Page 1 Cristina Chifor (a) Ken Phillips (b), Brian Dennis (c) a) DAMTP, University of Cambridge, UK b) Mullard Space Science Lab, UK c) NASA/GSFC, Maryland, USA RHESSI Spectroscopy of Thermal Solar Flare X-ray Emission ‘X-ray Spectroscopy and Plasma Diagnostics From the RHESSI,RESIK and SPIRIT Instruments’ 6-8 December 2005 Wroclaw, Poland

Page 2  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

Page 3 RHESSI Reuven Ramaty High Energy Solar Spectroscopic Imager NASA Small Explorer Imaging and spectroscopic observations of solar flares since February 5 th, 2002 Principal Investigator: Robert Lin, UCB Lead Co-investigator: Brian Dennis, NASA/GSFC

Page 4 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 RHESSI Reuven Ramaty High Energy Solar Spectroscopic Imager

Page 5 Object Oriented Software & GUI Distributed through the Solar Software package SSWIDL (hessi) hessi_data_access.htm RHESSI DATA: 1.Flare catalogue 2. “Quicklook” plots 3.Level 0 Telemetry Data How to Access RHESSI Data ?

Page 6 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 ) RHESSI Data I: Flare Catalogue

Page 7 Daily FITS files in the metadata/catalogue directory of the RHESSI data archive RHESSI Data II: « Quicklook »

Page 8 Packets in FITS files (up to ~ 110 Mb) One FITS file/single orbit between local midnights Multiple FITS files for large flares GSFC (Maryland) ftp://hercules.ethz.ch/pub/hessi/data ETH (Switzerland) RHESSI Data III: Level 0 Telemetry Data

Page 9 STEP 1. Generate count rate spectra. hessi -> RHESSI GUI OUTPUT: Count spectrum file + Response Matrix (srm) file Spectral Analysis Overview I

Page 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.

Page 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 T e ?  How do empirical correlation curves compare with theoretical curves calculated with coronal Fe abundances ?

Page 12  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

Page 13  30 flares between  GOES X-ray classification: C3 – X8  More than 2000 spectra of 20 – 60 s in the decaying stages of these flares Sampled Flares

Page 14 I.RHESSI GUI: spectral file + SRM file Energy bins: 1/3 keV in the 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

Page 15  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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Page 17 May 31 st 2002 M2 Flare

Page 18 Chianti 5.0 Coronal abundances

Page 19 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.

Page 20 A number of coincident flares: cross-calibration possible. RHESSI low energy end ~5 keV RESIK in 1 st -order mode observes from 2.0 to 3.7 keV RESIK in 3 rd –order mode sees Fe line feature at 6.7 keV RHESSI vs. RESIK

Page 21 RHESSI vs. RESIK ord.1 vs. GOES

Page 22 Getting Help I: RHESSI Home Page

Page 23 Getting Help II: Data & Software Center

Page 24 RHESSI Nuggets

Page 25 Thank you ! Thank You !

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Page 27 Fe Line Complexes: RHESSI Observations Counts/s/cm 2 /keV

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