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5. Heliosphere and Intersteller gas. Outline. Global Heliosphere; Neutral Intersteller gas; ENA imaging; IBEX mission and observation CASSINI mission and observation Summary. The Sun and Local Interstellar Medium (LISM). Image courtesy of L. Huff/P. Frisch. Our Heliosphere. Heliosphere. - PowerPoint PPT Presentation
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5. Heliosphere and Intersteller gas
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Outline
Global Heliosphere; Neutral Intersteller gas; ENA imaging; IBEX mission and observation CASSINI mission and observation Summary
The Sun and Local Interstellar Medium (LISM)
Image courtesy of L. Huff/P. Frisch
Our Heliosphere
Heliosphere
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Complicated Heliosphere – LISM Interaction■ Indirect observations
● Anomalous Cosmic Rays (ACR)
● Radio emissions
■ Inferred complications● Inner/Outer heliosheaths● Hydrogen wall
■ Until ~1 year ago, everything we thought we knew had been from models and indirect observations
Simulation courtesy of G. Zank.
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J.D. Richardson et al 2009
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Lyα spectrum of α Cen B, showing broad H I absorption at 1215.6 Å and D I absorption at 1215.25 Å.
Linsky and Wood (1996).
Supersonic solar wind must slow down and heat before it reaches the interstellar medium
Large numbers of interstellar neutrals drift into heliosphere Ly- backscatter interstellar pickup ions
Hot solar wind charge exchanges with interstellar neutrals to produce ENAs
Substantial ENA signal from outside the termination shock guaranteed from first principles
ENAs Illuminate the Global Termination Shock
Energetic Particles and ACRs
Energetic particle spectra just past TS Low energy particles fit
power law
High Energy ACRs Still modulated below ~100
MeV ACR spectrum not
“unfolded” into single power law as predicted
Decker et al., 2005
11J.D. Richardson et al 2009
Energetic particle flux looks like from Sun?
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Possible reason
J.D. Richardson et al 2009
IBEX missionRoutine Operations■ Nominal orbit – 25-50 Re x 7000
km altitude, 3-8 days per orbit■ Sun-pointing spinning S/C (4
rpm)■ Science Observations
> 10 Re■ Engineering < 10 Re
● Data download and command upload
● Adjust spin axis ~5° (Earth’s orbital motion)
■ Nearly full sky viewing each 6 months
Earth’s Magnetosphere
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Orbit of IBEX
How ENA Sensors Work
IBEX Payload
CEU:■ Provides electronic support and
control for payload■ Developed by SwRI
IBEX-Lo:■ Energy range: 0.01-2 keV■ Team: LMATC (Lead),
UNH, GSFC, APL
IBEX-Hi:■ Energy range: 0.3-6 keV■ Team: LANL (Lead), UNH, SwRI
IBEX’s Sole, Focused Science Objective IBEX’s sole, focused science objective is to discover the
global interaction between the solar wind and the interstellar medium.
IBEX achieves this objective by taking a set of global energetic neutral atom (ENA) images that answer four fundamental science questions:
I. What is the global strength and structure of the termination shock?
II. How are energetic protons accelerated at the termination shock?
III. What are the global properties of the solar wind flow beyond the termination shock and in the heliotail?
IV. How does the interstellar flow interact with the heliosphere beyond the heliopause?
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Low energy interstellar neutral gas
E. Moebius 2009
19E. Moebius 2009
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E. Moebius 2009
Neutral O flux as a function of velocity angle measured during optimum times twice each year. The filtered secondary population is slower, hotter and more strongly deflected than the primary population.
Interstellar Neutral Oxygen: Question Question -Interstellar Flow
and interaction First direct measurements of
filtered interstellar neutral oxygen
Measure speed, direction and temperature of the interstellar oxygen inside TS
Compare to unfiltered He Provide information about
filtration and the interstellar interaction further out, beyond the heliopause
22S.A. Fuselier 2009
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Recent IBEX observation
Energetic Neutral Atoms
Heating by Termination Shock
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Recent IBEX observation
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Energetic Neutral Atom (ENA) imaging
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Cassini-Huygens mission
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ENA imaging (INMS)
Fig. 1 Conventional concept of the heliosphere [(adapted from (3)]: The Sun is at the center, the region of the supersonic solar wind being asymmetric and compressed in the direction
facing the interstellar wind flow (nose).
S M Krimigis et al. Science 2009;326:971-973
Published by AAAS
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Fig. 2 (A) Image of heliospheric ENAs in the range of 5.2 to 13.5 keV (data from day 265, 2003, to day 184, 2009) plotted in ecliptic coordinates.
S M Krimigis et al. Science 2009;326:971-973
Published by AAAS
Fig. 3 Pressure contributed by protons beyond the TS computed from spectra deduced from the ENA observations in pPa (1 pPa = 10−11 dynes cm–2).
S M Krimigis et al. Science 2009;326:971-973
Published by AAAS
Fig. 4 Annotated summary of basic findings from the ENA maps of the heliosheath; the dominant interaction between the nonthermal heliosheath pressure with the ISMF tends to
produce a diamagnetic bubble, as envisioned by Parker (15), who neglected the effects of the ram pressure of the interstellar plasma.
S M Krimigis et al. Science 2009;326:971-973
Published by AAAS
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ENA imaging
ENA imaging is the only way to globally observe the interaction between the solar wind and the interstellar medium (structures, dynamics, energetic particle acceleration and charged particle propagation) in the complex region that separates our solar system from the galactic environment.
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For plasma sheet of the Earth’s magnetosphere
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Summary
ENA观测对星际间物质研究可以不受行星际磁场的影响;
ENA的观测帮助我们了解 Termination shock的离子加速机制及其本身的拓扑结构;
通过 ENA的观测了解 heliosphere的结构。