Solar wind interaction with LISM: theory and IBEX (NASA) andVoyager (NASA) data analyses Izmodenov V.V. Space Research Institute (IKI) RAS & Lomonosov Moscow State University
Subject: the region where the solar wind interacts with the local interstellar medium (global heliosphere, heliospheric boundaries, heliospheric interface, helioheath, heliospheric boundary layer) Question:Where does the solar wind stop and interstellnar medium begin? What are physical processes there? Baranov et al (1970, Doklady Acad.) Davis (1955), Parker (1961)
Properties of the heliospheric boundaries are determined by 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.
Spacecrafts exploring the heliospheric boundaries: Voyаger 1(launched: 1977, now at122 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
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 AU Voyager 2: September 2007, AU. = > Strong asymmetry of the TS=> estimate of interstellar magnetic field of 4-5 mG
Modeling of the interstellar magnetic field effect(Izmodenov et al., Space Sci. Rev., 2009) • The bow shock is absentThe conclusion was confirmed recently by McComas et al. (Science, 2012).
Main goal ofIBEX is remote (from the Earth’s orbit) mapping of the outer heliosphere in ENAs. КА Interstellar Boundary Explorer (launchedOct 18, 2008) 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.
IBEX – NASA SMEX mission КА • 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.
The first IBEX discovery: ENA ribbon \ Science, vol. 326, 2009
Nature of the ribbon is not finally established Possible correlation with Br=0 • The ribbon is due to secondary ENAs from outside the heliopause (Heerikhuisen et al, 2010, Chalov et al. 2010)
More recent discoveries from the heliospheric boundaries • Starting from middle of 2011 Voyager 1 entered «stagnation region/layer» • And it is probably near the heliopause;
КА IBEX: results ofIBEX-Lo • Measurements of interstellar helium suggest that LISM parameters are • somewhat different from what we thought previously (based on Ulysses helium data) • For the first time, IBEX has measured interstellar oxygen
Measurements of ACR and GCR: Voyager 1 crossed the heliopause? • Strong reduction of ACR and simultaneous increase of GCR • Does it mean that Voyager 1 crossed the heliopause? • The final answer will be know after magnetic field data will be published. • However, the location of the heliopause at 122 AU contradicts to all existing models of the global heliosphere (> 140 AU). July- August 2012 ACR GCR