Spectroscopy of the solar Transition Region and Corona · el is the relative abundance of the ionic specie. Strong function of Te N N el H is the element abundance with respect to

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L. Teriaca, IMPRS Seminar, Lindau 08/12/04

Spectroscopy of the solar Transition Region and Corona

L. Teriaca


The Solar Corona

Composite photo of the August 11, 1999 total eclipse.Lake Hazar, Turkey.

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The Solar Corona

Raw spectra obtainedon 19 June 1936 duringa total eclipse observedfrom the former SovietUnion.

Te=1 – 2 MK


The Solar Chromosphere

Photo of the August 11, 1999 total eclipse.Kastamonu, Turkey.

Te=104 K

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The Solar Transition Region


Radiant power density

Optically thin plasma

( ) ( ) ( )PhcN Aji j jiλ

λλ=

ji

-1 -3 -1erg s cm ÅΨSpectral radiantpower density:

( )PhcN Aji j ji

- -=λ ji

erg s cm1 3Radiant power density:

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( )Phc NN

NN

NN

NNN Aji

j

ion

ion

el

elji

- -=λ ji H

H

ee erg s cm1 3

NN

jj

ion is the fraction of ions in the upper level . Strong function of eN

NNion

el is the relative abundance of the ionic specie. eStrong function of T

NNel

H is the element abundance with respect to hydrogen.

NN

H

e is the hydrogen to electrons number density ratio. 0.85 ≈



( )ελji

ji

ion

j

ionji

-PN

hc NN

A= =ji

erg s 1

Normalised radiant power density

( ) ( )G T N ANNN

NN

NNel ji

ji ion

el

el -e e

e H

H

eerg s cm, , =

ε1 3

Contribution function

( ) ( )P G T N A Nji el ji- -= e e e erg s cm, , 2 1 3

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Line radiance

( ) ( )L G T N A N hji el jih

- -= ∫1

42 1 2

π e e e-1d erg s cm sr, ,

( ) ( )DEM T NhT

-= e-1d

dcm K2 5

( ) ( ) ( )L G T N A DEM T Tji el jih

- -= ∫1

41 2

π e e-1d erg s cm sr, ,


Differential emission measure

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Atomic processes

Characteristic times for the relevant atomic processesin the Transition region as calculated for the C IV lineat 154.8 nm (Te=105 K, Ne=1010 cm−3).


Thermal equilibrium

τee= 0.02

τpp= 0.7

τei= 1.3

τee= 0.03

τpp= 1.3

τei= 26

106

τee= 5×10−5

τpp= 2×10−3

τei= 0.04

τee= 10−3

τpp= 0.04

τei= 0.8

105

10105×108

Ne (cm−3)Te (K)

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Ionization (Nion/Nel)

q collisional ionizationαr radiative recombinationαd dielectronic recombination

ionization equilibrium z

→ =dNdt

0

N Nelz

z

Z

=∑ =

0


Ionisation (Nion/Nel)

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Excitation (Nj/Nion)

statistical equilibrium → =dNdti 0

N Nii

ion∑ =


Collisional rate coefficients( ) ( ) ( )C v f v v vij ij

v

=∞

∫ σ d cm s3 -1

0

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Allowed transition: ee

NN

NN

constj

ion

ij∝ ⇒ =ε

Intersystem transition: only if «

when »

e e

e

NN

N N C A

NN

const N C A

j

ionij ji

j

ionij ji

∝

=



CHIANTI atomic database: http:wwwsolar.nrl.navy.mil/chianti.html

ελji

j

ionji

NN

A=hc

ji

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Abundance (Nel/NH)

ANNelel= +logH

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Two – level atom

u

g

Ng=Nion

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Formation temperature


T = 0.7×104 K

T = 1.8×105 K

T = 2.5×105 K

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T = 2.5×105 K

T = 1.8×105 K

T = 1.0×106 K

T = 1.4×106 K

T ≈ 104 K


Emission Measure

( ) ( )L G T N hji jih

- -= ∫1

42 1 2

π e e-1d erg s cm sr

( )( )L

G TN hji

ji

h

- -=⟨ ⟩

∫e

e-1d erg s cm sr

42 1 2

π

( )( )

( ) ( ) ( )⟨ ⟩ =−

∫+ −G T

T

G T h

ji

jih

T T-

e

e derg s cm

110 100 15 0 15

1 3

max. .max max

( )EM d cmc e= ∫ N hh

-2 5

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Electron density

( )EM d cmc e= ∫ N hh

-2 5

( )⟨ ⟩ =⟨ ⟩

NL

G T fhe2 4 1π

( )R e= =εε

1

2f N

Density sensitive line radiance ratio

→ f=10−2 – 10−5


Coronaldensities

Banerjee, Teriaca, Doyle, Wilhelm, 1998, A&A 339, 208

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Electron temperatures

If we consider an isothermal plasma, the ratio of two allowedtransitions from adjacent ionization stages reduces to the ratioof their contribution functions.

If we consider two allowed transitions from the ground state ofthe same ion:

( )∆ ∆E E kTgk gi− » e

sensitive to the temperature if:


Line profile( ) ( ) ( ) ( ) ( )Ψ Ψ Ψ Ψ Ψλ λ λ λ λ= ∗ ∗ ∗NAT COLL Th Nth

∆ ∆ ∆λ λ λTh NAT COLL= +

In the solar corona:

Assuming that the ions follow a Maxwellian distribution:

( ) ( )Ψ

∆ ∆λ

π λλ λ

λThTh Th

= −−

1 0

2

2exp

∆ λλ λ

Th = =

0 0

1 22

cv

ckTmion

where:

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Line profile

As an example, for N V 123.8 nm, (Te=1.8×105 K),

∆ λTh-1 Å km s= =0 061 14 9. .

∆ λObs-1 Å km s= =01438 34 8. . .

However, we observe:

∆ λλ

ξλ

Sune= +

=

0 2

1 20

1 22 2

ckTm c

kTmion

eff

ion


Non–thermal velocity

Teriaca, Banerjee, Doyle, 1999, A&A, 349, 636

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Doppler shift

Teriaca, Banerjee, Doyle, 1999, A&A, 349, 636


Chromospheric evaporation in flaresL. Teriaca et al.

Large upflows inCDS Fe XIX lineat the footpointsof the flaring loopsystem during theimpulsive phase.

Red contours indicate Hαdownflows of ≈10 km s−1

One hour later the flaring loops start to appear in theTRACE 17.1 nm band andare fully visible around16:20 UT.

RHESSI data, starting at14:50 UT, shows nonthermal emission stillpresent at the right footpoint

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Supersonic flows in a Quiet Sun loopL. Teriaca et al. 2004, A&A 427, 1065

a) O VI SUMER raster of a smallQS area. Black contours showmagnetic flux of −10, −25, −40 G.Black + indicate the locations ofstrong non–Gaussian line profiles.The dashed red line indicates theprojection on the plane of the skyof a semicircular loop with adiameter of 13". The black dotsshow the position of the observedloop.b, d) Profiles on the legs of theloop with the results of a 3component Gaussian fitting.c) Profile at loop top. Thedotted line shows the averageQS profile times 4.9.Observed speeds are consistentwith the LOS component of asupersonic siphon–like flow of≈130 km s−1 along the loop.

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Spectroscopy of the solar Transition Region and Corona · el is the relative abundance of the ionic specie. Strong function of Te N N el H is the element abundance with respect to