443 Works

Global Hybrid Simulations of Interaction Between Interplanetary Rotational Discontinuity and Bow Shock/Magnetosphere: Can Ion-Scale Magnetic Reconnection be Driven by Rotational Discontinuity Downstream of Quasi-Parallel Shock?

Zhifang Guo, Yu Lin & X Wang
Ion-scale magnetic reconnection has been observed downstream of the terrestrial quasi-parallel (Q-parallel to) shock. Whether it is driven by interplanetary discontinuities or turbulent Q-parallel to shock, however, is unclear. Using three-dimensional global hybrid simulation, we investigate the generation of magnetic reconnection downstream of the Q-parallel to shock, while an interplanetary rotational discontinuity (RD) is launched to the bow shock. Cases with various solar wind Alfven Mach numbers, M-A = 3.0 to 8, and propagation directions...

Proton velocity ring-driven instabilities in the inner magnetosphere: Linear theory and particle-in-cell simulations

Kyungguk Min & Kaijun Liu
Linear dispersion theory and electromagnetic particle-in-cell (PIC) simulations are used to investigate linear growth and nonlinear saturation of the proton velocity ring-driven instabilities, namely, ion Bernstein instability and Alfven-cyclotron instability, which lead to fast magnetosonic waves and electromagnetic ion cyclotron waves in the inner magnetosphere, respectively. The proton velocity distribution is assumed to consist of 10% of a ring distribution and 90% of a low-temperature Maxwellian background. Here two cases with ring speeds v(r)/v(A)=1 and...

Fast magnetosonic waves driven by shell velocity distributions

Kyungguk Min & Kaijun Liu
Using linear dispersion theory and particle-in-cell simulations, we explore the ion Bernstein instability driven by the shell-type ion velocity distribution which is related to the excitation of fast magnetosonic waves in the terrestrial magnetosphere. We first demonstrate a novel idea to construct the shell velocity distribution out of multiple Maxwellian ring-beam velocity distributions. Applying this technique, we find that the convergence of the linear theory instability can be achieved with only a moderate number of...

Reversal of magnetic field rotation in the reconnection layer due to shear flow effects

Xiaoxia Sun, Yu Lin & Xiaogang Wang
We investigate the effects of shear flows on the so-called component reconnection, in which the guide field B-y not equal 0, by solving a one-dimensional Riemann problem for magnetopause reconnection using a resistive MHD simulation. Specifically, we consider the existence of a shear flow perpendicular to the antiparallel magnetic field B-z, while a finite shear flow tangential to B-z may also be present. In the cases without a magnetosheath flow and having thus a sheared...

Performance of ryegrass varieties in Alabama, 2021-2022

Henry G. Jordan
Caption title.

Population Demographics of Hiodon tergisus (Mooneye) in the Lower Tallapoosa River

Costas T. Katechis, Peter C. Sakaris & Elise R. Irwin
We describe age structure, growth, and fecundity of Hiodon tergisus (Mooneye) from the lower Tallapoosa River, AL. Mooneye (N = 49, 214–316 mm total length, 79–284 g) were aged using otoliths, and a von Bertalanffy growth model was derived for the species (L∞ = 316, K = 0.285, to = −0.7). Growth rates of Mooneye differed between the Tallapoosa River population and a previously studied population from the northern extent of the species' range (Assiniboine...

Sexual Dimorphism in Growth of Freshwater Drum

Andrew L. Rypel
I examined sexual dimorphism in the long-lived Aplodinotus grunniens (freshwater drum) from five lakes and four rivers in Alabama. Using the Von Bertalanffy growth function combined with nonparametric statistics, I found males and females had similar annual growth rates from years 0–4 years of age, but then showed significantly different growth rates across subsequent ages. Female drum grew significantly faster through adulthood, and ultimately attained significantly larger sizes (L∞ = 510.8 mm, TL) compared to...

Chemokine C-C motif ligand 33 is a key regulator of teleost fish barbel development

Tao Zhou, Ning Li, Yulin Jin, Qifan Zeng, Wendy Prabowo, Yang Liu, Changxu Tian, Lisui Bao, Shikai Liu, Zihao Yuan, Qiang Fu, Sen Gao, Dongya Gao, Rex Dunham, Neil H. Shubin & Zhanjiang Liu
Barbels are important sensory organs in teleosts, reptiles, and amphibians. The majority of similar to 4,000 catfish species, such as the channel catfish (Ictalurus punctatus), possess abundant whisker-like barbels. However, barbel-less catfish, such as the bottlenose catfish (Ageneiosus marmoratus), do exist. Barbeled catfish and barbel-less catfish are ideal natural models for determination of the genomic basis for barbel development. In this work, we generated and annotated the genome sequences of the bottlenose catfish, conducted comparative...

Hybrid simulation of foreshock waves and ion spectra and their linkage to cusp energetic ions

X Wang, Y Lin & S Chang
A three-dimensional global hybrid simulation is carried out to investigate energetic ions and electromagnetic waves in the quasi-parallel (Q-parallel to) bow shock and cusp for a typical interplanetary magnetic field configuration during the cusp energetic particle events. The bow shock, magnetosheath, and dayside magnetosphere form by interaction between the solar wind and geomagnetic dipole field. Ions of solar wind characteristics injected into the system evolve along with electromagnetic waves in a self-consistent manner. Several important...

Generation of near-Earth reconnection by divergent flows in the plasma sheet

Y Lin & D Swift
[1] A global two-dimensional hybrid simulation is carried out to study the evolution of the near-Earth plasma sheet. It is shown that reconnection X lines and plasmoids can be generated by diverging flows in the plasma sheet. These diverging flows can be caused by variations in the Maxwell stress due to variations of B-x and B-z components of the magnetic field outside the current sheet. In addition, the flow acceleration/deceleration in the plasma sheet can...

Performance of small grain varieties in Alabama, 2021-2022

Henry G. Jordan
Caption title.

Magnetosheath Reconnection Before Magnetopause Reconnection Driven by Interplanetary Tangential Discontinuity: A Three-Dimensional Global Hybrid Simulation With Oblique Interplanetary Magnetic Field

Zhifang Guo, Yu Lin, Xueyi Wang & Aimin Du
Terrestrial dayside dynamics associated with a southward turning, oblique interplanetary magnetic field (IMF) carried by an interplanetary tangential discontinuity (TD) is investigated by performing a three-dimensional global-scale hybrid simulation systematically for cases in which the incoming solar wind TD possesses various magnetic field rotation angles Delta Phi = 90 degrees to 180 degrees and half widths w = 2d(i0) to w = 30d(i0) where d(i0), is the ion inertial length in the solar wind. Overall,...

TWINS Observations of the Dynamics of Ring Currents Ion Spectra on March 17 and October 7, 2015

S Shekhar, J Perez & C Ferradas
Direct comparisons between RBSP (Van Allen Probes or Radiation Belt Storm Probes) and TWINS (Two Wide-angle Imaging Neutral-atom Spectrometers) for the main phase of two storms, March 17 and October 7, 2015, showed agreement between the in situ ion measurements and the ion spectra from the deconvolved energetic neutral-atom (ENA) measurements, except when O+ ions were significant. Spatial evolution of individual energy peaks in the ion spectra is studied using TWINS data. O+ ions are...

Foreshock wave interaction with the magnetopause: Signatures of mode conversion

Shi Feng, Lei Cheng, Yu Lin & Xueyi Wang
Our previous hybrid simulation (Shi et al., 2013) under a radial interplanetary magnetic field (IMF) and a supercritical solar wind Mach number has shown that foreshock compressional waves originated from the quasi-parallel (Q-parallel to) shock are mode converted to kinetic Alfven waves (KAWs) at the Alfven resonance surface of the subsolar magnetopause. In this paper, three-dimensional global dayside mode conversion is investigated for cases under various solar wind conditions using the global hybrid model. The...

Proton velocity ring-driven instabilities and their dependence on the ring speed: Linear theory

Kyungguk Min, Kaijun Liu & Peter Gary
Linear dispersion theory is used to study the Alfven-cyclotron, mirror and ion Bernstein instabilities driven by a tenuous (1%) warm proton ring velocity distribution with a ring speed, v(r), varying between 2v(A) and 10v(A), where v(A) is the Alfven speed. Relatively cool background protons and electrons are assumed. The modeled ring velocity distributions are unstable to both the Alfven-cyclotron and ion Bernstein instabilities whose maximum growth rates are roughly a linear function of the ring...

Contribution of increasing CO2 and climate change to the carbon cycle in China's ecosystems

Qiaozhen Mu, Maosheng Zhao, Steven Running, Mingliang Liu & Hanqin Tian
Atmospheric CO2 and China's climate have changed greatly during 1961-2000. The influence of increased CO2 and changing climate on the carbon cycle of the terrestrial ecosystems in China is still unclear. In this article we used a process-based ecosystem model, Biome-BGC, to assess the effects of changing climate and elevated atmospheric CO2 on terrestrial China's carbon cycle during two time periods: (1) the present (1961 2000) and (2) a future with projected climate change under...

Evaluating water stress controls on primary production in biogeochemical and remote sensing based models

Steven Running, Tian Hanqin, Liu Mingliang, Faith Heinsch, Zhao Maosheng & Qiaozhen Mu
Water stress is one of the most important limiting factors controlling terrestrial primary production, and the performance of a primary production model is largely determined by its capacity to capture environmental water stress. The algorithm that generates the global near-real-time MODIS GPP/NPP products (MOD17) uses VPD ( vapor pressure deficit) alone to estimate the environmental water stress. This paper compares the water stress calculation in the MOD17 algorithm with results simulated using a process-based biogeochemical...

Satellite Observations of the Recovery of Forests and Grasslands in Western China

Gang Chengcheng, Gao Xuerui, Peng Shouzhang, Chen Mingxun, Guo Liang & Jin Jingwei
The Grain for Green Program (GGP), which combats and reverses the landscape-scale habitat degradation by converting agricultural lands to forests and grasslands, was launched in 1999 in western China. An assessment of the extent to which the GGP has altered the vegetation cover and ecological functions in these regions is much needed. The present study initially analyzed land use and cover change of forests and grasslands over western China between 2000 and 2015. A variety...

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