Low-energy Ion Distributions at the Termination Shock

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Low-energy Ion Distributions at the Termination
Shock

• Rob Decker
• Johns Hopkins Univ., Applied Physics Lab.,
  Laurel, MD
• SHINE, 23-27-June-2008, Zermatt Resort, Utah

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Introduction

• V1 and V2 have been in inner heliosheath (HSH)
  downstream the solar wind (SW) termination shock
  (TS) since V1 crossed TS in Dec. 2004 1-4 and
  V2 did so in Jul.-Aug. 2007 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 R185.2 AU, L1N33.8,
  and F1172 (? const.). For comparison, coords.
  of LISMs inflow direction are LLISM ? 0, FLISM
  ? 175.
• V1 crossed TS into HSH at R194.0 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 R275.3 AU, L2S25.6, and F2215 (?
  const.), to enter TS foreshock, where V2
  instruments began measuring TS/HSH particles
  1,12.
• The TS crossed V2 at least five times at R283.65
  AU and L2S27.5 5-7 under comparatively calm
  SW conditions.

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V1 V2, Ions 0.04-1.0 MeV, 2002-2008.44
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Pre- post-TS 0.04-4 MeV ion spectra V1, V2
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Successive 78-day avg., post-TS energy spectra
V1 (squares), V2 (circles)
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Voyager 1 2 0.03-4.0 MeV ion spectraFirst
285 days in heliosheath
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V1 V2, selected channels, 2005-2008.44
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Voyager 2(through 2008 day 161)

• Top panel protons 3-17 MeV
• Bottom 3 panels Solar wind data
• Speed
• Proton density
• Thermal proton speed

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V2 ion electronsIntensities (left)
2007/183-2008/161 Spectra (right) 2007/242-2008
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V1 ions 0.04-4.0 MeV 2004-2008.36
V2 ions 0.03-3.5 MeV 2007.5-2008.44
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Predicted variations in TS Position at V1 and V2
Figure from Washimi et al., Astrophys. J. 670,
L139 (2007).
2003
2004
2006
2007
2002
2005
2008
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V1 V2 1-hour angular data near TS crossings,
ions 0.03-1.8 MeV, electrons 0.4-1.5 MeV
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End