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GEM 2013 Summer Workshop

GEM 2013 Summer Workshop. Student Tutorial __ _ Sunday 16 June 2013. The Outer Magnetosphere. David A. Mackler PhD Candidate The University of Texas at San Antonio Southwest Research Institute mackler.david@gmail.com. Outer Magnetospheric Structures.

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GEM 2013 Summer Workshop

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  1. GEM 2013 Summer Workshop Student Tutorial __ _ Sunday 16 June 2013 The Outer Magnetosphere David A. Mackler PhD Candidate The University of Texas at San Antonio Southwest Research Institute mackler.david@gmail.com

  2. Outer Magnetospheric Structures Student Tutorial __ _ Sunday 16 June 2013 • Bow Shock • Magnetosheath • Magnetopause • Magnetospheric Boundary Layers • Low-Latitude Boundary Layer (LLBL) • High-Latitude Boundary Layer (Plasma Mantle) • Exterior Cusp • Magnetotail

  3. Bow Shock Student Tutorial __ _ Sunday 16 June 2013 Solar wind is supersonic; standing shock front forms when the solar wind impinges on our magnetosphere and diverts plasma • Plasma in this region is largely collisionless; no viscosity for energy dissipation, wave modes are Alfvénic rather than sonic • Stands ~15-20 Re upstream. The shape is roughly parabolic • Fast mode shock: Shock front travels faster than the MHD fast mode wave https://ase.tufts.edu/cosmos/view_picture.asp?id=112 Slow Mode Fast Mode

  4. Bow Shock Student Tutorial __ _ Sunday 16 June 2013 • Bow shock slows and heats the solar wind plasma, strongest gradient near the sub-solar point • Bow shock includes perpendicular [dusk] and parallel [dawn] components. Perpendicular shocks increase both density and field strength • Perpendicular shocks above Critical Alfvén Mach number ~2.7: Super-Critical. Earth’s bow shock is typically super-critical Spreiter et al., [1966] Sckopke et al., [1983]

  5. Magnetosheath Student Tutorial __ _ Sunday 16 June 2013 Turbulent region of space between the bow shock and the magnetopause. Parameters fluctuate due to changes in the solar wind • Magnetic reconnection: When IMF Bz is south field lines carry magnetosheath particles into high latitude regions • Profound coupling to the ionosphere Particles are the shocked solar wind with contributions from the ionosphere [O+] when IMF Bz is NORTH and magnetosphere (higher eV) when IMF Bz is SOUTH

  6. Magnetosheath Student Tutorial __ _ Sunday 16 June 2013 • SW Vs. MS: Bt ↑, un ↓, T ↑, ρ ↑ • SW ~1.5 – 10 keV ~10 cm-3 ~400-750 km/s ~5-10 nT • MS ~0.1 - 1 keV ~20 cm-3 ~200-300 km/s ~20-40 nT B field is weaker than the magnetosphere IMF draping across and interacting with the magnetopause – Plasma Depletion Layer Magnetosheath particles entering the daysidecusps contribute to the dayside auroral precipitation (E < 0.5 keV ‘soft electrons’ mostly 6300 Å) Hu et al. [2009] BS MP Wang et al.[2003]

  7. Magnetopause Student Tutorial __ _ Sunday 16 June 2013 • Abrupt magnetic boundary between the Earth’s magnetosphere and the surrounding plasma • Controls the transport of mass/momentum/energy ~800 km 10’s km/s • IMF Bz North: • Closed field lines • No mass transport • Momentum and energy transported by waves • IMF Bz South: • Open field lines • Mass, momentum, and energy transport • Reconnection • Bn = 0: • Tangential Discontinuity, no mass transfer • Bn ≠ 0: • Rotational Discontinuity, transfer across MP Stand off distance can be approximated by pressure balance ~10 Re

  8. Magnetospheric Boundary Layers Student Tutorial __ _ Sunday 16 June 2013 • Not actual ‘Boundaries’ • Regions near Earth influenced by magnetosheath plasma • Connected by magnetopause reconnection • Map to high latitude regions near the cusp Newell and Meng, 1992 • Low Latitude Boundary Layer (LLBL) • Low latitude dayside, extending into dawn/dusk • Partially thermalized with MS • Sharp inner boundary • Flow can be seen in all directions, generally • tailward(~100 km up to MS) • less dense than MS (~0.5 - 10 cm3) • Energy similar to MS (~0.1 – 1 keV) Hasegawa, 2012

  9. Magnetospheric Boundary Layers Student Tutorial __ _ Sunday 16 June 2013 • IMF Bz South (open field lines): • Low lat. Reconnection • Higher velocity flow, KH instability might not grow • LLBL is thin (< 1 Re) or disappears • IMF Bz North (closed field lines): • High lat. reconnection, transports to LLBL • Low velocity flow, KH instability grows (non-linear) • LLBL is thick (many Re)

  10. Magnetospheric Boundary Layers Student Tutorial __ _ Sunday 16 June 2013 • High Latitude Boundary Layer (Plasma Mantle) • High latitude magnetosphere, tailward of the cusp • De-energized MS particles • Often has no sharp inner boundary Shodhan et al., 1996 • Tailward flow(~100 – 200 km/s) • Low density (~0.01 - 1 cm3) • Energy similar to MS (~0.1 – 1 keV) • Open field lines • Gradual transition from sheath to lobe MS Lobe Mantle Geotail satellite Far downtail (-170, 28, 20) Re [GSM] 4 distinct MS – PM – Lobe crossings

  11. Magnetospheric Boundary Layers Student Tutorial __ _ Sunday 16 June 2013 • IMF Bz South: • Mantle becomes thicker • O+, He+, from ionosphere (polar wind) • Velocity filter effect Flow speed, density, and temperature all decrease away from the magnetopause subsolar point • Faster particles can make it to lower L shells • Less energetic particles are convected more Trattner et al., 2001

  12. Magnetospheric Boundary Layers Student Tutorial __ _ Sunday 16 June 2013 • Exterior Cusp (High-altitude Cusp) • Dayside boundary of the polar cap • ~8-15 Re • Centered at noon LT, extends ~3 h each side • ~2 Re wide • Coupled to but distinct from low-altitude cusp • Plasma is characteristic of magnetosheath • Open field lines, both IMF Bz North and South • Low speed, disordered, possibly turbulent flows Cusp ion precipitation Northward IMF • Current exterior cusp research is diverse • High-frequency waves • Shock region/Rotational discontinuity • Stagnant Exterior Cusp (SEC) – higher density • Cusp Diamagnetic Cavity (CDC) – B ≈ 0 • MeV ions and electrons

  13. Magnetospheric Boundary Layers Student Tutorial __ _ Sunday 16 June 2013 Cluster observations of a Lobe – Exterior Cusp pass Lobe Cusp Lavraudet al., 2004

  14. Magnetotail Student Tutorial __ _ Sunday 16 June 2013 Nightside outer magnetosphere that is stretched out by the solar wind. Open field lines are ‘horizontal’ Site of nightside reconnection that leads to dipolarization, substorms, geomagnetic storms, plasmoids • Dungey [1965] estimated the magnetotail: • SW plasma flows over the polar cap in ~3 hours • LMT ~600 Re

  15. Magnetotail Student Tutorial __ _ Sunday 16 June 2013 • Lobes • Open, anti-parallel B field • Strong field, low density (~0.01 cm-3) • Central Plasma Sheet • Hot [Te ~0.1-1 keV, Ti ~0.5-5 keV] • higher density (~0.1-1 cm-3) • Plasma Sheet Boundary Layer (PSBL) • Intermediate energy and density • Sunward ‘counter streaming’ ions • Lobe Diameter: • Assume conservation of magnetic flux from cap to tail • DMT ~20 Re Eastman et al., 1984 FINAL NOTE: MT is highly dynamic, i.e. depending on the solar wind and IMF there is twisting, flapping, and flaring (diameter increases)

  16. Enjoy GEM and Snowmass Village!

  17. Extra Slides

  18. Earth’s Magnetosphere Student Tutorial __ _ Sunday 16 June 2013 • Rotating Earth (Dynamo Theory) • Magnetic field induced by liquid iron (conducting) in the outer core: coriolis force • Creates vertical convection: Taylor columns Structure and Dynamics • Solar wind impinging on the magnetosphere: compresses dayside, stretches nightside • Dayside / nightside reconnection • Dungey Cycle • Open / closed field lines • Convection ‘pumps’ energetic particles to the inner magnetosphere - aurora Kivelson, M., and Russell, C. Introduction to Space Physics

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