Presentation on theme: "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,"— Presentation transcript:
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) http://hesperia.gsfc.nasa.gov/ssw/hessi/doc/ 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 http://hesperia.gsfc.nasa.gov/hessidata/ GSFC (Maryland) ftp://hercules.ethz.ch/pub/hessi/data ETH (Switzerland) RHESSI Data III: Level 0 Telemetry Data
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 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
Page 14 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
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
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