Proton auroral observation using a meridian-scanning filter-tilting photometer at a subauroral latitude

We have been observing Hbeta emissions in proton aurora with a meridian-scanning filter-tilting photometer at the Athabasca station, Canada (54.7N, 246.7E, MLAT=62.6N) since September 2005. The photometer was installed with a highly sensitive monochromatic all-sky imager and an induction magnetometer. The Athabasca station is located equatorward of the auroral oval, where proton aurora measurement has not been made frequently from ground. The energy of auroral protons can be measured through Doppler-shift of the hydrogen Balmer line (486.1nm), by tilting a narrow-band interference filter. However, it has been difficult to measure wavelength of the Doppler shift accurately, because the peak wavelength of the filter drifts due to changes of the filter temperature. We have developed a meridian-scanning filter-tilting photometer with a new interference filter, for which the temperature drift coefficient (0.002 nm/K) is about 1/10 of that of previous filters. In the presentation, we will show two-years results of the proton aurora measurement in Athabasca.