Cristina Chifor (a)

1
RHESSI Spectroscopy of Thermal Solar Flare
X-ray Emission

• Cristina Chifor (a)
• Ken Phillips (b) , Brian Dennis (c)
• DAMTP, University of Cambridge, UK
• Mullard Space Science Lab, UK
• NASA/GSFC, Maryland, USA

X-ray Spectroscopy and Plasma Diagnostics From
the RHESSI,RESIK and SPIRIT Instruments 6-8
December 2005 Wroclaw, Poland
2
Presentation Outline

• Reuven Ramaty High Energy Solar Spectroscopic
  Imager Data Access and Analysis
• Fe Line Complexes Observations with RHESSI
• RHESSI / RESIK Cross - Calibration
• How to get more help with RHESSI data analysis

3
RHESSIReuven Ramaty High Energy Solar
Spectroscopic Imager

• NASA Small Explorer
• Imaging and spectroscopic observations of
  solar flares
• since February 5th, 2002
• Principal Investigator
• Robert Lin, UCB
• Lead Co-investigator
• Brian Dennis, NASA/GSFC

4
RHESSIReuven Ramaty High Energy Solar
Spectroscopic Imager

• 9 cylindrical cooled Ge detectors (lt 75 K)
• Energy range 5 keV to 17
  MeV
• ( 8 mÅ to 2.5 Å)
• FWHM 1 keV (12.4 Å) in the soft X-ray range
• (soft up to 20 keV)
• Movable shutters, high-rate electronics with
  pile-up suppression

5
How to Access RHESSI Data ?

• Object Oriented Software GUI
• Distributed through the Solar Software package
• SSWIDL (hessi)
• http//hesperia.gsfc.nasa.gov/ssw/hessi/doc/
• hessi_data_access.htm
• RHESSI DATA
• Flare catalogue
• Quicklook plots
• Level 0 Telemetry Data

6
RHESSI Data I Flare Catalogue

• Up to date text and binary FITS file
• Currently, containing more than 18,000 flares
• INCLUDING
• FLARE CATALOGUE NO.
• START, PEAK END TIMES
• DURATION
• PEAK COUNT FLUX (C/S)
• ENERGY RANGE
• X, Y COORDINATES (ARCSEC)
• FLAGS (i.e attenuator state, night-time, SAA )

7
RHESSI Data II  Quicklook 

• Daily FITS files in the metadata/catalogue
  directory of the RHESSI data archive

8
RHESSI Data III Level 0 Telemetry Data

• Packets in FITS files (up to 110 Mb)
• One FITS file/single orbit between local
  midnights
• Multiple FITS files for large flares
• http//hesperia.gsfc.nasa.gov/hessidata/
• GSFC (Maryland)
• ftp//hercules.ethz.ch/pub/hessi/data
• ETH (Switzerland) 

9
Spectral Analysis Overview I

• STEP 1. Generate count rate spectra.
• hessi -gt RHESSI GUI
• OUTPUT
• Count spectrum file
• Response Matrix (srm) file

10
Spectral Analysis Overview II

• STEP 2. OSPEX. Obtain photon spectra models.
• obj ospex()
• INPUT
• Count spectrum file
• Response Matrix
• (srm) file
• Until recently, used MEWE spectral model.
• Now changed to CHIANTI.

11

• "RHESSI Observations of the Iron - Line Feature
  at 6.7 keV,
• Phillips, K. J. H., Chifor, C. , Dennis, B. 
• submitted to the Astrophys. J
• Motivation
• RHESSI observes both continuum and Fe line
  complexes (at 6.7 keV and 8 keV)
• How does the empirical Fe/H abundance ratio in
  flares vary with Te ?
• How do empirical correlation curves compare with
  theoretical curves calculated with coronal Fe
  abundances ?

12
Flare Sampling Criteria

• Isothermal approximation OK in the late decay
  stages
• So, choose long duration, slowly decaying flares
• Used GOES to select flares according to this
  criteria

Example GOES fluxes, high-energy band ( 25 keV)
lightcurves for July 2002
13
Sampled Flares

• 30 flares between 2002 - 2005
• GOES X-ray classification C3 X8
• More than 2000 spectra of 20 60 s in the
  decaying stages of these flares

14
Spectral Modeling

• RHESSI GUI spectral file SRM file
• Energy bins 1/3 keV in the 3 - 20 keV
  range
• 1 keV in the 20 100 keV
  range
• Time bins 20 60 s
• Optional pulse pile-up corrections ( rate gt
  1000 counts/s)
• Input the 2 files in the Object Spectral
  Executive (OSPEX)
• Background subtraction
• One isothermal component to fit continuum
  2 Gaussian lines (1 keV FWHM) centered at 6.7
  and 8 keV to model the Fe and Fe/Ni complexes
• Reduced chi-squared for best fit

15
Some Instrumental Issues

• High count rates in RHESSI detectors decrease
  energy resolution in the soft X-ray range and
  increase calculated T.
• pulse pile-up problems at high count rates
• Therefore, for now, avoid A0 attenuator states
  (i.e. when no shutters are in front of detectors)

16
(No Transcript)
17
May 31st 2002 M2 Flare
18
Chianti 5.0 Coronal abundances
19
Fe Line Complexes Summary Conclusions

• Survey of gt 30 RHESSI flares (GOES class C3 -
  X5)
• Fe line features observed by RHESSI at 6.7 keV
  indicate a coronal abundance of Fe for the
  emitting flare plasma.
• Some differences between the observed and
  theoretical EWs of the lines may be due to
• Non-isothermal nature of the flare plasma (in
  particular at and shortly after the flare peak)
• Instrumental effects such as the resolving of
  the line features at high count rates
• Possible errors in atomic rates used in
  theoretical He-like Fe ion fractions.

20
RHESSI vs. RESIK

• A number of coincident flares cross-calibration
  possible.
• RHESSI low energy end 5 keV
• RESIK in 1st -order mode observes from 2.0 to 3.7
  keV
• RESIK in 3rdorder mode sees Fe line feature at
  6.7 keV

21
RHESSI vs. RESIKord.1 vs. GOES
22
http//hesperia.gsfc.nasa.gov/
Getting Help I RHESSI Home Page
23
http//hesperia.gsfc.nasa.gov/rhessidatacenter/
Getting Help II Data Software Center
24
RHESSI Nuggets
http//sprg.ssl.berkeley.edu/tohban/nuggets/
25

Thank you !
Thank You !
26
(No Transcript)
27
Fe Line Complexes RHESSI Observations
Counts/s/cm2/keV
28
(No Transcript)