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Discovery of suprathermal Fe + in Saturn's magnetosphere
Author(s) -
Christon S. P.,
Hamilton D. C.,
Plane J. M. C.,
Mitchell D. G.,
DiFabio R. D.,
Krimigis S. M.
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020906
Subject(s) - saturn , magnetosphere , physics , ion , magnetosphere of saturn , radius , atomic physics , plasma , astrophysics , planet , magnetopause , nuclear physics , computer security , quantum mechanics , computer science
Measurements in Saturn's equatorial magnetosphere from mid‐2004 through 2013 made by Cassini's charge‐energy‐mass ion spectrometer indicate the presence of a rare, suprathermal (83–167 keV/e) ion species at Saturn with mass ~56 amu that is likely Fe + . The abundance of Fe + is only ~10 −4 relative to that of W + (O + , OH + , H 2 O + , and H 3 O + ), the water group ions which dominate Saturn's suprathermal and thermal ions along with H + and H 2 + . The radial variation of the Fe + partial number density (PND) is distinctly different from that of W + and most ions that comprise Saturn's suprathermal ion populations which, unlike thermal energy plasma ions, typically have a prominent PND peak at ~8–9 Rs (1 Saturn radius, Rs = 60,268 km). In contrast, the Fe + PND decreases more or less exponentially from ~4 to ~20 Rs , our study's inner and outer limits. Fe + may originate from metal layers produced by meteoric ablation near Saturn's mesosphere‐ionosphere boundary and/or possibly impacted interplanetary dust particles or the Saturn system's dark material in the main rings.