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Solar wind interaction with LISM: theory and

IBEX (NASA) and Voyager (NASA) data analyses

Izmodenov V.V.Space Research Institute (IKI) RAS

&Lomonosov Moscow State University

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Subject: the region where the solar wind interacts with the local interstellar medium

Davis (1955), Parker (1961) Baranov et al (1970, Doklady Acad.)

Question: Where does the solar wind stop and interstellnar mediumbegin? What are physical processes there?

(global heliosphere, heliospheric boundaries, heliospheric interface, helioheath, heliospheric boundary layer)

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Properties of the heliospheric boundaries are determinedby the properties of the local interstellar medium

Local interstellar medium is partially-ionized plasma

Interaction of the solar wind with LISM has multi-component behavior (plasma, interstellar atoms of hydrogen, energetic particles – pickup protons, ACR, ENA).

Model: 3D non-stationary kinetic-MHD model is needes => supercomputers are needed.

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Voyаger 1 (launched: 1977, now at 122 AU) Voyager 2 (launched: 1977, now at 99.74 AU),

Interstellar Boundary Explorer (IBEX, launched 2009, Earth’s orbit)

+ other spacecraft instruments or specific observations:

SOHO/SWAN, HST, Ulysses/GAS, Cassini

Spacecrafts exploring the heliospheric boundaries:

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Before 2007 we “knew” physics of the heliospheric boundaries

(=> most of the existing by that time experimental data could be explained in the frame of theoretical models)

The heliospheric termination shock crossing:

Voyager 1: December 2004, 94 AUVoyager 2: September 2007, AU. = > Strong asymmetry of the TS=> estimate of interstellar magnetic field of 4-5 mG

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Modeling of the interstellar magnetic field effect (Izmodenov et al., Space Sci. Rev., 2009)

ÞThe bow shock is absent

The conclusion was confirmed recently by McComas et al. (Science, 2012).

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Main goal of IBEX is remote (from the Earth’s orbit) mapping of the outer heliosphere in ENAs.

IDEA (Mike Grntman, 80s, IKI): Charge-exchange of interstellar

atoms with energetic protons at the heliospheric boundaries => ENAs are created => part of the ENAs return back to the heliosphere, where they can be measured.

КА Interstellar Boundary Explorer (launched Oct 18, 2008)

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IBEX measures fluxes of ENAs of hydrogen, helium,oxygen, etc. in the energy range of ~0.2 eV to ~6 keV. =>Full sky maps is obtained in 6 months.

IBEX – NASA SMEX mission

КА

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THESE ARE TYPICAL ENA MAPS WHICH WERE EXPECTED BEFORE IBEX

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Science, vol. 326, 2009

The first IBEX discovery: ENA ribbon \

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Possible correlation with Br=0

ÞThe ribbon is due to secondary ENAs from outside the heliopause (Heerikhuisen et al, 2010, Chalov et al. 2010)

Nature of the ribbon is not finally established

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More recent discoveries from the heliospheric boundaries

1. Starting from middle of 2011 Voyager 1 entered «stagnation region/layer» And it is probably near the heliopause;

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- For the first time, IBEX has measured interstellar oxygen

- Measurements of interstellar helium suggest that LISM parameters aresomewhat different from what we thought previously (based on Ulysses helium data)

КА IBEX: results of IBEX-Lo

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Measurements of ACR and GCR: Voyager 1 crossed the heliopause?

ACR

GCR

Strong reduction of ACR and simultaneous increase of GCR

Þ Does it mean that Voyager 1 crossed the heliopause?

Þ The final answer will be know after magnetic field data will be published.

ÞHowever, the location of the heliopause at 122 AU contradicts to all existing models of the global heliosphere (> 140 AU).

July- August 2012

15СПАСИБО ЗА ВНИМАНИЕ!