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SWCX in the XMM era

SWCX in the XMM era. K.D.Kuntz The Henry A. Rowland Department of Physics and Astronomy The Johns Hopkins University. LSSO-10/2007. ROSAT. The Long-Term Enhancement (LTE) Problem Long observations of the cosmic background showed long-term (~days) variation ROSAT All-Sky Survey

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SWCX in the XMM era

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  1. SWCX in the XMM era K.D.Kuntz The Henry A. Rowland Department of Physics and Astronomy The Johns Hopkins University LSSO-10/2007

  2. ROSAT • The Long-Term Enhancement (LTE) Problem • Long observations of the cosmic background showed long-term (~days) variation • ROSAT All-Sky Survey • Each point observed multiple times • Deconvolved temporal and spatial variation • Removed LTE to some base/threshold/bias level • Formed fiducial for correcting pointed observations • Difference between obs. And RASS = “LTE Level” LSSO-10/2007 ROSAT

  3. ROSAT • Observed LTE rate correlated with solar wind • But mechanism not clear (Freyberg 1994) • X-ray count rate towards the dark side of moon consistent with the calculated LTE rate • Implied cis-lunar origin • “Flaming” comets (Lisse 1996) • Mechanism elucidated by Cravens (1997): SWCX • Mechanism quickly applied to LTEs and LHB LSSO-10/2007 ROSAT

  4. SWCX ionSW+n + H → ionSW+n-1 + H+ + ν ionSW+n + He → ionSW+n-1 + He+ + ν Neutral H&He from: geocoronal/exospheric neutrals ISM flowing through heliosphere Emitted spectrum has no continuum Since solar wind highly variable in ρ,v, & z, over both t & (r,θ,φ) so to is the X-ray emission LSSO-10/2007 SWCX

  5. ROSAT SWCX Spectrum is temporally variable: ¼ keV and ¾ keV only partially correlated SWCX Flux = proton flux× ion abundance CorrelationNon-Correlation x6 x15 SWCX stronger below 0.25 keV than above, but strong in important lines at 0.56 and 0.65 keV LSSO-10/2007 ROSAT

  6. SWCX:Time Variability SWCXtotal = SWCXnon-localheliospheric +SWCXlocal heliospheric + SWCXexospheric Highly time variable R>5 AU Not variable: Integrated over 5-100 AU And many different SW conditions XMM measurable component Component remaining in RASS LSSO-10/2007 SWCX

  7. Discovery of SWCX in XMM • Four successive observations of the same part of the sky • First 3 observations statistically the same • Last observation substantially different (1st½) • Difference exactly the type of spectrum expected from SWCX LSSO-10/2007 HDF

  8. Discovery of SWCX in XMM • Four successive observations of the same part of the sky • First 3 observations statistically the same • Last observation substantially different (1st½) • Difference exactly the type of spectrum expected from SWCX LSSO-10/2007 HDF

  9. The HDF Event • Light-curve made little sense • XMM high then low • Solar wind (ACE) spikes at XMM drop LSSO-10/2007 HDF

  10. The HDF Event • Solution: X-ray observations integrate LOS • If solar wind wave-front tilted it can enter the X-ray FOV before hitting ACE • Collier, Snowden, & Kuntz • Solution makes no assumption about neutral distribution other than it must be local LSSO-10/2007 HDF

  11. The HDF Event • Koutroumpa et al (2007) propose similar solution, but attribute tilted wavefront to Parker Spiral structure • Solution assumes neutral material to be heliospheric LSSO-10/2007 HDF

  12. The HDF Event HDF4 • Special geometry confuses the issue Magnetopause Earth Orbit Bowshock Magnetopause ion density 4X free solar wind LSSO-10/2007 HDF

  13. The HDF Event HDF1 HDF2 HDF4 • But how is HDF4 different from others? All observations have similar observation geometry through “nose” of magnetosheath Difference is in the solar wind flux LSSO-10/2007 HDF

  14. The Question • In order to see SWCX enhancement • Need solar wind enhancement • Is the special geometry also required? • Exospheric or Heliospheric? LSSO-10/2007 HDF

  15. The Project Correlate SWCX enhancements with observation geom. in sets of observations with exactly the same FOV 10-11 sets of observations at high galactic latitude Analysis without accurate ∫magnetospheric density (for now!) LSSO-10/2007 HDF

  16. Program • Compare spectra from different observations • Top: (raw-inst.back)M1/responseM1 +(raw-inst.back)M2/responseM2 • Bottom: spectrum – min(spectra) = difference spectrum • Middle: uncertainties in difference spectra LSSO-10/2007 HDF

  17. Program • The other discrepant observation is actually through the flank of the magnetosheath! (solar wind at 85th percentile) • Special observation geometry is not required • HDF6 & HDF7 have similar geometry but no excess • Observation through nose does not produce SWCX excess HDF5 LSSO-10/2007 HDF

  18. Program • Two observations through the flanks of the magnetosheath • Solar wind flux extremely high (99th percentile). LSSO-10/2007 HDF

  19. Program • Four observations with long LOS through the flanks • One observation has extremely high solar wind flux – but no SWCX! • (Ignore purple spectrum – due to soft proton contamination) LSSO-10/2007 HDF

  20. Program • Three sets of observations with no problems • Typically low values of solar wind flux • Observation SEP2 has ~high solar wind flux but no sig. SWCX LSSO-10/2007 HDF

  21. Program • Three sets of observations where SWCX correlates with S.W. • Within each set, observation geometries similar LSSO-10/2007 HDF

  22. Summary • Bulk of strongly contaminated spectra from LOS through nose of magnetosheath • Some notable counter-examples! • SWCX contamination often correlated with s.w. strength Sure SWCX Possible SWCX Flank LOS LSSO-10/2007 Program

  23. Summary • A LOS through nose of magnetosheath seems to be more sensitive to solar wind enhancements (80th percentile) than an LOS through flanks of the magnetosheath. • LOS through flanks of magnetosheath with strong SWCX but not so strong solar wind enhancement may be due to localized nature of our measure of the solar wind flux • May also be due to special geometries • A LOS through the nose may have no more SWCX than a LOS through the flank. • Of 46 observations, 9-12 have SWCX • From a larger sample (15%-25%) • Need much more detailed modeling of the magnetosheath and the rest of the heliosphere to understand the relative contributions to the total SWCX. LSSO-10/2007 Summary

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