Plasma dynamics in Saturn's middle-latitude ionosphere and implications for magnetosphere-ionosphere coupling

Shotaro Sakai, Shigeto Watanabe

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

A multifluid model is used to investigate how Saturn's magnetosphere affects ionosphere. The model includes a magnetospheric plasma temperature of 2eV as a boundary condition. The main results are: (1) H+ ions are accelerated along magnetic field lines by ambipolar electric fields and centrifugal force, and have an upward velocity of about 10km/s at 8000km; (2) the ionospheric plasma temperature is 10,000K at 5000km, and is significantly affected by magnetospheric heat flow at high altitudes; (3) modeled electron densities agree with densities from occultation observations if the maximum neutral temperature at a latitude of 54° is about 900K or if electrons are heated near an altitude of 2500km; (4) electron heating rates from photoelectrons (≈100K/s) can also give agreement with observed electron densities when the maximum neutral temperature is lower than 700K (note that Cassini observations give 520K); and (5) the ion temperature is high at altitudes above 4000km and is almost the same as the electron temperature. The ionospheric height-integrated Pedersen conductivity, which affects the magnetospheric plasma velocity, varies with local time with values between 0.4 and 10S. We suggest that the sub-corotating ion velocity in the inner magnetosphere depends on the local time, because the conductivity generated by dust-plasma interactions in the inner magnetosphere is almost comparable to the ionospheric conductivity. This indicates that magnetosphere-ionosphere coupling is highly important in the Saturn system.

Original languageEnglish
Pages (from-to)261-271
Number of pages11
JournalIcarus
Volume274
DOIs
Publication statusPublished - 2016 Aug 1
Externally publishedYes

Keywords

  • Aeronomy
  • Ionospheres
  • Magnetosphere
  • Saturn
  • Saturn, atmosphere

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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