Cristina ChiforCristina Chifor

SESI Student Intern 2005 SESI Student Intern 2005

Solar Physics, Code 612Solar Physics, Code 612

NASA/Goddard Space Flight CenterNASA/Goddard Space Flight Center

Mentors: Dr. Ken Phillips & Dr. Brian DennisMentors: Dr. Ken Phillips & Dr. Brian Dennis

FE AND FE/NI SPECTRAL LINE FE AND FE/NI SPECTRAL LINE COMPLEXES IN RHESSI SOFT X-COMPLEXES IN RHESSI SOFT X-RAYSRAYS

SOLAR FLARE X-RAYSSOLAR FLARE X-RAYS1. Non-Thermal Synchrotron radiation

Electron kinetic energy higher than average thermal energy of plasma

ELECTRONELECTRON

PROTONPROTON

PHOTONPHOTON

BREMSSTRAHLUNGBREMSSTRAHLUNG

2. 2. Thermal Depends on the random thermal motion of the heated electrons Maxwellian distribution of electron velocities

REUVEN RAMATY HIGH REUVEN RAMATY HIGH ENERGY SOLAR ENERGY SOLAR SPECTROSCOPIC IMAGERSPECTROSCOPIC IMAGER

X-ray/gamma-ray spectrometer : 3 keV – 17 MeV

9 Ge detectors

~ 1 keV resolution

Images through modulation collimators(~2 arcsec resolution)

Movable shutters control high photon fluxes

SPECTRAL MODELLINGSPECTRAL MODELLING

““One spectrum is worth a thousand images”…. A. Dupree.One spectrum is worth a thousand images”…. A. Dupree. Thermal

component of flare X-rays

( 3 keV -20 keV )

Physical plasma properties: T, emission measure, elemental abundances etc.

Analyze the Fe (~6.7 keV) and Fe/Ni (~8 keV) line complexes in the soft X-ray part of the solar flare spectra

from RHESSI.

MAIN PROJECT GOAL :MAIN PROJECT GOAL :

Why bother ?1. Valuable diagnostic information about emitting

plasma (e.g. T dependent)

2. Can determine the origin of flare plasma (since coronal Fe abundances ~ 4 x photospheric Fe abundances)

3. Better understand the RHESSI transmission as a function of energy in different attenuator states and the effects of increased count rates

FLARE SAMPLINGFLARE SAMPLING

Isothermal approximation OK in the late decay stages

So, hunt for long duration,

slowly decaying flares

IDL GUI to make quick plots of monthly GOES data

Any RHESSI data for

the selected times (no data gaps,

particle precipitation events, SAA) ?

Using the Geostationary Operational Environmental Satellites (GOES).

METHODMETHOD 1. 1. Count rate spectrum file + response matrix file

20 - 60 s time bins 0.3 keV energy bins

1 isothermal component + 2 Gaussian lines (1 keV FWHM) centered at ~ 6.7 and 8 keV

Reduce chi-squared

2. Background subtraction

3. Choose model functions to fit ~ 5 – 15 keV

4. Fit model to data:

In total, this summer: > 2000 spectra for > 30 flares5. Calculate complexes EQW + plot vs. T

THE BULK OF RESULTS:THE BULK OF RESULTS:

http://hesperia.gsfc.nasa.gov/hessi/chifor

COMPLICATIONS : COMPLICATIONS : MULTI-THERMAL FLARE PLASMAS MULTI-THERMAL FLARE PLASMAS

Most evident during flare rise, peak, soon after peak. Each T component in a multi-thermal plasma contribute to the

fluxes in the Fe and Fe/Ni complexes

To help with DEM analysis, we had guests this summer ! ! Dr. Janusz Sylwester (Polish Academy of Sciences)

RESIK (soft X-ray Bragg crystal spectrometer)

DEM – onology

RESIK vs RHESSI cross-calibrations

LiWei Lin (Harvard – Smithsonian Astrophysical Observatory)

Pint Of Ale

                   

         

MORE COMPLICATIONS: MORE COMPLICATIONS: INSTRUMENTALINSTRUMENTAL

High count rates in RHESSI detectors decrease energy resolution in the soft X-ray range and increase calculated T.

Line complexes difficult to detect. Fitting Gaussians vary in width.

Does this mean that results from lowest count rates (both sets of shutters in ) are most reliable ?

http://hesperia.gsfc.nasa.gov/hessi/chifor/may072002_html/feqw.htm

http://hesperia.gsfc.nasa.gov/hessi/chifor/nov112003_html/nov112003.htm

RHESSI instrumental effects are important (e.g. high count rates decrease energy resolution in the soft X-ray range). Multi – thermal flare plasma calls for DEM techniques. However, ok results where isothermal approximation appropriate.

Coronal origin of flare plasma (from calculated Fe abundances).

Fe and Fe/Ni EQWs vs. T follow theoretical diagnostic curves.

But, there may be a need for improved theoretical atomic calculations.

“RHESSI Observations of the Solar Flare Fe and Fe/Ni Lines” : paper to be submitted to the Astrophysical Journal soon.

CONCLUSIONS CONCLUSIONS

SPECIALSPECIALTHANK YOU:THANK YOU:

Dr. Ken PhillipsDr. Ken Phillips

Dr. Brian Dennis Dr. Brian Dennis

Ana RosasAna Rosas

Merrick BergMerrick Berg

CUA International OfficeCUA International Office

END OF PRESENTATION

Count rate spectral fit in OSPEX

RHESSI count flux vs. time

Ingredients % by number of atoms % by mass

Hydrogen - H 92.0 73.4

Helium - He 7.8 25.0

Oxygen - O 0.06 0.8

Carbon - C 0.03 0.3

Nitrogen - N 0.009 0.1

Neon - Ne 0.008 0.1

Silicon - Si 0.004 0.07

Iron - Fe 0.003 0.2

Magnesium - Mg  0.003 0.07

Sulfur - S 0.002 0.04

Argon - Ar 0.0008 0.032

Aluminum - Al 0.00025 0.007

Calcium - Ca 0.00021 0.008

Sodium - Na 0.00020 0.005

Nickel - Ni 0.00020 0.012

SUN RECIPESUN RECIPE