A statistical analysis of the location and width of Saturn's aurora, and implications for magnetospheric dynamics

Conference (2006)

We present the results of a statistical analysis of the location of commonly-occurring auroral features in Saturn's southern polar ionosphere. Using a magnetospheric model, modified for Saturn from a data ... [more ▼]

We present the results of a statistical analysis of the location of commonly-occurring auroral features in Saturn's southern polar ionosphere. Using a magnetospheric model, modified for Saturn from a data-based terrestrial model (Tsyganenko, 1996), we estimate the region in the equatorial plane of the outer magnetosphere that maps to the observed aurora. We then discuss the possible magnetospheric processes that may cause these auroral emissions. [less ▲]

A statistical analysis of the location and width of Saturn's southern auroras

in Annales Geophysicae [= ANGEO] (2006), 24(12), 3533-3545

A selection of twenty-two Hubble Space Telescope images of Saturn's ultraviolet auroras obtained during 1997-2004 has been analysed to determine the median location and width of the auroral oval, and ... [more ▼]

A selection of twenty-two Hubble Space Telescope images of Saturn's ultraviolet auroras obtained during 1997-2004 has been analysed to determine the median location and width of the auroral oval, and their variability. Limitations of coverage restrict the analysis to the southern hemisphere, and to local times from the post-midnight sector to just past dusk, via dawn and noon. It is found that the overall median location of the poleward and equatorward boundaries of the oval with respect to the southern pole are at similar to 14 degrees and similar to 16 degrees co-latitude, respectively, with a median latitudinal width of similar to 2 degrees. These median values vary only modestly with local time around the oval, though the poleward boundary moves closer to the pole near noon (similar to 12.5 degrees) such that the oval is wider in that sector (median width similar to 3.5 degrees) than it is at both dawn and dusk (similar to 1.5 degrees). It is also shown that the position of the auroral boundaries at Saturn are extremely variable, the poleward boundary being located between 2 degrees and 20 degrees co-latitude, and the equatorward boundary between 6 degrees and 23 degrees, this variability contrasting sharply with the essentially fixed location of the main oval at Jupiter. Comparison with Voyager plasma angular velocity data mapped magnetically from the equatorial magnetosphere into the southern ionosphere indicates that the dayside aurora lie poleward of the main upward-directed field-aligned current region associated with corotation enforcement, which maps to similar to 20 degrees-24 degrees co-latitude, while agreeing reasonably with the position of the open-closed field line boundary based on estimates of the open flux in Saturn's tail, located between similar to 11 degrees and similar to 15 degrees. In this case, the variability in location can be understood in terms of changes in the open flux present in the system, the changes implied by the Saturn data then matching those observed at Earth as fractions of the total planetary flux. We infer that the broad (few degrees) diffuse auroral emissions and sub-corotating auroral patches observed in the dayside sector at Saturn result from precipitation from hot plasma sub-corotating in the outer magnetosphere in a layer a few Saturn radii wide adjacent to the magnetopause, probably having been injected either by Dungey-cycle or Vasyliunas-cycle dynamics on the nightside. [less ▲]

Statistical Analysis of the night weather conditions favouring the epidemic of the brown rust in the Grand-Duchy of Luxemburg.

in Italian Journal of Agronomy/ Rivista di Agronomia (2008), 3

Statistical analysis of the validation results: diagnostic or decision tools

Conference (2002)

Statistical analysis of validation method revisited : the need to use the total error. Proceeding 9th international congress of the european association for Veterinary Pharmacology and Toxicology

in Journal of Veterinary Pharmacology & Therapeutics (2003), 26

Statistical approaches to dynamic security assessment : the data base generation problem

in Proc. 2nd IFAC Symposium on Control of Power Plants and Power Systems (1995)

A Statistical Comparison of the Mousterian and Aurignacian assemblages

in Otte, Marcel; Straus, Lawrence G. (Eds.) Le Trou Magrite : Fouilles 1991-1992. Résurrection d'un site classique en Wallonie (1995)

Statistical derivation of the evolution equation of liquid water path fluctuations in clouds

in Journal of Geophysical Research. Atmospheres (2002), 107(D23),

[1] How to distinguish and quantify deterministic and random influences on the statistics of turbulence data in meteorology cases is discussed from first principles. Liquid water path (LWP) changes in ... [more ▼]

[1] How to distinguish and quantify deterministic and random influences on the statistics of turbulence data in meteorology cases is discussed from first principles. Liquid water path (LWP) changes in clouds, as retrieved from radio signals, upon different delay times, can be regarded as a stochastic Markov process. A detrended fluctuation analysis method indicates the existence of long range time correlations. The Fokker-Planck equation which models very precisely the LWP fluctuation empirical probability distributions, in particular, their non-Gaussian heavy tails is explicitly derived and written in terms of a drift and a diffusion coefficient. Furthermore, Kramers-Moyal coefficients, as estimated from the empirical data, are found to be in good agreement with their first principle derivation. Finally, the equivalent Langevin equation is written for the LWP increments themselves. Thus rather than the existence of hierarchical structures, like an energy cascade process, strong correlations on different timescales, from small to large ones, are considered to be proven as intrinsic ingredients of such cloud evolutions. [less ▲]

Statistical determination of the precision obtained by a photometric reduction algorithm

in Statistical Methods in Astronomy (1983, November 01)

Numerical simulations were used to assess the multinight technique for UV by photometric data reduction. Observation sets were created for 1, 2, 4, 8 and 16 nights. The standard values were assumed to be ... [more ▼]

Numerical simulations were used to assess the multinight technique for UV by photometric data reduction. Observation sets were created for 1, 2, 4, 8 and 16 nights. The standard values were assumed to be accurate to 0.004 magn. and the error in the measurements was 0.006 magn. A total of 20 standard stars were kept, along with 20 constant stars, giving an average of 16 stars every night. Analysis shows that the multinight procedure leads to a dramatic improvement in the precision of the results. [less ▲]

Statistical hypothesis and orthogonal projections for unbalanced data

Poster (1992)