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that a complex intrication of features due to both spatial and temporal
non-adiabaticity is to be expected (e.g., Ref. 24). A future study will be
dedicated to comparative analysis of proton and heavy ion transport under
such conditions.
4. Summary
Single-particle simulations of ion circulation within Mercury's magneto-
sphere reveal prominent deviations from adiabaticity, be it due to small
spatial scales with respect to the particle Larmor radius or due to small
temporal scales with respect to the particle gyration period. Ions that cir-
culate in the inner magnetotail exhibit a prominent sensitivity to injection
conditions because of a sharp gradient in the magnetic field magnitude
and field line elongation. This leads to rapid changes from quasi-adiabatic
to quasi-trapped behaviors and vice versa. The small width of the her-
mean magnetotail also is of importance in this respect since ions with large
Larmor radii may not be reflected toward the planet after interaction with
the current sheet and intercept the dusk magnetopause. Ions are found
to be rapidly transported and energized within Mercury's magnetosphere,
the significance of recycling and/or down-stream loss depending upon the
occurrence of reconnection in the magnetotail and upon the global convec-
tion pattern. The characteristic scales of Mercury's magnetosphere are such
that electrons are found to behave non-adiabatically as well. In particular,
violation of the second adiabatic invariant due to the transient electric field
induced by dipolarization of the magnetic field lines may lead to short-
lived precipitation onto the planet surface as well as formation of bouncing
electron clusters in the inner magnetotail.
Acknowledgments
Part of this work was performed while D. C. Delcourt was residing at STEL,
Toyokawa, Nagoya University (Japan).
References
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S. Orsini and T. E. Moore,
Ann. Geophys.
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3. E. Kallio and P. Janhunen,
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21
30
(2003) DOI 10.1029/
2003GL017842.
