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Field-Aligned Current Systems: Comparison Between Earth and Mercury

Field-Aligned Current Systems: Comparison Between Earth and Mercury. Daniel Heyner. Field-Aligned Currents at Earth. Coupling of plasma regimes Momentum transfer Region 1: Close to pole (75°) Connected to magnetopause currents & neutral sheet Region 2:

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Field-Aligned Current Systems: Comparison Between Earth and Mercury

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  1. Field-AlignedCurrent Systems: ComparisonBetween Earth and Mercury Daniel Heyner

  2. Field-Aligned Currents at Earth • Coupling of plasmaregimes • Momentumtransfer • Region 1: • Close to pole (75°) • Connected to magnetopausecurrents& neutral sheet • Region 2: • Close to pole, butmoreequatorwardthanregion 1 (~60°) • Connected to ring current Clausen et al. (2012) Anderson et al. (2014) h=780km

  3. Current Closure: Earth FAC FAC Ionosphere(E-Region) Pederson Low. Atmosphere Crust & Mantle Core Current Closure via Pederson Currents in Ionosphere

  4. Magnetosphere of Mercury • In-Situ Data:Mariner 10 (1974/75)Messenger (2011-today)BepiColombo (2024) • Weakinternaldipole (190 nT) • Intense solar wind (psw = 14 nPa) • Small magnetosphere (Rss=1.4 RM) • No ring current (no region 2 currents?) • Intense (& lowshear) reconnection& dynamicmagnetosphere • Hot surface (max. T=700K) • Weakgravity (g=3.7 m/s2) • Exosphere • Lack of ionosphere |B| [nT] Z [RM] Richer et al. (2012) X [RM]

  5. Current Closure : Mercury FAC FAC Exosphere Pederson? Surf. Current? Crust & Mantle Core Current closure via surface currents, Pederson currents or both?

  6. Current Closure : Mercury FAC FAC Expected magnetic field signature: Messenger orbit Surf. Current? Bj,surface Surface alteration?

  7. Methods • 1D curl-B (Messenger), 2D curl-B (BepiColombo)(Ritter et al. (2013)) • Empirical mode decomposition • 3D Hybrid simulations • incorporation of realisticcrust & mantleconductivities • Incorporation of exosphere North Pole Sun

  8. First Impressions |B| in equatorial plane Thank You!

  9. Magnetospheric Current Systems

  10. Messenger 2nd extended mission

  11. Example conjunction under 200km (courtesy of H. Middleton) Z Y Z Y X X From Sun North pole, Sun to right Dawn terminator, Sun to right

  12. MMO-MPO Separation (Courtesy of H. Middleton) May 2024 – March 2026

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