Abstract. Measurements of hydroxyl nightglow emissions over Longyearbyen (78 • N, 16 • E) recorded simultaneously by the SABER instrument onboard the TIMED satellite and a ground-based Ebert-Fastie spectrometer have been used to derive an empirical formula for the height of the OH layer as a function of the integrated emission rate (IER). Altitude profiles of the OH volume emission rate (VER) derived from SABER observations over a period of more than six years provided a relation between the height of the OH layer peak and the integrated emission rate following the procedure described by Liu and Shepherd (2006). An extended period of overlap of SABER and ground-based spectrometer measurements of OH(6-2) IER during the 2003-2004 winter season allowed us to express ground-based IER values in terms of their satellite equivalents. The combination of these two formulae provided a method for inferring an altitude of the OH emission layer over Longyearbyen from ground-based measurements alone. Such a method is required when SABER is in a southward looking yaw cycle. In the SABER data for the period 2002-2008, the peak altitude of the OH layer ranged from a minimum near 76 km to a maximum near 90 km. The uncertainty in the inferred altitude of the peak emission, which includes a contribution for atmospheric extinction, was estimated to be ±2.7 km and is comparable with the ±2.6 km value quoted for the nominal altitude (87 km) of the OH layer. Longer periods of overlap of satellite and ground-based measurements together with simultaneous onsite measurements of atmospheric extinction could reduce the uncertainty to approximately 2 km.

[1] Temperatures at 90 km altitude above Svalbard (78 N, 16 E) have been determined using a meteor wind radar and subsequently calibrated by satellite measurements for the period autumn 2001 to present. The dependence of the temperatures on solar driving has been investigated using the Ottawa 10.7 cm flux as a proxy. Removing the response of the temperatures to the seasonal and solar cycle variations yields a residual time series which exhibits the negative trend of À4 AE 2 K decade À1 . We indicate that, given the month-to-month variability and memory in the time series, for a 90% confidence in this trend, we require only 55 months of data -considerably less than the amount available. Cooling of the middle atmosphere, which would be strongly supported by these results, would result in contraction and subsequent lowering of pressure surfaces; we explain that including a negative trend in the pressure model used to obtain temperatures from meteor train echo fading times would also merely serve to augment the observed 90 km cooling.Citation: Hall, C. M., M. E. Dyrland, M. Tsutsumi, and F. J. Mulligan (2012), Temperature trends at 90 km over Svalbard, Norway (78 N 16 E), seen in one decade of meteor radar observations,

Abstract. We document a characteristic spatial and temporal structure of the aurora in the postnoon sector present during a 10-h-long interval of very steady southeast IMF orientation (clock angle=135 • ) ending in a sharp south-to-north transition. Focus is placed on the detailed morphology of auroral forms/activities corresponding to merging and lobe convection cells obtained from SuperDARN convection data and Greenland magnetograms. The ground optical instruments at NyÅlesund, Svalbard (76 • MLAT) recorded different auroral forms/activities as the station moved to higher magnetic local times (MLTs) in the 13:00-17:00 MLT sector. Whereas the 13:00-15:00 MLT sector is characterized by classical poleward moving auroral forms (PMAFs) associated with merging cell transients, the aurora in the 15:00-17:00 MLT sector shows instead a characteristic latitudinal bifurcation consisting of standard oval forms and polar arcs, and a corresponding composite pattern of merging and lobe convection cells. The merging and lobe cells respond to the southward and northward IMF transitions by activation/fading and fading/activation, respectively. A sequence of brightening events is characterized by successive activations progressing in latitude from the merging cell regime to the lobe cell regime. Emphasis is placed on the association between polar arc brightenings and the activation of the channel of enhanced sunward flow in the lobe cell. The observations are discussed in relation to recent work on solar wind-magnetosphere-ionosphere interconnection topology.

[1] A technique for using satellite-derived temperatures to calibrate initial estimates of 90 km temperatures measured by meteor wind radar is presented. Temperatures derived from the Nippon/Norway Svalbard Meteor Radar, situated on Svalbard at 78°N, 16°E, are calibrated using data from the Aura spacecraft's Microwave Limb Sounder (MLS) experiment. The calibration was performed in a two-step process: after an initial calibration of first-guess temperatures, results were used to adjust the MLS values to reflect daily means rather than the 0200-1100 UT observation period of the satellite instrument; thereafter the calibration was repeated with the revised MLS temperatures. The resulting temperature time series represents a marked improvement on earlier results calibrated using hydroxyl emission and potassium/K-Lidar observations, as the uncertainty is reduced from 17 to 7 K. These latest results represent a new step toward reliable and continual monitoring of upper mesosphere/lower thermosphere temperature.Citation: Dyrland, M. E., C. M. Hall, F. J. Mulligan, M. Tsutsumi, and F. Sigernes (2010), Improved estimates for neutral air temperatures at 90 km and 78°N using satellite and meteor radar data, Radio Sci., 45, RS4006,

This paper reports on the daily mesospheric winter temperature series derived from ground-based spectral measurements of the hydroxyl airglow layer from the Auroral Station in Adventdalen near Longyearbyen, Svalbard (78°N, 15°E). Temperature estimates from the four latest seasons (2001–2002 to 2004–2005) have been added to the series reported by Sigernes et al. J. Geophys. Res. 108(A9), 1342 (2003). Lomb–Scargle periodogram analyses were performed on both hourly and daily average temperatures to look for significant periods. From the daily means, ∼24 and ∼26 d oscillations that are consistent with a solar rotation modulation of the atmosphere were identified. Analyses of the hourly averaged data did not reveal any considerable diurnal and semidiurnal periods in the temperatures. The 2003–2004 mesopause winter was one of the warmest reported over Svalbard during the last 25 years. It is common to observe within a few days temperature fluctuations in the range 20–40 K. Some years show far less variation than others. The overall daily average winter temperature is 209 K. The annual mean winter temperatures show a slightly positive temperature trend (+0.2 ± 0.1 K/year), on the verge of being a statistically significant change in the winter mesospheric temperatures over Svalbard.PACS Nos.: 92.60.hc, 07.20.Dt, 93.30.Sq, 92.60.hw

A new and improved method to obtain the average spectral pixel responsivity and the quantum efficiency of Digital Single Lens Reflex (DSLR) cameras is outlined. Two semi-professional cameras, the Nikon D300 and the Canon 40D, are evaluated. The cameras red, green and blue pixel responsivities and quantum efficiency are retrieved by illuminating an integrating sphere with a wavelength tunable monochromator. 31 intensity calibrated monochromatic spectral lines from 4000 to 7000 A, with a bandpass of approximately 12 A, were used as a library to solve the main equations of observation for the cameras. Both cameras have peak sensitivity in the blue and minimum sensitivity in the red. The Canon 40D has blue and green channel sensitivity close to the Nikon D300. The Canon red channel has half the sensitivity of the Nikon camera.

This work compares the methods by Starkov (1994a) and Zhang & Paxton (2008), that calculate the size and location of the auroral ovals as a function of planetary Kp index. The ovals are mapped in position and time onto a solar illuminated surface model of the Earth. It displays both the night-and dayside together with the location of the twilight zone as Earth rotates under the ovals. The graphical display serves as a tool to forecast auroral activity based on the predicted value of the Kp index. The forecast is installed as a service at http://kho.unis.no/. The Zhang & Paxton (2008) ovals are wider in latitude than the Starkov (1994a) ovals. The nightside model ovals coincide fairly well in shape for low to normal auroral conditions. The equatorward border of the diffuse aurora is well defined by both methods on the nightside for Kp 7. The dayside needs further studies in order to conclude.

A method to sensitivity calibrate Digital Single Lens Reflective (DSLR) cameras is outlined. A low intensity calibrated light source tunable in wavelength is described. 31 monochromatic lines from 4000 to 7000 A with a bandpass of approximately 12 A were used to find the spectral responses for the D70 and the D200 cameras manufactured by Nikon. The source radiance ranged from about 300 to 1.6k R/A. The cameras were operated in manual mode with 4 seconds exposure time at ISO 1600, which are typical settings required for night time photography of the aurora. For the Nikon D200 camera, the blue, green and red spectral responsivities peak at 4600, 5300 and 5900 A, respectively. The response was high for the blue colour channel with a clear cut-off at 4100 A for the UV part of the spectrum. The red channel response indicates low sensitivity above 6600 A. The D70 shows similar spectral responsivity, except that it peaks in the green colour channel and it is more sensitive to both UV and NIR radiation. Both cameras are capable of detecting night- and dayside auroral at 4 second exposure time. For optimal auroral imaging capability, the green and red spectral responsivities need to be shifted up by about 300 and 400 A in wavelength.