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Observations of reflected ions downstream of shocks in the heliosphere John Richardson M.I.T. (Voyager plasma experiment) 10 – 5950 eV/q.

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Presentation on theme: "Observations of reflected ions downstream of shocks in the heliosphere John Richardson M.I.T. (Voyager plasma experiment) 10 – 5950 eV/q."— Presentation transcript:

1 Observations of reflected ions downstream of shocks in the heliosphere John Richardson M.I.T. (Voyager plasma experiment) 10 – 5950 eV/q

2 Sheaths and Scales 100s AU 10 -4 -.1 AU ~R S - 10s AU

3 Outline A) Reflected ions: 1.Earth 2.Outer planets 3.Termination Shock 4.Interplanetary shocks B) Shocks in local interstellar medium? Shakespeare?

4 Sir Isaac Newton: The Principia: Book 3, De mundi systemate

5 Reflected ions: In high Mach number shocks energy is dissipated via reflected ions. Some thermal ions are reflected by the shock potential at their first shock encounter and gain additional energy. (Fuselier and Schmidt, 1994)

6 Ratio of reflected to total ion density: Observations, simulation, and theory Ratio increases with Mach number to plateau at about 20-25% T(ref)/T(th) = 3-5 (Fuselier and Schmidt, 1994). Earth’s bow shock

7 Ion Distributions Ion distributions, Jovian magnetosheath Fit with 2 isotropic Maxwellian proton components. V(R,T,N) = (114, 87, 1) km/s, N=(.68,.79) cm-3, T=(100, 598) eV 54% reflected; T(ref)/T(th)= 6.0 10 eV 6 keV

8 Outer Planets Jupiter Saturn Uranus Neptune N H /N T.34.45 0.48 T H /T C 6.3 7.5 0 13.0 T 5.1e6 4.8e6 2.6e6 3.6e6 Comparison of Reflected Ions Jupiter % reflected ions and T H /T C increase with distance (with exception of Uranus).  >25%, not consistent with theory.  70-85% of energy in reflected ions

9 Downstream of termination shock No reflected ions observed in HSH T ~ 150,000 K V > Wth Most of SW energy goes into pickup ions, some of which are reflected. (Zank et al., 1996)

10 Interstellar neutrals dominate density outside ~10 AU Pickup ions dominate thermal pressure outside 30 AU First effects of LIC on solar wind are from these neutrals.

11 Energy/proton |B| Energy/proton decreases before and at TS: shock mediated by energetic particles (Florinski et al.). ~20 % of flow energy to thermal plasma: rest to pickup ions and energetic particles.

12 Interplanetary Shocks: Select largest (CME driven, mainly MIRs)

13 % of Reflected ions vs. distance: IP shocks and bow shocks 40 30 20 10 0 FF (IP) and FR (BS and TS) shocks 35

14 T(ref)/T(th) vs. distance: IP shocks and bow shocks

15 Jupiter Saturn Uranus Neptune ICME TS N H /N T.34.45 0.48 0 -.5 0 T H /T C 6.3 7.5 0 13.0 0-10 0 T 5.1e6 4.8e6 2.6e6 3.6e6 --- 1.5e5 Uranus has H corona - perhaps creates own pickup ions? Comparison of Reflected Ions Jupiter ICME Termination shock

16 Summary Reflected ions increase with distance to ~35 AU, then disappear. Pickup ions gain most of flow energy after 35 AU Weak shock-like structures observed in LISM with very large widths.


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