IBEX discoveries over a half decade of observing the outer heliosphere

Transcription

1 IBEX discoveries over a half decade of observing the outer heliosphere David J. McComas 1,2,3 1 Southwest Research Institute, San Antonio, TX 78228, USA 2 University of Texas at San Antonio, San Antonio, TX 78249, USA 3 On behalf of the entire IBEX Project and Science Teams Dave McComas: 1 Queenstown, New Zeeland 2/11/15

2 IBEX Mission Summary NASA Small Explorer (SMEX) PI Mission (SwRI prime) ~$100M plus Pegasus launch International support: Switzerland, Poland, Germany, Russia Launched 19 October 2008 ~100 kg, <0.5 m 3 IBEX-developed capability included ~400 kg SRM and adapter Launched with cost under run Extended Mission since Jan 2011 >180 Refereed papers and counting Dave McComas: 2

3 Dave McComas: 3 Our Heliosphere

4 Dave McComas: 4 Galactic Cosmic Ray Shielding

5 ENAs From the Sun to IBEX Dave McComas: 5 10 billion mile hole in one

6 ENAs Illuminate Invisible Heliosheath J ENA = dx n H J ION Dave McComas: 6

7 Dave McComas: 7 Voyager 1 & 2 in Heliosheath

8 Dave McComas: 8 Mollweide all-sky projection showing locations of Voyagers Voyagers provide detailed information in these two directions

9 Dave McComas: 9

10 Independent Confirmation IBEX-Lo & Hi observations independently confirm ribbon (Hi at ~1.1 kev and Lo at ~0.9 kev shown) Dave McComas: 10 McComas et al., Science 2009

11 Dave McComas: 11 McComas et al., Science 2009

12 Ribbon Correlates with B r=0 Parker [1961] Interactions Dave McComas: 12 Schwadron et al., Science 2009 IBEX results indicate both external forces are important! McComas et al., Science 2009

13 The Start of a New Paradigm Dave McComas: 13 McComas et al., Science 2009

14 Science - IBEX Special Section Dave McComas: November 2009 Issue McComas et al., First Global Observations of the Interstellar Interaction from the Interstellar Boundary Explorer Fuselier et al., Width and Variation of the ENA Flux Ribbon Observed by the Interstellar Boundary Explorer Funsten et al., Structures and Spectral Variations of the Outer Heliosphere in the IBEX Energetic Neutral Atom Sky Maps Schwadron et al., Comparison of Interstellar Boundary Explorer Observations with 3-D Global Heliospheric Models Möbius et al., Direct Observations of Interstellar H, He, and O by the Interstellar Boundary Explorer Krimigis et al., Imaging the Interaction of the Heliosphere with the Interstellar Medium from Saturn with Cassini

15 Circularity of the IBEX ribbon Funsten et al., ApJ, 2013 Dave McComas: 15

16 Schwadron et al. Science, 2014 Global anisotropies in TeV cosmic rays related to the Sun s local galactic environment from IBEX IBEX Ribbon (B) and ISN flow direction consistent with interstellar modulation of TeV CRs and diffusive prop from supernova sources Simple model reproduces global anisotropy maps of ground-based highenergy cosmic-ray observatories (Milagro, Asg, and IceCube) Larger local interstellar magnetic field direction consistent with IBEX Dave McComas: 16

17 6 of 13 Proposed Ribbon Sources Dave McComas: others McComas et al., JGR 2010

18 Dave McComas: 18 More New Ribbon Ideas Emerge

19 McComas et al. Rev Geophys, 2014 Model / Scenario Strengths Weaknesses IHS 1: Shock-processed PUIs / ACRs Inner Heliosheath Produces ring of enhanced 1 kev ENA emissions resembling Ribbon. Relative intensities of ring and global emissions consistent with observations. Ordering of Ribbon by draped ISMF not explained. Uses idealized symmetric TS/HP geometry. IHS 2: Specularly reflected SW ions/puis IHS 3: Stagnation Region IHS 4: H-wave HP 1: Magnetic Reconnection HP 2: K-H & R-T Instabilities Explains enhancement of Ribbon emissions vis-à-vis globally distributed flux in terms of well-established shock-physical processes. Region of enhanced IHS plasma density to balance external JxB force may explain Ribbon s ordering by ISMF and enhanced intensity vis-à-vis global flux. Possible HP extrusions may explain fine structure. Predicts ring-like emission feature ordered by ISMF. Accounts for broadening of Ribbon at higher energies. Heliopause Potentially accounts for Ribbon s ordering by ISMF. May explain Ribbon fine structure. May explain Ribbon fine structure. Ribbon s ordering by ISMF not explicitly addressed. Uses ad hoc TS/HP geometry. LOS path length for global emissions not consistent with estimates of IHS thickness. Ring-beam distribution of Ribbon ENA source may not be stable (cf. OHS 2). Does not predict different energy spectra for the Ribbon and global flux. MHD models including external JxB force do not find enhanced pressure. Stagnation scenario still requires some missing non-mhd physics. To satisfy B r=0, assumes that normal of H-wave phase front is not significantly tilted from ISMF direction. Difference between Ribbon and global flux energy spectra not satisfactorily explained. Likely to produce multiple distributed source regions instead of continuous Ribbon owing to alternating IMF polarity. Does not explain Ribbon s shape and position and may not provide large enough structures for factor of 2 enhanced flux. Outer Heliosheath OHS 1: ISMF Compression Produces Ribbon ordered by draped ISMF as a result of conservation of first adiabatic invariant / increased density in compressed field region. (Cf. OHS 3) Assumes unspecified suprathermal source in OHS. OHS 2: Secondary ENAs OHS 3: Magnetic Mirror Produces narrow Ribbon ordered by draped ISMF. Can reproduce observed ordering of ENA energies by heliographic latitude. Produces Ribbon-like structure ordered by draped ISMF from PUIs transported along ISMF to regions of increased B (magnetic mirror points). (Cf. OHS 1) PUI ring-beam distribution must remain stable against pitch-angle scattering long enough for re-neutralization to occur. Assumes no pitch-angle scattering in OHS as limiting case. OHS 4: Retention Region ISM 1: LIC/LB Interaction Dave McComas: 19 Produces Ribbon ordered by draped ISMF. Does not require maintenance of ring-beam distribution. Reproduces observed ordering of ENA energies by heliographic latitude. Interface of Local Interstellar Cloud and Local Bubble Calculates ENA intensity profiles at 1 kev for viewing geometries that produce circular emission feature. Intensities are consistent with observations. Includes only neutral SW but not ENAs from IHS source. Modeled Ribbon thus narrower than observed. Does not explain Ribbon s apparent ordering by ISMF or features reflecting solar wind structure and temporal behavior. Overestimates ENA survival probability, especially for lowest energies.

20 Dave McComas: 20

21 Secondary ENAs McComas et al., Science, 2009; McComas et al., JGR 2010 Simulated IBEX Data BUT something missing still need to solve problem of source PADs Dave McComas: 21 Heerikhuisen et al., ApJ 2010

22 Latitude-Dependant & Direct Ribbon Source Dave McComas: 22 McComas et al., ApJS, 2012

23 Spatial Retention of Ions & the IBEX Ribbon Simulation IBEX Data Dave McComas: 23 Schwadron and McComas, ApJ, 2013

24 Dave McComas: 24 Additional Detailed Mechanisms

25 Spectral Slopes of ENAs Dave McComas: 25 McComas et al., Science 2009

26 Dave McComas: 26 Pickup Ions k Distributions

27 Livadiotis et al. ApJ, 2013 Pressure of the proton plasma in inner heliosheath Dave McComas: 27

28 Zirnstein et al. ApJL, 2014 Multi-component nature of the inner and outer heliosheath plasma and its effect on ENA flux Dave McComas: 28

29 Desai et al. ApJ, 2014 ENAs: Evidence for multiple heliosheath populations Suggests a significant fraction of kev ENAs may originate from ISNs charge-exchanging with a non-thermalized (hot) PUIs in the outer heliosheath Dave McComas: 29

30 Dave McComas: 30 Ribbon/GDF Separation

31 Dave McComas: 31 Flow Away from Pressure Max

32 Dave McComas: 32 Heliotail

33 Dave McComas: 33

34 McComas et al. ApJ, 2013 The heliotail revealed by IBEX Dave McComas: 34

35 Tail Structured by Slow/Fast SW E-folding losses (cooling length) ~ AU Starboard looking downtail Port looking downtail Dave McComas: 35

36 Dave McComas: 36 Local IS Field Twists Heliotail

37 Pogorelov et al. ApJ, 2013 Three-dimensional features of outer HSp due to coupling between the interstellar and interplanetary magnetic fields - Solar cycle model based on Ulysses obs Dave McComas: 37

38 Dave McComas: 38 LISM Interaction Alfven Wings?

39 Dave McComas: 39 5 Years of IBEX Data

40 5-Year Update ApJS Follows on from 2012 ApJS 3 year paper Complete and validated observations from first five years ( ) of IBEX mission Corrected ENA fluxes Time-variable CR background (updated) Survival prob from outer HSp (orbit-by-orbit) New ion gun background removal ENA maps, data, and supporting documentation full release of these data to broad community and provide the citable reference for data, data processing and use Examine time variations in epoch Dave McComas: 40

41 Ribbon Discontinuous through Tail Tail structure dominates across the downwind region with Ribbon continuous around rest of arc If the Ribbon produced by ENA emissions from the TS or inner heliosheath, no a priori reason that similar emissions would not also arise from the nearby tailward portions Dave McComas: 41

42 Leveling Off of ENA Fluxes Heliotail fluxes continue to drop owing to greater distance and longer recycling time for SW ions Dave McComas: 42

43 SW Dynamic Pressure and IMF Parameter Units /2013 Difference Rel. Change Dyn Press npa % B R nt % Dave McComas: 43 McComas et al., JGR 2013

44 2013 ENAs ~0.7 of 2009 Energy (kev) Ratio of weighted fluxes in annual SC Ram maps (Flux 2013 /Flux 2009 ) 1) Ribbon 2) Nose/Npole 3) S pole/flank 4) Heliotail All Sky ~ ± ± ± ± ± 0.01 ~ ± ± ± ± ± 0<.01 ~ ± ± ± ± ± <0.01 ~ ± < ± ± ± ± <0.01 ~ ± < ± ± ± ± <0.01 McComas et al. [ApJS, 2012] predicted 0.72 based on SW data and 2-4 year average time delay for SW ENA recycling Dave McComas: 44

45 Dave McComas: 45 Recycled Solar Wind

46 Dave McComas: 46 Ribbon Changes by Region

47 Dave McComas: 47 Ribbon Emissions over Time Leveling off near the nose/south, but continued drop at higher northern latitudes consistent with a great distance to the source of the Ribbon around the high latitude flanks on the downwind side of the north pole Consistent with an inner heliosheath or secondary ENA source at greater distances in the north than south Possible issue with the time variation from both the Ribbon and GDF not generally beginning with the highest energies (time dispersion) But - Möbius et al. [2013] pointed out secondary ENA Ribbon source might not show owing to more distant source for higher energies compared to lower energies could compensate for faster speed of higher energy ENAs and allow the change in slope or even turn up to appear to occur simultaneously

48 Dave McComas: 48 Motions of Sun and Local Clouds

49 IBEX ISN Observations Möbius et al., Science 2009 Dave McComas: 49

50 Ulysses/GAS Dave McComas: 50 Direct Sampling of ISNs First measurements of He [Witte et al. 2004] IBEX the Interstellar Boundary Explorer First measurements of H and O [Möbius et al. 2009] First measurements of Ne and the Ne/O ratio [Bochsler et al. 2012; Park et al. 2014] First observation of deuterium [Rodriquez et al. 2013;14] Detailed analyses of He [e.g., Möbius et al. 2009; Bzowski et al. 2012; Möbius et al. 2012; McComas et al. 2012] First measurements of secondary O (O from interstellar O+ charge exchange in outer heliosheath) [Möbius et al. 2009] Discovery of secondary He population: Warm Breeze [Kubiak et al. 2014]

51 Direct Detection of Interstellar Neutrals Dave McComas: 51 McComas, D.J., Editorial Lee, M. et al., An Analytical Model of Interstellar Gas in the Heliosphere Tailored to IBEX Observations Hlond, M., et al., Precision pointing of IBEX-Lo observations Möbius, E. et al., Interstellar Gas Flow Parameters Derived from IBEX- Lo Observations in 2009 and Analytical Analysis Bzowski, M., et al., Neutral interstellar helium parameters based on IBEX-Lo observations and test particle calculations Bochsler, P., et al., Estimation of the neon/oxygen abundance ratio at the heliospheric termination shock and in the local interstellar medium from IBEX observations Saul, L., et al., Local Interstellar Neutral Hydrogen sampled in-situ by IBEX

52 Dave McComas: 52 McComas et al., Science, 2012

53 4-D Tubes of Possible Parameters Interstellar T and flow speed as functions of ecliptic longitude IBEX observations allow narrow tube in the 4-D space of the interstellar flow vector and temp Shading represents 1 possible ranges Old Ulysses Value ISM o cos 1 ( 1/(1 R 2 EV ISM GM S )) o cos 1 ( 1/(1 V 2 ISM 2 )) V E tan ISM sin( ISM o ) Dave McComas: 53 T ( ISM ) V ( a a 0 2 ISM 1 ( ISM ISM ) ) VISM ( ( ISM ISM ) )

54 Zieger et al. GRL, 2013 A slow bow shock ahead of the heliosphere Modeled possibility of slow magnetosonic shock ahead of the heliosphere where angle between the interstellar magnetic field and the interstellar plasma flow velocity is quite small (e.g., 15 to 30 ). Produced spatially confined quasi-parallel slow BS Voyager 1 is heading toward while Voyager 2 isn t Dave McComas: 54

55 Leonard et al., 2015 (submitted) Lee et al. [2012] analytic model not good for S/C pointing out of ecliptic In ecliptic consistent values Dave McComas: 55

56 Ecliptic Pointing Flow Vectors Converge McComas et al. [2012] tube still consistent McComas et al., ApJ 2015 Dave McComas: 56

57 But Requires Much Warmer ISM He now isothermal with O/Ne Old Ulysses Value McComas et al., ApJ 2015 Dave McComas: 57

58 Dave McComas: 58 Implications ~26 km s -1 squarely back between speeds of LIC (~24) and the G-Cloud (~30) [Redfield & Linsky 2008] Reopens question of fast magnetosonic (MS) Bow Shock LISM He + reduces fast MS speed [Scherer and Fichtner 2014] Zank et al. [2013] showed shock mediated to wave via charge exchange and still consistent w/ H wall observations Consistent w/ remote sensing observations of warmer ISM [Redfield & Linsky 2004, Frisch et al., 2014] Warmer ISM requires either additional heating from the cloud interface or reduced cooling rates to maintain LIC equilibrium Roughly isothermal for He and O/Ne [Möbius et al. 2014] B ISM V ISM plane consistent w/ Ly-a data [Lallement et al., 2005] and IBEX Ribbon center He distribution complicated, suggesting multi-components and additional physics needed for lower flux wings

59 Rodriquez et al. A&A, 2013 Evidence of direct detection of deuterium in the LISM We find that D/HLISM =1.6 ± , which agrees with D/HLIC = 1.6 ± for the local interstellar cloud Dave McComas: 59

60 ISN Current Status IBEX has made groundbreaking first observations and discoveries about numerous interstellar neutral species Tight coupling of possible He inflow speed, longitude, latitude, and temperature along narrow 4-D tube ecliptic pointing data indicate region along tube is close to Ulysses speed/angles, but much hotter Recommend combined IBEX/Ulysses values of V ISM ~26 km s -1, ISM ~75, ISM ~ -5, and T He ~ K. Heliosphere in substantially warmer region of ISM that may be roughly isothermal (O/Ne temperatures similar) Complicated non-maxwellian distributions and possible multiple populations (e.g., Warm Breeze [Kubiak et al. 2014]) much more to discover!!! Dave McComas: 60

61 First: Neutral Atoms from Moon ENA Albedo ~ 10% Moon Emits ~150 ton/yr of Hydrogen First Observations of Neutralized/Reflected Solar Wind from Lunar Regolith Dave McComas: 61 McComas et al., GRL 2009

62 Firsts: Dayside Magnetosphere Northern cusp emissions Magnetopause emissions Southern cusp emissions First ENA imaging of Magnetopause: Fuselier et al., GRL 2010 First ENA imaging of Cusps: Petrinec et al., JGR 2011 Dave McComas: 62

63 First: Plasma Sheet Images Orbit 52 Orbit 51 Dave McComas: 63 McComas et al., JGR 2011

64 New IBEX Orit Stable to >2050 Discovery of new class of long term stable lunar-synch orbits June of successful IBEX maneuver into new orbit Dave McComas: 64 IBEX s journey of discovery continues McComas et al., Space Weather 2011

65 Dave McComas: 65