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MESSENGER Observations of Extreme Space Weather at Mercury

MESSENGER Observations of Extreme Space Weather at Mercury. James A. Slavin Department of Atmospheric, Oceanic and Space Sciences University of Michigan. SERENA – HEWG Key Largo May 14 , 2013. Solar System’s Most Dynamic Magnetosphere.

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MESSENGER Observations of Extreme Space Weather at Mercury

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  1. MESSENGER Observationsof Extreme Space Weather at Mercury James A. Slavin Department of Atmospheric, Oceanic and Space Sciences University of Michigan SERENA – HEWG Key Largo May 14, 2013

  2. Solar System’s Most Dynamic Magnetosphere • Dipolar, axial aligned planetary magnetic field with the magnetic dipole offset 484 km north of the planetary center. • [Anderson et al., 2008; 2011] • Small magnetosphere drive by reconnection rate 10x Earth; Large flux transfer events at the dayside magnetopause; Plasmoids in the magnetotail. • [Slavin et al., 2009; 2010] • Large-amplitude ULF waves in equatorial magnetosphere and non-linear Kelvin-Helmholtz waves on magnetopause boundary – but only on the dusk-side. • [Boardsen et al., 2009; 2010; • Sundberg et al., 2011; 2012] Slavin et al. [2009]

  3. 2011_104 Orbit

  4. Example – Tail Crossings Crossing #1 λ2/λ1 = 11.13 λ3/λ2 = 6.99 |BN| = 0.54 nT Crossing #2 λ2/λ1 = 11.38 λ3/λ2 = 26.81 |BN| = 3.15 nT Crossing #3 λ2/λ1 = 17.40 λ3/λ2 = 6.31 |BN| = 2.83 nT Crossing #4 λ2/λ1 = 19.70 λ3/λ2 = 14.18 |BN| = 0.57 nT Crossing #5 λ2/λ1 = 27.75 λ3/λ2 = 4.67 |BN| = 0.91 nT Subscript 1 – Normal direction

  5. Dayside Crossing – Rotational Discontinuity λ2/λ1 = 25.18 λ3/λ2 = 17.41 |BN| = 15.94 nT Subscript 1 – Normal direction

  6. Does Reconnection works differently at Mercury? Earth: Strong dependence on interplanetary magnetic field direction. [Mozer et al., 2011] Mercury: Reconnection is most intense when the interplanetary magnetic field is strong, but there is little or no dependence upon its direction [DiBraccio et al., 2012].

  7. FTE identification

  8. FTE identification

  9. FTE Shower on April 11, 2011: IMF Bz > 0 Slavin et al. (2012)

  10. Plasmoid Shower in Current Sheet

  11. Example: DOY 2012 135 BX (nT) BY (nT) BZ (nT) Borg et al. 2012 |B| (nT) 13 March 2013 G. A. DiBraccio

  12. MVA: DOY 2012 135 B3 (nT) B2 (nT) B2 (nT) λ2/λ1 = 16.34 λ3/λ2 = 3.20 B1 (nT) 13 March 2013 G. A. DiBraccio

  13. Mercury Tail Loading/Unloading

  14. Dipolarizations • Repeated 1-s 40-nT increases in the Bz component, followed by a gradual (~10 s) decrease back are observed in the night-side plasma sheet. • [Sundberg et al., 2012]

  15. Mystery of Mariner 10 Energetic Particle Bursts Solved: The Particles are 30 – 300 keV Electrons! Ho et al. (2012)

  16. Why are extreme solar wind conditions important? • Does the magnetopause reach the surface of Mercury when SW ram pressure become extreme? If so, what is the effect on Sputtering and Space Weathering rates? • Are strong interplanetary magnetic fields with special orientations required to “erode” the dayside magnetosphere like at Earth? • Mercury’s metallic core extends to within 400 km of the surface; does electromagnetic induction in outer core play a significant role in shielding Mercury from the solar wind? • What effects do these extreme conditions have on magnetospheric configuration and dynamics?

  17. November 23, 2011

  18. Magnetosphere – Core Coupling at Mercury

  19. Induction Currents in Outer Layer of Core

  20. Stronger Solar Wind InputsStronger Induction

  21. Reconnection Vs. Induction

  22. Effect of Reconnection Vs. Conducting Core on Rss [Slavin and Holzer, 1979] [Schubert and Hood, 1979] [Goldstein and Suess, 1979]

  23. Effect of Induction on Magnetopause Altitude No Induction & No Erosion: Pss ~ 1/Rss**6 [Winslow et al., 2012] Induction [Glassmeier et al., 2007] Magnetopause Inflation by Induction Magnetopause Erosion by Reconnection

  24. Reconnection Vs. Induction Reconnection

  25. Magnetospheric Structure • Northward displacement of magnetic equator implies substantial N-S asymmetry in the surface field. • Surface field at north pole is 3.4x larger than at south pole. • Surface area of open magnetic flux in the southern hemisphere is 4x larger than in the northern hemisphere. • Weak southern polar field and larger open field area imply greater particle-stimulated surface sputtering in the southern polar regions. Anderson et al. [this meeting]

  26. Effect of 0.2 RM Magnetic Dipole Offset

  27. BepiColombowill Explore Mercury’s Exposed Southern Hemisphere!

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