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Numerical forecasts of plasma convective instability in the postsunset equatorial ionosphere are made based on data from the Ionospheric Connections Explorer satellite (ICON) following the method outlined in a previous study. Data are selected from pairs of successive orbits. Data from the first orbit in the pair are used to initialize and force a numerical forecast simulation, and data from the second orbit are used to validate the results 104 min later. Data from the IVM plasma density and drifts instrument and the MIGHTI red‐line thermospheric winds instrument are used to force the forecast model. Thirteen (16) data set pairs from August (October), 2022, are considered. Forecasts produced one false negative in August and another false negative in October. Possible causes of forecast discrepancies are evaluated including the failure to initialize the numerical simulations with electron density profiles measured concurrently. Volume emission 135.6‐nm OI profiles from the Far Ultraviolet (FUV) instrument on ICON are considered in the evaluation. Plain Language Summary: Numerical forecasts of disruptions in the postsunset equatorial ionosphere are made from data from the Ionospheric Connections Explorer (ICON) satellite using the method outlined in a previous study. Data are selected from pairs of successive orbits–the first providing data for the numerical forecast model, and the second providing a means of validation. Specifically, measurements of vertical plasma drifts and horizontal wind profiles are used. Thirteen (16) orbital pairs from August (October) of 2022 are considered. The forecasts were accurate in the main but produced one false negative in August and another false negative in October. Reasons for the forecast discrepancies are analyzed including the failure to include electron density profile measurements in the forecast model initialization. Data from the Far Ultraviolet instrument on Icon are considered in the analysis. Key Points: ICON‐based numerical forecasts of plasma convective instability in the equatorial ionosphere extended through 2022Results mainly consistent with earlier ICON‐based forecastsICON FUV profiles used to investigate forecast discrepancies further [ABSTRACT FROM AUTHOR]

The NASA Ionospheric Connection Explorer (ICON) was launched in October 2019 and has been observing the upper atmosphere and ionosphere to understand the sources of their strong variability, to understand the energy and momentum transfer, and to determine how the solar wind and magnetospheric effects modify the internally-driven atmosphere-space system. The Far Ultraviolet Instrument (FUV) supports these goals by observing the ultraviolet airglow in day and night, determining the atmospheric and ionospheric composition and density distribution. Based on the combination of ground calibration and flight data, this paper describes how major instrument parameters have been verified or refined since launch, how science data are collected, and how the instrument has performed over the first 3 years of the science mission. It also provides a brief summary of science results obtained so far. [ABSTRACT FROM AUTHOR]

The Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) was launched aboard NASA's Ionospheric Connection (ICON) Explorer satellite in October 2019 to measure winds and temperatures on the limb in the upper mesosphere and lower thermosphere (MLT). Temperatures are observed using the molecular oxygen atmospheric band near 763 nm from 90–127 km altitude in the daytime and 90–108 km in the nighttime. Here we describe the measurement approach and methodology of the temperature retrieval, including unique on-orbit operations that allow for a better understanding of the instrument response. The MIGHTI measurement approach for temperatures is distinguished by concurrent observations from two different sensors, allowing for two self-consistent temperature products. We compare the MIGHTI temperatures against existing MLT space-borne and ground-based observations. The MIGHTI temperatures are within 7 K of these observations on average from 90–95 km throughout the day and night. In the daytime on average from 99–105 km, MIGHTI temperatures are higher than coincident observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on NASA's TIMED satellite by 18 K. Because the difference between the MIGHTI and SABER observations is predominantly a constant bias at a given altitude, conclusions of scientific analyses that are based on temperature variations are largely unaffected. [ABSTRACT FROM AUTHOR]

One of the objectives of the Far UltraViolet (FUV) imager on the Ionospheric Connection Explorer (ICON) spacecraft is to make high resolution images of the nighttime near equatorial oxygen 135.6 nm airglow emission. This emission is largely the product of O+ ion re-combination and therefore the emission intensity is a proxy for remote measurement of ionospheric density. The ICON FUV instrument is capable of high resolution imaging of the night glow by viewing the Earth's limb from above on the left side of the spacecraft and taking rapid exposures and co-adding the resultant images for 12 seconds. To improve the resolution and compress the resulting data a new type of Time Delay Integration (TDI) technique was developed, which involves transforming the images into a distorted frame so that the displacement due to orbital motion becomes a singular constant vector for all pixels. Operating in this transformed frame it is possible to co-add and shift the images to retain the resolution and minimize the required data bandwidth. The transformation needs modeling of the object distance for all pixels. Two models, the "limb" and "sub-limb" models, are used for transforming the upper and lower parts of the ICON FUV images, respectively. At the input of the instrument there is a rotatable mirror, which allows directing the optic axis near to the plane of the local magnetic field. The images are co-added for 12 sec and are down linked and re-assembled on the ground into maps of the O emission showing an entire night pass. This is the first report on the performance of this newly developed TDI system. ICON with its low inclination (27 degree) orbit provides an extensive longitudinal coverage on each orbit complementing the coverage of GOLD or TIMED. During 179 orbits in October 2021 ICON FUV saw significant nighttime ion densities on 76% of the orbits. At low latitudes the ionization was clearly associated with the equatorial ionospheric anomaly (EIA). The maps showed significant structuring during 34% of the orbits when ICON was in the position to view the EIA. In coordinated observations GOLD and ICON FUV observed regular structuring in the form of Equatorial Plasma Bubbles (EPB-s). Comparing to GOLD observations in 2018, ICON saw significantly fewer EPB-s in the month of October 2021. ICON TDI integrated sub-limb view was tested for resolution using star images and should have seen structures less than 10 km. From the 179 orbits taken in October 2021 the shortest repetition EPB-were 350 km from peak to peaks. [ABSTRACT FROM AUTHOR]

Simultaneous measurements of F‐region neutral winds near 250 km and topside field‐aligned interhemispheric plasma flow near 600 km, made by the ionospheric connections satellite, allow the connection between these parameters to be observationally established for the first time. The largest variations in the topside plasma flows are seen as a function of season and are shown to depend on trans‐equatorial neutral winds near the F peak in a manner that is essentially the same during the daytime and the nighttime for the solar minimum conditions that prevail in 2020. This finding is consistent with established principles of a servo model of the ionosphere for which both production and loss rates in the topside are specified by the O/N2 ratio at the F‐peak height. The intermediate relationships, describing how the neutral wind influences the F‐peak height and how the O+ plasma pressure gradient across the equator influences the interhemispheric plasma flow are also investigated and found to be consistent with expectations. Plain Language Summary: Neutral winds in the upper atmosphere apply collisional forces to the charged particles that produce motions parallel and perpendicular to the magnetic field. Motions parallel to the magnetic field influence the distribution of charged particle pressure and thus change the plasma motion everywhere along the magnetic field. Simultaneous measurements of the neutral winds and the plasma motions at remote locations connected by the magnetic field allow the relationships between these quantities to be observationally established for the first time. These relationships show the direct relationships between the meridional winds near 250 km, the peak height of the ionospheric density and the field‐aligned interhemispheric plasma transport velocity at the apex of the magnetic field near 600 km. Key Points: Meridional winds near the F‐peak directly drive F‐peak height and topside field‐aligned interhemispheric plasma flowsMeridional wind across the magnetic equator at 250 km is linearly related to field‐aligned plasma flow across the magnetic equator at 600 kmIonospheric Connections satellite provides the first simultaneous observations of F‐region winds and topside field‐aligned interhemispheric plasma flows [ABSTRACT FROM AUTHOR]

We present a method for estimating incident photoelectrons' energy spectra as a function of altitude by combining global scale far‐ultraviolet (FUV) and radio‐occultation (RO) measurements. This characterization provides timely insights important for accurate interpretation of ionospheric parameters inferred from the recently launched Ionospheric Connection Explorer (ICON) observations. Quantification of photoelectron impact is enabled by the fact that conjugate photoelectrons (CPEs) directly affect FUV airglow emissions but not RO measurements. We demonstrate a technique for estimation of photoelectron fluxes and their spectra by combining coincident ICON and COSMIC2 measurements and show that a significant fraction of ICON‐FUV measurements is affected by CPEs during the winter solstice. A comparison of estimated photoelectron fluxes with measured photoelectron spectra is used to gain further insights into the estimation method and reveals consistent values within 10–60 eV. Plain Language Summary: The impact of solar radiation on the atmosphere produces highly energetic electrons, which travel freely along the magnetic Earth's field lines from one hemisphere to the other. When these electrons flow from the sunlit side into the nightside hemisphere, they interact with the neutral species and produce noticeable effects in the ionosphere such as an increase in electron temperature and enhancement of airglow emissions. This study presents a method to quantify the amount of precipitating electrons and their energy on a global scale using two recent satellite missions, ICON and COSMIC2. Our results demonstrate that coincident far‐ultraviolet (ICON) and radio‐occultation (COSMIC2) measurements from space are valuable resources to study precipitating electrons in the ionosphere and their impact on inferring ionospheric plasma parameters. Key Points: Nightglow emissions excited by photoelectrons originating in the magnetically conjugate hemisphere are observed by the ICON missionConjugate photoelectron energy spectra are derived for the first time using global scale far‐ultraviolet and radio‐occultation observationsComparison of estimated photoelectron fluxes with measurements on a rocket flight shows consistent characteristics at all altitudes [ABSTRACT FROM AUTHOR]

The Far Ultra Violet (FUV) ultraviolet imager onboard the NASA‐ICON mission is dedicated to the observation and study of the ionosphere dynamics at mid and low latitudes. We compare O+ density profiles provided by the ICON FUV instrument during nighttime with electron density profiles measured by the COSMIC‐2 constellation (C2) and ground‐based ionosondes. Co‐located simultaneous observations are compared, covering the period from November 2019 to July 2020, which produces several thousands of coincidences. Manual scaling of ionogram sequences ensures the reliability of the ionosonde profiles, while C2 data are carefully selected using an automatic quality control algorithm. Photoelectron contribution coming from the magnetically conjugated hemisphere is clearly visible in FUV data around solstices and has been filtered out from our analysis. We find that the FUV observations are consistent with the C2 and ionosonde measurements, with an average positive bias lower than 1 × 1011e/m3. When restricting the analysis to cases having an NmF2 value larger than 5 × 1011e/m3, FUV provides the peak electron density with a mean difference with C2 of 10%. The peak altitude, also determined from FUV observations, is found to be 15 km above that obtained from C2, and 38 km above the ionosonde value on average. Key Points: We compare ICON‐FUV NmF2 and hmF2 observations with those provided by COSMIC‐2 and ionosondesFar Ultra Violet Imaging Spectrograph (FUV) observations are affected by conjugate photoelectrons mainly around solsticesThe FUV performance during nighttime allows for reliable electron density measurement [ABSTRACT FROM AUTHOR]

Subauroral emissions known as STEVEs (Strong Thermal Emission Velocity Enhancements) are sometimes accompanied by green arcs containing magnetic field‐aligned "picket fence" structures. In a newly published spectrum of a green picket fence arc Gillies et al. (2019, https://doi.org/10.1029/2019GL083272) showed that the visible emission in such arcs is mostly OI 557.7 nm with minimal N2+ 1N. This finding is consistent with the color ratios found in digital camera photos (Mende & Turner, 2019, https://doi.org/10.1029/2019JA026851) and is distinct from the ratios in auroral precipitation. The spectrum also contains intense N2 first positive (1P) emission. The presence of OI 557.7 (~4.19 eV excitation energy) and N2 1P (~7.35 eV), combined with the lack of N2+ first negative (~18.75 eV) commonly seen in the aurora, suggests that the particles exciting the emission have energy <18.75 eV. This is strong evidence against the precipitation hypothesis recently put forth (Nishimura et al., 2019, https://doi.org/10.1029/2019GL082460; Gillies et al., 2019, https://doi.org/10.1029/2019GL083272). Key Points: Recent spectra of a green STEVE arc shows intense 557.7 nm OI and N2 1P nitrogen emission in the IR but minimal N2+ 1N in the blueColor ratios in photos of the green "picket fence" arcs are consistent with the spectrospcopic resultsSpectra and the color ratios show low energy excitation which is inconsistent with auroral source from the magnetosphere [ABSTRACT FROM AUTHOR]

Photos of a spectacular optical phenomenon, nicknamed STEVE, show finely structured, purple‐colored, east‐west arcs spanning the sky. These purple Sub‐auroral Arc Emissions are associated with Sub‐Auroral Ion Drifts, often accompanied by separate green arcs frequently displaying magnetic field aligned rays suggesting charge particle excitation. Both types of these arcs and polar auroras appear in some photos. Splitting the images into red, green, and blue channels allowed comparison of color ratios of the three phenomena. Wavelength calibration of the camera verified that the dominant atmospheric auroral emissions, 630.0 nm O(1D), O(1S) 557.7 nm, and N2+1N bands, were cleanly separated in the red, green, and blue channels of the camera. In the absence of a spectrogram the ratios between the color channels were interpreted in terms of possible excitation mechanisms. The purple arcs contained an excess of blue, presumably N2+1N intensity. This excess production could be due to the excitation of N2+ ions that were ionized through charge exchange with O+. The green companion arcs appear to be purely green (557.7) with almost no blue and minimal red suggesting excitation by low‐energy electrons excitation at altitudes >100 and <150 km. Key Points: The color ratios of purple and green subauroral arcs were compared to normal aurora using there red, green and blue intensisitiesIn purple arcs blue emission is enhanced, perhaps due to soft electron acting on charge exchanged N2+, and red due to 630 nm from OGreen companion arcs are likely to be soft electron excited green line at low altitudes with no blue. Source of soft electrons is unknown [ABSTRACT FROM AUTHOR]

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. However, it has been recognized in the 21st century that equally significant changes in ionospheric conditions are apparently associated with energy and momentum propagating upward from our own atmosphere. ICON's goal is to weigh the competing impacts of these two drivers as they influence our space environment. Here we describe the specific science objectives that address this goal, as well as the means by which they will be achieved. The instruments selected, the overall performance requirements of the science payload and the operational requirements are also described. ICON's development began in 2013 and the mission is on track for launch in 2018. ICON is developed and managed by the Space Sciences Laboratory at the University of California, Berkeley, with key contributions from several partner institutions. [ABSTRACT FROM AUTHOR]

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of $\mathrm{O}^{+}$ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny-Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft. [ABSTRACT FROM AUTHOR]

Lactose-free dairy products become increasingly important for lactose-intolerant consumers, but there are only few studies concerning the rheological properties of fermented dairy products from lactose-hydrolysed milk. Hydrolysation was performed with commercial β-galactosidase either before or during fermentation (co-hydrolysis). In each trial, fermentation of the base milk was carried out simultaneously using the same starter cultures for (a) untreated milk (reference) (b) hydrolysed milk as substrate and (c) by performing lactose hydrolysis and fermentation simultaneously (co-hydrolysis). In total, five thermophilic starter cultures and two products (yoghurt and Greek-style yoghurt) were investigated. Results show that the influence of hydrolysis of lactose on the properties of the fermented dairy products strongly depends on starter culture and substrate. For starters C and D, apparent viscosity (extracted from flow curves at a shear rate of 75 s) of fermented milks was only marginally affected by lactose hydrolysis, ranging between approx. 0.34-0.31 and 0.37-0.31 Pa.s, respectively. Hydrolysed products from starters A and E exhibited significant lower apparent viscosity (0.16 and 0.24 Pa.s) compared with their respective references (0.29 and 0.35 Pa.s). Fermentation of both substrates (regular yoghurt, Greek-style yoghurt) with starter B resulted in a decrease of yield stress and apparent viscosity because of lactose hydrolysis only for Greek-style yoghurt. Furthermore, a trend towards higher EPS synthesis was found when using hydrolysed milk. The results clearly show that products made from lactose-hydrolysed milk with similar rheological properties as the reference product can be obtained but that there is a lack of information concerning the complex interactions between starter culture and milk substrate. [ABSTRACT FROM AUTHOR]

Two substorms occurred at ∼04:05 and ∼04:55 UT on February 26, 2008 are studied with the in-situ observations of THEMIS satellites and ground-based aurora and magnetic field measurements. Angelopoulos et al. have made a comprehensive study of the 04:55 UT event. We showed detailed features of the two substorms with much attention to the first event and to the relationship between mid-tail magnetic reconnection (MR) and substorm activities. It was found that in the earlier stage of each substorm, a first auroral intensification occurred 2-3 min soon after the start of mid-tail MR, followed by a slow and very limited expansion. The auroral arcs were weak, short-lived, and localized, characterizing all features of a pseudobreakup. We regarded the first auroral brightening as the initial onset of the substorms. A few minutes later, a second stronger auroral intensification appeared, followed by quick and extensive expansions. It was interesting to note that the second brightening and related poleward expansion happened almost simultaneously (within a couple of minutes) with the onset of earthward flow and dipolarization in the near-Earth tail and other phenomenon of the substorm expansion phase. We thus regarded the second auroral brightening as the major onset of the substorms. Furthermore, it was seen that during the growth phase of the two substorms, the polar cap open flux Ψ kept increasing, while it quickly reduced during the substorm expansion and recovery phase. These variations of Ψ implied that the evolution of the two substorm expansion phases were closely related to MR of tail lobe open field lines. Analysis of substorm activities revealed that the two events studied were small substorms; while estimate of MR rate indicated that the MR processes in the two substorms were weak. The aforementioned observations suggested that mid-tail MR initiated the pseudobreakup first; the earthward flow generated by MR transported magnetic flux and energy to the near-Earth tail to cause the formation of SCW and CD, which induced near-Earth dipolarization and major auroral brightening, and eventually led to the onset of the substorm expansion phase. These results were clearly consistent with the picture of NENL and RCS models and supported the two step initiation scenario of substorms. [ABSTRACT FROM AUTHOR]