THE INNER AND OUTER THE INNER AND OUTER HELIOSPHEREHELIOSPHERE

Elena ProvornikovaElena ProvornikovaBoston UniversityBoston University

Moscow State UniversityMoscow State University

Student Day SHINE-2011, July 10 2011

MOSCOW STATEUNIVERSITY

Outline• Inner heliosphere

– Solar wind– Interplanetary magnetic field– Shocks and CIRs– PUIs, ENAs, ACR

• Outer heliosphere– Global model of the solar wind interaction with the local interstellar

medium– Observations: Voyagers, IBEX– Interstellar magnetic field – Non-stationary effects

• Conclusions

Solar wind. Parker`s model.

(Parker, 1958) Solar wind solution

But there is a local interstellar wind on the way!

Slow and fast solar wind

McComas et al, JRL, 2003

Interplanetary magnetic field

Tornado-like structure

Opher et al. 2003

At large distance from the Sun r>>RS

We can see that and

As we go outward in the solar system the magnetic field becomes more and more azimuthal

Solar wind structures: shocks, streams, CIRs

• Origin of shocks: ICME/CME, high-speed streams, corotating interaction regions, solar flares• Shocks: Forward and Reverse• Shock strength and shock speed change as the shocks propagate in the solar wind• Shock-shock interaction: Collision, merging, generation new discontinuities

Pizzo, 1978 Whang, 1991

Evolution of CIRs - CMIRs

Burlaga et al.,1997

Merging of two adjacent CIRs produces the Corotating Merged Interaction Region (CMIR) bounded by forward-reverse shock pair. CMIRs are the dominant dynamical structures between a few AU and 30 AU (Burlaga et al. 2003)

PUIs, ENA, ACR

• PUIs (Pick-up Ions) –Non thermal ions in environments like the solar wind formed by the pick-up process (charge exchange or photoionization) ~ 10 keV

• ENA (Energetic Neutral Atoms)– neutral atoms originating from high energy ions; in heliosphere- atoms, produced in charge-exchange of interstellar atoms and hot plasma protons in the heliosheath, from 10 eV to 1 MeV

• ACRs (Anomalous Cosmic Rays) - High energy ions with the energy 1-100 MeV

Acknowledge K. Schoeffler tutorial-2010

Lets travel to the boundary of the Heliosphere!

Interaction of the solar wind with the local interstellar medium

• Multi-component and complex• Interstellar gas: plasma,

neutrals, magnetic field, GCRs, dust

• Solar wind: plasma, interplanetary magnetic field, PUIs, ACRs

• Local interstellar medium:– np ~ 0.02 – 0.1 cm-3

– nH ~ 0.1-0.2 cm -3

– T ~ 6700 K

– Magnetic field:

~ 3.7 5.5 , ~ 20 30B G (Opher et al (2009))

RTS ~ 90 AURHP ~ 150 AU

Modeling:Interstellar hydrogen atoms

Interstellar neutral atoms determine or influence all physics of the heliospheric interface!

• Charge- exchange with the plasma ions

• H mean free path is comparable with the size of the heliospheric interface (~ 150 AU) => kinetic description!

Modern models take into account the interstellar magnetic field (Opher et al. 2007, 2009, Izmodenov et al. 2005, 2006; Pogorelov et al 2005, 2006, 2007), interplanetary magnetic field, PUIs (Malama et al. 2006), GCR, ACR, solar cycle variations etc.

How does the charge-exchange modify the plasma flow?

Baranov, Malama (1993)

No neutral atoms With neutral atoms!

Observations: Voyager 1, 2

• Crossing TS by Voyagers: – Voyager 1- 94 AU in

2004– Voyager 2- 84 AU in

2007• Asymmetric Heliosphere!

Possible reasons: – Time-dependent effects

(~ 3 AU)– Interstellar magnetic

field! Voyagers in the Heliosheath, NASA

Recent news! Voyager 1: Zero radial component of the plasma velocity

• Voyager 1 has entered afinite transition layer of zero-radial-velocity plasma flow, indicating that the spacecraft may be close to the heliopause, the border between the heliosheath and the interstellar plasma (Krimigis et al., Nature, 2011)

• At the same time - radial velocity at Voyager 2 ~ 100 km/s(Richardson, AGU talk, 2010)

IBEX: Global maps of ENA

The influence of Interstellar magnetic field is seen in IBEX maps!

Effect of the Interstellar magnetic field

The IMF pushes Termination shock and Heliopause toward the Sun in V2 direction

Izmodenov et al., 2005Opher et al., 2006, 2007

Asymmetric Heliosphere~ 3.7 5.5 , ~ 20 30IMFB G

The orientation and magnitude of the magnetic field is still under debate

Time-dependent effects: Breathing heliosphere

Solar wind dynamic pressure varies by factor of ~2 from solar maximum to solar minimum

Provornikova et al., 2010,AGU

Conclusions:• The Heliosphere combines a lot of physical processes, components and

structures • Observational data send us more and more challenges (IBEX ribbon,

recent Voayger plasma data)• To explain and predict the observational data we need to use correct

theoretical description for physical processes:– Kinetic description for interstellar neural atoms and PUIs– MHD is valid for the solar wind plasma– Interstellar magnetic field, latitudinal variation of the solar wind and 11 solar cycle

effects should be included in the model

• The problem of the solar wind interaction with the local interstellar medium is a good example when a combination of kinetic-MHD modeling and remote observations leads to the understanding of the structure of distant heliospheric boundaries

Thank you!Any

questions?!

Voyager is almost there!

Modeling:Interstellar hydrogen atoms

Interstellar neutral atoms determine or influence all physics of the heliospheric interface!

• Charge- exchange with the plasma ions

• H mean free path is comparable with the size of the heliospheric interface (~ 150 AU) => kinetic description!