Aurora at the North Pole of Saturn as Seen by Cassini ISS' Ulyana A' Dyudina, A' P' Ingersoll, S' P'

1
Aurora at the North Pole of Saturn as Seen by
Cassini ISS. Ulyana A.
Dyudina, A. P. Ingersoll, S. P. Ewald (Caltech),
P31A-0188
Cassini ISS saw the visible aurora at Saturn for
the first time. Brighter parts of the auroral
circle are seen at latitude 75 N. We compare the
brightness and structure of the aurora at several
wavelengths, including the broadband clear
filter, H-alpha (656 nm),Near-IR (825-925 nm),
and UV (300-370 nm). We discuss temporal
variation of the aurora on the timescale of hours
and between two Cassini observations separated by
6 months.
July 2006 observations in different wavelengths.
January 2007 observations.
Broadband image.
Broadband polar map
Spectrum
The polar map produced from wide angle images
shows detailed structure of the auroral arcs.
The location of aurora approximately follows
75 latitude, as it does in the 2006
observations.
A
B
The approximate intensities of the brightest
aurora feature A in different filters. The
horizontal extent of the lines shows the width of
respective filter. The filter names are labeled
above the lines. The errors in spectral flux are
at least 100 , the detection of UV1 aurora is
uncertain (see the UV1 map below).
Image of aurora in clear filter with coordinates
on Saturn overlaid. Aurora is marked by arrows.
Bright segments of auroral arcs are labeled by
letters A, B, C to compare with the features on
the maps below.
Change with time
7h 01m
7h 36m
8h 11m
Polar maps
The polar map projection of the aurora images in
different filters. The area was imaged in 6
other filters (MT2, MT3, CB2, CB3, UV2, UV3) but
no apparent aurora had been seen above the noise.
The area not covered by images are is shown in
grey. The cross-shaped coverage of the
observations is due to the 2.5 hour (quarter
Saturns rotation) interval between the
images. Because aurora changes on the timescales
of hours (see the images on the right) and the
time between observations is of the same order,
the features on different maps are only
approximately related to each other.
The two features (labeled 1 and 2 in the images)
can be seen disappearing within half an hour
between the observations
Conclusions Aurora is observed in visible
wavelengths on Saturn The observations are
consistent with line emission (several narrow
band filters capture larger intensity than the
broadband) Northern aurora forms arcs and
separate light blobs around 75 latitude. Aurora
changes on the timescale of hours. This poster
reports work in progress. More aurora images are
taken and are to be processed.. More auroral
observations, including simultaneous
UV/visible/infrared observations are planned for
the Cassini extended mission.
IR2(825-925 nm)
Clear filter image
HAL (651-661 nm)
UV1 (300-370 nm)