During recent years several research institutes in northern Fennoscandia have deployed imaging instruments of a new generation, electron multiplying charge coupled devices (EMCCDs), for imaging the northern lights (Aurora Borealis). EMCCDs eliminate readout noise by on-chip electron multiplication before the readout amplifier, and therefore the much higher quantum efficiency of the bare CCD as compared with image-intensified cameras can be utilized[1]. Therefore EMCCDs allow high-speed imaging or imaging of very weak emissions, improving the understanding of plasma-physical processes in the Earth's environment and auroral energy deposition into the atmosphere. Other applications include meteor and airglow research.

Challenges in the use of these instruments include

1. Geometrical calibration (i.e. modelling the projection from geographical to pixel coordinates). A study of different projection models based on star mapping is presented.

2. Intensity calibration, including flat-field and absolute radiometric calibration. The use of star spectra for this purpose is discussed.

In this study applications of remote sensing of auroral volume emissions are investigated. Data from the Auroral Large Imaging System (ALIS) cameras at field stations in northern Sweden and Norway are used to calculate tomography-like estimates of the N2+(1N) emission at 4278 Å and the O(1S) emission att 5577 Å. Applications of the spectroscopic ratios include 1) estimates of electron energy spectra, which have applications in auroral theory and in estimating ionisation rates for incoherent scatter radar and ion chemistry model studies and 2) direct estimates of the chemical composition of the lower thermosphere, as the 5577 emission is excited at least partly through chemistry.

A summary of the submitted JASTP paper on HotPay2 was given at the 4th NordAuropt workshop

We present the results of radar measurements during the 4.5-day campaign around the Leonid maximum in November 15-20 2009, in which we conducted simultaneous tristatic EISCAT UHF measurements along with optical EMCCD observations. During the last 24 hours, we also performed dual-polarization measurements with the two remote receiving stations. Due to significantly improved sensitivity of the detection algorithms, we obtained a larger meteor detection rate than in previous studies at EISCAT UHF, peaking at 200 detections per hour at 6 UT. No significant increase in meteor detection rate was observed during the peak of the Leonid shower. We detected several low altitude trail-like structures, the lowest one at 60 km. An overview plot of the results is shown in Fig 1.

We present results of an investigation of the fine structure of the night sector diffuse auroral zone, observed simultaneously with optical instruments (ALIS) from the ground and the FAST electron spectrometer from space 16 February 1997. Both the optical and particle data show that the diffuse auroral zone consisted of two regions. The equatorward part of the diffuse aurora was occupied by a pattern of regular, parallel auroral stripes. The auroral stripes were significantly brighter than the background luminosity, had widths of approximately 5 km and moved southward with a velocity of about 100 m/s. The second region, located between the region with auroral stripes and the discrete auroral arcs to the north, was filled with weak and almost homogeneous luminosity, against which short-lived auroral rays and small patches appeared chaotically. From analysis of the electron differential fluxes corresponding to the different regions of the diffuse aurora and based on existing theories of the scattering process we conclude the following: Strong pitch angle diffusion by electron cyclotron harmonic waves (ECH) of plasma sheet electrons in the energy range from a few hundred eV to 3 4 keV was responsible for the electron precipitation, that produced the background luminosity within the whole diffuse zone. The fine structure, represented by the auroral stripes, was created by precipitation of electrons above 3 4 keV as a result of pitch angle diffusion into the loss cone by whistler mode waves. A so called

Black auroras are recognized as spatially well-defined regions within a uniform diffuse auroral background where the optical emission is significantly reduced. Black auroras typically appear post-magnetic midnight and during the substorm recovery phase, but not exclusively so. We report on the first combined multimonochromatic optical imaging, bistatic white-light TV recordings and incoherent scatter radar observations of black aurora by EISCAT of the phenomenon. From the relatively larger reduction in luminosity at 4278 Å than at 8446 Å we show that nonsheared black auroras are most probably not caused by downward directed electrical fields at low altitude. From the observations, we determine this by relating the height and intensity of the black aurora to precipitating particle energy within the surrounding background diffuse aurora. The observations are more consistent with an energy selective loss cone. Hence the mechanism causing black aurora is most probably active in the magnetosphere rather than close to Earth.

Keywords: Atmospheric Composition and Structure: Airglow and aurora, Magnetospheric Physics: Energetic particles: precipitating, Magnetospheric Physics: Electric fields (2411), Ionosphere: Ionosphere/magnetosphere interactions (2736)

The shape of the electron energy distribution has long been a central question in the field of high-frequency radio-induced optical emission experiments. This report presents estimates of the electron energy distribution function, f_e(E), from 0 to 60 eV based on optical multi-wavelength (6300, 5577, 8446, 4278 Å) data and 930-MHz incoherent scatter radar measurements of ion temperature, electron temperature and electron concentration. According to our estimate, the electron energy distribution has a depression at around 2 eV, probably caused by electron excitation of vibrational states in N₂, and a high energy tail that is clearly supra-thermal. The temporal evolution of the emissions indicates that the electron temperature still plays an important role in providing electrons with energies close to 2 eV. At the higher energies the electron energy distribution has a non-thermal tail.

Keywords: electron distribution, artificial airglow, active experiments