11:00 〜 11:15
[PEM15-08] Initial results of NIRAS-2 and NIRAC installed at KHO/UNIS, Longyearbyen, Svalbard (78.1°N, 16.0°E)
キーワード：オーロラ、短波長赤外、分光観測、OH大気光、EISCAT スバールバル レーダー
A new ground-based optical observation of aurora and airglow in short-wavelength infrared (SWIR) at 1.05-1.35 µm has been initiated at The Kjell Henriksen Observatory (KHO), Longyearbyen (78.1°N, 16.0°E) since November 2022. Two state-of-the-art instruments, a SWIR imaging spectrograph and a monochromatic imager, are being operated to focus on study on dayside magnetosphere-ionosphere-atmosphere coupling processes in the high polar region.
The 2-D imaging spectrograph, NIRAS-2, is designed for SWIR wavelength in which sky background intensity is weaker than in visible with field-of-view (FOV) and angular resolution corresponding to 55 degrees and 0.11 degrees per pixel, respectively. If a 30-microns slit is used, spectral bandpass around 1.1 microns are 0.53 nm and 0.21 nm with two different gratings (950 lpmm and 1500 lpmm). It successfully measured SWIR auroral emissions such as N2+ Meinel band (0,0), N2 1st Positive bands (0,1), and OI- line with time resolution of 30 seconds. The N2+ and N2 bands correspond well to strong intensifications of aurora arc, while the OI- emission shows a correspondence with aurora ray structure, probably due to soft electron precipitation. Using high spectral resolution mode, N2+ ion rotational temperature is supposed to be estimated. For the upper mesosphere, the OH (8,5) band was measured and its rotational temperature can be estimated with 10-min resolutions and errors less than 5 K. It is important to note that this OH emission band is almost completely uncontaminated by aurora emissions overlapping wavelength range such as OI- line. So it is possible to measure OH rotaional temperature precisely even during geomagnetically disturbed period. In addition, O2 IR band at 1.27 µm and thermospheric He emission at 1.08 µm, which is difficult to resolve from Q-branch in OH (5,2) band, were already identified.
On the other hand, the brand-new SWIR camera, NIRAC, can visualize two-dimensional structures (FOV, 69° x 83°) of not only aurora (N2+) but also even weak airglow (OH) with a cadence of less than 30 seconds. This is the monochromatic imaging of SWIR aurora for the first time so far, and the NIRAC is used as a twin instrument to the NIRAS-2 to help in interpreting meridional scan data obtained from the NIRAS-2.
Taking geographical advantage of the observatory, 24-hours continuous observations have been done near the winter solstice. We have ran EISCAT Svalbard radar experiment for total 14 hours on January 23 and 24, 2023. The experment demonstrates intermittent enhancements of electron density down to 100 km altitudes between 1100 and 1400 UT on January 23, which implies that intermittent energetic electron precipitations occurred during this period. We will show initial results of this event and highlights of NIRAS-2 and NIRAC observations in 2022-2023 seasons along with a disucussion on observational strategies and future collaborations.
The 2-D imaging spectrograph, NIRAS-2, is designed for SWIR wavelength in which sky background intensity is weaker than in visible with field-of-view (FOV) and angular resolution corresponding to 55 degrees and 0.11 degrees per pixel, respectively. If a 30-microns slit is used, spectral bandpass around 1.1 microns are 0.53 nm and 0.21 nm with two different gratings (950 lpmm and 1500 lpmm). It successfully measured SWIR auroral emissions such as N2+ Meinel band (0,0), N2 1st Positive bands (0,1), and OI- line with time resolution of 30 seconds. The N2+ and N2 bands correspond well to strong intensifications of aurora arc, while the OI- emission shows a correspondence with aurora ray structure, probably due to soft electron precipitation. Using high spectral resolution mode, N2+ ion rotational temperature is supposed to be estimated. For the upper mesosphere, the OH (8,5) band was measured and its rotational temperature can be estimated with 10-min resolutions and errors less than 5 K. It is important to note that this OH emission band is almost completely uncontaminated by aurora emissions overlapping wavelength range such as OI- line. So it is possible to measure OH rotaional temperature precisely even during geomagnetically disturbed period. In addition, O2 IR band at 1.27 µm and thermospheric He emission at 1.08 µm, which is difficult to resolve from Q-branch in OH (5,2) band, were already identified.
On the other hand, the brand-new SWIR camera, NIRAC, can visualize two-dimensional structures (FOV, 69° x 83°) of not only aurora (N2+) but also even weak airglow (OH) with a cadence of less than 30 seconds. This is the monochromatic imaging of SWIR aurora for the first time so far, and the NIRAC is used as a twin instrument to the NIRAS-2 to help in interpreting meridional scan data obtained from the NIRAS-2.
Taking geographical advantage of the observatory, 24-hours continuous observations have been done near the winter solstice. We have ran EISCAT Svalbard radar experiment for total 14 hours on January 23 and 24, 2023. The experment demonstrates intermittent enhancements of electron density down to 100 km altitudes between 1100 and 1400 UT on January 23, which implies that intermittent energetic electron precipitations occurred during this period. We will show initial results of this event and highlights of NIRAS-2 and NIRAC observations in 2022-2023 seasons along with a disucussion on observational strategies and future collaborations.