Substorm Conclusion • Compared with Earth, Mercury thought to have much faster dipolarizations • Mercury will tend to energize light rather than heavy ions
An Hypothesis • Appreciable ring current requires internal plasma sources • Corollary: • Substorm to storm transition generated by increase in internal source • “appreciable,” adj. - comparable with solar wind pressure, or greater Moore, Chandler, Fok, Giles, Delcourt, Horwitz, Pollock, 2001 SSR
Falsifiability • Proposed tests: • observed correlations: see Nosé [2005 JGR] • global simulations: Moore et al. [2007 JASTP] • Messenger: ring current? solar or hermean? • Bepi Colombo: comprehensive observations
Questions for BC? • How much internal plasma of what composition is released into Hermean magnetosphere? • What are composition and kinetics of RC? • How large is RC pressure compared with solar wind driver? • If RC pressure lacking, lacking internal plasma or lacking room for energetic particles?
Possible Outcomes • Negligible RC • Insufficient source of internal plasma • Insufficient room for hot plasma gyroradii • Appreciable RC, solar origin: • Hypothesis disproven • Appreciable RC, internal light ions • RC built from internal plasmas • Appreciable RC, internal heavy ions • Low temperature / high density??
Planetary Plasma Sources and Ring Currents:Mercury T E Moore and M-C Fok Is Mercury the magnetosphere we always thought we had at Earth, with little or no internal plasma source? Does it have a solar wind dominated ring current? Does it have any appreciable ring current?
“What gets us into trouble is what we know, but just ain’t so.” -- Mark Twain • Ring current: • is carried by opposite e- and i+ drifts. not! • Solar wind enters via central plasma sheet. not! • Requires energetic particles. not! • Can’t fit in Mercury’s magnetosphere. ???
Or what we think ain’t so, but just don’t know: • Trapped plasma pressure inflates magnetosphere • RC pressure exceeds solar wind pressure by an order of magnitude • O+ pressure overtakes H+ as a source • Mercury could have low temperature ring current