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Cristina Chifor (a) Ken Phillips (b) , Brian Dennis (c)

a) DAMTP, University of Cambridge, UKb) Mullard Space Science Lab, UK

c) NASA/GSFC, Maryland, USA

RHESSI Spectroscopy of Thermal RHESSI Spectroscopy of Thermal Solar Flare X-ray Emission Solar Flare X-ray Emission

‘X-ray Spectroscopy and Plasma Diagnostics From the RHESSI,RESIK and SPIRIT Instruments’ 6-8 December 2005

Wroclaw, Poland

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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

Presentation Outline

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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

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9 cylindrical cooled Ge detectors (< 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

RHESSIReuven Ramaty High Energy Solar Spectroscopic Imager

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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:1.Flare catalogue2. “Quicklook” plots3.Level 0 Telemetry Data

How to Access RHESSI Data ?

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Up to date text and binary FITS file Currently, containing more than 18,000 flares

INCLUDING…:

FLARE CATALOGUE NO.START, PEAK & END TIMESDURATION PEAK COUNT FLUX (C/S)ENERGY RANGE X, Y COORDINATES (ARCSEC)FLAGS (i.e attenuator state, night-time, SAA )

RHESSI Data I: Flare Catalogue

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

RHESSI Data II: « Quicklook »

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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) 

RHESSI Data III: Level 0 Telemetry Data

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STEP 1. Generate count rate spectra.

hessi -> RHESSI GUI

OUTPUT: Count spectrum file

+ Response Matrix (srm) file

Spectral Analysis Overview I

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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.

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"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 ?

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

Flare Sampling Criteria

Example: GOES fluxes, high-energy band (~ 25 keV) lightcurves for July 2002

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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

Sampled Flares

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I. 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 > 1000 counts/s)

II. 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

Spectral Modeling

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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)

Some Instrumental Issues

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May 31st 2002 M2 Flare

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Chianti 5.0

Coronal abundances

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Fe Line Complexes: Summary & Conclusions

Survey of > 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 EW’s 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.

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A number of coincident flares: cross-calibration possible.

RHESSI low energy end ~5 keVRESIK in 1st -order mode observes from 2.0 to 3.7 keV

RESIK in 3rd–order mode sees Fe line feature at 6.7 keV

RHESSI vs. RESIK

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RHESSI vs. RESIKord.1 vs. GOES

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

Getting Help I: RHESSI Home Page

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http://hesperia.gsfc.nasa.gov/rhessidatacenter/

Getting Help II: Data & Software Center

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RHESSI Nuggetshttp://sprg.ssl.berkeley.edu/~tohban/nuggets/

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Thank you ! Thank You !

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Fe Line Complexes: RHESSI Observations Co

unts

/s/c

m2 /k

eV

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