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Abstracts of Presentations

 

Research Experiences for Undergraduates (REU)
Abstracts of Presentations
August 6, 2015

 

2014 REUs

 

Enhancing Low-Cost Ozone Spectrometers to Measure Mesospheric Winds and Tides

Poster (PDF)
Omar Alam, Cornell University

Ground-based spectrometers have been developed to measure the concentration, velocity, and temperature of ozone in the mesosphere and lower thermosphere (MLT) using low-cost satellite television electronics to observe the 11.072 GHz spectral line of ozone. A two-channel spectrometer has been engineered to yield various performance improvements, including a doubling of the signal-to-noise ratio, improved data processing efficiency, and lower power consumption at 15 W. Following 2009 and 2012 observations of the seasonal and diurnal variations in ozone concentration near the mesopause, the ozone line was observed at an altitude near 95 km and latitude of 38 degrees north using three single-channel spectrometers located at the MIT Haystack Observatory (Westford, MA), Chelmsford High School (Chelmsford, MA), and Union College (Schenectady, NY) pointed south at 8 degrees. Observations from 2009 through 2014 are used to derive the nightly-averaged seasonal variation in meridional velocity, as well as the seasonally-averaged variation with local solar time. The results indicate a seasonal trend in which the winds at 95 km come from the north at about 10 m/s in the summer of the northern hemisphere, and from the south at about 10 m/s in the winter. Nighttime data from -5 to +5 hours local solar time show a gradual transition of the meridional wind velocity from about -20 m/s to +20 m/s. These two trends correlate with nighttime wind measurements from the Millstone Hill High-Resolution Fábry-Perot Interferometer (FPI) in Westford, MA, which uses the 557.7 nm green line nightglow from atomic oxygen centered at 95 km. The results have also been compared with average meridional winds measured with meteor radar.

 

Optimization of Solar Imaging Using the Murchison Widefield Array
Presentation (PDF)
Kirsten Baker, Carleton College

 

The Murchison Widefield Array (MWA) in Western Australia is currently the best tool available to observe Faraday rotation in the heliosphere that will improve predictions of when coronal mass ejections are going to occur. In order to further study this phenomenon, the dynamic range of solar data from the MWA must be improved to be able to accurately show the bright and highly variable radio emission from the Sun. One such improvement is an extension of the Van Vleck correction formula that corrects the 4-bit signal correlation quantization used by the MWA. This correction has shown an increase in dynamic range from 228:1 to 1425:1, or 6.25 times greater, for a particular half-second interval across three 40 kHz spectral channels. This is just the beginning of a long investigation where the ultimate goal is solar observation with a dynamic range of upwards of 100,000:1.

 

Machine Learning in Ionospheric Phenomena Detection Using Passive Radar
Presentation (PDF)
Soubhik Barari, Tufts University

 

Distributed passive radar networks are powerful sources for large amounts of ionospheric data. At the MIT Haystack Observatory, the ISIS Array (Intercepted Signals for Ionospheric Science) collects petabytes (1,000,000 GB+) of passive radar images daily. While useful for the study of E-region irregularities and other atmospheric events, such large datasets are infeasible for manual annotation and require algorithmic detection and classification. In this project, we discuss a novel statistical learning framework for computer-aided discovery in ionospheric 'big data'. Using techniques from computer vision, image processing, and machine learning, we present a automated discovery pipeline, reporting over 95% accuracy in classifying a generated passive radar dataset of over 200 images.

 

A Comparison of VLBI and GPS Total Electron Content Measurements of the Ionosphere and the Effects of Geomagnetic Anomalies
Poster (PDF)
Avery Bruni, University of Michigan

 

Two different techniques for measuring differenced ionospheric total electron content have previously been established: Very Long Baseline Interferometry, and GPS, but they are subject to different radii of sensitivity. The goal of this research was to compare measurements of the ionosphere between the two methods, hypothesizing that they are both valid techniques for such measurements. It is conceivable that geomagnetic storms could affect the agreement of these two methods, due to the shrinking of the plasmasphere to within the range of detection shared by both, but since VLBI measures differenced TEC, it is hypothesized that the effect of a storm should largely be subtracted out of our detections. The development of a program that can compare these two methods and the results that it has yielded are described and presented in this paper.

 

An Empirical Model for the F1-Region Lower Transition Height from Incoherent Scatter Measurements
Presentation (PDF)
Zachary Hall, Boston University

 

We present the results of applying Bill Oliver’s six parameter fit for resolving the ion mass-temperature ambiguity in the F1 region of the ionosphere on hourly timescales to the entirety of the MIT Haystack dataset of Incoherent Scatter Radar experiments from 2002 to 2015. We find empirically that the transition height, z{50}, key for determining unambiguously the temperature and mass of ions in the lower transition region, reaches a local diurnal minimum between 10 and 12 local time, is maximized during summer periods, and is minimized during winter periods. We also find that the lower transition height has a significant and positive dependence on A{p} index. We present an empirical model for the lower transition height as a function of local time, day number, year, f{10.7}, and A{p} index and find that the amplitude of the annual variation of the lower transition height is 4.31 km, the amplitude of the semiannual variation is 0.51 km, the amplitude of the diurnal variation is 5.73 km, and the amplitude of the semidiurnal variation is 2.87 km. The typical mean value of the lower transition height about which these annual and diurnal variations occur for median geomagnetic and solar activity conditions is found to be 185.9 km.

 

GPGPU Acceleration of ISR Plasma Line Analysis and Application to Arecibo Plasma Line Striations
Poster (PDF)
Nathaniel Hilliard, University of Wisconsin, Madison

 

Weak incoherent scatter radar (ISR) scatter from naturally occuring Langmuir oscillations, or plasma lines, contain high precision information on the altitude-dependent thermal ionospheric electron density. However, analyzing this frequency-dependent scatter over a large number of radar ranges requires large computational power, especially when the goal is realtime analysis. General purpose computing on graphics processing units (GPGPU) offers immense computational speedup when compared to traditional central processing unit (CPU) calculations for highly parallelizable tasks, and it is well suited for ISR analysis. We extend a single graphics processing unit (GPU) algorithmic solution and discuss the algorithm developed. Results indicate an order-of-magnitude improvement over CPU analysis and suggest that GPGPU can achieve realtime speed for plasma line applications.

Arecibo incoherent scatter radar measurements of plasma lines are known to have sharp striations in plasma line power, which vary as a function of the plasma frequency and the aspect angle of the radar beam with respect to the Earth's magnetic field. We explain these striations as a manifestation of a low pitch angle photo-electron population with peaks at energies of approximately 15.5, 23, 27 eV, and 50 eV, corresponding to sharp features known to be present in the photoelectron energy spectrum. Through forward modeling, we predict the locations of the amplitude striations in upshifted plasma-line measurements obtained at Arecibo for different magnetic field aspect angles.

 

An Updated Study of the O+ -O Collision Frequency Using Corresponding FPI
and ISR Thermospheric Wind Experiments at Millstone Hill
Poster (PDF)
Anthony Lima, University of Colorado at Boulder

 

O+-O collision frequency is an important aeronomic parameter associated with upper atmospheric momentum and energy exchanges between O+ and O. In an analysis of Fabry-Perot Interferometer (FPI) and Incoherent Scatter Radar (ISR) data, Burnside [1987] suggested a modification factor (1.7) to the traditional value of O+-O collision frequency. Determining more accurately the Burnside Factor has been the subject for many prior studies with different techniques. This study revisits the Burnside Factor by using an extended FPI and ISR dataset from Millstone Hill. The FPI data used are from an updated high-resolution instrument, which began operation in 2009. The study included data from 95 nights between 2010 and 2015 when the FPI and ISR (with both zenith and steerable antennas) were all operating. Nights with high AP were excluded, leaving 1235 data points in total. The same frequentist approach applied previously in Buonsanto et al. [1997] (using 21 experiments) yields similar right-skewed Burnside Factor distribution on this data. In this study we will discuss results derived using different statistical approaches, including median, mean, and the Bayes theorem. The latter method gives an estimate of 0.68 ± 0.02.

 

Scientific Data Processing on Mobile Devices
Presentation (PDF)
David Mascharka, Drake University

 

Scientific data acquisition in the field is often constrained by data transfer backchannels to analysis environments. Geoscientists are therefore facing practical bottlenecks with increasing sensor density and variety. Mobile devices, such as smartphones and tablets, offer promising solutions to key problems in scientific data acquisition, pre-processing, and validation by providing advanced capabilities in the field. This is due to affordable network connectivity options and the increasing computational power of mobile devices.
This contribution exemplifies a scenario faced by scientists in the field and presents the ''Mahali TEC Processing App'' developed in the context of the NSF-funded Mahali project. Aimed at atmospheric science and the study of ionospheric Total Electron Content (TEC), this app is able to gather data from various dual-frequency GPS receivers. It demonstrates parsing of full-day GPS observation files on mobile devices and on-the-fly computation of vertical TEC values based on satellite ephemeris models that are obtained from NASA. Our experiments show how parallel computing on the mobile device GPU enables fast processing and visualization of up to 2 million datapoints in real-time using OpenGL. GPS receiver bias is estimated through minimum TEC approximations that can be interactively adjusted by scientists in the graphical user interface. Scientists can also perform approximate computations for ''quickviews'' to reduce CPU processing time and memory consumption. In the final stage of our mobile processing pipeline, scientists can upload data to the cloud for further processing.

 

Analysis of the Relationship between a Change in Wind Field Curl Rate and Sea Surface Height within the Beaufort Gyre Region of the Arctic
Presentation (PDF)
Tyler Pelle, State University of New York, Oswego

 

Numerous interconnections exist between atmospheric, oceanic, and sea ice processes that impact the delicate climate system within the Arctic. In particular, the effect of the surface wind's frictional drag on the large scale movement of ocean water and sea ice within the Beaufort Gyre has gained notoriety due to its perceived impact on freshwater doming and oceanic circulation systems. An analysis of the wind field curl is undertaken for the time period of 1996 to 2010 in order to determine if a negative wind curl regime occurred within this time period, which would act to increase the anticyclonic rotation (and possibly freshwater doming) of the Beaufort Gyre. Using surface wind data from the NCEP/NCAR, ECMWF Interim, and JRA-55 reanalyses, a marginal negative wind curl anomaly slope of −0.113 ±0.037 (106m s-2 yr1) was calculated along with insignificant wind curl trend values within this region. Additionally, SI04 autonomous ice drifting platform location data was manipulated to obtain the velocity field and power spectrum of its track. An approximate 12-hour cycle of maximum sea ice velocity is found, which is a product of the Coriolis effect; however, no strong conclusions can be made due to the preliminary nature of these findings. Future research includes a study of the sea surface height and the full power spectrum of the Arctic Ocean in order to draw more concrete conclusions.

 

A New Software User Interface for the Upgraded Haystack 37-meter Radio Telescope
Presentation (PDF)
Matthew Siebert, Cornell University

 

Recently the 37m Haystack antenna has undergone major hardware upgrades that have significantly enhanced its capabilities for radio astronomy observations. A new software user interface was developed to accommodate the new antenna and radiometer capabilities. The UI was designed for both real-time data acquisition and post-processing data pipelines. The software includes three applications that facilitate astronomical observation. The main application is a sky map of radio sources that displays important antenna status information. There is also a discrete source scan (DSS) plotting application, and an application to provide an astronomer with an idea of what is currently up in the sky. These tools give both astronomers and engineers a means to operate and collect data effectively from the 37m telescope.

 

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