Growth of Three Pine Species after Eleven Years on Reclaimed Minesoils In Virginia

Abstract A reforestation experiment was established to test the growth of three pine species on two different surface-mined sites in the Appalachian coalfields of southwest Virginia. One site was mined just prior to enactment of the 1977 Surface Mining Control and Reclamation Act (SMCRA), and one site was mined and reclaimed to its approximate original contour in accordance with post-SMCRA regulations. Three pine species (Pinus taeda, P. virginiana, and P. strobus) were planted on each site in 1981. A fertilization and an herbaceous weed control treatment were tested. Half the plots were fertilized with a 21 g fertilizer tablet at time of planting and a broadcast application of 50 kg/ha N as ammonium nitrate prior to the fourth growing season. Each plot was split to accommodate an herbaceous weed control treatment during the first 3 yr. After 11 yr, all three tree species grew very well on the prelaw bench site, but were less productive on the postlaw AOC site. The fastest growing species was loblolly pine, which averaged 22 ft tall. Aggressive herbaceous ground covers commonly established on surface-mined land to reduce erosion were successfully controlled by herbicides, resulting in a significant improvement in survival and growth for all tree species. Fertilization as used in this study had little effect on growth and was not as beneficial for tree establishment as the herbicide treatment. The performance of these commercial tree species in this study demonstrates that good forest management opportunities exist for the owners of surface-mined land. North. J. Appl. For. 17(3):95–99.</jats:p

Observation of chaotic fluctuations in turbulent plasma

Turbulence is a prevalent phenomenon in space and astrophysical plasmas, often characterized by stochastic fluctuations. While laboratory experiments and numerical simulations have revealed chaotic behavior, in situ observations of turbulent plasmas in natural environments have predominantly shown highly stochastic signatures. Here, we present unprecedented in situ evidence of chaotic fluctuations in the turbulent solar wind plasma downstream of the Earth&apos;s bow shock. By analyzing the relative location of magnetic-field fluctuations on the permutation entropy-complexity plane, we demonstrate that turbulence in the magnetosheath plasma exhibits characteristics of chaotic fluctuations rather than stochastic behavior, diverging from the expected traits of well-developed turbulence. This finding challenges established notions of plasma turbulence and reveals the need for caution when using the magnetosheath as a laboratory for studying plasma turbulence. © 2024 Author(s)

Observations of magnetic reconnection in the transition region of quasi-parallel shocks

Using observations of Earth's bow shock by the Magnetospheric Multiscale mission, we show for the first time that active magnetic reconnection is occurring at current sheets embedded within the quasi-parallel shock's transition layer. We observe an electron jet and heating but no ion response, suggesting we have observed an electron-only mode. The lack of ion response is consistent with simulations showing reconnection onset on sub-ion time scales. We also discuss the impact of electron heating in shocks via reconnection.</p

Bifurcated Current Sheet Observed on the Boundary of Kelvin-Helmholtz Vortices

On May 5, 2017 MMS observed a bifurcated current sheet at the boundary of Kelvin-Helmholtz vortices (KHVs) developed on the dawnside tailward magnetopause. We use the event to enhance our understanding of the formation and structure of asymmetric current sheets in the presence of density asymmetry, flow shear, and guide field, which have been rarely studied. The entire current layer comprises three separate current sheets, each corresponding to magnetosphere-side sunward separatrix region, central near-X-line region, and magnetosheath-side tailward separatrix region. Two off-center structures are identified as slow-mode discontinuities. All three current sheets have a thickness of ∼0.2 ion inertial length, demonstrating the sub-ion-scale current layer, where electrons mainly carry the current. We find that both the diamagnetic and electron anisotropy currents substantially support the bifurcated currents in the presence of density asymmetry and weak velocity shear. The combined effects of strong guide field, low density asymmetry, and weak flow shear appear to lead to asymmetries in the streamlines and the current-layer structure of the quadrupolar reconnection geometry. We also investigate intense electrostatics waves observed on the magnetosheath side of the KHV boundary. These waves may pre-heat a magnetosheath population that is to participate into the reconnection process, leading to two-step energization of the magnetosheath plasma entering into the magnetosphere via KHV-driven reconnection

Microscale processes determining macroscale evolution of magnetic flux tubes along Earth's magnetopause

An important process affecting solar wind-Earth's magnetosphere coupling is nonsteady dayside magnetic reconnection, observationally evidenced by a flux transfer event (FTE) that shows a bipolar variation of the magnetic field component normal to the magnetopause. FTEs often consist of two interlinked flux tubes, but, local kinetic processes between the flux tubes are not understood in the context of the FTE structuring, evolution, and impact. An FTE observed by the Magnetospheric Multiscale mission on 2017 December 18 consisted of two flux tubes of different topology. One includes field lines with ends connected to the northern and southern hemispheres while the other includes field lines with both ends connected to the magnetosheath. Reconnection occurring at the flux-tube interface indicates how interacting flux tubes evolve into a flux rope with helical magnetic topology that is either closed or open. This study demonstrates a new aspect of how micro- to meso-scale dynamics occurring within FTEs determines their macroscale characteristics and evolution.</p