ty (

Al.1

)

Flux d

ensi

ty (

AlM

gM

n)

Magnetic dissipation versus Magnetic dissipation versus temperature and emission temperature and emission

measuremeasure

Energy Flux EstimationEnergy Flux Estimation

η = (150 ÷ 300) km2/s

If we accept the effective thickness of the photosphere h = 500 km,the energy flux F=∫ εَ dh for different ARs varies in the range of

F = (1 ÷ 14)×10F = (1 ÷ 14)×106 6 erg cmerg cm-2-2 s s-1-1

Abramenko, Pevtsov, Romano,2006, ApJL 646

Poynting Flux vs X-ray Flux:Poynting Flux vs X-ray Flux:area-averaged valuesarea-averaged values

Follow-up study: Tan, Jing, Abramenko, Pevtsov, Song, Park, Haimin Wang, 2007 ApJ, accepted

Poynting Flux ~ Bh Bz Vh

Bz Bz Vh

Poynting Flux vs X-ray Flux:Poynting Flux vs X-ray Flux:area-integrated valuesarea-integrated values

Follow-up study: Tan, Jing, Abramenko, Pevtsov, Song, Park, Haimin Wang,

2007 ApJ, accepted

•ConclusionsConclusions

Energy input due to the random motions Energy input due to the random motions strongly correlates with brightness, strongly correlates with brightness, temperature and emission measure of the temperature and emission measure of the corona.corona.

Energy flux is (1 ÷ 14)×10Energy flux is (1 ÷ 14)×1066 erg cm erg cm-2-2 s s-1-1, which , which is quite sufficient to heat the corona above is quite sufficient to heat the corona above ARs.ARs.

Magnetic diffusivity in ARs is Magnetic diffusivity in ARs is (150 ÷ 300) km2/s, which is twice lower than in QS areas., which is twice lower than in QS areas.

Index of the magnetic power spectrumIndex of the magnetic power spectrum

Index of the magnetic power spectrum Index of the magnetic power spectrum versus averaged flux in Al.1 and versus averaged flux in Al.1 and

AlMgMn channelsAlMgMn channels