MIMI LEMMS at SOI Compared to Voyager LECP Thomas P Armstrong Fundamental Technologies, LLC Report to MIMI Team April Scott Wadley, Presenter

Search for Microsignatures SOI was not designed to search, but we may have gotten lucky. Microsignatures can reveal a lot about instrument performance—especially electron background.

Note the apparent absorption signature at 2.54 Rs for G1, E1,E2, and E3 inbound

Take a closer look and include subsectors. The feature minimum occurs in subsectors 2 and 3. There are 2 peaks (7,15)and minima (3,11) per revolution elsewhere.

Further interpretative remarks Two peaks and two minima per revolution are expected for radiation axisymmetric around B, i.e. trapped radiation. The feature appears to have resulted from a deepening of a routinely occurring minimum. If the orbiter approached a flux tube depleted of electrons by absorption at latitude different from the spacecraft, then it would be reasonable to expect the absorption to be most evident for electrons not mirroring near the spacecraft which LEMMS would observe as a peak, The may be the most likely geometry to explain the nature of the absorption.

E4, E5, and E6 show the inbound microsignature less distinctly than do the lower energy channels.

Note the lack of apparent absorption signature at 2.54 Rs for G1, E1,E2, and E3 outbound

Inbound absorption feature is also present in BE, C0, and C1 channel (other electron channels also show it—omitted for clarity)

Ion Channels do not show the microsignature but show substantial drift shell absorption! The microsignature occurs at the outer edge of the drift shell absorption.

Is there a candidate object at 2.54 Rs? Answer—not in the identified lists from Pioneer 11 and Voyager investigations. Have the Cassini SSI folks shown anything at 2.54 Rs?

Another Interesting effect—inbound/outbound flux assymmetries. Note the clear difference for C2 (43 to 57 keV electrons)

Note that A5 (0.49 to.78 MeV) protons are nicely symmetric—but a suspicious plateau exists in the range inbound.