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In 1961, Dungey suggested that magnetic reconnection occurs due to the solar-terrestrial interaction. The interplanetary magnetic field (IMF) is thought to merge with Earth's geomagnetic field (GMF). After the reconnection process the newly formed magnetic flux tube, consisting of both the IMF and GMF, moves anti-sunward. Poleward-moving auroral forms (PMAFs) are believed to be the ionospheric signatures of this process, which transfers magnetic flux from the dayside to the nightside. This paper looks at the connection between the solar wind speed and the motion of the PMAF as it moves from the auroral oval, anti-sunward, into the polar cap. PMAFs are identified using both the meridian scanning photometer (MSP) and colored all-sky camera (ASC). Once the PMAFs are identified, the PMAF-SLOPE, v[sub α] (units of degrees per time) and the angle (αPMAF) the PMAF makes with the horizontal (Time axis), in the MSP plot are calculated. These values (vα and αPMAF) are individually plotted against the vx-component of the solar wind speed and the flow speed (total solar wind speed). The plots generate linear a relationship between PMAF-SLOPEs, vα, [or PMAF angles (αPMAF)], and the vx-component of the solar wind speed (or the flow speed). A total of 57 PMAF events from 8 different days were associated with solar wind speeds (vx-component) ranging from 344 to 679 km/s. The first linear plot, between the PMAF-SLOPE and solar wind speed (vx-component), shows a high correlation: rvα = 0.944. A second linear plot, between αPMAF and the solar wind speed (vx-component) shows a very high correlation: rα[sub PMAF] =0.973. The conclusions obtained from this statistical study are: 1) both the PMAF-SLOPE vα and αPMAF are highly correlated to the vx-component of the solar wind, increasing when vx increases and vice versa, 2) PMAFs must be connected to both the IMF and GMF and are dragged anti-sunward, mostly by the vx-component of the solar wind, and 3) PMAFs are indeed the ionospheric footprints of a newly formed magnetic flux tube, due to dayside magnetic reconnection, being transferred from the dayside to nightside. [ABSTRACT FROM AUTHOR]

This study presents a number of previously unreported auroral features that form shortly after the IMF Bz ${\mathrm{B}}_{\mathrm{z}}$–component turns sharply northward. The auroral images were captured by the Boreal Aurora Camera Constellation (BACC) All‐sky camera at the Kjell Henriksen Observatory, located in Longyearbyen, Svalbard. These observations are different from those previously reported. There are several differences: (a) The Eastward‐Moving Auroral Forms (EMAFs) do not originate from type 1 or type 2 aurora. The EMAFs originate from a diffuse vertical auroral form in the far west part of the ASC image. Vertical refers to the auroral form oriented in the north‐south direction in the frame of the ASC image. (b) The EMAFs form crescent shapes after they begin to drift eastward. (c) The EMAFs are discrete auroral forms; previously reported ionospheric signatures of high‐latitude reconnection are described as patches of brightness that form within a pre‐existing auroral band. (d) The EMAFs are observed to first move eastward and then slightly poleward during their journey. The movements of previously reported Ionospheric signatures of high‐latitude reconnection are described as expanding patches of brightness within a pre‐existing auroral band. (e) Some of the EMAFs brighten again after fading, during their northeastward drift across the field of view. (f) The EMAFs begin their eastward motion aligned in the north‐south direction. During their northeast drift, they begin to tilt toward the east. Some of the EMAFs keep tilting until they are aligned in the east‐west direction. Plain Language Summary: Magnetic reconnection is a process which combines antiparallel magnetic field lines from different sources. Since magnetic field lines permeate our universe, there are many places where magnetic reconnection can occur. The solar‐terrestrial environment provides a great laboratory to study magnetic reconnection. Different orientations of the interplanetary magnetic field (IMF) allow it to connect to different regions of the Earth's geomagnetic field. Information from a magnetic reconnection event is transmitted to the ionosphere via the terrestrial magnetic field and is manifested in dazzling auroral displays. This paper presents ionospheric signatures of magnetic reconnection at high‐latitudes which are extremely different than past studies: (a) the origin of the observations in this study are different, (b) the ionospheric signatures form crescent shapes after they begin to drift eastward, (c) the ionospheric signatures are discrete auroral forms, (d) The ionospheric signatures are observed to first move eastward and then slightly poleward during their journey, (e) some of the ionospheric signatures brighten again after fading, during their northeastward drift across the sky, (f) during their northeast drift, they begin to tilt toward the east. Some of the EMAFs keep tilting until they are aligned in the east‐west direction. Key Points: Discrete auroral forms for northward IMF are aligned in the north‐south direction, propagating eastwardThese discrete auroral forms rotate clockwise during their eastward drift, some becoming aligned in the east west directionHigh‐latitude reconnection is a possible explanation for these discrete dayside auroral forms since the IMF clock angle is less than 90° [ABSTRACT FROM AUTHOR]

Abstract: Simultaneous optical ground-based observations of auroral Balmer excited hydrogen atoms were performed during the boreal winters of 2002-2003 and 2003-2004 at Ny-Alesund, Svalbard (NYA 76.26°N 110.98°E geomagnetic) and Longyearbyen, [...]

Abstract: 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 [...]

Auroral whistler‐mode radio emissions called saucers are of fundamental interest because they require an unusually stationary emission process in the dynamic auroral environment, and it is a mystery how that can happen in this or similar conditions elsewhere in geospace. The Cusp Alfvén and Plasma Electrodynamics Rocket (CAPER‐2), launched into the cusp, obtained the first rocket measurements of a large‐scale, multiple‐armed dayside saucer, similar to those observed by the DEMETER satellite, with the addition of particle measurements and ground‐based measurements. Analysis of saucer shapes, directional measurements using waveforms, and ground‐based data show that, accounting for estimated uncertainties, these originate at altitudes ∼4,000 km within the cusp, the eastern side of which is penetrated by the rocket ∼100 s after the saucers are encountered. On‐board particle instruments show dispersed electron bursts in the cusp, Alfvénically accelerated at altitudes at or above the saucer sources. Plain Language Summary: Electrons, precipitating down Earth's high‐latitude magnetic field lines, emit radio waves at angles to the background magnetic field, depending on frequency. When spacecrafts traverse through a region close to the source, they observe descending and ascending frequency signatures referred to as saucers. This research focused on rocket measurements of large‐scale, multiarmed saucers on the dayside. Using ray‐tracing software and hodogram analysis of the electric field waveforms combined with ground‐based measurements, we were able to determine the source location of the saucers to be in the magnetic field's cusp at altitudes near 4,000 km. Additionally, particle measurements on‐board the rocket showed time dispersed bursts of electrons typically associated with Alfvénic acceleration, which can be traced back to a source height that is equal to or above the source heights of the observed saucers. This is the first time that dayside large‐scale saucers have been associated with the cusp. Key Points: First observation of large‐scale dayside saucers from a sounding rocketThe saucers are estimated to originate at ∼4,000 km on cusp field lines to within estimated uncertaintiesDispersed electrons observed in the cusp were accelerated at altitudes at or above the saucer signal source region [ABSTRACT FROM AUTHOR]

A two-step procedure to calibrate the spectral sensitivity to visible light of auroral all-sky cameras is outlined. Center pixel response is obtained by the use of a Lambertian surface and a standard 45W tungsten lamp. Screen brightness is regulated by the distance between the lamp and the screen. All-sky flat-field correction is carried out with a 1m diameter integrating sphere. A transparent Lexan dome at the exit port of the sphere is used to simulate observing conditions at the Kjell Henriksen Observatory (KHO). A certified portable low brightness source from Keo Scientific Ltd was used to test the procedure. Transfer lamp certificates in units of Rayleigh per Ångstrøm (R/Å) are found to be within a relative error of 2%. An all-sky camera flat-field correction method is presented with only 6 required coefficients per channel. [ABSTRACT FROM AUTHOR]

The polarisation of the atomic oxygen red line in the Earth's thermosphere is observed in different configurations with respect to the magnetic field line at high latitude during several coordinated Incoherent Scatter radar/optical experiment campaigns. When pointing northward with a line-of-sight nearly perpendicular to the magnetic field, we show that, as expected, the polarisation is due to precipitated electrons with characteristic energies of a few hundreds of electron Volts. When pointing toward the zenith or southward with a line-of-sight more parallel to the magnetic field, we show that the polarisation practically disappears. This confirms experimentally the predictions deduced from the recent discovery of the red line polarisation. We show that the polarisation direction is parallel to the magnetic field line during geomagnetic activity intensification and that these results are in agreement with theoretical work. [ABSTRACT FROM AUTHOR]

We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007--2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by the stratosphere. If one is to exploit the potential of tropopause height as a metric for climate change at high latitude and elsewhere, it is imperative to observe and understand the processes which establish the tropopause -- an understanding to which this study contributes. [ABSTRACT FROM AUTHOR]

The article investigates the suitability of visible/near-infrared (VIS/NIR) spectroscopy as a tool to estimate the freshness of a lean and fat fish species during storage time in ice. The study analyzed the wavelength regions on cod Gadus morhua and salmon Salmo Salar for freshness determination. Statistical analysis showed the correlation between spectroscopic measurements of the inside, skin side and skin of fillet and fish at storage time.

The Meinel bands of OH in the night airglow have been monitored from the Northern Lights Station near Longyearbyen, Svalbard (15°E, 78°N) for the past 20 years. The rotational lines of the (6–2) and (8–3) bands yield a trustworthy measure of the neutral temperature in the upper mesosphere. There is a seasonal winter maximum, but wide variations predominate throughout the winter months. The variations of less than one day have been shown to be due to direct gravity wave forcing and those greater than one day are correlated with warmings in the polar stratosphere. Our analysis shows that the polar upper mesospheric temperature variations correlate best overall with the zonal stratospheric wind at 45°N and 30 hPa, indicating gravity wave filtering at that height and gravity wave forcing from that latitude region. The trend of the timeseries calculated from weekly averages of the rotational temperatures is −0.6 K/year. If the stratospheric wind at 45°N is included in a multiple regression the trend becomes −0.3 K/year. [Copyright &y& Elsevier]

The present study confirms that the auroras of the nightside oval population consist of two main types, namely storm and substorm aurora. Storm-type aurora, which is relatively infrequent, results from bombardment of the upper ionosphere by fast particle streams generated in the solar wind by cataclysmic solar events related to coronal mass ejections. The associated turbulent plasma that is injected into the magnetosphere produces great magnetic storms of world-wide dimensions that may last for days. In contrast, substorm aurora is a frequent (almost daily) occurrence that lasts for an hour or two around geomagnetic midnight. It is generated by the impulsive release of stored magnetospheric energy from the substorm onset region in the Earth's magnetotail and is associated with localised negative magnetic bays in the H (horizontal)-component of the Earth's magnetic field in the vicinity of the auroral oval. [ABSTRACT FROM PUBLISHER]

This paper introduces a new system that can monitor aurora and atmospheric airglow using a low-cost Watec monochromatic imager (WMI) equipped with a sensitive camera, a filter with high transmittance, and the non-telecentric optics. The WMI system with 486-nm, 558-nm, and 630-nm band-pass filters has observable luminosity of about ~200–4000 Rayleigh for 1.07-sec exposure time and about ~40–1200 Rayleigh for 4.27-sec exposure time, for example. It is demonstrated that the WMI system is capable of detecting 428-nm auroral intensities properly, through comparison with those measured with a collocated electron-multiplying charge-coupled device (EMCCD) imager system with narrower band-pass filter. The WMI system has two distinct advantages over the existing system: One makes it possible to reduce overall costs, and the other is that it enables the continuous observation even under twilight and moonlight conditions. Since 2013 a set of multi-wavelength WMIs has been operating in northern Scandinavia, Svalbard, and Antarctica to study meso- and large-scale aurora and airglow phenomena. Future development of the low-cost WMI system is expected to provide a great opportunity for constructing a global network for multi-wavelength aurora and airglow monitoring. [ABSTRACT FROM AUTHOR]

Abstract: The radar phenomenon PMSE (Polar Mesospheric Summer Echoes), which is associated with charged dust particles, can be affected by artificial electron heating. showed that if the heater is run in a cycle with equal, and comparatively, short (10–20s) off and on periods, the PMSE strength is observed to weaken when the heater is on, and recover to approximately the same strength when the heater is switched off. With a new heater cycling, where the heater is on for a short time and then off for a long enough time for the dusty plasma conditions to return to its undisturbed conditions, a PMSE overshoot effect is produced. In the overshoot the PMSE strength, when the heater is switched off, can increase by a factor of several fold compared to what it was directly before the heater was switched on. By analyzing the shape of the overshoot characteristic curve as the PMSE varies through a weakening as the heater is switched on, an overshoot as it is switched off and a subsequent relaxation back to an unaffected strength, we can obtain a considerable amount of information on the state of the PMSE dusty plasma. In the present paper, we will show results from a large EISCAT overshoot campaign in July 2004 where the PMSE overshoot was observed frequently. The shape of the PMSE power variations in each overshoot cycle is shown to vary considerably with height in the PMSE layer and also from cycle to cycle. We will show that very different PMSE overshoot shapes can occur at various occasions, and heights, and how they can be dependent on the local dust and plasma conditions. [Copyright &y& Elsevier]

This study describes rapid prototype construction of small and lightweight push broom Hyper Spectral Imagers (HSI). The dispersive element housings are printed by a thermoplastic 3D printer combined with S-mount optical components and commercial off-the-shelf camera heads. Four models with a mass less than 200 g are presented with a spectral range in the visible to the near-infrared part of the electromagnetic spectrum. The bandpass is in the range from 1.4 - 5 nm. Three test experiments with motorized gimbals to stabilize attitude show that the instruments are capable of push broom spectral imaging from various platforms, including airborne drone to handheld operations.

A prototype auroral hyperspectral all-sky camera has been constructed and tested. It uses electro-optical tunable filters to image the night sky as a function of wavelength throughout the visible spectrum with no moving mechanical parts. The core optical system includes a new high power all-sky lens with F-number equal to f/1.1. The camera has been tested at the Kjell Henriksen Observatory (KHO) during the auroral season of 2011/2012. It detects all sub classes of aurora above ~½ of the sub visual 1kR green intensity threshold at an exposure time of only one second. Supervised classification of the hyperspectral data shows promise as a new method to process and identify auroral forms.

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.

In the presented study a hyperspectral imager (400-700 nm) mounted on a stereo-microscope was used to separate differences in in vivo optical signatures identifying different pigment groups of bloom-forming phytoplankton and macroalgae by comparing spectral absorption, transmittance, and reflectance from 400-700 nm. The results show that the hyperspectral imager could be used to detect spectral characteristics on the microm level to calibrate, validate, identify, and separate objects with differences in color (optical fingerprinting). This information can be used for pigment group specific taxonomy (bio-optical taxonomy), eco-physiological information (e.g., health status), monitoring, and mapping applications.

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.

A small spectral imaging system is presented that images static or moving objects simultaneously as a function of wavelength. The main physical principle is outlined and demonstrated. The instrument is capable of resolving both spectral and spatial information from targets throughout the entire visible region. The spectral domain has a bandpass of 12 A. One can achieve the spatial domain by rotating the system's front mirror with a high-resolution stepper motor. The spatial resolution range from millimeters to several meters depends mainly on the front optics used and whether the target is fixed (static) or movable relative to the instrument. Different applications and examples are explored, including outdoor landscapes, industrial fish-related targets, and ground-level objects observed in the more traditional way from an airborne carrier (remote sensing). Through the examples, we found that the instrument correctly classifies whether a shrimp is peeled and whether it can disclose the spectral and spatial microcharacteristics of targets such as a fish nematode (parasite). In the macroregime, we were able to distinguish a marine vessel from the surrounding sea and sky. A study of the directional spectral albedo from clouds, mountains, snow cover, and vegetation has also been included. With the airborne experiment, the imager successfully classified snow cover, leads, and new and rafted ice, as seen from 10.000 ft (3.048 m).