THE INNER AND OUTER HELIOSPHERE Elena Provornikova Boston
THE INNER AND OUTER HELIOSPHERE Elena Provornikova Boston University Moscow State University Student Day SHINE-2011, July 10 2011 MOSCOW STATE UNIVERSITY
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 Mc. Comas et al, JRL, 2003
Interplanetary magnetic field 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 Tornado-like structure Opher et al. 2003
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 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) Burlaga et al. , 1997
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 ke. V • 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 e. V to 1 Me. V • ACRs (Anomalous Cosmic Rays) - High energy ions with the energy � 1 -100 Me. V Acknowledge K. Schoeffler tutorial-2010
Lets travel to the boundary of the Heliosphere! r e g a y o V
Interaction of the solar wind with the local interstellar medium • Multi-component and RTS ~ 90 AU complex RHP ~ 150 AU • 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 n. H ~ 0. 1 -0. 2 cm -3 T ~ 6700 K Magnetic field: (Opher et al (2009))
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? No neutral atoms With neutral atoms! Baranov, Malama (1993)
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 a finite transition layer of zeroradial-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 Izmodenov et al. , 2005 The IMF pushes Termination shock and Heliopause toward the Sun in V 2 direction Opher et al. , 2006, 2007 Asymmetric Heliosphere 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
Voyager is almost there! Thank you! Any questions? !
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!
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