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Articles 1 - 30 of 44
Full-Text Articles in Physical Sciences and Mathematics
Two Substellar Survivor Candidates; One Found And One Missing, T. Von Hippel, N. Walters, J. Farihi, T.R. Marsh, E. Breedt, P.W. Cauley, J.J. Hermes
Two Substellar Survivor Candidates; One Found And One Missing, T. Von Hippel, N. Walters, J. Farihi, T.R. Marsh, E. Breedt, P.W. Cauley, J.J. Hermes
Publications
This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveal a 9.98 h orbital period, where the benchmark brown dwarf has ��2 = 68 ± 8 MJup, ��eff ≈ 2100 K, and a cooling age under 1 Gyr. A substellar mass in the lower range of allowed values is favoured by the gravitational redshift of the primary. Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but lines below the bandhead are notably overpredicted. The known infrared excess towards PG 0010+281 …
One-Parameter Darboux-Deformed Fibonacci Numbers, Stefani C. Mancas, H. C. Rosu
One-Parameter Darboux-Deformed Fibonacci Numbers, Stefani C. Mancas, H. C. Rosu
Publications
One-parameter Darboux deformations are effected for the simple ODE satisfied by the continuous generalizations of the Fibonacci sequence recently discussed by Faraoni and Atieh [Symmetry 13, 200 (2021)], who promoted a formal analogy with the Friedmann equation in the FLRW homogeneous cosmology. The method allows the introduction of deformations of the continuous Fibonacci sequences, hence of Darboux-deformed Fibonacci (non integer) numbers. Considering the same ODE as a parametric oscillator equation, the Ermakov-Lewis invariants for these sequences are also discussed.
On A Guiding Of Whistler-Mode Waves By Density Gradients, Anatoly V. Streltsov
On A Guiding Of Whistler-Mode Waves By Density Gradients, Anatoly V. Streltsov
Publications
Observations from satellites demonstrate that in the magnetosphere, VLF whistler-mode waves are frequently detected in the narrow transition regions, where the plasma density changes its magnitude over a short distance across the ambient magnetic field. These observations suggest that the small-scale, isolated density gradients can guide the VLF whistler-mode waves along the field. We investigate the guiding of the whistler-mode waves by the transverse density gradients with a size much less than the characteristic perpendicular size of the wave. We found analytical solutions describing these waves in the plasma with a sharp density discontinuity between two homogeneous regions, and confirm …
Wavenumbers 3 And 4 Quasi 2-Day Wave Activities Observed By Multiple Meteor Radars In The Two Hemispheres During Austral Summer, Hao Cheng, Kai Ming Huang, Alan Z. Liu, Shao Dong Zhang, Chun Ming Huang, Yun Gong
Wavenumbers 3 And 4 Quasi 2-Day Wave Activities Observed By Multiple Meteor Radars In The Two Hemispheres During Austral Summer, Hao Cheng, Kai Ming Huang, Alan Z. Liu, Shao Dong Zhang, Chun Ming Huang, Yun Gong
Publications
Combining observations from three meteor radars in the Northern Hemisphere (NH) and a meteor radar in the Southern Hemisphere (SH) and reanalysis data, we present successive wavenumbers 3 and 4 (W3 and W4) quasi 2 day wave activities in austral summer. In the mesosphere and lower thermosphere, the wave exhibits two burst activities. The W3 dominates the first burst, while the W4 is the predominate mode in the second burst. The mode transition arises in the late January and is completed around the end of January. The W3 and W4 have the nearly same dominate period of about 46 hr …
Coupling Evidence From Lower Atmosphere To Mesosphere And Ionosphere Through Quasi 27-Day Oscillation, Alan Z. Liu, Kaiming Huang, Hao Cheng, Shaodong Zhang, Chunming Huang, Yun Gong, Gang Chen
Coupling Evidence From Lower Atmosphere To Mesosphere And Ionosphere Through Quasi 27-Day Oscillation, Alan Z. Liu, Kaiming Huang, Hao Cheng, Shaodong Zhang, Chunming Huang, Yun Gong, Gang Chen
Publications
Using meteor radar, radiosonde and digisonde observations and MERRA-2 reanalysis data from 12 August to 31 October 2006, we report a dynamical coupling from the tropical lower atmosphere to the mesosphere and ionospheric F2 region through a quasi 27-day intraseasonal oscillation (ISO). It is interesting that the quasi 27-day ISO is active in the troposphere and stratopause and mesopause regions, exhibiting a three-layer structure. In the mesosphere and lower thermosphere (MLT), the amplitude in the zonal wind increases from about 4 ms at 90 km to 15 ms at 100 km, which is different from previous observations that ISOs generally …
The Dynamics Of Tsunamigenic Acoustic-Gravity Waves And Bathymetry Effect, Pavel Alexandrovich Inchin, Christopher James Heale, Jonathan Brian Snively, Matthew David Zettergren
The Dynamics Of Tsunamigenic Acoustic-Gravity Waves And Bathymetry Effect, Pavel Alexandrovich Inchin, Christopher James Heale, Jonathan Brian Snively, Matthew David Zettergren
Publications
The investigation of atmospheric tsunamigenic acoustic and gravity wave (TAGW) dynamics, from the ocean surface to the thermosphere, is performed through the numerical computations of the 3D compressible nonlinear Navier-Stokes equations. Tsunami propagation is first simulated using a nonlinear shallow water model, which incorporates instantaneous or temporal evolutions of initial tsunami distributions (ITD). Surface dynamics are then imposed as a boundary condition to excite TAGWs into the atmosphere from the ground level. We perform a case study of a large tsunami associated with the 2011 M9.1 Tohuku-Oki earthquake, and parametric studies with simplified and demonstrative bathymetry and ITD. Our results …
Climatology Of High-Frequency Gravity Waves Observed By An Airglow Imager At Andes Lidar Observatory, Alan Z. Liu, Bing Cao
Climatology Of High-Frequency Gravity Waves Observed By An Airglow Imager At Andes Lidar Observatory, Alan Z. Liu, Bing Cao
Publications
The long-term climatology of high-frequency quasi-monochromatic gravity waves is presented using multi-year airglow images observed at Andes Lidar Observatory (ALO, 30.3ºS, 70.7ºW) in northern Chile. A large number of high-frequency gravity waves were retrieved from OH airglow images. The distribution of primary wave parameters including horizontal wavelength, vertical wavelength, intrinsic wave speed, and intrinsic wave period are obtained and are in the ranges of 20–30 km, 15–25 km, 50–100 ms-1, and 5–10 min, respectively. The waves tend to propagate against the local background winds and show clear seasonal variations. In austral winter (Ma–Aug), the observed wave occurrence frequency is higher …
Response Of Planetary Waves And Tides To The 2019 Southern Hemisphere Ssw And Q2dw Enhancement In Jan-Feb 2020 Observed By Condor Meteor Radar In Chile And Adelaide Meteor Radar In Australia, Alan Liu, Zishun Qiao, Iain Reid, Javier Fuentes, Chris Adami
Response Of Planetary Waves And Tides To The 2019 Southern Hemisphere Ssw And Q2dw Enhancement In Jan-Feb 2020 Observed By Condor Meteor Radar In Chile And Adelaide Meteor Radar In Australia, Alan Liu, Zishun Qiao, Iain Reid, Javier Fuentes, Chris Adami
Publications
A new multi-static meteor radar (CONDOR) has recently been installed in northern Chile. This CONDOR meteor radar (30.3°S, 70.7°W) and the Adelaide meteor radar (35°S, 138°E) have provided longitudinally spaced observations of the mean winds, tides and planetary waves of the PW-tides interaction cases we present here. We have observed a Quasi-6-Day Wave (Q6DW) enhancement in MLT winds at the middle latitudes (30.3°S, 35°S) during the unusual minor South Hemisphere SSW 2019 by the ground-based meteor radars. Tidal analysis also indicates modulation of the Q6DW w/ amplitude ~15 [m/s] and diurnal tides w/ amplitude ~60 [m/s]. Another case we present …
Characteristics Of Kelvin-Helmholtz Waves As Observed By The Mms From September 2015 To June 2017, Katariina Nykyri, Xuanye Ma, Rachel C. Rice
Characteristics Of Kelvin-Helmholtz Waves As Observed By The Mms From September 2015 To June 2017, Katariina Nykyri, Xuanye Ma, Rachel C. Rice
Publications
The Magnetospheric Multiscale (MMS) mission has presented a new opportunity to study the fine scale structures and phenomena of Earth’s magnetosphere, including cross scale processes associated with the Kelvin-Helmholtz Instability (KHI). We present an overview of 19 MMS observations of the KHI from September 2015 to June 2017. Unitless growth rates and unstable solid angles for each of the 19 events were calculated using 5 techniques to automatically detect plasma regions on either side of the magnetopause boundary. There was no apparent correlation between solar wind conditions during the KHI and its growth rate and unstable solid angle, though we …
Hydrodynamics, Andrei Ludu
Hydrodynamics, Andrei Ludu
Publications
The mathematical description of the states of a fluid is based on the study of three fields defined on the domain occupied by the fluid: the velocity field V, the density ρ, and the pressure field P. These three “unknowns” are determined by integrating other five scalar equations, namely the mass conservation (continuity equation), the three components of the equation of momentum balance (Euler or Navier–Stokes), and the energy balance. This last equation needs in addition information about the thermodynamics of the fluid, so it may need to be supplied with some equation of state. In addition to these five …
Kinematics Of Fluids, Andrei Ludu
Kinematics Of Fluids, Andrei Ludu
Publications
The goal of this chapter is to discuss the general frame of hydrodynamics, like particle trajectories (path lines), streamlines, streak lines, free surfaces, and fluid surfaces, and to compare their behavior in the Eulerian and Lagrangian frames. The following sections and chapters proceed on the assumption that the fluid is practically continuous and homogeneous in structure. Of course, the concept of continuum is an abstraction that does not take into account the molecular and nuclear structure of matter. In that, we assume that the properties of the fluid do not change if we consider smaller and smaller amounts of matter …
Tutorial: Neuro-Symbolic Ai For Mental Healthcare, Kaushik Roy, Usha Lokala, Manas Gaur, Amit Sheth
Tutorial: Neuro-Symbolic Ai For Mental Healthcare, Kaushik Roy, Usha Lokala, Manas Gaur, Amit Sheth
Publications
Artificial Intelligence (AI) systems for mental healthcare (MHCare) have been ever-growing after realizing the importance of early interventions for patients with chronic mental health (MH) conditions. Social media (SocMedia) emerged as the go-to platform for supporting patients seeking MHCare. The creation of peer-support groups without social stigma has resulted in patients transitioning from clinical settings to SocMedia supported interactions for quick help. Researchers started exploring SocMedia content in search of cues that showcase correlation or causation between different MH conditions to design better interventional strategies. User-level Classification-based AI systems were designed to leverage diverse SocMedia data from various MH conditions, …
Meteor Radar Vertical Wind Observation Biases And Mathematical Debiasing Strategies Including The 3dvar+Div Algorithm, Alan Z. Liu, Zishun Qiao, Gunter Stober, Alexander Kozlovsky, Ales Kuchar, Christoph Jacobi, Chris Meek, Diego Janches, Guiping Liu, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Nicholas Mitchell
Meteor Radar Vertical Wind Observation Biases And Mathematical Debiasing Strategies Including The 3dvar+Div Algorithm, Alan Z. Liu, Zishun Qiao, Gunter Stober, Alexander Kozlovsky, Ales Kuchar, Christoph Jacobi, Chris Meek, Diego Janches, Guiping Liu, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Nicholas Mitchell
Publications
Meteor radars have become widely used instruments to study atmospheric dynamics, particularly in the 70 to 110 km altitude region. These systems have been proven to provide reliable and continuous measurements of horizontal winds in the mesosphere and lower thermosphere. Recently, there have been many attempts to utilize specular and/or transverse scatter meteor measurements to estimate vertical winds and vertical wind variability. In this study we investigate potential biases in vertical wind estimation that are intrinsic to the meteor radar observation geometry and scattering mechanism, and we introduce a mathematical debiasing process to mitigate them. This process makes use of …
Overview Of The Clpsych 2022 Shared Task: Capturing Moments Of Change In Longitudinal User Posts, Adam Tsakalidis, Jenny Chim, Iman Munire Bilal, Ayah Zirikly, Dana Atzil-Slonim, Federico Nanni, Philip Resnik, Manas Gaur, Kaushik Roy, Becky Inkster, Jeff Leintz, Maria Liakata
Overview Of The Clpsych 2022 Shared Task: Capturing Moments Of Change In Longitudinal User Posts, Adam Tsakalidis, Jenny Chim, Iman Munire Bilal, Ayah Zirikly, Dana Atzil-Slonim, Federico Nanni, Philip Resnik, Manas Gaur, Kaushik Roy, Becky Inkster, Jeff Leintz, Maria Liakata
Publications
We provide an overview of the CLPsych 2022 Shared Task, which focusses on the automatic identification of Moments of Change in longitudinal posts by individuals on social media and its connection with information regarding mental health . This year's task introduced the notion of longitudinal modelling of the text generated by an individual online over time, along with appropriate temporally sensitive evaluation metrics. The Shared Task consisted of two subtasks: (a) the main task of capturing changes in an individual's mood (drastic changes-`Switches'- and gradual changes -`Escalations'- on the basis of textual content shared online; and subsequently (b) the sub-task …
Learning To Automate Follow-Up Question Generation Using Process Knowledge For Depression Triage On Reddit Posts, Shrey Gupta, Anmol Agarwal, Manas Gaur, Kaushik Roy, Vignesh Narayanan, Ponnurangam Kumaraguru, Amit Sheth
Learning To Automate Follow-Up Question Generation Using Process Knowledge For Depression Triage On Reddit Posts, Shrey Gupta, Anmol Agarwal, Manas Gaur, Kaushik Roy, Vignesh Narayanan, Ponnurangam Kumaraguru, Amit Sheth
Publications
Conversational Agents (CAs) powered with deep language models (DLMs) have shown tremendous promise in the domain of mental health. Prominently, the CAs have been used to provide informational or therapeutic services (e.g., cognitive behavioral therapy) to patients. However, the utility of CAs to assist in mental health triaging has not been explored in the existing work as it requires a controlled generation of follow-up questions (FQs), which are often initiated and guided by the mental health professionals (MHPs) in clinical settings. In the context of `depression', our experiments show that DLMs coupled with process knowledge in a mental health questionnaire …
Applying Expansive Framing To An Integrated Mathematics-Computer Science Unit, Kimberly Evagelatos Beck, Jessica F. Shumway
Applying Expansive Framing To An Integrated Mathematics-Computer Science Unit, Kimberly Evagelatos Beck, Jessica F. Shumway
Publications
In this research report for the National Council of Teachers of Mathematics 2022 Research Conference, we discuss the theory of Expansive Framing and its application to an interdisciplinary mathematics-computer science curricular unit.
How Education On Climate Change Affects Consumers' Willingness To Participate In Carbon Offsetting Programs?, Leila Halawi, Deanna Demattio
How Education On Climate Change Affects Consumers' Willingness To Participate In Carbon Offsetting Programs?, Leila Halawi, Deanna Demattio
Publications
If airlines could have a better understanding of how to induce sustainable behavior in their customers, they can use these methods when building sustainable initiatives such as voluntary carbon offsetting programs. The purpose of the study was to determine if education on the consequences of climate change affects how consumers behave related to their interaction with carbon offsetting programs. Regional Scenarios were introduced with a natural disaster comparable to the region under review. A multistage sampling technique was utilized in this study. Firstly, using a cluster sample, groups were used rather than individual units of the target population. The results …
Ionospheric Feedback And Ulf Quarter-Waves, Anatoly Streltsov, Evgeny V. Mishin
Ionospheric Feedback And Ulf Quarter-Waves, Anatoly Streltsov, Evgeny V. Mishin
Publications
This paper presents results from the numerical investigation of nonlinear feedback interactions between ULF field-aligned currents (FACs) and the ionospheric plasma in the global magnetospheric resonator with a non-symmetrical distribution of the plasma density in the conjugate hemispheres. The density asymmetry is enhanced by the introduction of the ionospheric valley in the hemisphere where the plasma density is already lower. The main result from this study is that in the non-symmetrical resonator, the ionospheric feedback mechanism, driven by the electric field with the maximum amplitude of 50 mV/m, develops nonlinear, intense, small-scale upward currents with a characteristic quarter-wavelength structure along …
Rocket Measurements Of Electron Energy Spectra From Earth’S Photoelectron Production Layer, Glyn A. Collinson, Alex Glocer, Dennis Chornay, Robert Mitchell, Rob Pfaff, Tim Cameron, Et. Al.
Rocket Measurements Of Electron Energy Spectra From Earth’S Photoelectron Production Layer, Glyn A. Collinson, Alex Glocer, Dennis Chornay, Robert Mitchell, Rob Pfaff, Tim Cameron, Et. Al.
Publications
Photoelectrons are crucial to atmospheric physics. They heat the atmosphere, strengthen 28 planetary ambipolar electric fields, and enhance the outflow of ions to space. However, 29 there exist only a handful of measurements of their energy spectrum near the peak of 30 photoproduction. We present calibrated energy spectra of pristine photoelectrons at their 31 source by a prototype Dual Electrostatic Analyzer (DESA) instrument flown on July 11 32 2021 aboard the Dynamo-2 sounding rocket (NASA № 36.357). Photopeaks arising from 33 30.4nm He-II spectral line were observed throughout the flight above 120km. DESA also 34 successfully resolved the rarely observed …
Stability Characteristics Of The Mesopause Region Above The Andes, Fan Yang, Alan Z. Liu
Stability Characteristics Of The Mesopause Region Above The Andes, Fan Yang, Alan Z. Liu
Publications
We report a detailed analysis of atmospheric stabilities in the mesopause region (85–100 km) based on over 2,000 hr of high-resolution temperature and horizontal wind measurements made with a Na lidar at the Andes Lidar Observatory, located in Cerro Pachón, Chile (30.25°S, 70.74°W). The square of Brunt–Väisälä frequency and the Richardson number are calculated, and occurrence probabilities of convective and dynamic instabilities are derived. An approach to assess the biases due to measurement uncertainties is used to obtain more accurate occurrence probabilities. The overall occurrence probabilities of convective and dynamic instabilities are 2.7% and 6.7%, respectively. High-, medium-, and low- …
"Design For Co-Design" In A Computer Science Curriculum Research-Practice Partnership, Victor R. Lee, Jody Clarke-Midura, Jessica F. Shumway, Mimi Recker
"Design For Co-Design" In A Computer Science Curriculum Research-Practice Partnership, Victor R. Lee, Jody Clarke-Midura, Jessica F. Shumway, Mimi Recker
Publications
This paper reports on a study of the dynamics of a Research-Practice Partnership (RPP) oriented around design, specifically the co-design model. The RPP is focused on supporting elementary school computer science (CS) instruction by involving paraprofessional educators and teachers in curricular co-design. A problem of practice addressed is that few elementary educators have backgrounds in teaching CS and have limited available instructional time and budget for CS. The co-design strategy entailed highlighting CS concepts in the mathematics curriculum during classroom instruction and designing computer lab lessons that explored related ideas through programming. Analyses focused on tensions within RPP interaction dynamics …
Revisit Of Open Clusters Upk 39, Upk 41 And Phoc 39 : A New Binary Open Cluster Found, Xianhao Ye, Terry D. Oswalt, Jingkun Zhao, Yong Yang, Gang Zhao
Revisit Of Open Clusters Upk 39, Upk 41 And Phoc 39 : A New Binary Open Cluster Found, Xianhao Ye, Terry D. Oswalt, Jingkun Zhao, Yong Yang, Gang Zhao
Publications
We investigate the three open clusters near Aquila Rift cloud, named as UPK 39 (c1 hereafter), UPK 41 (c2 hereafter) in Sim et al. (2019) and PHOC 39 (c3 hereafter) in Hunt & Reffert (2021), respectively. Using photometric passpands, reddening, and extinction from Gaia DR3, we construct the color-absolute-magnitude diagram (CAMD). Using isochrone fits their ages are estimated as 6.3 ± 0.9, 8.1 ± 1.4 and 21.8 ± 2.2 Myr, respectively. Their proper motions and radial velocities, estimated using data from Gaia and LAMOST are very similar. From their orbits, relative distances among them at different times, kinematics, ages, and …
Adapting To Low Colorado River Flows And Storage: Lessons From 3 Computer Exercises, David E. Rosenberg
Adapting To Low Colorado River Flows And Storage: Lessons From 3 Computer Exercises, David E. Rosenberg
Publications
As Colorado River flows and reservoir levels decline, discussion is ramping up about adapting operations to low flow and storage because existing operations adapt only to storage. This post reviews three recent computer exercises that adapted Colorado River operations to low flow and low storage. Three final paragraphs synthesize lessons to build towards more equitable and sustainable operations.
Climatology Of Deep O+ Dropouts In The Night-Time F-Region In Solar Minimum Measured By A Langmuir Probe Onboard The International Space Station, Shantanab Debchoudhury, Aroh Barjatya, Joseh I. Minow, Victoria N. Coffey, Linda N. Parker
Climatology Of Deep O+ Dropouts In The Night-Time F-Region In Solar Minimum Measured By A Langmuir Probe Onboard The International Space Station, Shantanab Debchoudhury, Aroh Barjatya, Joseh I. Minow, Victoria N. Coffey, Linda N. Parker
Publications
The Floating Potential Measurement Unit (FPMU) onboard the International Space Station includes a Wide sweeping Langmuir Probe (WLP) that has been operating in the F-region of the ionosphere at ∼400 km since 2006. While traditional Langmuir probe estimates include critical plasma parameters like electron density and temperature, we have also extracted the O+ percentage from the total ion constituents. This O+ composition dataset from the recent minimum in the Solar Cycle 24 reveals orbits with dropouts in O+ to below 80% of the total background ion density at ISS orbital altitudes. The observed O+ percentages during these dropouts are much …
Modeling Studies Of Gravity Wave Dynamics In Highly Structured Environments: Reflection, Trapping, Instability, Momentum Transport, Secondary Gravity Waves, And Induced Flow Responses, Wenjun Dong, David C. Fritts, Michael P. Hickey, Alan Z. Liu, Thomas S. Lund, Shaodong Zhang, Yanying Yan, Fan Yang
Modeling Studies Of Gravity Wave Dynamics In Highly Structured Environments: Reflection, Trapping, Instability, Momentum Transport, Secondary Gravity Waves, And Induced Flow Responses, Wenjun Dong, David C. Fritts, Michael P. Hickey, Alan Z. Liu, Thomas S. Lund, Shaodong Zhang, Yanying Yan, Fan Yang
Publications
A compressible numerical model is applied for three-dimensional (3-D) gravity wave (GW) packets undergoing momentum deposition, self-acceleration (SA), breaking, and secondary GW (SGW) generation in the presence of highly-structured environments enabling thermal and/or Doppler ducts, such as a mesospheric inversion layer (MIL), tidal wind (TW), or combination of MIL and TW. Simulations reveal that ducts can strongly modulate GW dynamics. Responses modeled here include reflection, trapping, suppressed transmission, strong local instabilities, reduced SGW generations, higher altitude SGW responses, and induced large-scale flows. Instabilities that arise in ducts experience strong dissipation after they emerge, while trapped smaller-amplitude and smaller-scale GWs can …
Statistical Characteristics Of High-Frequency Gravity Waves Observed By An Airglow Imager At Andes Lidar Observatory, Alan Z. Liu, Bing Cao
Statistical Characteristics Of High-Frequency Gravity Waves Observed By An Airglow Imager At Andes Lidar Observatory, Alan Z. Liu, Bing Cao
Publications
The long-term statistical characteristics of high-frequency quasi-monochromatic gravity waves are presented using multi-year airglow images observed at Andes Lidar Observatory (ALO, 30.3° S, 70.7° W) in northern Chile. The distribution of primary gravity wave parameters including horizontal wavelength, vertical wavelength, intrinsic wave speed, and intrinsic wave period are obtained and are in the ranges of 20–30 km, 15–25 km, 50–100 m s−1, and 5–10 min, respectively. The duration of persistent gravity wave events captured by the imager approximately follows an exponential distribution with an average duration of 7–9 min. The waves tend to propagate against the local background winds and …
Mesosphere And Lower Thermosphere Changes Associated With The 2 July 2019 Total Eclipse In South America Over The Andes Lidar Observatory, Cerro Pachon, Chile, A. Liu, F. Vargas, G. Swenson, C. Segura, P. Vega, J. Fuentes, D. Pautet, M. Taylor, Y. Zhao, Y. Morton, H. Bourne
Mesosphere And Lower Thermosphere Changes Associated With The 2 July 2019 Total Eclipse In South America Over The Andes Lidar Observatory, Cerro Pachon, Chile, A. Liu, F. Vargas, G. Swenson, C. Segura, P. Vega, J. Fuentes, D. Pautet, M. Taylor, Y. Zhao, Y. Morton, H. Bourne
Publications
This article presents the results of a week of observations around the 2 July 2019, total Chilean eclipse. The eclipse occurred between 19:22 and 21:46 UTC, with complete sun disc obscuration at 20:38–20:40 UTC (16:38–16:40 LT) over the Andes Lidar Observatory (ALO) at (30.3°S, 70.7°W). Observations were carried out using ALO instrumentation with the goal to observe possible eclipse-induced effects on the mesosphere and lower thermosphere region (MLT; 75–105 km altitude). To complement our data set, we have also utilized TIMED/SABER temperatures and ionosonde electron density measurements taken at the University of La Serena's Juan Soldado Observatory. Observed events include …
A Monte Carlo Method For Evaluating Empirical Gyrochronology Models And Its Application To Wide Binary Benchmarks, Tomomi Otani, Ted Von Hippel, Derek Buzasi, Terry Oswalt, Alexander Stone-Martinez, Patrice Majewski
A Monte Carlo Method For Evaluating Empirical Gyrochronology Models And Its Application To Wide Binary Benchmarks, Tomomi Otani, Ted Von Hippel, Derek Buzasi, Terry Oswalt, Alexander Stone-Martinez, Patrice Majewski
Publications
No abstract provided.
The Replacement Rule For Nonlinear Shallow Water Waves, A. Ludu, Z. Zong
The Replacement Rule For Nonlinear Shallow Water Waves, A. Ludu, Z. Zong
Publications
When a (1 + 1)-dimensional nonlinear PDE in real function η(x, t) admits localized traveling solutions we can consider L to be the average width of the envelope, A the average value of the amplitude of the envelope, and V the group velocity of such a solution. The replacement rule (RR or nonlinear dispersion relation) procedure is able to provide a simple qualitative relation between these three parameters, without actually solve the equation. Examples are provided from KdV, C-H and BBM equations, but the procedure appears to be almost universally valid for such (1 + 1)-dimensional nonlinear PDE and their …
Improving White Dwarfs As Chronometers With Gaia Parallaxes And Spectroscopic Metallicities, Adam Moss, Ted Von Hippel, Elliot Robinson, Kareem El-Badry, David C. Stenning, David Van Dyk, Morgan Fouesneau, Coryn A.L. Bailer-Jones, Elizabeth Jeffery, Jimmy Sargent, Isabelle Kloc, Natalie Moticska
Improving White Dwarfs As Chronometers With Gaia Parallaxes And Spectroscopic Metallicities, Adam Moss, Ted Von Hippel, Elliot Robinson, Kareem El-Badry, David C. Stenning, David Van Dyk, Morgan Fouesneau, Coryn A.L. Bailer-Jones, Elizabeth Jeffery, Jimmy Sargent, Isabelle Kloc, Natalie Moticska
Publications
White dwarfs (WDs) offer unrealized potential in solving two problems in astrophysics: stellar age accuracy and precision. WD cooling ages can be inferred from surface temperatures and radii, which can be constrained with precision by high-quality photometry and parallaxes. Accurate and precise Gaia parallaxes along with photometric surveys provide information to derive cooling and total ages for vast numbers of WDs. Here we analyze 1372 WDs found in wide binaries with main-sequence (MS) companions and report on the cooling and total age precision attainable in these WD+MS systems. The total age of a WD can be further constrained if its …