A dayside auroral energy deposition case study using the Polar Ultraviolet Imager

In this letter, we report preliminary results from a study of dayside auroral energy deposition during quiet times using global auroral images acquired by the Ultraviolet Imager experiment on the Polar spacecraft. Solar wind plasma and interplanetary magnetic field measurements from the Wind spacecraft and Kp values were used to characterize the state of the magnetosphere. The auroral oval was observed for a two-hour period in spring and summer during relatively quiet times (K-P similar or equal to 0 to 1). We find that, although the nightside energy deposition rate varied by an order of magnitude to as low as 1 x 10(16) erg s(-1) (1 gigawatt), the dayside was much less variable and remained between 4 and 10 x 10(16) erg s(-1).