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Astrophysics and Astronomy

Embry-Riddle Aeronautical University

Series

2013

Articles 1 - 18 of 18

Full-Text Articles in Physical Sciences and Mathematics

Mapping Of The Quasi-Periodic Oscillations At The Flank Magnetopause Into The Ionosphere, E. R. Dougal, K. Nykyri, T. W. Moore Nov 2013

Mapping Of The Quasi-Periodic Oscillations At The Flank Magnetopause Into The Ionosphere, E. R. Dougal, K. Nykyri, T. W. Moore

Publications

We have estimated the ionospheric location, area, and travel time of quasi-periodic oscillations originating from the magnetospheric flanks. This was accomplished by utilizing global and local MHD models and Tsyganenko semi-empirical magnetic field model on multiple published and four new cases believed to be caused by the Kelvin– Helmholtz Instability. Finally, we used auroral, magnetometer, and radar instruments to observe the ionospheric signatures. The ionospheric magnetic latitude determined using global MHD and Tsyganenko models ranged from 58.3–80.2 degrees in the Northern Hemisphere and −59.6 degrees to −83.4 degrees in the Southern Hemisphere. The ionospheric magnetic local time ranged between 5.0–13.8 …

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A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk Sep 2013

A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk

Publications

We apply a self-consistent and robust Bayesian statistical approach to determine the ages, distances, and zero-age main sequence (ZAMS) masses of 28 field DA white dwarfs (WDs) with ages of approximately 4–8 Gyr. Our technique requires only quality optical and near-infrared photometry to derive ages with <15% uncertainties, generally with little sensitivity to our choice of modern initial–final mass relation. We find that age, distance, and ZAMS mass are correlated in a manner that is too complex to be captured by traditional error propagation techniques. We further find that the posterior distributions of age are often asymmetric, indicating that the …

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Moving Objects In The Hubble Ultra Deep Field, Mukremin Kilic, Alexandros Gianninas, Ted Von Hippel Sep 2013

Moving Objects In The Hubble Ultra Deep Field, Mukremin Kilic, Alexandros Gianninas, Ted Von Hippel

Publications

We identify proper motion objects in the Hubble Ultra Deep Field (UDF) using the optical data from the original UDF program in 2004 and the near-infrared data from the 128 orbit UDF 2012 campaign. There are 12 sources brighter than I = 27 mag that display >3σ significant proper motions. We do not find any proper motion objects fainter than this magnitude limit. Combining optical and near-infrared photometry, we model the spectral energy distribution of each point-source using stellar templates and state-of-the-art white dwarf models. For I ≤ 27 mag, we identify 23 stars with K0-M6 spectral types and two …

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Book Review: Heart Of Darkness: Unraveling The Mysteries Of The Invisible Universe, T. D. Oswalt Sep 2013

Book Review: Heart Of Darkness: Unraveling The Mysteries Of The Invisible Universe, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Heart of Darkness : Unraveling the Mysteries of the Invisible Universe by Jeremiah P. Ostriker and Simon Mitton Princeton, 2013 299p, 9780691134307 $27.95, 9781400844647 $27.95

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First Magnetic Seismology Of The Cme Reconnection Outflow Layer In The Low Corona With 2.5-D Mhd Simulations Of The Kelvin-Helmholtz Instability, Katariina Nykyri, Claire Foullon Aug 2013

First Magnetic Seismology Of The Cme Reconnection Outflow Layer In The Low Corona With 2.5-D Mhd Simulations Of The Kelvin-Helmholtz Instability, Katariina Nykyri, Claire Foullon

Publications

For conditions observed in the low corona, we perform 2.5-D magnetohydrodynamic (MHD) simulations of the Kelvin-Helmholtz instability (KHI) at the surface of a coronal mass ejection (CME). We match the observed time development of the KHI with simulated growth from 110 MHD experiments representing a parametric range of realistic magnetic field strengths and orientations and two key values of the velocity shear, ΔV, inferred from observations. The results are field strengths Be≈ 8–9 G and Bs≈ 10–11 G in the CME reconnection outflow layer and the surrounding sheath, respectively, for ΔV≈770kms−1; for nearly perpendicular orientation (1° tilt) of Bs with …

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Impact Of Mhd Shock Physics On Magnetosheath Symmetry And Kelvin-Helmholtz Instability, K. Nykyri Aug 2013

Impact Of Mhd Shock Physics On Magnetosheath Symmetry And Kelvin-Helmholtz Instability, K. Nykyri

Publications

We have performed 13 three-dimensional global magnetohydrodynamic (MHD) simulations of the magnetosheath plasma and magnetic field properties for Parker spiral (PS) and ortho-Parker spiral interplanetary magnetic field (IMF) orientations corresponding to a wide range of solar wind plasma conditions. To study the growth of the Kelvin-Helmholtz instability on the dawn and dusk flank magnetopause, we have performed 26 local two-dimensional MHD simulations, with the initial conditions taken from global simulations on both sides of the velocity shear layer at the dawn-dusk terminator. These simulations indicate that while the MHD physics of the fast shocks does not directly lead to strong …

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The Statistical Mapping Of Magnetosheath Plasma Properties Based On Themis Measurements In The Magnetosheath Interplanetary Medium Reference Frame, A. P. Dimmock, K. Nykyri Aug 2013

The Statistical Mapping Of Magnetosheath Plasma Properties Based On Themis Measurements In The Magnetosheath Interplanetary Medium Reference Frame, A. P. Dimmock, K. Nykyri

Publications

The magnetosheath operates as a natural filter between the solar wind and the magnetospheric plasma. As a result of this, the magnetosheath plays a crucial role in the plasma momentum and energy transport from the interplanetary medium into the magnetosphere. Statistical studies of the magnetosheath are difficult due to the dynamic nature of the terrestrial bow shock and the magnetopause. As a result of this, the spatial and temporal dependence of magnetosheath plasma properties under varying solar wind conditions is still not completely understood. We present a study of magnetosheath plasma properties using 5 years of THEMIS and OMNI data …

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Mechanisms Of Field-Aligned Current Formation In Magnetic Reconnection, Xuanye Ma, Antonius Otto Aug 2013

Mechanisms Of Field-Aligned Current Formation In Magnetic Reconnection, Xuanye Ma, Antonius Otto

Publications

Satellite observations provide strong evidence for the generation of significant field-aligned currents (FACs) during magnetic reconnection. Reconnection of antiparallel magnetic field does not generate FACs in magnetohydrodynamics (MHD) due to coplanarity in MHD shocks. However, a guide magnetic field and a sheared velocity component are almost always present at the magnetopause and their absence is a singular case. It is illustrated that the presence of these noncoplanar fields requires FACs. Contrary to intuition, such currents are generated more efficiently for a small guide field and are more likely to be a result of the redistribution of already present FACs for …

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Field Localization And Mass Generation In An Alternative 5-Dimensional Brane Model, Preston Jones, Doug Singleton, Gerardo Muñoz, Triyanta Aug 2013

Field Localization And Mass Generation In An Alternative 5-Dimensional Brane Model, Preston Jones, Doug Singleton, Gerardo Muñoz, Triyanta

Publications

This proceedings is from a talk given at the APS DPF 2013 on a 5- dimensional brane world model. This alternative brane world model is formally related but physically distinct from the Randall-Sundrum brane world model. The spin dependent localization of 5D fields for the alternative model are different and in some ways superior to the RandallSundrum. The alternative model also exhibits a cutoff in the localization of massive scalar fields not seen in the Randall-Sundrum model. This revision includes a correction to the integrand for the scalar field action appearing in the principle reference [1].

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Field Localization And The Nambu-Jona-Lasinio Mass Generation Mechanism In An Alternative 5-Dimensional Brane Model, Preston Jones, Gerardo Muñoz, Douglas Singleton, Triyanta Jul 2013

Field Localization And The Nambu-Jona-Lasinio Mass Generation Mechanism In An Alternative 5-Dimensional Brane Model, Preston Jones, Gerardo Muñoz, Douglas Singleton, Triyanta

Publications

We consider a five-dimensional brane world model with a single brane which is distinct from the well known Randall-Sundrum model. We discuss the similarities and differences between our brane model and the Randall-Sundrum brane model. In particular we focus on the localization of five-dimensional fields with different spins—spin 0, spin 1 / 2 , and spin 1—to the brane, and a self-consistent mass-generation mechanism. We find that the brane model studied here has different (and in some cases superior) localization properties for fields/particles with different spins to the brane, as compared to the original five-dimensional brane models. In addition this …

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Measuring The Evolutionary Rate Of Cooling Of Zz Ceti, Anjum S. Mukadam, Ted Von Hippel, Et Al. Jul 2013

Measuring The Evolutionary Rate Of Cooling Of Zz Ceti, Anjum S. Mukadam, Ted Von Hippel, Et Al.

Publications

We have finally measured the evolutionary rate of cooling of the pulsating hydrogen atmosphere (DA) white dwarf ZZ Ceti (Ross 548), as reflected by the drift rate of the 213.13260694 s period. Using 41 yr of time-series photometry from 1970 November to 2012 January, we determine the rate of change of this period with time to be dP/dt = (5.2 ± 1.4) × 10–15 s s–1 employing the O – C method and (5.45 ± 0.79) × 10–15 s s–1 using a direct nonlinear least squares fit to the entire lightcurve. We adopt the dP/dt obtained …

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70 Da White Dwarfs Identified In Lamost Pilot Survey, J. K. Zhao, A. L. Luo, Terry D. Oswalt, G. Zhao Jun 2013

70 Da White Dwarfs Identified In Lamost Pilot Survey, J. K. Zhao, A. L. Luo, Terry D. Oswalt, G. Zhao

Publications

We present a spectroscopically identified catalog of 70 DA white dwarfs (WDs) from the LAMOST pilot survey. Thirty-five are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogs. The effective temperature and gravity of these WDs are estimated by Balmer lines fitting. Most of them are hot WDs. The cooling times and masses of these WDs are estimated by interpolation in theoretical evolution tracks. The peak of the mass distribution is found to be ∼0.6M, which is consistent with prior work in the literature. The distances of these WDs are estimated using the method …

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Tracers Of Chromospheric Structure. I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, A. L. Luo, L. Y. Zhang Apr 2013

Tracers Of Chromospheric Structure. I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, A. L. Luo, L. Y. Zhang

Publications

We present chromospheric activity index SHK measurements for over 13,000 F, G, and K disk stars with high signal-to-noise ratio (>60) spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopic sample. A parameter δS is defined as the difference between SHK and a “zero” emission line fitted by several of the most inactive stars. The SHK indices of subgiant stars tend to be much lower than dwarfs, which provide a way to distinguish dwarfs and giants with relatively low-resolution spectra. Cooler stars are generally more active and display a larger scatter than …

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Tracers Of Chromospheric Structure. I. Caii H&K Emission Distribution Of 13000 F, G And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, L. Y. Zhang Apr 2013

Tracers Of Chromospheric Structure. I. Caii H&K Emission Distribution Of 13000 F, G And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, L. Y. Zhang

Publications

We present chromospheric activity index SHK measurements for over 13,000 F, G and K disk stars with high signal-to-noise ratio (> 60) spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopic sample. A parameter S is defined as the difference between SHK and a ‘zero’ emission line fitted by several of the most inactive stars. The SHK indices of subgiant stars tend to be much lower than dwarfs, which provide a way to distinguish dwarfs and giants with relatively low resolution spectra. Cooler stars are generally more active and display a larger scatter than hotter stars. …

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Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona, Claire Foullon, Erwin Verwichte, Katariina Nykyri, Markus J. Aschwanden, Iain G. Hannah Apr 2013

Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona, Claire Foullon, Erwin Verwichte, Katariina Nykyri, Markus J. Aschwanden, Iain G. Hannah

Publications

New capabilities for studying the Sun allow us to image for the first time the magnetic Kelvin–Helmholtz (KH) instability developing at the surface of a fast coronal mass ejecta (CME) less than 150 Mm above the solar surface. We conduct a detailed observational investigation of this phenomenon, observed off the east solar limb on 2010 November 3, in the EUV with SDO/AIA. In conjunction with STEREO-B/EUVI, we derive the CME source surface position. We ascertain the timing and early evolution of the CME outflow leading to the instability onset. We perform image and spectral analysis, exploring the CME plasma structuring …

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Asymmetry Of Magnetosheath Flows And Magnetopause Shape During Low Alfvén Mach Number Solar Wind, B. Lavraud, E. Larroque, E. Budnik, V. Génot, J. E. Borovsky, M. W. Dunlop, K. Nykyri, Et Al. Mar 2013

Asymmetry Of Magnetosheath Flows And Magnetopause Shape During Low Alfvén Mach Number Solar Wind, B. Lavraud, E. Larroque, E. Budnik, V. Génot, J. E. Borovsky, M. W. Dunlop, K. Nykyri, Et Al.

Publications

Previous works have emphasized the significant influence of the solar wind Alfvén Mach number (MA) on magnetospheric dynamics. Here we report statistical, observational results that pertain to changes in the magnetosheath flow distribution and magnetopause shape as a function of solar wind MA and interplanetary magnetic field (IMF) clock angle orientation. We use all Cluster 1 data in the magnetosheath during the period 2001–2010, using an appropriate spatial superposition procedure, to produce magnetosheath flow distributions as a function of location in themagnetosheath relative to the IMF and other parameters. The results demonstrate that enhanced flows in the magnetosheath are expected …

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Heteroclinic And Homoclinic Connections Between The Sun-Earth Triangular Points And Quasi-Satellite Orbits For Solar Observations, Pedro J. Llanos, Gerald R. Hintz, Martin W. Lo, James K. Miller Jan 2013

Heteroclinic And Homoclinic Connections Between The Sun-Earth Triangular Points And Quasi-Satellite Orbits For Solar Observations, Pedro J. Llanos, Gerald R. Hintz, Martin W. Lo, James K. Miller

Publications

Investigation of new orbit geometries exhibits a very attractive behavior for a spacecraft to monitor space weather coming from the Sun. Several orbit transfer mechanisms are analyzed as potential alternatives to monitor solar activity such as a sub-solar orbit or quasi-satellite orbit and short and long heteroclinic and homoclinic connections between the triangular points L4 and L5 and the collinear point L3 of the CRTBP (circular restricted three-body problem) in the Sun-Earth system. These trajectories could serve as channels through where material can be transported from L5 to L3 by performing small maneuvers at the departure of the Trojan orbit. …

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Book Review: Weird Worlds: Bizarre Bodies Of The Solar System And Beyond, T. D. Oswalt Jan 2013

Book Review: Weird Worlds: Bizarre Bodies Of The Solar System And Beyond, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Weird Worlds : Bizarre Bodies of the Solar System and Beyond by David A. J. Seargent. Springer, 2013 309p, 1461470633 $34.95, 9781461470632 $34.95.

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