Energetic Ion Fluxes in the TNO Region

The New Outer Heliosphere Meets the New Outer Solar System

John F. Cooper

Space Physics Data Facility Laboratory for Solar and Space Physics

NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A.

Acknowledgements

Matt Hill, John Richardson, Steve Sturner, Eric Christian, George Gloeckler, General Duff Green

Or

Space Weathering Fantasies,

Facts and SuggestionsNiagara FallsHoly Grail (Monty Python)

Related References

Giani Strazzulla, John F. Cooper, Eric R. Christian, and Robert E. Johnson, Ion irradiation of TNOs: from the fluxes measured in space to the laboratory experiments, Comptes Rendus Physique, 4, 791-801, 2003.

John F. Cooper, Eric R. Christian, John D. Richardson, and Chi Wang, Proton irradiation of Centaur, Kuiper Belt, and Oort Cloud Objects at Plasma to Cosmic Ray Energy, Earth, Moon, and Planets, 92, 261-277, June 2003.

Proceedings of the First Decadal Review of the Edgeworth-Kuiper-Belt - Towards New Frontiers, European Southern Observatory and

Universidad Catolica de Norte, Antofagasta, Chile, March 11 – 14, 2003.

John F. Cooper, Matthew E. Hill, John D. Richardson, and Steven Sturner, Heliospheric Space Weathering of Icy Bodies in the Kuiper Belt and Beyond, Review chapter in progress for the Kuiper Belt Book Project, Editors: A. Barucci, H. Boehnhardt, D. Cruikshank, and A. Morbidelli, Fall 2006.

International Workshop, Trans Neptunian Objects Dynamical and Physical properties, Hotel Nettuno, Catania, Italy, July 3-7, 2006

My Birthday Present

“But choose wisely, for while the true Grail will bring you life, the false Grail will take it”.

The Grail Knight’s Warning, Indiana Jones and the Last

Crusade, 1989

A Few Old Fantasies• For the Planetary Astronomer (mass focused)

a. Outer Solar System = lots of cool objects + total vacuumb. Space weathering may safely be ignored for observation of objects that have been in contact with the space environment for millions to billions of yearsc. Atmospheres can only arise from internal processesd. Ice chemistry far from stars has no other energy sources

• For the Heliophysicist (energy focused)a. Plasma-planetary interactions are minor defects on the perfection of the Sun-Heliosphere-LISM systemb. Solar wind termination shock is the holy grail of heliophysics and will explain everything (WMD theory)c. Interstellar neutral atoms are important, ions are notd. Cometary (e.g., Halley) and KBO bodies all have dark radiation mantles (previously a shared fantasy)

From Voyager Senior Review Proposal 2005

V1

V2

A New View of the Outer Heliosphere from Voyager

Heliospheric & Planetary Spacecraft Exploration of Solar System

Interstellar Boundary Explorer (IBEX), Neutral Atom Imager. Earth orbit launch in 2008

V-1

V-2

P-10

P-11

Ulysses

Future Facts – the ongoing New Horizons Mission

The Conventional View as of December 15, 2004

Interstellar energetic ions deflected away at heliopause

Interstellar neutral atoms injected into solar wind as pickup ions by ionization

from solar UV

Primary acceleration at

termination shock

L. F. Burlaga et al., Voyager Magnetometer Team

Decker et al. (2005)

Low Energy Charged Particle Detector (LECP)

Energetic Particle Measurements for the

Termination Shock Crossing Epoch

Locally, the shock appeared as a boundary,

not a source, for enhanced particle fluxes in the post-shock region, the heliosheath.

Voyager LECP-CRS

38 – 74 AU cosmic ray proton spectra vary more with solar cycle phase than with heliocentric distance

Solar cycle averaging needed for cumulative surface irradiation modeling

LECP heliosheath spectra (M. E. Hill) approaching Cooper et al. (2003) limits on local interstellar spectra!

What is the actual source,

TS/HS acceleration ?

Local interstellar ?

Galactic interstellar ?

Cosmic Ray Flux Evolution vs. Time and Position

LISM Proton Fluxes

Local interstellar flow 26 km/s, density 0.1/cc, and temperature ~ 104 K limit low energy flux

E-2.7 GCR spectrum at GeV energies fixed by high altitude balloon cosmic ray fluxes

Interstellar limit spectrum close to Gloeckler et al.’s E–1.5 ‘universal’ spectrum over eight orders of magnitude !!!

Asymptotic limit of heliosheath H spectra ?

Is TS/HS acceleration really needed to explain the TSP and ACR data?

preshock

Full Particle Flux Evolution, Foreshock to LISM

Universal Suprathermal Cascade Spectra Measurements in Inner Heliosphere

Fisk et al. (2006)

Same spectral forms (J ~ E–1.5 differential flux) observed in outer heliosphere

Suggestion – Niagara Falls Model for Heliosheath Particle Fluxes

• Interstellar hot ions flow in through semi-permeable heliopause boundary

• Heliosheath ions evolve from interstellar source via common cascade spectra

• Acceleration at the termination shock is neither yet observed nor necessary

Upstream LISM Heliosheath

Cascade

Downstream Heliosphere

Now on to the True Holy Grail(The Color Diversity Code)

Pluto

Neptune

Uranus

Saturn

Jupiter

Fig. 1. B–R histograms. (a) Centaurs have bimodal colors. (b) Dynamical cold objects with small-i, small-e, and q > 40 AU are red, B – R > 1.5. (c) Dynamically hot objects with large-i, large-e, and Q > 70 AU are mostly gray, B – R < 1.5.

Tegler et al., ApJ, 599, L49-L52, 2003.Keck, Steward, and Vatican !!! Observatory B–R Color Spectra for 91 Total Objects

21 of 21 “dynamically cold old” q > 40 AU KBOs are red.

17 of 20 “dynamically hot” Scattered Disk (Q > 70) Objects are grey.

Centaurs (a < 40) may ??? be bimodal dependent on measurement error analysis.

Diameters

MPC On-Line Catalog: May 7, 2O06 990 Transneptunian Objects 167 Centaurs & Scattered-Disk Objects

Other Large Objects

2004 DW D = 1500 km Ixion D = 1065 km 2002 AW197 D = 890 km Varuna D = 900 km

2,400 ± 100 km

A = 0.86±0.07

A = 0.60

A = 0.12

A > 0.2A = 0.1

A = 0.8

A = 0.7

A = 0.4

Other albedoes: Europa (0.68), Enceladus (1.0), Tethys (0.9)

Elliot et al., Nature 424, 165-168, 2003.

Seasonal effect of Pluto’s 248-year eccentric (29.7 – 49.7) AU orbit around the Sun ?

Atmospheric T = +1.3º (N2 frost) surface albedo change,

0.64 to 0.59 ?

Solar cycle irradiation effects on atmospheric heating and/or surface chemistry?

Radiolytic Gas Exospheres on Kuiper Belt Objects ?

100 eV produces ~ 0.1 H2 molecules in irradiated H2O ice.

Solar UV lifetime for H2 ~ 5x1010 sec at 100 AU

Heliosheath proton energy flux ~ 3x106 100-eV/cm2-s

Exospheric column density < 1.5x1016 H2/cm2

Compare to ~ 1015 O2/cm2 for Europa from Jovian magnetospheric ion sputtering

H2 will tend to escape but other species (O2, N2, CO2,

CO) could be surface bound by cold trapping.

Other atmospheric sources, e,.g. from outgassing ?

Enceladus Outgassing of Water Vapor from South Pole

Cassini Orbiter Images - 2005

Radiation-driven plumes on EnceladusRadiation-driven plumes on Enceladus

Energetic electron and ion bombardment

H2

O2

O3

H2O2

HO2

OHHO3

Oxidants

Fuel

NH3 – H2O slush

H2O Mass flux = 150 – 350 kg/s

240 m/s Escape Speed

Input Power 0.04–0.09 mW/m2

Magnetospheric e-

2 mW/m2

Galactic Cosmic Rays 0.5 mW/m2

G(H2O2) ~ 0.1 0.25 mW/m2

Decker et al. (2005)

Low Energy Charged Particle Detector (LECP)

Energetic Particle Measurements for the

Termination Shock Crossing Epoch

Locally, the shock appeared as a boundary,

not a source, for enhanced particle fluxes in the post-shock region, the heliosheath.

Concluding Facts and Suggestions

• Many Scattered Disk Objects traverse the heliosheath and some reach the LISM

• Heliosheath proton fluxes approaching extrapolated absolute flux and spectral shape of the LISM flux

• Termination shock acceleration may not be the dominant ion source for the outer heliosphere

• Proton fluxes generally increase from the Classical Kuiper Belt towards the LISM and towards the Sun

• Cold, old Classicals may be red due to deep cosmic ray irradiation, thin top crust, and erosion

• Sputtering and micrometeoroid impacts could work as rotationally-averaged erosion processes

• Europa to Pluto atmospheres, and Enceladus-like outgassing plumes, could be radiation driven and likely contribute to high albedo and color diversity