solar radiation physical modeling: tools for understanding

Solar Radiation Physical Modeling: Tools for understanding and

forecasting solar EUV and UV irradiance variations

2008/7/12J. Fontenla, E. Quemerais, M. Haberreiter

LASP – Univ. of [email protected]

SRPM Project Goals•Diagnosis of physical conditions through the solar atmosphere; energy balance of radiative losses and mechanical heating.

•Evaluating proposed physical processes to determine the solar atmosphere structure and spectrum at all spatial and temporal scales.

•Synthesizing solar irradiance spectrum and its variations to improve the above and produce complete and quantitative physical models.

•Forecasting spectral irradiance at any time and position in the Heliosphere. Weekly and monthly forecast is now becoming possible.

Layers of the solar atmosphere• Photosphere (using average 1D models and external 3D simulations)

– Slow motions (few km/s) dominated by convection overshoot – Weak ionization– All particles are unmagnetized– Plasma beta > 1– At or near LTE

• Chromosphere (using average 1D models and 3D MHD simulations)– Motions and inhomogeneities change from weak to strong– Weak ionization (np<<ne~10-4 nH)– Ions unmagnetized, electrons magnetized (implies tensor conductivity)– Plasma beta crosses 1 somewhere within the chromosphere– Needs to consider full non-LTE radiative transfer radiative losses

• Corona (will use results from groups carrying coronal loops modeling)– Motions and ihomogeneities are very strong– Highly ionized– All species are magnetized– Plasma beta << 1– Non-LTE effects are extreme and but optically thin applies– Particle transport is large and probably large departures from Maxwellian

SRPM Flow Scheme

Emitted Spectrum

Physical Models& Processes

ObservedSpectrum

Intermediate Parameters

I(λ,µ,φ,t)

T,ne,nh,U,...(x,y,z,t)

nlev,nion,…(x,y,z,t)

I(λ,µ,φ,t)

0.8

0.6

0.4

0.2

0.0

Ioniz

atio

nFra

ctio

n

1042 3 4 5 6 7 8 9

1052 3 4 5 6 7 8 9

106

Temperature (K)

Carbon Ionization and Mass FLow......... Static case (w/dif)_____ Upflow case (w/dif)

Photosphere (radiation/convection)

500 nm 800 nm 1200 nm 1600 nm

Stein & Nordlund 2000 convection simulations snapshotsSRPM absolute radiance, wavelength and CLV dependence

Slit spectrum

1 .103

1 .104

1 .105

1 .106

0

200

400

SRPM 306Stein & NordlundSRPM 306 + 30 km

Pressure (dyne cm^-2)

Hei

ght (

km)

Comparison of spatial averages with semi-empirical modelspoints to improvements in average models and in simulations

Mg I 4572C I 5381 CN band

1 .103

1 .104

1 .105

1 .106

4000

6000

8000

SRP M 306Stein & NordlundSRP M 306 * 0.95


Tem

per

atu

re (K

)

Solar Chromosphere (radiation/plasma heating)

UV (1540 A) continuum MDI magnetogram

UV continuumLyα

Ca II K3 Red cont.

Log-normal distribution of heated areas in quiet Sun, probably due to similar distribution of magnetic features.

B

Discrete set of features assigned to various heating levels.

D F

Active Sun chromospheric features

0.9 0.95 1 1.05 1.1 1.151 .10

4

1 .103

0.01

0.1

1

Intensity (relat ive to median)

Nu

mb

er o

f Pix

els

(rel

ativ

e to

tota

l)

H P

Super-heated (plage) features in active regions are discretized by two components.

Sunspot umbra and penumbra taken from continuum images, but plage and network pixels from Ca II K data.

A set of models discretizes the distribution of heated areas

(other models for sunspot umbra & penumbra are not shown here)

0.1 1 10 100 1.103

1 .104

1 .105

4000

6000

8000

B 1001D 1002F 1003H 1004P 1005

B 1001D 1002F 1003H 1004P 1005

Pressure (dyn cm^-2)

Tem

per

atur

e (K

)

Semi-empirical, in-pixel. NLTE radiative transfer models built to account for the radiance observations.

Upper chromosphere Lower chromosphere

Transition region (radiation/conduction+diffusion+flows)

1.9.108

1.95.108

2 .108

2.05.108

2.1.108

2.15.108

2.2.108

1 .103

1 .104

1 .105

1 .106

Vernazza & Reeves dataDeere et alB 1001


Quiet Sun

Height (cm)

Tem

pera

ture

(K

)

hva hvas+ hda hdas+, h4,

1.82.108

1.83.108

1.84.108

1.85.108

1.86.108

1 .103

1 .104

1 .105

1 .106

AR Vernazza & Reeves dataAR Deere et alH 1004

AR Vernazza & Reeves dataAR Deere et alH 1004

Height (cm)

Tem

pera

ture

(K

)The low transition-region (T < 200,000 K) is strongly affected by optically thick NLTE radiative transfer and particle diffusion effects up to ~60,000 K. Above that the energy balance model is close to the DEM standard curves for comparable abundances (note that SRPM uses abundances similar to Dere values).

Upper transition-region

2 .108

4 .108

6 .108

8 .108

1 .109

1.2.109

1.4.109

5 .105

1 .106

1.5.106



Height (cm)

Tem

pera

ture

(K

)

5 .108

1 .109

1.5.109

5 .105

1 .106

1.5.106

2 .106

2.5.106

3 .106

AR Vernazza & Reeves dataAR Deere et alP 1015

AR Vernazza & Reeves dataAR Deere et alP 1015

Height (cm)

Tem

per

atu

re (

K)

Upper transition-region (T > 200,000 K) energy balance models are also close to the DEM ones with similar abundances. In the energy balance models conduction dominates at the bottom but local energy dissipation becomes important at the top.

Corona and upper transition region(radiation+conduction+solar wind)

The temperature reaches a maximum value (local energy dissipation is essential) and decreases again in the heliosphere. DEM cannot handle this behavior. Solar wind and coronal holes are features to consider. In active regions, groups of hot loops are the key feature.

5 .109

1 .1010

1.5.1010

2 .1010

2.5.1010

2 .106

4 .106

6 .106

AR Vernazza & Reeves dataAR Deere et alSRPM 1015

AR Vernazza & Reeves dataAR Deere et alSRPM 1015

Height (cm)

Tem

per

atur

e (K

)

Quiet Active

5 .109

1 .1010

1.5.1010

2 .1010

2.5.1010

2 .106

4 .106

6 .106

Vernazza & Reeves dataDeere et alSRPM 1001

Vernazza & Reeves dataDeere et alSRPM 1001

Height (cm)

Tem

pera

ture

(K

)

Courtesy of D. Braun

E

A

R

T

H

Courtesy of D. Braun

E

A

R

T

H

E

A

R

T

H

10 20 30 40 50 60 70 80 900.006

0.0065

0.007

0.0075

Current rotationShifted previous rotation

Days since 2005/8/1

Ly

alp

ha

irra

dia

nce

Assuming previous curve is bad

10 20 30 40 50 60 70 80 900.006

0.0065

0.007

0.0075

Current rotationShifted previous rotation

Days since 2005/8/1

Ly

alp

ha

irra

dia

nce

Assuming previous curve is badImages of the near-side produce daily masks of features

Using atmospheric models the spectrum is computed for any day

0.01 0.1 1 10 100 1.103

1 .104

1 .105

4

5

6 CEFH


Lo

g(T

)

1215.5 12161 .10

3

1 .104

1 .105

1 .106

1 .107

CEFH

Wavelength

Inte

nsi

ty (e

rg c

m^-

2 s^

-1 s

r^-1

)

0.01 0.1 1 10 100 1.103

1 .104

1 .105

4

5

6 CEFH


Lo

g(T

)

1215.5 12161 .10

3

1 .104

1 .105

1 .106

1 .107

CEFH

Wavelength

Inte

nsi

ty (e

rg c

m^-

2 s^

-1 s

r^-1

)

Without refinement the synoptic mask features obsolescence makes it bad

Synoptic masks are refined by applying trends and far-side imaging:

NOAA 10808

(far side)

NOAA 10808

(near side)

NOAA 10808

(far side)

NOAA 10808

(near side)

AR helioseismic image

AR backscattered image

Tools for forecasting solar irradiance

EUV radiance spectra of solar features

The models computed radiance matches the SOHO/SUMER spectra as the models were build for that. They provide other spectral ranges and extremely high resolution too. The QS combination of models (0.75 B+0.22 D+0.03 F) nearly matches the average QS in Curdt et al. atlas. (Preliminary spectra, work in progress..)

600 700 800 900 1000 1100 1200 1300 1400 1500 16000.1

1

10

100

1 .103

1 .104

1 .105

B 1001D 1002F 1003SUMER QS

B 1001D 1002F 1003SUMER QS

Wavelength (A)

Inte

nsi

ty (

mW

m^-

2 A

^-1

sr^-

1)

Features radiance spectra Combined QS radiance spectrum

600 700 800 900 1000 1100 1200 1300 1400 1500 16000.1

1

10

100

1 .103

1 .104

1 .105

SRPM QSSUMER QSSRPM QSSUMER QS

Wavelength (A)

Inte

nsi

ty (

mW

m^-

2 A

^-1

sr^-

1)

EUV irradiance spectra

The irradiance from a uniform disk is higher and lower for each feature but the combination at wavelengths longer than 50 nm is close to the recent Rocket flight during practically quiet Sun conditions. Shorter than 50 nm coronal/upper TR lines form a pseudo continuum.

20 30 40 50 60 70 80 90 1001 .10

8

1 .107

1 .106

1 .105

1 .104

1 .103

0.01

0.1

1

10

100

SRPM QSRocket flightSRPM QSRocket flight

Wavelength (nm)

Irra

dian

ce (

W m

^-2

nm^-

1)

Chromospheric +Lower transition-region

10 15 20 25 301 .10

8

1 .107

1 .106

1 .105

1 .104

1 .103

0.01

0.1

1

10

100

1 .103

B 1001Rocket flightB 1001Rocket flight

Wavelength (nm)

Irra

dia

nce

(W m

^-2

nm

^-1

)

10 15 20 25 30 35 401 .10

8

1 .107

1 .106

1 .105

1 .104

1 .103

0.01

0.1

1

10

100

1 .103


Wavelength (nm)

Irra

dia

nce

(W m

^-2

nm

^-1

)

Corona-upper TR only

High resolution examples

1455 1460 1465 1470 14750

200

400

600

SRPM QSSUMER QSSRPM QSSUMER QS

Wavelength (A)

Inte

nsi

ty (

mW

m^-

2 A

^-1

sr^-

1)

50 52 54 56 58 601 .10

8

1 .107

1 .106

1 .105

1 .104

1 .103

0.01

0.1

1

10

100

1 .103


Wavelength (nm)

Irra

dia

nce

(W m

^-2

nm

^-1

)

Chromosphericradiance example

Low transition-regionirradiance example

In general there is good agreement on lines but individual linescan be off because of uncertainties in atomic data (mainly collisional excitation rates). Also, so far we have not completed the runs for the spectra of upper transition-region+coronal parts of the models which contribute many lines.

Preliminary Active Region

1250 1300 1350 1400 1450 15001

10

100

1 .103

1 .104

1 .105

1 .106

SRPM QSH 1004SUMER QSSUMER Plage


Wavelength (A)

Inte

nsi

ty (

erg

s^-1

cm

^-2

A^-

1 s

r^-1

)

The UV chromospheric continuum matches fine in model P. However, improvement is needed in the lower transition-region of the active region models.

700 750 800 850 900 950 1000 1050 1100 1150 12001

10

100

1 .103

1 .104

1 .105

1 .106



Wavelength (A)In

ten

sity

(er

g s^

-1 c

m^-

2 A

^-1

sr^

-1)

Chromospheric Lower transition-region

solar radiation physical modeling: tools for understanding

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