  We aim at constraining the diffusive and advective transport processes in
Jupiter's stratosphere. The IR spectrum recorded by Cassini/CIRS during the
Jupiter flyby contains the fingerprints of several atmospheric compounds and
allows probing its atmospheric composition. C2H2 and C2H6, the main compounds
produced by methane photochemistry, were retrieved as a function of latitude at
certain pressure levels. CIRS observations suggest a different meridional
distribution for these two species, difficult to reconcile with their
photochemical histories, which are thought to be coupled to the methane
photolysis. While the C2H2 abundance decreases with latitude, C2H6 becomes more
abundant at high latitudes. A new 2D (latitude-altitude) seasonal photochemical
model is developed to study whether the addition of stratospheric transport
processes, such as meridional diffusion and advection, can explain the
latitudinal behavior of C2H2 and C2H6. C2H2 observations are fairly well
reproduced without meridional diffusion. Adding meridional diffusion to the
model provides an improved agreement with the C2H6 observations by flattening
its meridional distribution, but degrades the fit to the C2H2 distribution.
Meridional diffusion alone cannot produce the observed increase with latitude
of C2H6. When adding advective transport between 30 mbar and 0.01 mbar, with
upwelling winds at the equator and downwelling winds at high latitudes, we can
reproduce the C2H6 abundance increase with latitude. However, the fit to the
C2H2 distribution is degraded. The strength of the advective winds needed to
reproduce the C2H6 abundances is very sensitive to the value of the meridional
eddy diffusion coefficient. The coupled fate of C2H2 and C2H6 suggests that an
additional process is missing in the model. Ion-neutral chemistry was not
accounted for in this work and might be a good candidate to solve this issue.
