Solar System X-ray Targets for AXIS

Transcription

1 Solar System X-ray Targets for AXIS C.M. Lisse (JHU APL) & B. Snios (Harvard-SAO) Comets Venus Scattering Mars Aurorae Charge Exchange Rings Disk Disk Saturn Jupiter S. Wolk 2009 Some of the currently known sources of X-rays in the Solar System. The complete list incl s the Sun, Planets, Comets, Moons, the Io Flux Torus, and the Heliosphere itself. [See review in PSS 55,1135 (2007) and update in Encyclopedia of the Solar System, 2014 by Bhardwaj et al.]

2 It all starts with Living With the Sun, an average G2V Main sequence star of 4.56 Gyr whose corona actively emits Lx ~10 27 erg/sec

3 and streams of Solar Wind H +, He +2, plus Highly Stripped Minor Ions (CV, NVI, OVII, NeIX, etc., at ~10-3 of the H + abundance) emitted at a total rate of MSW ~ M /yr into the Heliosphere & InterPlanetary Space. Ulysses - Solar wind properties at: Solar Minimum Solar Maximum Polar Solar Wind: fast (~700 km/s), low density, cold, less ionized, regular McComas et al Equatorial Solar Wind: Slow (~400 km/s), warm, more ionized, high density, quiet From coronal holes : fast, cold, less ionized, disturbed (like polar wind) With CMEs or flares : fast, hot, highly ionized, disturbed. Chandra 10th Symposium

4 Thus our Solar System is awash in MEASURABLE 10 6 K Solar Wind particles and High Energy photons from the Sun, driving NEARBY soft ( kev) X-ray emission in response from the interplanetary and heliospheric environments.

5 4 Main Soft X-ray Processes Govern Solar System X-ray Generation : Auroral Precipitation Charge Exchange Scattering Fluorescence Importance & Relevance : SW Diagnostics flux density, composition, charge state SW & X-ray Effects on Planetary Bodies (atmospheric ionization & destruction, high energy chemical alteration [Comets, MAVEN at Mars]) Heliosphere Structure & Dynamics (Sun in the ISM) Giant Planet Magnetohydrodynamics

6 Example #1 of Solar System Processes Producing X-rays: Charge Exchange Interaction between the Gravitationally Unbound Neutral Atmospheres of Comets and the Solar Wind km Ion Tail 10 6 km Bowshock km Dust Tail (Cravens 2000) Sola r Win d 10 km Nucleus 10 3 km Contact Surface Solar Wind Charge Exchange (SWCXE) is the Dominant Ionization Process for Outflowing Cometary Gases D/Linear S Chandra ACIS-S kev

7 Comets Display Diverse X-ray Morpholgies, Extents, and Luminosities 73P/SW Wolk et al P/Tuttle 2008 Christian et al P/Hartley Qgas (mol/sec) 2P/Encke 2003 Lisse et al.2013 C/ISON P/Tempel Lisse et al Deep Impact! Snios et al Predicted Morpholgical Neutral Gas Production Dependence C/Hyakutake 1996 B2 Lisse et al D/Linear S ~22 Yrs of Solar Wind Comet Neutral CXE Comet Morphologies : Sunward Facing, Coma Localized, Collisionally Thin or Thick Lisse et al Lisse et al. 1996

8 SWCX Depends on the Solar Wind (r,t,v) & Coma Density & Composition Coma Neutral Density Ions Are Not Fully Depleted At Nucleus SW Ion Flux A q+ + B A (q-1)+ (nl) + B + + hn SWCX cross sections are target and velocity dependent Quasi resonant Excited state X-ray: C 5,6+, O 7,8+, N 6,7+ FUV: He 2+, He +

9 ENAs! X-rays?? X-rays! ROSAT LTEs Cravens et al Heliosphere: In-Streaming neutral ISM H, He gas CXE s with the SW & emit X-rays SOHO/SWAN Ly-Alpha Koutroumpa et al. 2008

10 SWCXE spectral signature in heliospheric background observations. DXS Background XMM MOS, Snowden et al ACIS-S Lunar nightside emission, Wargelin et al (see also Wargelin et al Chandra this meeting)

11 Lunar X-rays : Scattering on Day Side + SWCX in Fore-Column on the Nightside Dayside : O, Si, Mg, Al fluorescence lines from lunar soil + rock. Non-zero Emission! Non-zero Emission! Nightside : ~1% Dayside Rate, Oxygen SWCXE lines.

12 Dennerl et al Chandra 10th Symposium

13 First evidence for Exospheric X-ray Emission from Another Planet: Disk = Scattering + Halo = Exopsheric Charge Exchange Chandra Observation Dennerl 2002 Chandra 10th Symposium

14 SWCX at Mars Singlet State 1s 2p 1 Triplet State O 6+ P1 SWCX: f+i/r = 5.8 (6 by thery; ~1 for thermal) 1s 2s 1 S s 2p 3 P0,1, Ǻ ev Ǻ ev 1s 2s 3 S 1 (2 photon continuum) 1s 2 1 S Ǻ ev Dennerl et al AOGS 2008

15 January 2001: first X-ray image of Venus (Chandra ACIS-I) First X-ray observation of Venus during solar maximum: Scattering of solar X-rays detected, but no conclusive evidence of SWCX. Solar X-rays Venus ACIS-I Dennerl et al. 2002, A&A 386, 319

16 Yohkoh SXT kev 1995 Venus emission Is dominated by a large x-ray scattering component due to Its proximity to the Sun Chandra ACIS-I kev GOES-7, 8, 10, kev Dennerl et al Chandra 10th Symposium

17 Second Chandra observation of Venus, 2006 March 27 (ACIS-S, 74.9 ks) First evidence for exospheric X-ray emission from Venus SWCX During Solar Max! O 6+ charge exchange N 6+ charge exchange limb disk Dennerl et al charge exchange fluorescence charge exchange 400* ev 615* ev 660* ev 900* ev * energies shifted by ~110 ev due to optical loading Chandra 10th Symposium

18 Jovian X-rays : Disk Scattering of Solar X-rays + Auroral Precipitation + Polar SWCX

19 Jovian Disk X-rays Correlate With Solar X-ray Output

20 and the Polar X-ray Spectrum can be fit by a Combination of Io s (not the Sun s!) O and S undergoing CXE (no solar wind C, Hui et al. 2009) at an Unexpected Polar Location. Hui et al. 2009

21 Io, Europa, Ganymede, and the Io Plasma Torus have been detected in the X-ray. Does the IPT provide the S, O atoms for Jupiter s Polar X-ray emission? Have we detected the root of Europa s Neutral Atom Torus (Mauk et al. 2003)?

22 and now X-ray (Bhardwaj et al. 2005), showing high variability and polar enhancement, and now recent new Cassini evidence of polar e- precipitation & UV auroral emission]). Chandra ACIS

23 Saturn s Rings Shine in Oxygen Ka Fluorescence

24 Saturn s X-ray Lightcurve Follows the Sun s Closely (Much More Than Jupiter)

25 Cassini s UVIS Observation of the Saturnian Aurora (Pryor et al. 2011)

26 Generalization: Do Exo-Jupiters Make X-rays? Giant Planet w/ strong magnetic field, rapid rotation, and moon source of neutral gas species? => Saturn + Enceladus should show intrinsic x-ray production, like Jupiter + Io (& Europa?) Or will a close-in hot Jupiter with a strong magnetic field + incommensurate orbital and stellar rotation periods do? Ex. : HD (Pilliteri et al. 2011)

27 Near-Future Solar System X-rays Low Hanging Fruit With AXIS Detection of X-ray Emission from Uranus & Neptune, examples of the most common type of exoplanets Heliosphere & Heliopause Spectral Profiles & Maps (+Nearby Astrospheres?) Saturnian Aurora Tracking Flares & CMEs through the Solar System Deep Comet Survey => Mapping the Solar System With Comet CXE : High Latitude & Main Belt Comets, Active Centaurs. Ceres = Comet Pizzaro?

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30 Pluto X-ray vs. optical flux levels for solar system objects detected in the X-ray. Pluto s relatively high X-ray/optical flux ratio is similar to that of comets and the Io plasma torus in the Jupiter system. (After Dennerl+ 2012)

31 Jovian UV and X-ray Emission are Coupled? Footprints are off. X-rays

32 1 st High Resolution Comet X-ray Spectrum: XMM/RGS of C/2000 WM1 Dennerl et al. 2010

33 The Study of Solar System X-rays is a Very Rich Field, Still Developing. Low Lx but important plasma &scattering processes. Next Up : Mercury, Uranus? High Latitude & Main Belt Comets? Trojan Asteroids? Active Centaurs? YSO dust evolution? Other Astrospheres & the Soft (1/4 kev) X-ray Background? Bhardwaj, Lisse, et al & Encyclopedia of the Solar System II, 2008

34 Current Work & Speculations Main Belt Comets not Detected by XMM (Dennerl et al. 2011) Heliopause complicated, ribbon-like structure?? Total energy in Heliosphere, other astrospheres, galaxy from CXU ~ erg/sec/sun*10 11 Suns = erg/sec (compare to Starburst rate) Assumes all stars have solar value but can different types of stars dominate? Lx ~ nsw * nneutral (assuming collisionally thin SWCX) where have both high? Protostars, AGB stars? HD lightcurve, WASP-12-b may be very good exosystem SWCX candidates both contain Jovian planets experiencing very high SW particle fluxes Giant planets all have SWCX Jupiter) but maybe not Ice Giants because of much different magnetic field structure?

35 Pluto ACIS-S Observation in Support of NASA New Horizons Flyby Mission 24 February ksec stare performed to detect CXE from SW vs mol/sec of N2 escaping Pluto s atmosphere SW monitored by New Horizons/PEPPSI 4 AU upstream of Pluto No obvious ACIS-S detection found. Maximal potential signal due to Pluto estimated as 3 photons above background. 3 photons over background => 1.8 x mol/sec N2 loss rate, a useful upper limit for Pluto global atmospheeic models preencounter

36 Pluto Track ACIS-S Pt Source Photometry in the Pluto Field BD ? B-V = 1.19 (K5V?) TYC ? B-V = 1.71 (M7V?) Box Photometry Very Bright PN or Galaxy?

37 X-ray grating spectrum of Venus (Chandra LETG/ACIS-S) C-Kα N-Kα? O-Kα O-Kα CO,CO2: 1s π*? Dennerl et al Chandra 10th Symposium

38 High resolution X-ray spectroscopy of Mars with RGS disk dispersion direction Dennerl et al Chandra 10th Symposium

39 High resolution X-ray spectroscopy of Mars with XMM/RGS? O N Ne O C 5+ C 4+ halo CO Dennerl et al Chandra 10th Symposium

40 X-ray images of Mars in individual emission lines (!) Emission centered on disk (scattering). Emission in crescent offset towards the Sun. Emission above and below Poles (!?) or in limb-effect crescent. Alas, no obvious variation of x-ray signal in/out of hemisphere covering dust storm.

41 SWCX Processes in the Earth s GeoCorona. Detection of heavy neutral atoms in the Earth s Magnetosphere implies interaction of the extended cold H envelope of the Earth with the solar wind via SWCX N.B. - SWCX more important than Jeans escape for terrestrial H loss budget. Evidence : - Atmosphere Explorer C Arecibo Incoherent Scatter Radar of e- and neutral H abundances (Maher and Tinsley 1977) - IMAGE/LENA observations of magnetosheath quiescent solar behavior (Collier et al. 2001) - IMAGE/HENA - CME response (Brandt 2001)

42 X-rays at the Earth : Auroral Precipitation + Atmospheric Scattering of Solar X-ray Radiation Chandra : Soft e- Auroral X-rays Polar PIXIE : 3-10 kev SW Particle Auroral X-rays Polar PIXIE : 3-10 kev In-Flare Scattering + Ar fluorescence

43 Simulated X-ray images using detailed atmospheric and exospheric models of Venus for.... scattering of solar X-rays (logarithmic intensity scale).. solar wind charge exchange (logarithmic intensity scale) ~ solar maximum Dennerl et al. 2002, A&A 386 Gunell et al. 2007, GRL 34 AOGS 2008

44 Simulated X-ray images using detailed atmospheric and exospheric models of Venus for.... scattering of solar X-rays (logarithmic intensity scale).. solar wind charge exchange (logarithmic intensity scale) ~ solar minimum Dennerl et al. 2002, A&A 386 Gunell et al. 2007, GRL 34 AOGS 2008

45 ACE: Space Weather at 9P/Tempel 1 Solar wind data from ACE Proton v, n Composition Map SW from ACE to comet SOHO EIT + LASCO Checks for Solar Oubursts

46 X-ray Luminosity Trending of 9P/Tempel 1 Chandra (triangles) SWIFT (squares) swift chandra SWCX model Proton Flux QGas. Natural Outburst Solar CME SOHO/LASCO Swift data from Willingale et al ( 06); Comet gas production from Schleicher ( 06) and Lisse ( 06) Deep Impact! Results : No prompt X-ray flash detected Increased X-ray flux 20% over 2 days à consistent with coma observations (Kuppers 05, Keller 05, Farnham 07) Good agreement between observed flux & SWCX model

47 Chandra Spectra of Comets: Three competing emission features: 1. C and N emission below 500 ev 2. O VII emission at 565 ev 3. O VIII emission at 654 ev low abundance of highly charged oxygen à cold wind Bodewits et al high abundance of highly charged oxygen à hot wind à flux ratios of all observed comets: C+N / O VII O VIII / O VII cold, fast, polar warm, slow, equatorial hot, fast, disturbed H H E E F F G G C C A A B B D D C+N ~ O VII O VIII / O VII flux increases C+N O VII Bodewits et al. 2007

48 Studies of Planets and Comets in the X-ray C.M. Lisse (JHU Applied Physics Laboratory); A. Bhardwaj (SPL, Vikram Sarabhai Space Centre); K. Dennerl (MPI für extraterrestrische Physik); S. J. Wolk (Chandra X-ray Center)D. J. Christian (Queens University Belfast);; D. Bodewits (NASA/GSFC); T.H. Zurbuchen (University of Michigan) Chandra s First Decade of Discovery Boston, MA, 25 Sept 2009

49 Questions from Talk: Careful with Lx ~ nsw * nneutral; only for collisionally thin systems, and for lowdust systems (Auger electron) Lgalaxy ~ 10^36 erg/sec assumes all stars like the Sun NOW. Need to take stellar luminosity function in x-rays and sum over the galaxy. Can detect SW-dust charge exchange from heating of dust? (Randall Smith) Does SW shock at a comet bowshock? How much heating of the ions does it cause? Can see heating in narrow lines, like O+7 at ~600 ev? Is Snowden et al. XMM SWCX flarng result from Geocoronal or Heliospheric emission? Not clear but do need a huge density of SW texplain it via heliosphere alone. (N.B. : Expect hard bowshock for the Earth, factor of 4-5 density enhancement in SW and cold H-atoms streaming from the Earth) If Helisopheric emission dominates & is strong, then should expect to see astropsheric emission from the Alpha Centauri system, but don t. Wargelin et al. worked this out & published it? SWCX: (f+i)/r = 5.8, Thermal : (f+i)/r ~ 1

50 Spectral Modeling & Lab Measurements of Cometary CXE LS4: EUVE/Chandra Solar Wind Coma OVII/OVII line ratios variable He +,background signal huge at E < 250 ev All lines, or lines + continuum? Fast vs slow solar wind - expect different spectra Auger e - quenching on dust, surfaces (Hale-Bopp)? Role of Collisions in the cometary atmosphere?

51 SOHO/CELIAS

52 X-ray Emission from the North Pole Number of Counts Theoretical CX spectra Oxygen and Sulfur Ions (Kharchenko et al. JGR 2008) Observations: Bhardwaj et al. (2005) Chandra S/O ratio = 0.28 <EO>=1.8 MeV/u <ES>=1.05 MeV/u Photon Energy [ kev ]

53 ~40-min Periodicity Seen in X-rays and THz Radio, But Not by Galileo and Cassini s/c in Any Other Passband!