[1] We employ a newly developed Navier-Stokes model, the Titan Global Ionosphere-Thermosphere Model (T-GITM) to address the one dimensional (1-D) coupled composition, dynamics, and energetics of Titan's upper atmosphere. Our main goals are to delineate the details of this new theoretical tool and to present benchmark calibration simulations compared against the Ion-Neutral Mass Spectrometer (INMS) neutral density measurements. First, we outline the key physical routines contained in T-GITM and their computational formulation. Then, we compare a series of model simulations against recent 1-D work by Cui et al. (2008), Strobel (2008 in order to provide a fiducial for calibrating this new model. In paper 2 and a future paper, we explore the uncertainties in our knowledge of Titan's atmosphere between ∼500 km and 1000 km in order to determine how the present measurements constrain our theoretical understanding of atmospheric structures and processes.

Plasma ion data from the Cassini Plasma Spectrometer (CAPS) are examined for all orbits from October 25, 2004 through Dec. 26, 2007. To eliminate effects of incomplete angular coverage, data are only used from the CAPS anode that is closest to viewing into the corotational flow and within 20° of that flow. The data are plotted in the SKR‐based SLS3 longitude system. The result is a cam‐shaped distribution in radial distance and SLS3 that has an outer lobe extending beyond 20 RS at SLS3 longitudes in the range ∼270° − 50°. The western edge of this outer lobe maps to the inner extent of a previously observed spiral pattern of periodic ion enhancements, which had the magnetic signature of plasmoids at distances >35 Rs. The plasma cam and the plasmoid spiral emanating from it are responsible for plasma periodicities observed at radial distances beyond ∼15 Rs in Saturn's magnetosphere.

[1] Different magnetospheric dynamic processes, such as sawtooth events, isolated substorms, and steady magnetospheric convection (SMC), can occur, depending on the solar wind condition. The purpose of this study is to calculate the magnetic flux in the magnetotail and in the polar cap during these magnetospheric modes and to establish a quantitative relation between the magnetic flux and the solar wind parameters. We use the Imager for Magnetopause-to-Aurora Global Exploration Far Ultraviolet Imager and Polar Ultraviolet Imager measurements to derive the magnetic flux in the polar cap and the Geotail measurements to derive the magnetic flux in the magnetotail. The average value of the magnetic flux at the sawtooth onset is $1 GWb in the polar cap and magnetotail, and the relative decrease of the magnetic flux from the maximum value at the sawtooth onset to the minimum value after the onset is 24-26.5%. The average magnetic flux in the polar cap at the onset of isolated substorms is 0.68 GWb and decreases by 26.5% after the expansion phase. The magnetic flux in the polar cap during SMC events varies between 0.3 and 0.8 GWb. The magnetic flux at the isolated substorm onset is at the upper limit of the magnetic flux of SMC events for the same merging electric field, and the magnetic flux at the sawtooth onset is always higher than that during isolated substorms and during SMC events. The magnetic flux in the magnetotail and polar cap during sawtooth events and isolated substorms increases gradually before the onset and then decreases rapidly after the onset, which is consistent with the traditional energy loading-unloading scenario. However, the maximum magnetic flux at the sawtooth or isolated substorm onset is not a constant but increases with the merging electric field and with the corrected Dst index. The results also provide reasonable explanation of the relatively constant period of sawtooth events.Citation: Huang, C.-S., A. D. DeJong, and X. Cai (2009), Magnetic flux in the magnetotail and polar cap during sawteeth, isolated substorms, and steady magnetospheric convection events,

[1] There are many similarities and differences in the solar wind drivers during three of the main modes of convection in the magnetosphere (isolated substorms, global sawtooth oscillations, and steady magnetospheric convection (SMC) events, which we term here balanced reconnection intervals (BRI)). Thus, this investigation utilizes statistical analysis to compare the solar wind and interplanetary magnetic field (IMF) drivers and their steadiness (standard deviation divided by the mean) during these three different event types. By including the steadiness of the drivers, the importance of magnitude, sign, and stability of the drivers for the different modes can be investigated. A series of histograms with each mode plotted over top of 6 years of background is used to measure the deviation of the mode drivers from the nominal data, and also allows for a comparison between each event type. We found that the magnitude and direction of B z are the dominate driver for substorms, while BRIs and sawteeth require both magnitude and steadiness of certain drivers to occur. Both BRIs and sawteeth show similar steadiness in their drivers, while the magnitude of the drivers is much stronger for the sawtooth oscillations. Also included in this study are the substorms that initiate BRIs. The solar wind and IMF drivers for the initiating substorms are similar to drivers for BRIs; thus initiating substorms of BRIs are different from isolated substorms and may play a role in preconditioning the magnetosphere for BRIs.