This page contains all entries posted to Physics Announcements in November 2011. They are listed from oldest to newest.
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Announcements for the Department of Physics at UMBC
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November 2011 Archives
UMBC's Prof. Strow, NPP/CrIS, & the future of weather predictions
On 2011 Oct 28 the NPP satellite was launched successfully from Vandenberg AFB. NPP is an acronym for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project [acronyms can be your friend!]
NPP is the first of a new generation of satellites to monitor/predict the long-term climate change AND short-term weather conditions. One of the several instruments on board is the Cross-track Infrared Sounder (CrIS) that provides spectra in ~1300 bins in 3 important bands in the infrared part of the electromagnetic spectrum. UMBC Physics Professor Dr Larrabee Strow leads a team calibrate CrIS. The instrument can measure Earth's surface temperature and atmospheric parameters such as the major 'Greenhouse Gases' H20, CO2 (carbon dioxide) & CH4 (methane).
Gradient Magnetometry in Arbitrary Magnetic Fields.
Dr. Francesco Narducci
Naval Air Systems
Field-able scalar magnetometers have now reached impressive sensitivities on the order of0.1pT √ Hz with laboratory versions promising a few orders of magnitude improvement. However, at this level, practical applications at low frequencies, e.g. anti-submarine warfare (ASW), are limited by environmental noise and not fundamental sensor noise. A standard technique to circumvent this limitation is to employ two magnetometers separated by a given distance (Δz) and subtract the measurements (ΔB), resulting in a so called gradient measurement (ΔB / Δz) that can cancel out common noise. Recently, I proposed a method to measure magnetic field gradients using an atom interferometer1. This method has the unique advantage of being an intrinsic gradiometer with a very short baseline. At the very heart of this device is an atom beam-splitter that can create super-positions of magnetic sensitive transitions using Raman pulses, in contrast with other existing atom interferometer sensors that use magnetically insensitive transitions. In this talk, I’ll discuss our work to measure Raman spectra in the presence of an arbitrary magnetic field. I’ll present the results (and pitfalls!) of our multi-level theoretical model and present the results of our recent measurements.
Location: Physics Bldg., Room 401
Congratulations to our 2010-2011 Doctoral Candidates!
November 2, 2011: Congratulations to our Physics Graduate Students who passed into PhD Candidacy during the past year: Sheng Liu (mentor: Dr. Johnson), Felipe Vallejo Monsalve (mentor: Dr. Hayden), Tao Peng (mentor: Dr. Shih), Malachi Tatum (mentor: Dr. Turner), Anthony Davidson (mentor: Dr. Worchesky), Gergely Dolgos (mentor: Dr. Martins), Steven Buczkowski (mentor: Dr. Martins). These students were honored at the annual Graduate School Doctoral Candidates Reception last night. Pictured (left to right) are Anthony Davidson, Dr. T. Worchesky, and Malachi Tatum.
Debra successfully defended her PhD dissertation on November 10, 2011.
The Impact of Upper Tropospheric Dynamics on Surface Air Quality over the United States
Monitoring air quality and source attribution at the surface requires a vast understanding of radiative and dynamical effects in the lower atmosphere to capture influential processes affecting human health, the environment, and current pollutant standards. In order to accurately determine all sources impacting lower atmospheric composition, a more thorough comprehension of the dynamical, chemical, and radiative coupling of the stratosphere and troposphere is required. Particularly significant is the transport or exchange of trace gases, both natural and anthropogenic, between the stratosphere and troposphere also known as stratosphere-troposphere exchange (STE). During previous research campaigns, STE was found to contribute to the tropospheric ozone budget. In this work, a plan was designed to determine whether or not stratosphere-to-troposphere transport (STT) was a viable mechanism for elevated ozone at the surface, particularly in cases where unhealthy air quality conditions were detected.
An investigation of several case studies in which high levels of surface ozone appear to originate from the stratosphere shows that a variety of dynamical processes from the boundary layer to the lower stratosphere are involved. Starting with the quasigeostrophic equations of vertical and horizontal motion, dynamical parameters can be derived and evaluated from the North American Regional Reanalysis (NARR) meteorological fields. Reanalysis diagnostics, such as Q-vector, can locate the prevailing STT mechanism and capture the extent of vertical transport and mixing into the lower troposphere. Back trajectories from the University of Maryland Baltimore County - Lagrangian Trajectory (UMBC-LT) model released at the ground sites present additional support.
Along with the reanalysis dataset, a combination of satellite-retrieved and surface observations of chemical tracers were utilized to demonstrate the plausibility of a stratospheric source and to rule out anthropogenic surface contributions where possible. The practicality of Atmospheric InfraRed Sounder (AIRS), Tropospheric Emission Spectrometer (TES), and High Resolution Dynamics Limb Sounder (HIRDLS) satellite observations to infer stratospheric transport as the probable source was tested for these case studies and the results supported dynamical evidence of STE using tracer correlations, as in the ozone-water vapor relationship. The overall strategy of implementing satellite, reanalysis, and surface measurements together provided strong evidence that unhealthy ozone anomalies at the ground were incurred primarily by STE in these events and setup future studies of resulting ozone signatures.
Towards High-Speed Optical Quantum Memories.
Dr. Virginia Lorenz
University of Delaware
Quantum memories, capable of controllably storing and releasing a photon, are a crucial component for quantum computing and quantum communication. The majority of quantum memories to date have operated with bandwidths that limit data rates to megahertz. I will present results demonstrating the coherent storage and retrieval of sub-nanosecond low-intensity light pulses with spectral bandwidths exceeding 1 GHz in cesium vapor. The novel memory interaction takes place through a far off-resonant two-photon transition in which the memory bandwidth is dynamically generated by a strong control field.
Location: Physics Bldg., Room 401
Erika successfully defended her PhD Proposal on November 21, 2011.
A Collisional Algorithm for Modeling Debris Disks
Many stars harbor disks of debris, in the form of dust and planetesimals, left over from planet formation. Any planets orbiting in these debris disks will gravitationally perturb the planetesimals, creating morphological features in the disk. These features have a large angular extent on the sky compared to planets, and can be more easily resolved than the planets themselves. We can therefore use images of a resolved debris disk to predict the presence of a perturbing planet and constrain its mass and orbital elements, even when the planet is too faint to be observed.
But to use this planet-finding technique, we need accurate models of the evolution of the disk as it is shaped by the planet. This problem has previously been addressed using N-body integrators to simulate the dynamics of a planet-disk system, but these models neglect or over-approximate the effects of catastrophic collisions between planetesimals. Such collisions affect the dynamics of the planetesimals as well as their size distribution as the kinetic energy of the colliding planetesimals is used to shatter them into smaller fragments.
I propose to develop a debris disk model that combines an N-body integrator to solve the equations of motion for the planetesimals and planets in a disk and a collisional algo- rithm to correct the trajectories of colliding planetesimals and calculate the evolution of the planetesimal size distribution as fragments are created. My model will take as its inputs various parameters such as planetary and stellar mass, the planets’ initial orbital elements, and the initial distribution of planetesimals. The output of my model will be simulated images of the evolved disk. After the model has been completed and tested, I will apply it to archived data of several different resolved debris disks to constrain the mass and orbital elements of confirmed planets and to predict the presence, mass, and orbits of undetected planets.
Chris successfully defended his PhD dissertation on November 29, 2011.
Multivariate Retrieval of Carbon Monoxide
A new technique is presented here to retrieve carbon monoxide (CO) profiles from Atmospheric Emitted Radiance Interferometer (AERI) spectra. This retrieval version deviates from the previous AERI CO retrieval method, which utilized signal processing to determine a constant CO mixing ratio representative of the entire troposphere. Instead, this retrieval version utilizes linear mapping to ascertain an estimate of the CO profile. A detailed analysis is conducted to estimate the error from all aspects of the the linear mapping procedure including measurements, forward modeling of atmospheric radiation, and uncertainty from inputs to the forward model. It was found that the dominant sources of error were from cloud contaminated spectra and uncertainty in absorption line strengths inside the forward model, A new cloud flagging technique that uses a neural network to identify spectra affected by clouds was tested and compared to the previously used version based on brightness temperature contrast. The neural network method decreased uncertainty between AERI and forward model spectra by 30 percent when compared with the previously used version.
First guess CO profiles to the AERI retrieval were from two different sources. One source was an a priori CO profile calculated as the mean profile from 56 individual measurements where each CO profile encompasses tower, aircraft, and satellite CO measurements. The other first guess CO profile came from the AIRS version 5 (AIRSv5) retrieved CO product. Incorporating the AIRS CO profile to the AERI retrieval provided a better estimate of free tropospheric CO when compared with the a priori profile. Using a better upper tropospheric CO estimate resulted in more accurate results from the AERI retrieval below 2 km, thus revealing that an AERI plus AIRS retrieved CO product is superior to either instrument's own CO retrieval working alone. The combined retrieval product is shown to have an RMSE of 10% in the first 2 km of the atmosphere.
The Role of Physics in Industry
Research and Development Updated with Cold Fusion Discussion
Michael M. Fitelson
Chief Scientist, Micro-Systems Enablers
Northrop Grumman Electronic Systems
Today’s High Technology companies, particularly those involved in defense related research, are utilizing advances associated with physics research to an increasing extent. Many of the devices and technologies employed in advanced sensors and computing are leveraging breakthroughs in physics and related disciplines. These breakthroughs encompass quantum optics, quantum information, nano-science, solid state physics, superconductivity, materials science and many other disciplines. One of the more interesting recent developments are the significant advances being made in explaining low energy Nuclear Fusion and the associated experimental results. I will be summarizing some of the leading theoretical and experimental results in the area of “Cold Fusion”.
Location: Physics Bldg., Room 401