BG3 Glass Filter Effects on Quantifying Rapidly Pulsating Auroral Structures

The extensive use of Schott BG3 glass filters in auroral physics demands an accurate characterization of the filter performance when observing actual auroral structures. We present observations from two identical Andor DU-888 imagers operated side-by-side, one equipped with a BG3 glass filter and the other one unfiltered, observing the same auroral structures. The BG3 glass filter decreased the overall signal levels, increasing the relative intensity variations of the fast pulsating aurora by a few percent. This, however, also produced a slightly decreased signal-to-noise ratio, making it more difficult to quantify the rapidly varying auroral structures. This comparison shows that BG3 glass filters can be useful in reducing the overall signal levels which is important in dynamic, bright, substorm onset aurora, where EMCCD imager saturation has been known to occur. Consequently their use does not significantly affect the observation of the dynamics within the aurora but it also does not enhance the ability to quantify the features of rapidly varying auroral structures.