Energy input into the upper atmosphere associated with high-speed solar wind streams in 2005

A 9 day periodic oscillation in solar wind properties, geomagnetic activity, and upper atmosphere has been reported for the year 2005. To understand the energy transfer processes from the high-speed solar wind streams into the upper atmosphere, we examined Joule heating and hemispheric power (HP) from the assimilative mapping of ionospheric electrodynamics (AMIE) outputs for 2005. There are clear 9 day period variations in all AMIE outputs, and the 9 day periodic oscillation in the global integrated Joule heating is presented for the first time. The band-pass filter centered at 9 day period shows that both Joule heating and HP variations are correlated very well to the neutral density variation. It indicates that the energy transfer process into the upper atmosphere associated with high-speed solar wind streams is a combination of Joule heating and particle precipitation, while Joule heating plays a dominant role. The sensitivities of Joule heating and HP to the solar wind speed are close to 0.40 and 0.15 GW/(km/s), respectively.