Part 1 Internal Plasma Sources and Ring Currents

2 Substorms at Earth 2

3 Hermean H+ Energization 3

4 Dipolarization Effects 4

5 H+ versus Na+ 5

6 H+ tail X-sections 6

7 Detrapping & cusp losses 7

Substorm Conclusion Compared with Earth, Mercury thought to have much faster dipolarizations Mercury will tend to energize light rather than heavy ions 8

9 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

10 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

11 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?

12 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??

Backup Charts 13

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?

15 “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. ???

16 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