NRLEUV and SDO/EVE

Harry Warren

Judith Lean, John Mariska

NRL

EVE Workshop

November 9-11, 2005

Overview

Overview of NRLEUV modelingIntroduction

Quiet Sun

Activity

Flares

NRLEUV and SDO/EVEPractical applications

Science applications

Modeling: Overview

The NRLEUV model uses emission measures to

compute intensities

= dTTTIee)()(

Emissivity

Differential Emission Measure

IR

RF

sun

2

2

=

The flux at Earth:

NRLEUV: Quiet Sun

Recently (2005) updated NRLEUV quiet

Sun spectrum

CDS and SUMER observations

CHIANTI 4

Results are generally consistent with

previous version

NRLEUV: Activity

NRLEUV 1 accounts for

solar activity

Skylab/HCO Spectra

CHIANTI 3.0

BBSO Ca II k and SXT full

disk images

F10.7 and Mg c/w ratio

Comparisons With TIMED SEE EGS

EGS generally

shows stronger

rotational

modulation

EGS irradiances

are generally

higher

NRLEUV: Solar Flares

Solar flares can be used

to test models of the

Earth’s upper atmosphere

Solar EUV irradiance

measurements during

flares are not common

New Methods for Simulating Solar

Flares

Instead of single loop

model the flare as a

succession of

independently heated

threads

Use GOES observations

to derive heating

parameters for each

filament in the simulation

Example

Simulation: 13-

Jan-92

Example

Simulation: 05-

Jan-92

Comparison with BCS S XV and Ca

XIX Spectra

Ionospheric

Simulation

Huba & Joyce (NRL)

SAMI3 ionosphere

model

Use irradiance spectra

calculated from multi-

filament simulation

(NRLEUV) + FUDGE

factor

Comparisons with GPS

data are encouraging

From Huba, Warren, & Joyce, GRL, 2005

NRLEUV & SDO/EVE: Practical

applications

NRLEUV modeling techniques can be used to

Check the consistency of EVE irradiance measurements

MEGS-A, MEGS-B, SAM, ESP

Extrapolate EVE irradiance measurements to other wavelength

ranges

Interpolate EVE irradiance measurements to higher spectral

resolution

Magnetic Fields and Irradiance Variability

The soft X-ray luminosity is

proportional to the total

unsigned magnetic flux

From Pevtsov at al., ApJ, 2003

Changes in the irradiance are driven by changes in the

surface magnetic fields

Two Levels of Understanding

Empirical Level

Use DEMs derived from AIA

to quantify the thermal

structure of the solar

atmosphere

Use flux-luminosity

relationships to quantify the

link between surface magnetic

fields and the solar irradiance

Physical Level

Use magnetic field

extrapolations and loop

models to calculate the

irradiance