Dayside magnetic reconnection allows for the transfer of the solar wind's energy into Earth's magnetosphere. This process takes place in electron diffusion regions (EDRs) embedded in ion diffusion ...regions (IDRs), which form in the magnetopause boundary's current sheet. A significant out-of-plane parallel current contribution in the diffusion regions was reported in Beedle et al. 2023. In order to understand the underlying structure of this parallel current, we compared EDR statistical results with a 2.5D Particle-In Cell (PIC) simulation. From this comparison, we identified out-of-plane parallel current signatures as defining features of the outer EDR and IDR. This significant out-of-plane parallel current indicates the interaction of the IDR and EDR systems, and provides implications for not only understanding energy dissipation in the diffusion regions, but also determining the location of the outer EDR.
ABSTRACT
Elevated atmospheric CO2 can result in larger plants returning greater amounts of residue to the soil. However, the effects of elevated CO2 on carbon (C) and nitrogen (N) cycling for ...different soybean varieties have not been examined. Aboveground residue of eight soybean Glycine max (L.) Merr. varieties was collected from a field study where crops had been grown under two different atmospheric CO2 levels 370 μmol mol−1 (ambient) and 550 μmol mol−1 (free‐air carbon dioxide enrichment, FACE). Senesced residue material was used in a 60‐d laboratory incubation study to evaluate potential C and N mineralization. In addition to assessing the overall effects of CO2 level and variety, a few specific variety comparisons were also made. Across varieties, overall residue N concentration was increased by FACE, but residue C concentration was only slightly increased. Overall residue C to N ratio was lower under FACE and total mineralized N was increased by FACE, suggesting that increased N2 fixation impacted residue decomposition; total mineralized C was also slightly increased by FACE. Across CO2 levels, varietal differences were also observed with the oldest variety having the lowest residue N concentration and highest residue C to N ratio; mineralized N was lowest in the oldest variety, illustrating the influence of high residue C to N ratio. It appears (based on our few specific varietal comparisons) that the breeding selection process may have resulted in some varietal differences in residue quality which can result in increased N or C mineralization under elevated CO2 conditions. This limited number of varietal comparisons indicated that more work investigating varietal influences on soil C and N cycling under elevated CO2 conditions is required.
On April 24th, 2023, a CME event caused the solar wind to become sub-Alfvenic, leading to the development of an Alfven Wing configuration in the Earth's Magnetosphere. Alfven Wings have previously ...been observed as cavities of low flow in Jupiter's magnetosphere, but the observing satellites did not have the ability to directly measure the Alfven Wings' current structures. Through in situ measurements made by the Magnetospheric Multiscale (MMS) spacecraft, the April 24th event provides us with the first direct measurements of current structures during an Alfven Wing configuration. We have found two distinct types of current structures associated with the Alfven Wing transformation as well as the magnetosphere recovery. These structures are observed to be significantly more anti-field-aligned and electron-driven than typical magnetopause currents, indicating the disruptions caused to the magnetosphere current system by the Alfven Wing formation.
Agriculture is a large contributor of trace gas emissions and much of the work on reducing greenhouse gas (GHG) emissions has focused on row crops and pastures, as well as forestry and animal ...production systems; however, little emphasis has been placed on specialty crop industries such as horticulture. Our objective was to determine efflux patterns of CO2, CH4, and N2O associated with four different nursery container sizes 3.0 liter (trade gal; TG), 3.8 liter (#1; 1 gal), 7.6 liter (#2; 2 gal), and 11.4 liter (#3; 3 gal) using dwarf yaupon holly (Ilex vomitoria ‘Nana’ L.) grown under common production practices for one year. Weekly measurements indicated that carbon dioxide (CO2) and nitrous oxide (N2O) fluxes were highest in the largest containers (#3). There was a significant positive relationship between container size and CO2 efflux. Nitrous oxide efflux followed a similar pattern, except there were no differences between the two smallest container sizes. In general, CO2 and N2O fluxes increased with increasing temperature. Methane flux was consistently low and had no significant effect on total trace gas emissions. Results from this study begin to address uncertainties regarding the environmental impact of the horticulture industry on climate change while providing baseline data of trace gas emissions from container production systems needed to develop future mitigation strategies.
Clean chip residual (CCR) is a potential replacement for pine bark (PB) in nursery crop substrates. It is a by-product of in-field forestry harvesting practices and has been shown to produce annual ...plants and perennials similar in size to plants grown in PB. Studies were conducted in two locations, Auburn, AL, and Poplarville, MS, to evaluate growth of woody ornamentals grown in CCR or PB. Five species were tested; Loropetalum chinensis var. rubrum, Buddleja davidii 'Black Knight', Lagerstroemia indica 'Hopi', Lagerstroemia x fauriei 'Natchez', and Rhododendron indicum 'Mrs. G.G. Gerbing'. There were few differences in plant growth indices, leaf chlorophyll content, and inflorescence number over the course of the year for all species at both sites. Percent rootball coverage was generally similar among treatments, though those grown in PB had the greatest percent rootball coverage for loropetalum and buddleja (at both sites) and azalea at Auburn. Shoot dry weight of loropetalum and crapemytrle grown in PB at Poplarville was greater than plants grown in CCR.
Global-scale energy flow throughout Earth's magnetosphere (MSP) is catalyzed by processes that occur at Earth's magnetopause (MP). Magnetic reconnection is one process responsible for solar wind ...entry into and global convection within the MSP, and the MP location, orientation, and motion have an impact on the dynamics. Statistical studies that focus on these and other MP phenomena and characteristics inherently require MP identification in their event search criteria, a task that can be automated using machine learning. We introduce a Long-Short Term Memory (LSTM) Recurrent Neural Network model to detect MP crossings and assist studies of energy transfer into the MSP. As its first application, the LSTM has been implemented into the operational data stream of the Magnetospheric Multiscale (MMS) mission. MMS focuses on the electron diffusion region of reconnection, where electron dynamics break magnetic field lines and plasma is energized. MMS employs automated burst triggers onboard the spacecraft and a Scientist-in-the-Loop (SITL) on the ground to select intervals likely to contain diffusion regions. Only low-resolution data is available to the SITL, which is insufficient to resolve electron dynamics. A strategy for the SITL, then, is to select all MP crossings. Of all 219 SITL selections classified as MP crossings during the first five months of model operations, the model predicted 166 (76%) of them, and of all 360 model predictions, 257 (71%) were selected by the SITL. Most predictions that were not classified as MP crossings by the SITL were still MP-like; the intervals contained mixed magnetosheath and magnetospheric plasmas. The LSTM model and its predictions are public to ease the burden of arduous event searches involving the MP, including those for EDRs. For MMS, this helps free up mission operation costs by consolidating manual classification processes into automated routines.
ACTIVE SPACECRAFT POTENTIAL CONTROL Riedler, W; Torkar, K; RÜdenauer, F ...
Space science reviews,
01/1997, Volume:
79, Issue:
1-2
Journal Article
Peer reviewed
Charging of the outer surface or of the entire structure of a spacecraft in orbit can have a severe impact on the scientific output of the instruments. Typical floating potentials for magnetospheric ...satellites (from +1 to several tens of volts in sunlight) make it practically impossible to measure the cold (several eV) component of the ambient plasma. Effects of spacecraft charging are reduced by an entirely conductive surface of the spacecraft and by active charge neutralisation, which in the case of Cluster only deals with a positive potential. The Cluster spacecraft are instrumented with ion emitters of the liquid-metal ion-source type, which will produce indium ions at 5 to 8 keV energy. The operating principle is field evaporation of indium in the apex field of a needle. The advantages are low power consumption, compactness and high mass efficiency. The ion current will be adjusted in a feedback loop with instruments measuring the spacecraft potential (EFW and PEACE). A stand-alone mode is also foreseen as a back-up. The design and principles of the operation of the active spacecraft potential control instrument (ASPOC) are presented in detail. Flight experience with a similar instrument on the Geotail spacecraft is outlined.PUBLICATION ABSTRACT
Pine bark (PB) for horticultural uses is becoming less available and as a result, there is a need to develop alternative substrates for continued profi tability of the nursery industry. This study, ...conducted at Poplarville, MS, and Auburn, AL, evaluated the growth of nine perennial species in a substrate composed of a pulpwood harvesting by-product called clean chip residual (CCR) which contains approximately 50% wood fi ber. Two CCR particle sizes were used alone or amended with peat moss (PM) (4:1 by vol) and compared with control treatments PB and PB:PM. Substrates composed of 100% PB or 100% CCR had high air space (AS) and low water holding capacity (WHC) which resulted in less available water to plants. Addition of PM lowered AS and increased WHC. There were no significant differences among growth indices at Poplarville for 6 of 8 species and for 3 of 7 species at Auburn, though the remaining 4 species were only slightly smaller when grown in 100% CCR. Shoot dry weight was greatest in substrates amended with PM. Results of this study indicate that acceptable growth of perennial plants can be obtained in substrates composed of CCR when compared to PB and PB amended with PM.
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