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

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” ROSAT LSSO-10/2007

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 ROSAT LSSO-10/2007

SWCX ion SW +n + H → ion SW +n-1 + H + + ν ion SW +n + He → ion SW +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 SWCX LSSO-10/2007

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

SWCX:Time Variability SWCX total = SWCX non-local heliospheric + SWCX local heliospheric + SWCX exospheric SWCX LSSO-10/2007 Highly time variable Component remaining in RASS R>5 AU Not variable: Integrated over AU And many different SW conditions XMM measurable component

Discovery of SWCX in XMM HDF LSSO-10/2007 Four successive observations of the same part of the sky First 3 observations statistically the same Last observation substantially different (1 st ½) Difference exactly the type of spectrum expected from SWCX

Discovery of SWCX in XMM HDF LSSO-10/2007 Four successive observations of the same part of the sky First 3 observations statistically the same Last observation substantially different (1 st ½) Difference exactly the type of spectrum expected from SWCX

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

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 HDF LSSO-10/2007 Solution makes no assumption about neutral distribution other than it must be local

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

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

The HDF Event But how is HDF4 different from others? HDF LSSO-10/2007 HDF1HDF2HDF4 All observations have similar observation geometry through “nose” of magnetosheath Difference is in the solar wind flux

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

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

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

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

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

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) HDF LSSO-10/2007

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 HDF LSSO-10/2007

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

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

Summary A LOS through nose of magnetosheath seems to be more sensitive to solar wind enhancements (80 th 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. Summary LSSO-10/2007