Low-energy Ion Distributions at the Termination Shock Rob Decker Johns Hopkins Univ., Applied Physics Lab., Laurel, MD SHINE, June-2008, Zermatt Resort, Utah

Introduction V1 and V2 have been in inner heliosheath (HSH) downstream the solar wind (SW) termination shock (TS) since V1 crossed TS in Dec [1-4] and V2 did so in Jul.-Aug [5-9]. Particle instruments on V1 began to measure high intensities of TS/HSH ions and electrons in pre-TS SW in mid-2002 at R 1 =85.2 AU, L 1 =N33.8°, and F 1 =172° ( ≅ const.). For comparison, coords. of LISM’s inflow direction are L LISM ≅ 0°, F LISM ≅ 175°. V1 crossed TS into HSH at R 1 =94.0 AU under disturbed SW conditions, as TS moved sunward over V1 due to decreasing solar wind dynamic pressure [10,11]. Sunward shift of asymmetric TS enabled V2 in SW at R 2 =75.3 AU, L 2 =S25.6°, and F 2 =215° ( ≅ const.), to enter TS foreshock, where V2 instruments began measuring TS/HSH particles [1,12]. The TS crossed V2 at least five times at R 2 =83.65 AU and L 2 =S27.5° [5-7] under comparatively calm SW conditions.

V1 & V2, Ions MeV,

Pre- & post-TS ≈ MeV ion spectra: V1, V2

Successive 78-day avg., post-TS energy spectra: V1 (squares), V2 (circles)

Voyager 1 & 2: ≈ MeV ion spectra: First 285 days in heliosheath

V1 & V2, selected channels,

Voyager 2 (through 2008 day 161) Top panel: protons 3-17 MeV Bottom 3 panels: Solar wind data –Speed –Proton density –Thermal proton speed

V2 ion & electrons: Intensities (left): 2007/ /161 Spectra (right): 2007/

V1 ions MeV: V2 ions MeV:

Predicted variations in TS Position at V1 and V2 Figure from: Washimi et al., Astrophys. J. 670, L139 (2007)

V1 & V2 1-hour angular data near TS crossings, ions ≈ MeV, electrons MeV

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