We report on spectroscopic observations of Saturn ’ s stratosphere in July 2011 with the Texas Echelon Cross Echelle Spectrograph ( TEXES ) mounted on the NASA InfraRed Telescope Facility ( IRTF ) .
The observations , targeting several lines of the CH _ { 4 } \nu _ { 4 } band and the H _ { 2 } S ( 1 ) quadrupolar line , were designed to determine how Saturn ’ s stratospheric thermal structure was disturbed by the 2010 Great White Spot .
A study of Cassini Composite Infrared Spectrometer ( CIRS ) spectra had already shown the presence of a large stratospheric disturbance centered at a pressure of 2 hPa , nicknamed the beacon B0 , and a tail of warm air at lower pressures ( Fletcher et al .
2012 .
Icarus 221 , 560–586 ) .
Our observations confirm that the beacon B0 vertical structure determined by CIRS , with a maximum temperature of 180 \pm 1 K at 2 hPa , is overlain by a temperature decrease up to the 0.2-hPa pressure level .
Our retrieved maximum temperature of 180 \pm 1 K is colder than that derived by CIRS ( 200 \pm 1 K ) , a difference that may be quantitatively explained by terrestrial atmospheric smearing .
We propose a scenario for the formation of the beacon based on the saturation of gravity waves emitted by the GWS .
Our observations also reveal that the tail is a planet-encircling disturbance in Saturn ’ s upper stratosphere , oscillating between 0.2 and 0.02 hPa , showing a distinct wavenumber-2 pattern .
We propose that this pattern in the upper stratosphere is either the signature of thermal tides generated by the presence of the warm beacon in the mid-stratosphere , or the signature of Rossby wave activity .