Emerging infectious diseases (EIDs) pose a risk to human welfare, both directly and indirectly, by affecting managed livestock and wildlife that provide valuable resources and ecosystem services, ...such as the pollination of crops. Honeybees (Apis mellifera), the prevailing managed insect crop pollinator, suffer from a range of emerging and exotic high-impact pathogens, and population maintenance requires active management by beekeepers to control them. Wild pollinators such as bumblebees (Bombus spp.) are in global decline, one cause of which may be pathogen spillover from managed pollinators like honeybees or commercial colonies of bumblebees. Here we use a combination of infection experiments and landscape-scale field data to show that honeybee EIDs are indeed widespread infectious agents within the pollinator assemblage. The prevalence of deformed wing virus (DWV) and the exotic parasite Nosema ceranae in honeybees and bumblebees is linked; as honeybees have higher DWV prevalence, and sympatric bumblebees and honeybees are infected by the same DWV strains, Apis is the likely source of at least one major EID in wild pollinators. Lessons learned from vertebrates highlight the need for increased pathogen control in managed bee species to maintain wild pollinators, as declines in native pollinators may be caused by interspecies pathogen transmission originating from managed pollinators.
A comparison between storm‐time TIMED/GUVI FUV spectra in thermospheric composition disturbed (O/N2 <∼140 km> depleted and NO <∼110 km> enhanced) and undisturbed regions reveals the following ...features: (1) A clear decrease in N2 LBHS (140–150 nm) band intensities compared to that between 150 and 160 nm; (2) A significant spectral decrease around O 164.1 nm; (3) Two enhanced peaks between 170 and 185 nm. The feature (2) is clearly due to atomic oxygen density decrease in the low thermosphere. The feature (3) is caused by storm‐time production and transport of nitric oxide. An AURIC simulation reproduced feature (1) confirming that storm‐time enhancement in O2 density (∼120–170 km) and the wavelength dependent O2 absorption cross section are the source of observed feature (1). On the other hand, the feature (1) was not observed in the regions without O/N2 depletion. This further supports that O2 density enhancement is responsible for feature (1).
Plain Language Summary
Observations by a FUV spectrograph imager on NASA TIMED satellite revealed two interesting features in the storm‐time disturbed thermosphere: (1) a relative decrease in N2 LBH intensities at 140–150 nm versus 150–160 nm, (2) significant decrease in O 164.1 nm radiance and enhanced emission between 170 and 185 nm. The feature (2) is well known and due to O density depletion and production of nitric oxide. The feature is not well understood. A model simulation indicates the feature (1) is due to storm‐time O2 density increase and wavelength dependent O2 absorption cross section which peaked around 140 nm. This result indicates that FUV spectrograph imager is capable to detect storm‐time O2 density changes.
Key Points
(1) FUV spectral difference between storm‐quiet time shows a relative decrease in N2 LBH intensities at 140–150 nm versus 150–160 nm
The FUV spectrograph difference between undisturbed regions did not show the above feature
(3) Simulations confirm indicate that enhanced O2 density and absorption causes the observed FUV spectral differences
A newly discovered 1000‐km scale longitudinal variation in ionospheric densities is an unexpected and heretofore unexplained phenomenon. Here we show that ionospheric densities vary with the strength ...of non‐migrating, diurnal atmospheric tides that are, in turn, driven mainly by weather in the tropics. A strong connection between tropospheric and ionospheric conditions is unexpected, as these upward propagating tides are damped far below the peak in ionospheric density. The observations can be explained by consideration of the dynamo interaction of the tides with the lower ionosphere (E‐layer) in daytime. The influence of persistent tropical rainstorms is therefore an important new consideration for space weather.
Despite only 8% of cattle being found in Europe, European breeds dominate current genetic resources. This adversely impacts cattle research in other important global cattle breeds, especially those ...from Africa for which genomic resources are particularly limited, despite their disproportionate importance to the continent's economies. To mitigate this issue, we have generated assemblies of African breeds, which have been integrated with genomic data for 294 diverse cattle into a graph genome that incorporates global cattle diversity. We illustrate how this more representative reference assembly contains an extra 116.1 Mb (4.2%) of sequence absent from the current Hereford sequence and consequently inaccessible to current studies. We further demonstrate how using this graph genome increases read mapping rates, reduces allelic biases and improves the agreement of structural variant calling with independent optical mapping data. Consequently, we present an improved, more representative, reference assembly that will improve global cattle research.
This paper presents a comprehensive modeling investigation of ionospheric and thermospheric variations during a prompt penetration electric field (PPEF) event that took place on 9 November 2004, ...using the Thermosphere‐Ionosphere‐Mesosphere Electrodynamic General Circulation Model (TIMEGCM). The simulation results reveal complex latitudinal and longitudinal/local‐time variations in vertical ion drift in the middle‐ and low‐latitude regions owing to the competing influences of electric fields and neutral winds. It is found that electric fields are the dominant driver of vertical ion drift at the magnetic equator; at midlatitudes, however, vertical ion drift driven by disturbance meridional winds exceeds that driven by electric fields. The temporal evolution of the UT‐latitude electron density profile from the simulation depicts clearly a super‐fountain effect caused by the PPEF, including the initial slow‐rise of the equatorial F‐layer peak height, the split of the F‐layer peak density, and the subsequent downward diffusion of the density peaks along magnetic field lines. Correspondingly, low‐latitude total electron content (TEC) becomes bifurcated around the magnetic equator. The O/N2column density ratio, on the other hand, shows very little variations during this PPEF event, excluding composition change as a potential mechanism for the TEC variations. By using realistic, time‐dependent, high‐latitude electric potential and auroral precipitation patterns to drive the TIMEGCM, the model is able to successfully reproduce the large vertical ion drift of ∼120 m/s over the Jicamarca incoherent radar (IS) in Peru, which is the largest daytime ion drift ever recorded by the radar. The simulation results are validated with several key observations from IS radars, ground GPS‐TEC network, and the TIMED‐GUVI O/N2column density ratio. The model‐data intercomparison also reveals some deficiencies in the TIMEGCM, particularly the limitations imposed by its upper boundary height as well as the prescribed O+ flux.
Key Points
Strong upward ion drift at Jacamarca during PPEF is successfully simulated
Low‐latitude dayside TEC bifurcates around the magnetic equator during PPEF
Relative importance of electric fields and neutral winds varies with latitudes
To understand magnetosphere‐ionosphere conditions that result in thermal emission velocity enhancement (STEVE) and subauroral ion drifts (SAID) during the substorm recovery phase, we present substorm ...aurora, particle injection, and current systems during two STEVE events. Those events are compared to substorm events with similar strength but without STEVE. We found that the substorm surge and intense upward currents for the events with STEVE reach the dusk, while those for the non‐STEVE substorms are localized around midnight. The Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations show that location of particle injection and fast plasma sheet flows for the STEVE events also shifts duskward. Electron injection is stronger and ion injection is weaker for the STEVE events compared to the non‐STEVE events. SAID are measured by Super Dual Auroral Radar Network during the STEVE events, but the non‐STEVE events only showed latitudinally wide subauroral polarization streams without SAID. To interpret the observations, Rice Convection Model (RCM) simulations with injection at premidnight and midnight have been conducted. The simulations successfully explain the stronger electron injection, weaker ion injection, and formation of SAID for injection at premidnight, because injected electrons reach the premidnight inner magnetosphere and form a narrower separation between the ion and electron inner boundaries. We suggest that substorms and particle injections extending far duskward away from midnight offer a condition for creating STEVE and SAID due to stronger electron injection to premidnight. The THEMIS all‐sky imager network identified the east‐west length of the STEVE arc to be ~1900 km (~2.5 h magnetic local time) and the duration to be 1–1.5 h.
Plain Language Summary
STEVE (strong thermal emission velocity enhancement) occurs during auroral activation called substorm, but only a small fraction of substorms come with STEVE. This study addresses what special auroral conditions are needed to create STEVE, and how the near‐Earth space creates conditions for driving STEVE. We found that aurora during STEVE spreads much farther away from midnight than during non‐STEVE substorms. In this situation, high‐energy electrons access the near‐Earth space more efficiently and drive a stronger plasma jet stream. The strong jet stream and related wave processes provide energy for driving the STEVE emission. NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites and Rice Convection Model simulations confirm the supply of high‐energy electrons and the formation of the jet stream during the STEVE events.
Key Points
STEVE and SAID are associated with the substorm surge and upward currents extending more duskward than non‐STEVE/SAID events
Injection and fast plasma sheet flows also shift duskward; electron injection is stronger and ion injection is weaker
Substorm injection extending far duskward offers a condition for STEVE and SAID due to stronger electron injection to premidnight
In this paper, a new empirical formulation of the mean energy and energy flux of precipitating electrons in the auroral oval is presented. Global far ultraviolet (FUV) observations by Thermosphere ...Ionosphere Mesosphere Energetics and Dynamics (TIMED)/Global Ultraviolet Imager (GUVI) (N
2 Lyman–Birge–Hopfield small (LBHS) 140.0–150.0
nm and Lyman–Birge–Hopfield long (LBHL) 165.0–180.0
nm) are used to estimate the mean energy (Eo) and energy flux (
Q) of precipitating electrons based on an auroral model (Boltzman Three Constituent—B3C) and airglow model (Atmospheric Ultraviolet Radiance Integrated Code—AURIC). For the first time, a FUV-based and Kp-dependent model of global auroral products (Eo,
Q) was developed using 4 years (2002–2005) of GUVI data and Epstein function fitting. This FUV-based model covers all Kp ranges (0–9). Due to the large spatial coverage of FUV auroral images, the FUV measurements lead to a more consistent estimation of the auroral hemispheric power. The model described here will be useful in a number of applications: global ionosphere/thermosphere simulations, space weather forecasting and nowcasting, and global ionospheric models.
The plausible effect of atmospheric tides on the longitudinal structure of the equatorial ionosphere is observed by the FORMOSAT‐3/COSMIC (F3/C) constellation during September Equinox, 2006, near ...solar minimum. The longitudinal structure was first reported in IMAGE satellite airglow observations at the far‐ultraviolet (FUV) 135.6‐nm wavelength during March Equinox, 2002, near solar maximum. The global three‐dimensional ionospheric electron density observed by F3/C shows a prominent four‐peaked wave‐like longitudinal enhancement in the equatorial ionization anomaly (EIA). The vertical electron density structures observed by F3/C reveal that the feature exists mainly above 250 km altitude indicating that the feature is an F‐region phenomenon. The four longitudinal F‐region enhancements of the EIA peaks may result from a stronger equatorial plasma fountain at each longitude region produced by a stronger F‐region eastward electric field transmitted along the magnetic field lines from E‐region where longitudinal variations in atmospheric tides affect the ionospheric dynamo process.
An understanding of ionospheric conductances is important for models of large‐scale dynamics in the Earth's magnetosphere. We parameterize height‐integrated Pedersen and Hall conductances in the ...ionosphere, derived from images of auroral emissions obtained by the Defense Meteorological Satellite Programme low‐altitude orbiting spacecraft, under different interplanetary and solar wind conditions. For the dayside, conductances are parameterized by interplanetary magnetic field clock angle and magnitude, and by season. These dayside conductances are compared to distributions of field‐aligned currents determined from measurements of the Active Magnetosphere and Planetary Electrodynamic Response Experiment. We use these currents to spatially determine a return flow region. We find that the return flow regions exhibit marginally larger conductances than those observed in the polar cap. Conductances in summer exceed those in winter for both the return flow and polar cap regions, on average by a factor of 1.2. On the nightside, we track changes in height‐integrated conductance across the Southern Hemisphere polar regions during an average substorm, following a substorm onset list derived from the SuperMAG database. Mean conductances peak approximately 0.75 hr after substorm onset, with maximum conductances seen in the 23 hr magnetic local time sector.
Plain Language Summary
Low‐altitude spacecraft are able to build up images of aurora in the polar regions with low temporal resolution. Using a combination of these images taken in different wavebands, and after applying a model of atmospheric conditions, we can derive parameters such as ionospheric conductance, integrated along the line of sight from the spacecraft. Knowledge of conductances in the high‐latitude polar regions is important for our understanding of the large‐scale dynamics of the Earth's magnetosphere. We divide our results into two sections. The first section explores conductances in the dayside Northern Hemisphere under the effects of the incoming solar wind and interplanetary magnetic field. We compare these conductances to large‐scale patterns of ionospheric currents derived from a separate constellation of satellites. The currents can be used to define certain polar regions, and we compare conductances between these regions. The second section examines conductances under different phases of a substorm, when the magnetosphere is rearranged under the influence of particular driving conditions in the incoming solar wind. The behavior of the conductances is consistent with known patterns of substorm progression, and we show that peak conductances are seen half an hour after substorm onset.
Key Points
The return flow region exhibits marginally larger conductances than those in the polar cap
Peak conductances occur at 23 hr magnetic local time within 1 hr after substorm onset
Conductances remain elevated at 02 hr magnetic local time for a prolonged period after substorm onset
Occurrence Statistics of Horse Collar Aurora Bower, G. E.; Milan, S. E.; Paxton, L. J. ...
Journal of geophysical research. Space physics,
20/May , Letnik:
127, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Horse collar aurora (HCA) are an auroral feature where the dawn and dusk sector auroral oval moves polewards and the polar cap becomes teardrop shaped. They form during prolonged periods of northward ...interplanetary magnetic field (IMF), when the IMF clock angle is small. Their formation has been linked to dual‐lobe reconnection (DLR) closing magnetic flux at the dayside magnetopause. The conditions necessary for DLR are currently not well‐understood therefore understanding HCA statistics will allow DLR to be studied in more detail. We have identified over 600 HCA events between 2010 and 2016 in UV images captured by the Special Sensor Ultraviolet Spectrographic Imager instrument on‐board the Defense Meteorological Satellite Program spacecraft F16, F17 and F18. As expected, there is a clear preference for HCA occurring during northward IMF. We find no clear seasonal dependence in their occurrence, with an average of 8 HCA events per month. The occurrence of HCA events does not appear to depend on the Bx component of the IMF. Considering the average radiance intensity across the dusk‐dawn meridian shows the HCA as a separate bulge inside the auroral oval and that the dawn side arc of the HCA is usually brighter than the dusk in the Lyman‐Birge‐Hopfield short band. We relate this to the expected field aligned current pattern of HCA formation. We further suggest that transpolar arcs observed in the dawn sector simultaneously in both northern and southern hemispheres are misidentified HCA.
Plain Language Summary
Horse collar auroras (HCA) form when the auroras move to high latitudes at dawn and dusk. They have been proposed to be formed by a process called dual‐lobe reconnection, which takes place when the interplanetary magnetic field (IMF) embedded in the solar wind is directed almost exactly northwards. We study the occurrence of HCA in auroral observations from the Special Sensor Ultraviolet Spectrographic Imager instrument onboard satellites of the Defense Meteorological Satellite Program for the years 2010 to 2016. Studying the occurrence of HCA and the solar wind conditions under which they form allows us to gain new insights into the conditions necessary for dual‐lobe reconnection (DLR) to occur which are currently not well‐understood. We find that there are approximately 8 HCA events per month, with no seasonal dependence, and that the IMF must be within 30 degrees of northwards. When looked at by season no variation is seen in the IMF Bx component therefore suggesting that Bx is not an important factor in the occurrence of HCA. We also note a dawn‐dusk asymmetry in the brightness of the HCAs, which we attribute to the polarity of the field‐aligned electrical currents which produce the auroras.
Key Points
Horse collar aurora, teardrop shaped polar cap, occur frequently approximately 8 times per month and are linked to dual lobe reconnection
Interplanetary magnetic field Bx does not appear to be an important factor in determining the occurrence of horse collar aurora
The dawn arc of the horse collar auroras is usually brighter than the dusk
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