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Titan's ionosphere: A survey of solar EUV influences
Author(s) -
Shebanits O.,
Vigren E.,
Wahlund J.E.,
Holmberg M. K. G.,
Morooka M.,
Edberg N. J. T.,
Mandt K. E.,
Waite J. H.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja023987
Subject(s) - ionosphere , titan (rocket family) , physics , solar zenith angle , ion , atmospheric sciences , extreme ultraviolet lithography , magnetosphere , plasma , astronomy , optics , quantum mechanics
Effects of solar EUV on positive ions and heavy negative charge carriers (molecular ions, aerosol, and/or dust) in Titan's ionosphere are studied over the course of almost 12 years, including 78 flybys below 1400 km altitude between TA (October 2004) and T120 (June 2016). The Radio and Plasma Wave Science/Langmuir Probe‐measured ion charge densities (normalized by the solar zenith angle) show statistically significant variations with respect to the solar EUV flux. Dayside charge densities increase by a factor of ≈2 from solar minimum to maximum, while nightside charge densities are found to anticorrelate with the EUV flux and decrease by a factor of ≈3–4. The overall EUV dependence of the ion charge densities suggest inapplicability of the idealized Chapman theory below 1200 km in Titan's ionosphere. Nightside charge densities are also found to vary along Titan's orbit, with higher values in the sunward magnetosphere of Saturn compared to the magnetotail.