Study of Global Storm Time Energy Transport in the Lower Thermosphere using SABER Temperatures

The SABER (Sounding of the Atmosphere using Broadband Radiation) observations represent one of the few long duration data sets of thermospheric properties between the altitude ranges of 100 to 130 km. These altitudes correspond to the region of geomagnetic storm energy deposition. The ensuing global redistribution of the geomagnetic storm energy is yet to be understood. The SABER instrument onboard the TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite, provides kinetic temperatures in this region of the thermosphere. We have used this temperature dataset to study the response of the lower thermosphere to geomagnetic storms. A quiet time empirical model has been formulated to isolate only the storm time response from these temperature measurements. This isolated storm time temperature response has been used as an index to study the global redistribution of the storm energy. An important result of this investigation is indications of the relative importance of gravity wave circulation vs. the meridional circulation in redistribution of the geomagnetic storm energy from the high auroral latitudes to the lower latitudes. This study encompasses various storm periods between the periods of 2002-2010. Hence this interval comprises of both the solar maximum and minimum, and also of storm periods having different intensity. As a result of having different storm intensities, we can investigate the relative effect of joule heating dominant storms vs. particle precipitation dominant storms, in this global energy redistribution. Also, the availability of data spread across a solar cycle has helped us to investigate the influence of the phase of the solar cycle in the energy redistribution and circulation following a storm period.