Optical observations of critical ionization velocity chemical releases in the ionosphere: The role of collisions

Thesis (Ph.D.) University of Alaska Fairbanks, 1996In recent years researchers have pointed out the importance of collisional processes in ionospheric chemical releases performed to study Alfven's critical ionization velocity effect (CIV). Ionizing collisions, including charge exchange with ambient O\sp+ and associative ionization, can not only help initiate CIV, but can also lead to 'contamination' of the ion cloud. Most of the proposed collisions have associated emissions which should be observable with sensitive detectors, but until now have not been attempted since atomic processes had not been considered important. The first four releases of the CRRES satellite were performed to study CIV. The releases were at local dusk over the south Pacific in September, 1990, and were observed from two aircraft with low light level cameras, both filtered and broadband. Ion inventories of the releases show ionization yields (number of ions per number of available neutrals) of 0.02% for Sr, 0.15% for the first Ba release, 0.27% for Ca and 1.48 for the second Ba release. The release clouds were seen to glow quite strongly, below the terminator. The measured light is found to be primarily from line emissions which indicates that it is due to collisional processes in the release cloud. Two measurements were made on the release cloud data; (1) the absolute intensity of the release clouds and (2) the ratio between a broadband intensified CCD (ICCD) and an imaging photon detector filtered for the Ba\sp+ 455.4 nm emission line. The measured ratio is compared to the expected ratio for charge exchange collisions, and to electron impact excitation of Ba. The measured ratio is consistent with emissions being from charge exchange collisions. However, when compared to the total intensity of emissions expected from charge exchange, the absolute intensity in the release cloud measured by the ICCD is five times greater. The two measurements are in conflict, and with this limited set of data cannot be fully resolved. The ratio measurement does indicate that any CIV discharge in the Ba releases was extremely weak, and that charge exchange is the dominant collisional process in Ba releases

Fast flickering aurora within traveling current vortices

第6回極域科学シンポジウム[OS] 宙空圏11月16日（月）　国立極地研究所１階交流アトリウ

A Comparative Study of Spectral Auroral Intensity Predictions from Multiple Electron Transport Models

It is important to routinely examine and update models used to predict auroral emissions resulting from precipitating electrons in Earth's magnetotail. These models are commonly used to invert spectral auroral ground-based images to infer characteristics about incident electron populations when in situ measurements are unavailable. In this work, we examine and compare auroral emission intensities predicted by three commonly used electron transport models using varying electron population characteristics. We then compare model predictions to same-volume in situ electron measurements and ground-based imaging to qualitatively examine modeling prediction error. Initial comparisons showed di erences in predictions by the GLobal airglOW (GLOW) model and the other transport models examined. Chemical reaction rates and radiative rates in GLOW were updated using recent publications and predictions showed better agreement with the other models and the samevolume data, stressing that these rates are important to consider when modeling auroral processes. Predictions by each model exhibit similar behavior for varying atmospheric constants, energies, and energy fluxes. Same-volume electron data and images are highly correlated with predictions by each model, showing that these models can be used to accurately derive electron characteristics and ionospheric parameters based solely on multispectral optical imaging data

Compound auroral micromorphology: ground-based high-speed imaging

Auroral microphysics still remains partly unexplored. Cutting-edge ground-based optical observations using scientific complementary metal-oxide semiconductor (sCMOS) cameras recently enabled us to observe the fine-scale morphology of bright aurora at magnetic zenith for a variety of rapidly varying features for long uninterrupted periods. We report two interesting examples of combinations of fine-scale rapidly varying auroral features as observed by the sCMOS cameras installed at Poker Flat Research Range (PFRR), Alaska, in February 2014. The first example shows that flickering rays and pulsating modulation simultaneously appeared at the middle of a surge in the pre-midnight sector. The second example shows localized flickering aurora associated with growing eddies at the poleward edge of an arc in the midnight secto

Effects of traumatic brain injury on cognitive functioning and cerebral metabolites in HIV-infected individuals.

We explored the possible augmenting effect of traumatic brain injury (TBI) history on HIV (human immunodeficiency virus) associated neurocognitive complications. HIV-infected participants with self-reported history of definite TBI were compared to HIV patients without TBI history. Groups were equated for relevant demographic and HIV-associated characteristics. The TBI group evidenced significantly greater deficits in executive functioning and working memory. N-acetylaspartate, a putative marker of neuronal integrity, was significantly lower in the frontal gray matter and basal ganglia brain regions of the TBI group. Together, these results suggest an additional brain impact of TBI over that from HIV alone. One clinical implication is that HIV patients with TBI history may need to be monitored more closely for increased risk of HIV-associated neurocognitive disorder signs or symptoms

May 2022 School of Graduate Studies Newsletter

Message from the Associate Dean Ph.D. in Aviation News MS in Aviation News MSOSM News MSUS News Eagle News Forever an Eagle College of Aviation Academic Awards Scholarly Activity Daytona Beach Campus Nhttps://commons.erau.edu/db-sgs-newletter/1020/thumbnail.jp

Deletion of Neurturin Impairs Development of Cholinergic Nerves and Heart Rate Control in Postnatal Mouse Hearts

The neurotrophic factor neurturin is required for normal cholinergic innervation of adult mouse heart and bradycardic responses to vagal stimulation. Our goals were to determine effects of neurturin deletion on development of cardiac chronotropic and dromotropic functions, vagal baroreflex response, and cholinergic nerve density in nodal regions of postnatal mice. Experiments were performed on postnatal C57BL/6 wild-type (WT) and neurturin knockout (KO) mice. Serial electrocardiograms were recorded noninvasively from conscious pups using an ECGenie apparatus. Mice were treated with atenolol to evaluate and block sympathetic effects on heart rate (HR) and phenylephrine (PE) to stimulate the baroreflex. Immunohistochemistry was used to label cholinergic nerves in paraffin sections. WT and KO mice showed similar age-dependent increases in HR and decreases in PR interval between postnatal days (P) 2.5 and 21. Treatment with atenolol reduced HR significantly in WT and KO pups at P7.5. PE caused a reflex bradycardia that was significantly smaller in KO pups. Cholinergic nerve density was significantly less in nodal regions of P7.5 KO mice. We conclude that cholinergic nerves have minimal influence on developmental changes in HR and PR, QRS, and QTc intervals in mouse pups. However, cholinergic nerves mediate reflex bradycardia by 1 week postnatally. Deletion of neurturin impairs cholinergic innervation of the heart and the vagal efferent component of the baroreflex early during postnatal development

Observations of Reduced Turbulence and Wave Activity in the Arctic Middle Atmosphere Following the January 2015 Sudden Stratospheric Warming

Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m2/s with an average value of 10 m2/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground-based lidar measurements characterized the ensemble of inertia-gravity waves and monochromatic gravity waves. The ensemble of inertia-gravity waves had a specific potential energy of 0.8 J/kg over the 40- to 50-km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5-hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters