Study of the Magnetic Pile-up at Titan: Cassini observations from flyby TA through T93

ROMANELLI, N. J.; BERTUCCI, C.; GOMEZ, D. O.; ACHILLEOS, N. A.; MODOLO, R.; AGREN, K.; EDBERG, N. J.

Congreso; AGU Fall Meeting 2013; 2013

The interaction of Titan with its plasma environment bears some resemblance to that of the Solar Wind with Venus and Mars. Under pressure balance conditions, the highly conducting ionosphere forms an obstacle to the incoming magnetized flow which, in addition to the exospheric mass loading, produces the pile up of the external magnetic field in front of the body. Observations at Mars and Venus show that the maximum magnetic pressure in the so-called magnetic barrier region occurs in the sub-solar/sub-flow point and depends on the pressure of the upstream flow (which in the Solar Wind is mainly of the dynamic type). For most of the time, Titan interacts with Saturn's sub-corotating magnetospheric plasma flow. As a result, the angle between the solar radiation (one of the sources of Titan's ionospheric plasma) and the rotating Kronian plasma varies with the moon's local time with respect to Saturn (SLT). In addition, Titan's proximity to Saturn's dynamic magnetodisk results in a strong variability of the properties of the external flow impinging on the moon, and different pressure terms are expected to dominate depending on its distance to the central current sheet. In this work we investigate which are the main properties of Titan's magnetic barrier using Cassini magnetometer measurements during flybys TA through T93. In particular, we identify the peaks in the magnetic pressure located in the vicinity of the moon and study their distribution with respect to several variables including the angle between Cassini and the nominal magnetospheric flow direction, the solar zenith angle (SZA), the Saturn Local Time (SLT), Saturn Kilometric radiation (SKR) longitude, and their altitude. Preliminary results show that high values of maximum magnetic pressure (normalized by the background magnetic field intensity) are more frequent for for SZA smaller than ~ 130°, for angles with respect to the nominal ram direction smaller than ~ 120°, and for SLTs around noon. In addition, peak magnetic pressures clearly display a decreasing trend with increasing altitude. We discuss these results and compare them with previous studies at other unmagnetized atmospheric objects.