1. Plasma in the Heliosheath John Richardson M.I.T. Collaborators: J. Belcher, J. Kasper, E. Stone, C. Wang

2. Outline The termination shock Overview of the first year-plus of plasma data from the heliosheath V1 and V2 speed differences Flow angles and the TS shape Comparisons of the HSH and magnetosheath plasmas and implications for TS variability Summary

3. -3 Asia IHY School 2007 Sticking our Head out E. Möbius UNH/SSC Apropos: Sticking Our Head Out Heliosphere: pressure balance between solar wind and local interstellar medium. Magnetized plasmas cannot mix. Boundary is the Heliopause Shocks form in both flows, plasma moves downstream. Solar wind is observed (IGY).

4. V1 (94 AU) 84 AU Belcher Plasma Flow

6. Heliospheric Asymmetry. V1 enters TS foreshock region At 85 AU, V2 enters At 75 AU. Why? A LIC magnetic field at an angle to the flow can cause asymmetries. 84 AU 75 AU

7. -7 Asia IHY School 2007 Sticking our Head out E. Möbius UNH/SSC Shape of the Termination Shock TS is blunt, as evidenced by streaming of foreshock beams at V1 and V2

8. Simulation of sheath (Opher) Tilted LIC magnetic field gives asymmetry TS and HP closer in South than North. Magnitude of asymmetry was subject of controversy Large asymmetry implies large LIC B field. B

9. V2 V1 T N View from SUN: R is outward

10. HS on DOY 261, 2007 V(R,T,N) = 157, 59, -21 km/s N =.0041 /cc T = 240,000 K Heating occurs at shock PLS SPECTRA

11. V2 TS Overview Speed decrease starts 82 days, 0.7 AU before TS Crossing clear in plasma data Flow deflected as expected Crossing was at 84 AU, 10 AU closer than at V1 Speed decreases before shock Asymmetry Observed: V2 crosses the TS In Aug. 2007 at 84 AU

12. Days 242-245

13. Speed drops in discrete steps as shock approaches.

14. Total H+ energy (flow + thermal) Discrete steps AFTER increased B regions Lose 40% of energy before TS After TS, only 20% of energy in thermal plasma. Need T(pu) of order 6-10 keV.

15. Mach number wrt thermal plasma > 1 in heliosheath

16. Structures of TS crossings a few hours apart are very different: there appear to be two ramps in first crossing. Shock may be reforming downstream (Burlaga et al.)

17. Shock jump comparison Interplanetary shock (blue), Neptune’s bow shock (black), The TS (red) Normalized to SW upstream of the TS

18. Jupiter Saturn Uranus Neptune ICME TS N H /N C.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 1.8e5 Uranus has H corona - perhaps creates own pickup ions? Study of ICME sheaths may help understand this heating. Comparison of Reflected Ions Jupiter ICME Termination shock

19. Daily Averages |V| ~ 150 km/s N - decreasing; from.002 to.0011 /cc (Avg =.0016 /cc) Decrease in SW flux? T decreasing (Avg = 118,000 K)

20. Daily Averages VR fluctuates |Vr| = 137 km/s VT constant 51 km/s VN periodic -17 km/s Transient at 2008.62

21. Model (Pogorelov) 4  G, field in HDP, tilted 30 o from ecliptic plane V1 V R > V2 V R V1 |V N | >V2 |V T | V1 V2 V1 -V N V1 V T V2

22. V1 and V2 radial speeds are different V1 LECP Speeds in the heliosheath (Decker et al.) V2 PLS speeds in the heliosheath Vr -Vt LECP PLS

23. V1 (LECP) V2 (PLS) V R V T V R V T V N 67±16 -42±15 138 48 -14 V  V  V  -32º 20º -6º V1 - V2 comparison: Velocity

24. If the TS normal is not parallel to the upstream solar wind, the solar wind is deflected at the TS. If shock deflection gives initial flow angle in HSH, then 1) For V T after TS of 25 km/s, TS angle = 10  in RT plane 2) To make average V N angle, need 5.5° angle in RN plane. Suggests TS more blunt in T than N directions T N

25. Periodicities in RN and TN planes 110-day period Averages: -6 º, 20 º Amplitudes: 8º (R-N plane), 17º (T-N plane) |V| R-T angle R-N angle T-N

26. 110-120 day period in V N, V R (Lomb-Scargill) Power in V N, V R Vn

27. How to get oscillations? Change shock angle? (Deflection At TS depends on shock normal) Waves on shock? Change in TS shape? To make V N oscillation, need ±6º change in TS angle with a 110 day period.

28. Why 110 days? If fast mode speed determined by pickup ions, then round trip wave time from TS to HP is ~ 110 days. Changes in solar wind (heliospheric current sheet tilt, polar coronal hole boundaries, MIRs?)

29. TEMPERATURE DISTRIBUTIONS SW - 10,000K HSH - 100,000 K HSH - numerous very low T spectra Fluctuations (∆T/T) similar in SW and HSH, but likely a coincidence. T(HSH) = 13 T(SW) We look at HSH T distributions

30. Lots of scatter in T - caused by changes in TS motion? T depends on TS speed Using R-H relations, if TS speed varies ±100 km/s, T changes by a factor of 5 Good upper bound (inward motion 100 km/s) Lower bound not as good: faster outward motion or reforming shock Need very dynamic TS

31. VR (km/s) Jup Sat Ura Nep ICME TS 35 61 42 115 140 87 114 Jup HSH Comparison of plasmas in magnetosheaths and the heliosheath HSH scales larger by factor of 1000 VR less variable In HSH Boundary motion less important in HSH Speeds determined by large-scale motions VRVR

32. Relative Standard Deviation of VR Jupiter Saturn Uranus Neptune TS V2 0.38 0.46 2.2 0.14 0.19 V1 0.58 0.35 HSH Jup

33. Relative Standard Deviation of N Jupiter Saturn Uranus Neptune TS 0.62 0.41 0.41 0.13 0.52 0.43 0.67 185 DAY 186 210210 N Density variation also from small scale shock motion?  DEN similar in MSHs and HSH. Shock speeds similar? Density

34. Thermal speed w Place  (w)/ HSH 0.41 V1 Jup 0.26 V2 Jup 0.22 V1 Sat 0.10 V2 Sat 0.14 W more variable in HSH than in MSH  √5 variation fits data  √5 variation too big HSH V2 JUP MSH