INVESTIGADORES
BERTUCCI Cesar
artículos
Título:
Titan ionospheric conductivities from Cassini measurements
Autor/es:
L. ROSENQVIST; WAHLUND, J.-E.; ÅGREN, K.; MODOLO, R.; OPGENOORTH, H. J.; STROBEL, D.; MÜLLER-WODARG, I.; GARNIER, P.; BERTUCCI, C.
Revista:
PLANETARY AND SPACE SCIENCE
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Año: 2009 p. 1828 - 1833
ISSN:
0032-0633
Resumen:
We present the first results of ionospheric conductivities at Titan
based on measurements during 17 Titan flybys from the Cassini
spacecraft. We identify an ionospheric region ranging from
1450±95km (approximately the location of the exobase) to
approximately 1000 km where electrical currents perpendicular to the
magnetic field may become important. In this region the ionosphere is
highly conductive with peak Pedersen conductivities of 0.002-0.05 S/m
and peak Hall conductivities of 0.01-0.3 S/m depending on Solar
illumination and magnetospheric conditions. Ionospheric conductivities
are found to be typically higher on the sunlit side of Titan. However,
Hall and Pedersen conductivities depend strongly on the magnetic field
magnitude which is highly variable, both in altitude and with respect to
the draping configuration of Saturn's magnetic field around Titan.
Furthermore, a consistent double peak nature is found in the altitude
profile of the Pedersen conductivity. A high altitude peak is found to
be located between 1300 and 1400 km. A second and typically more
conductive region is observed below 1000 km, where the magnetic field
strength drops sharply while the electron density still remains high.
This nature of the Pedersen conductivity profile may give rise to
complicated ionospheric-atmospheric dynamics and may be expected also at
other unmagnetized objects with a substantial atmosphere, such as e.g.
Mars and Venus. Estimates of the total Pedersen conductance are found to
range between 1300 and 22,000 S. The Pedersen conductance is always
higher than the local Alfvén conductance but the difference
varies by two orders of magnitude (from a factor 4 to 100). Thus, the
conditions for reflection or absorption of Alfvén waves in Titans
ionosphere are highly variable and depends strongly on the magnetic
field strength.