L. Teriaca, IMPRS Seminar, Lindau 08/12/04 Spectroscopy of the solar Transition Region and Corona L....

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.


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


The Solar Transition Region


Radiant power density

Optically thin plasma

Phc

N Aji j ji

ji

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

Phc

N Aji j ji- -

ji

erg s cm1 3Radiant power density:



Phc N

N

N

N

N

N

N

NN Aji

j

ion

ion

el

e lji

- - ji H

H

ee erg s cm1 3

N

Nj

j

ion

is th e frac tio n o f io n s in th e u p p e r lev e l . Strong fun ction of eN

N

Nion

el

is th e re la tiv e ab u n d an ce o f th e io n ic sp ec ie . eStrong fun ction of T

N

Nel

H

is th e e lem en t ab u n d an ce w ith resp ec t to h y d ro g en .

N

NH

e

is th e h y d ro g en to e lec tro n s n u m b er d en sity ra tio . 0 .8 5



ji

ji

ion

j

ionji

-P

N

hc N

NA

ji

erg s 1

Normalised radiant power density

G T N AN

N

N

N

N

N

Nel ji

ji ion

el

e l -e e

e H

H

e

erg s cm, ,

1 3

Contribution function

P G T N A Nji e l ji

- - e e e erg s cm, , 2 1 3


Line radiance

L G T N A N hji e l jih

- - 1

42 1 2

e e e-1d erg s cm sr, ,

DEM T Nh

T- e

-1d

dcm K2 5

L G T N A DEM T Tji e l jih

- - 1

41 2

e e-1d erg s cm sr, ,


Differential emission measure


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

Ne (cm−3)

Te (K)5×108 1010

105

τee= 10−3

τpp= 0.04

τei= 0.8

τee= 5×10−5

τpp= 2×10−3

τei= 0.04

106

τee= 0.03

τpp= 1.3

τei= 26

τee= 0.02

τpp= 0.7

τei= 1.3


Ionization (Nion/Nel)

q collisional ionizationαr radiative recombinationαd dielectronic recombination

io n iza tio n eq u ilib riu m z

dN

dt0

N N elz

z

Z

0


Ionisation (Nion/Nel)


Excitation (Nj/Nion)

sta tis tica l eq u ilib riu m dN

dti 0

N Nii

ion


Collisional rate coefficients C v f v v vij ij

v

d cm s3 -1

0



A llo w ed tran sitio n : ee

N

NN

Nconst

j

ion

ij

In te rsy stem tran sitio n : o n ly if «

w h en »

e e

e

N

NN N C A

N

Nconst N C A

j

ionij ji

j

ionij ji



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

ji

j

ionji

N

NA

h c

ji


Abundance (Nel/NH)

AN

Nele l lo gH

1 2


Two – level atom

u

g

Ng=Nion


Formation temperature


T = 0.7×104 K

T = 1.8×105 K

T = 2.5×105 K


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

e e-1d erg s cm sr

L

G TN hji

ji

h

- -

e

e-1d erg s cm sr

42 1 2

G TT

G T h

ji

jih

T T

-e

e d

erg s cm1

1 0 1 00 1 5 0 1 5

1 3

m ax. .m ax m ax

E M d cmc e N hh

-2 5


Electron density

E M d cmc e N hh

-2 5

NL

G T fhe2 4 1

R e

1

2

f N

Density sensitive line radiance ratio

→ f=10−2 – 10−5


Coronaldensities

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


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 g i » e

sensitive to the temperature if:


Line profile

N A T C O L L T h N th

T h N A T C O L L

In the solar corona:

Assuming that the ions follow a Maxwellian distribution:

T hT h T h

1 0

2

2ex p

T h

0 0

1 22

cv

c

kT

m ion

where:


Line profile

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

T h-1 Å k m s 0 0 6 1 1 4 9. .

O b s-1 Å k m s 0 1 4 3 8 3 4 8. . .

However, we observe:

S u ne

0 2

1 2

0

1 22 2

c

kT

m c

kT

mion

eff

ion


Non–thermal velocity

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


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 Hα downflows 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


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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L. Teriaca, IMPRS Seminar, Lindau 08/12/04 Spectroscopy of the solar Transition Region and Corona L....

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