Solar Radiation Physical Modeling

(SRPM)

J. FontenlaJune 30, 2005a

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SRPM Objectives•Diagnosis of the physical conditions through the solar atmosphere, and in particular the radiative losses that must be explained by mechanical heating.

•Evaluating the role of proposed physical processes in defining the solar atmosphere structure and spectrum at all spatial and temporal scales.

•Synthesizing the solar irradiance spectrum and its variations in order to understand the physical processes behind the observations and improve the models.

•Computing the effects of until now unobserved conditions on the Sun by applying physically plausible hypothesis and knowledge of other stars.

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SRPM Scheme

Emitted Spectrum

Physical Models ObservedSpectrum

Intermediate Parameters

I(λ,μ,φ,t)

I(λ,μ,φ,t)T,ne,nh,U,...(x,y,z)

nlev, S, κ,,…(x,y,z)

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Basic Equations

Mass Conservation:

0

Ut

Momentum Conservation: PFΓUU

U

pt

Energy Conservation:

Qqpt H

FUU

Particle Conservation (or Statistical Equilibrium):

ilililil Rnt

n

UV

Radiation Transport: ''''''

ddIRII nnnnn n

MHD Version of Maxwell’s Equations:

ctc

c

iii

BUVEσJ

BE

JBB

;1

4;0

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Technology• Modular structure (currently 5 services)• Use of relational SQL database storage:

– Atomic and molecular data– Physical models and simulations– Intermediate data (e.g., level populations)

• Object Oriented C++ (currently ~300 classes)

• I/O interfaces to NETCDF and HDF5• Parallel computing + 3rd party libraries

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New Developments In SRPM Version 2

1. Constantly improving atomic and molecular data

2. Constantly improving physical models3. Detailed non-LTE for all species4. Abundance variation and non-local ionization

due to diffusion and flows 5. 3-dimensional non-LTE radiative transfer

extension of Net Radiative Brackett Operator6. MHD simulation based on standard Adaptive

Mesh Refinement

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Heritage

• Extensive work by many people on observations, radiative transfer, non-LTE, and modeling.

• Net Radiative Brackett Operator (NRBO) multilevel non-LTE method developed by JF for modeling solar prominences in the 70s.

• Energy balance and particle diffusion developed by JF for the transition-region in the 80s.

• Fontenla, Avrett, and Loeser (FAL) series of papers from the early 90s, the last paper (FAL4).(They used JF earlier methods and PANDORA.)

• Solar irradiance modeling C++ code from the late 90s (RISE).

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Magnetic Features on the Sun

Sunspots Active Regions

Network Coronal Loops

Prominences

•Medium spatial resolution structures produced by the magnetic fields are observed on the Sun.

•Effects of magnetic fields on the energy-transport and magnetic-heating at various layers are not well known.

•Physical processes responsible for the observed structure and spectra from these features are a major topic of SRPM research.

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Models try to describe a rangeof spectral characteristics

Histograms of brightness distribution in Ca II K3 and Ly alpha images of quiet Sun and active region

0.8 1 1.2 1.4 1.6 1.8 2 2.20

0.005

0.01

0.015

0.02

Active RegionQuiet Region

Ca II K3 Intensity (arbitrary units)

Relat

ive A

rea

0 1 2 3 4 5 6 7 8 9 10 11 120

0.005

0.01

0.015

0.02

Active RegionQuiet Region

Ly alpha Intensity (arbitrary units)

Relat

ive A

rea

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Models of Representative Features

C – quiet Sun cell center

E, F – Regular and active network

H, P – Plage and Faculae

R, S – Sunspot penumbra and umbra

Quiet Sun

Active Sun

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V1.5 1-dimensional Models

Model C - CLV Contrast - CLV

Line profiles Spectral irradiance

Physical model

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V1.5 Computed and Observed Lines

5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 59010

1 106

2 106

3 106

4 106

Model CObserved Kitt Peak

Wavelength (A)

Inten

sity (

...)

6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 65700

5 105

1 106

1.5 106

2 106

2.5 106

3 106

Model CObserved Kitt Peak

Wavelength (A)

Inten

sity (

...)

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V1.5 Computed and Observed IR Irradiance Spectra for Quiet Sun

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Power Delivered by each Model at 1 AU (W/m2)

Model 0.4-5μ 0.4-0.5μ 0.5-0.6μ 0.6-1μ 1-5μ

C 1297 186 196 485 430

E 1293 185 195 483 430

F 1294 185 195 483 430

H 12944 185 195 483 4302

P 1341 199 204 504 434

R 269 7 13 83 167

S 1079 131 153 407 388

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Spectral Irradiance SynthesisPSPT red band image

PSPT Ca II K image

Solar Features Mask on 2005/01/15

C E F H P R S

0.789 0.146 0.041 1.45e-2 6.44e-3 3.45e-3 9.03e-4

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Spectral Irradiance Synthesis

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Critical Next Steps

• Adjust photospheric models and abundances– Low first-ionization-potential (FIP) contribute to ne and

photospheric opacity– High FIP are needed for upper layers

• Re-think lower chromosphere– Account for radio data showing Tmin<4200 K– Account for UV continua from SOHO-SUMER showing high Tmin

– Account for molecular lines (CN, CH, CO) showing low Tmin

• Re-think upper chromosphere with current abundances and observations

• Re-compute transition region with updated abundances, atomic data, diffusion and flows, and energy-balance

• MHD, full-NLTE, 3D simulations of chromospheric variations