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Science Nugget from NAG5-10850 : Superposed Epoch Analysis of Ring Current Geoeffectiveness

Science Nugget from NAG5-10850 : Superposed Epoch Analysis of Ring Current Geoeffectiveness. PI: Michael Liemohn Institution: University of Michigan Key Personnel: Jichun Zhang, U-M grad student Michelle Thomsen, LANL. Intense Storms vs. Moderate Storms @ Solar Maximum. Comparison.

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Science Nugget from NAG5-10850 : Superposed Epoch Analysis of Ring Current Geoeffectiveness

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  1. Science Nugget from NAG5-10850:Superposed Epoch Analysis of Ring Current Geoeffectiveness PI: Michael Liemohn Institution: University of Michigan Key Personnel: Jichun Zhang, U-M grad student Michelle Thomsen, LANL

  2. Intense Storms vs. Moderate Storms @ Solar Maximum

  3. Comparison Differences • Intense Storms with average Dst*min= -169 nT are driven by Bz < -10nT lasting for >3 hrs; moderate storms with average Dst*min= -67 nT are driven by Bz < -5nT lasting for >2 hrs. • At solar maximum, hot ions at geosynchronous orbit are denser during intense storms than during moderate storms. • At solar maximum, hot ions at geosynchronous orbit are hotter during moderate storms than during intense storms, especially around dusk. Similarities • A geomagnetic storm is driven by sufficiently intense and long-lasting southward IMF [Gonzalez et al., 1994]. • During geomagnetic storms, the density of hot ions at geosynchronous orbit vary with time and local time, peaking near dawn side near Dst*min • The temperature of hot-ions at geosynchronous orbit vary with time and local time, with a minimum in the dawn/noon sector. • Punchline: Storm intensity increases because of... • A stronger convective flow (deeper injection) • A denser plasma sheet (more source particles) • A colder plasma sheet (less B-drift, deeper injection)

  4. Figure Footnotes • MPA NHP, MPA THP, IMF Bz, and Dst* vs. epoch time • July 1999 to June 2002 • 34 intense storms (Dst*min < -100 nT) • 63 moderate storms (-100 nT < Dst*min < -50 nT) • Tail Lobe, Magnetosheath, and Boundary Layer intervals are excluded by accepting only: • NHP < 3 cm-3 • THP > 2 keV • UT-LT Maps: Color-coded Geosynchronous Observations • White Bins: No Data Available; • Black Bins: Lower Than Corresponding Min. of Color Bar; • Purple Bins: Higher Than Corresponding Max. of Color Bar • Bz and Dst* Plots: • Solid Line: Mean Values • Boundaries of Shades: Plus/Minus 1 Standard Deviation

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