Physics
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/52
The Physics department is committed to education and research in physics, the study of the fundamental universal laws that govern the behavior of matter and energy, and the exploration of the consequences and applications of those laws. Our department is widely known for its excellent teaching and student mentoring. Our department plays an important role in the university’s Core Curriculum. We have strong academic programs with several options for undergraduate physics majors, leading to the B.S. degree, as well as graduate curricula leading to the M.S. and Ph.D. degrees. Our research groups span a variety of fields within physics. Our principal concentrations are in Astrophysics, Relativity, Gravitation and Cosmology, Condensed Matter Physics, Lasers and Optics, Physics Education, Solar Physics, and the Space Science and Engineering Lab.
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Item Comparing exploratory factor models of the Brief Electricity and Magnetism Assessment and the Conceptual Survey of Electricity and Magnetism(2019-10) Eaton, Philip; Frank, Barrett; Johnson, Keith; Willoughby, Shannon D.While numerous studies have analyzed the conceptions probed by the Force Concept Inventory (FCI), assessments dedicated to electricity and magnetism lack similar analyses. This paper investigated the conceptions explored by the Brief Electricity and Magnetism Assessment (BEMA) and the Conceptual Survey of Electricity and Magnetism (CSEM) using exploratory factor analysis techniques. Exploratory factor analysis (EFA) was performed on both assessments using 5368 and 4941 postinstruction student responses for the BEMA and CSEM, respectively. A 6-factor EFA generated model was found for the CSEM, and was fit against another sample of 4964 student responses using confirmatory factor analysis to supply evidence for the possible generalizability of the model. The 5-factor EFA generated model for the BEMA could not be fit against another sample when trying to check for generalizability. The EFA generated factor models for the BEMA and CSEM were then compared and found to be similar in conceptual content, with the exception of one or two factors. Thus, from a factor analysis perspective, the BEMA and CSEM were found to be similar in conceptual content as revealed by student responses. With a better understanding of these electricity and magnetism assessments, future research into this domain of physics will then be able to make stronger conclusions based on students’ results within these assessments.Item Electron Spin Coherence in Optically Excited States of Rare-Earth Ions for Microwave to Optical Quantum Transducers(2019-06) Welinski, Sacha; Woodburn, Philip J.; Lauk, Nikolai; Cone, Rufus L.; Simon, Christoph; Goldner, Philippe; Thiel, Charles W.Efficient and reversible optical to microwave transducers are required for entanglement transfer between superconducting qubits and light in quantum networks. Rare-earth-doped crystals with narrow optical and spin transitions are a promising system for enabling these devices. Current resonant transduction approaches use ground-state electron spin transitions that have coherence lifetimes often limited by spin flip-flop processes and spectral diffusion, even at very low temperatures. We investigate spin coherence in an optically excited state of an Er3+: Y2SiO5 crystal at temperatures from 1.6 to 3.5 K for a low 8.7 mT magnetic field compatible with superconducting resonators. Spin coherence and population lifetimes of up to 1.6 μs and 1.2 ms, respectively, are measured by optically detected spin echo experiments. Analysis of decoherence processes suggest that ms coherence can be reached at lower temperatures for the excited-state spins, whereas ground-state spin coherence would be limited to a few μs due to resonant interactions with other Er3+ spins in the lattice and greater instantaneous spectral diffusion from the radio-frequency control pulses. We propose a quantum transducer scheme with potential for close to unity efficiency that exploits the advantages offered by spin states of the optically excited electronic energy levels.Item Can We Probe Planckian Corrections at the Horizon Scale with Gravitational Waves?(2019-02) Addazi, Andrea; Marcianò, Antonino; Yunes, NicolásFuture detectors can be used as gravitational microscopes to probe the horizon structure of merging black holes with gravitational waves. But, can this microscope probe the quantum regime? We study this interesting question and find that (i) the error in the distance resolution is exponentially sensitive to errors in the Love number, (ii) the uncertainty principle of quantum gravity forces a fundamental resolution limit, and (iii) conclusions about the structure of spacetime at small distances rely on assumptions about the properties of the (unknown) compact objects considered.Item Identifying Sagittarius Stream Stars by Their APOGEE Chemical Abundance Signatures(2019-02) Hasselquist, Sten; Carlin, Jeffrey L.; Holtzman, Jon A.; Shetrone, Matthew; Hayes, Christian R.; Cunha, Katia; Smith, Verne; Beaton, Rachael L.; Sobeck, Jennifer; Allende Prieto, Carlos; Majewski, Steven R.; Anguiano, Borja; Bizyaev, Dmitry; Garcia-Hernandez, D. A.; Lane, Richard R.; Pan, Kaike; Nidever, David L.; Fernandez-Trincado, Jose G.; Wilson, John C.; Zamora, OlgaThe SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey provides precise chemical abundances of 18 chemical elements for similar to 176,000 red giant stars distributed over much of the Milky Way Galaxy (MW), and includes observations of the core of the Sagittarius dwarf spheroidal galaxy (Sgr). The APOGEE chemical abundance patterns of Sgr have revealed that it is chemically distinct from the MW in most chemical elements. We employ a k-means clustering algorithm to six-dimensional chemical space defined by [(C+N)/Fe], [O/Fe], [Mg/Fe], [Al/Fe], [Mn/Fe], and [Ni/Fe] to identify 62 MW stars in the APOGEE sample that have Sgr-like chemical abundances. Of the 62 stars, 35 have Gaia kinematics and positions consistent with those predicted by N-body simulations of the Sgr stream, and are likely stars that have been stripped from Sgr during the last two pericenter passages (<2 Gyr ago). Another 20 of the 62 stars exhibit chemical abundances indistinguishable from the Sgr stream stars, but are on highly eccentric orbits with median r(apo) similar to 25 kpc. These stars are likely the "accreted" halo population thought to be the result of a separate merger with the MW 8-11 Gyr ago. We also find one hypervelocity star candidate. We conclude that Sgr was enriched to [Fe/H] similar to -0.2 before its most recent pericenter passage. If the "accreted halo" population is from one major accretion event, then this progenitor galaxy was enriched to at least [Fe/H] similar to -0.6, and had a similar star formation history to Sgr before merging.Item Evidence of Microbursts Observed Near the Equatorial Plane in the Outer Van Allen Radiation Belt(2018-08) Shumko, Mykhaylo; Turner, Drew L.; O'Brien, T. P.; Claudepierre, Seth G.; Sample, John; Hartley, D. P.; Fennel, Joseph; Blake, J. Bernard; Gkioulidou, Matina; Mitchell, Donald G.We present the first evidence of electron microbursts observed near the equatorial plane in Earth’s outer radiation belt. We observed the microbursts on 31 March 2017 with the Magnetic Electron Ion Spectrometer and Radiation Belt Storm Probes Ion Composition Experiment on the Van Allen Probes. Microburst electrons with kinetic energies of 29–92 keV were scattered over a substantial range of pitch angles, and over time intervals of 150–500 ms. Furthermore, the microbursts arrived without dispersion in energy, indicating that they were recently scattered near the spacecraft. We have applied the relativistic theory of wave-particle resonant diffusion to the calculated phase space density, revealing that the observed transport of microburst electrons is not consistent with the hypothesized quasi-linear approximation.Item Microburst Scale Size Derived From Multiple Bounces of a Microburst Simultaneously Observed With the FIREBIRD-II CubeSats(2018-09) Shumko, Mykhaylo; Sample, John; Johnson, Arlo; Blake, Bern; Crew, Alex; Spence, Harlan; Klumpar, David; Agapitov, Oleksiy; Handley, MatthewWe present the observation of a spatially large microburst with multiple bounces made simultaneously by the Focused Investigation of Relativistic Electron Bursts: Intensity, Range, and Dynamics II (FIREBIRD‐II) CubeSats on 2 February 2015. This is the first observation of a microburst with a subsequent decay made by two coorbiting but spatially separated spacecraft. From these unique measurements, we place estimates on the lower bounds of the spatial scales as well as quantify the electron bounce periods. The microburst's lower bound latitudinal scale size was 29 ± 1 km and the longitudinal scale size was 51 ± 1 km in low Earth orbit. We mapped these scale sizes to the magnetic equator and found that the radial and azimuthal scale sizes were at least 500 ± 10 km and 530 ± 10 km, respectively. These lower bound equatorial scale sizes are similar to whistler mode chorus wave source scale sizes, which supports the hypothesis that microbursts are a product of electron scattering by chorus waves. Lastly, we estimated the bounce periods for 200‐ to 800‐keV electrons and found good agreement with four common magnetic field models.Item Using local correlation tracking to recover solar spectral information from a slitless spectrograph(2018-01) Courrier, Hans T.; Kankelborg, Charles C.The Multi-Order Solar EUV Spectrograph (MOSES) is a sounding rocket instrument that utilizes a concave spherical diffraction rating to form simultaneous images in the diffraction orders m=0, +1, and -1. MOSES is designed to capture high-resolution cotemporal spectral and spatial information of solar features over a large two-dimensional field of view. Our goal is to estimate the Doppler shift as a function of position for every MOSES exposure. Since the instrument is designed to operate without an entrance slit, this requires disentangling overlapping spectral and spatial information in the m=±1 images. Dispersion in these images leads to a field-dependent displacement that is proportional to Doppler shift. We identify these Doppler shift-induced displacements for the single bright emission line in the instrument passband by comparing images from each spectral order. We demonstrate the use of local correlation tracking as a means to quantify these differences between a pair of cotemporal image orders. The resulting vector displacement field is interpreted as a measurement of the Doppler shift. Since three image orders are available, we generate three Doppler maps from each exposure. These may be compared to produce an error estimate.Item An on Orbit Determination of Point Spread Functions for the Interface Region Imaging Spectrograph.(2018-09) Kankelborg, Charles C.; Courrier, Hans T.; De Pontieu, Bart; Wülser, Jean-PierreDecades of research into the Bacteria and Archaea living in geothermal spring ecosystems have yielded great insight into the diversity of life and organismal adaptations to extreme environmental conditions. Surprisingly, while microbial eukaryotes (protists) are also ubiquitous in many environments, their diversity across geothermal springs has mostly been ignored. We used high-throughput sequencing to illuminate the diversity and structure of microbial eukaryotic communities found in 160 geothermal springs with broad ranges in temperature and pH across the Taupō Volcanic Zone in New Zealand. Protistan communities were moderately predictable in composition and varied most strongly across gradients in pH and temperature. Moreover, this variation mirrored patterns observed for bacterial and archaeal communities across the same spring samples, highlighting that there are similar ecological constraints across the tree of life. While extreme pH values were associated with declining protist diversity, high temperature springs harbored substantial amounts of protist diversity. Although protists are often overlooked in geothermal springs and other extreme environments, our results indicate that such environments can host distinct and diverse protistan communities.Item Blind technique for point spread function equalization with application to the Multi-Order Solar Extreme Ultraviolet Spectrograph(2018-05) Atwood, Shane; Kankelborg, Charles C.When combining remote sensing data from multiple instruments or multiple imaging channels, differences in point spread function (PSF) can lead to systematic error. If the PSFs are not well known, then it is difficult to determine which differences in the image data are meaningful for the object being observed and which are artifacts of PSF. Direct PSF measurements can be problematic. For example, in a sounding rocket payload, launch vibrations and acceleration, subsequent operations in micro gravity, and the impact on return to Earth may all affect PSFs. We have developed a blind method to equalize the PSFs of three distinct instrument channels, as found in the Multi-Order Solar Extreme Ultraviolet Spectrograph (MOSES). To validate our technique, we generate three synthetic images with three different PSFs, with some spectrally interesting features. Thence, we demonstrate the successful removal of PSF-induced artifacts is possible, with the genuine spectral features left intact. We also perform blind PSF equalizations on three copies of the same solar image, but with differing PSFs, after applying independent noise to each. The results accurately reproduce corrections performed in the absence of noise, with full knowledge of the PSFs. Finally, we apply PSF equalization to solar images obtained in the 2006 MOSES flight and demonstrate the removal of artifacts.Item Water Vapor Profiling using a Widely Tunable, Amplified Diode Laser Based Differential Absorption Lidar (DIAL)(2009-04) Nehrir, Amin R.; Repasky, Kevin S.; Carlsten, John L.; Obland, Michael D.; Shaw, Joseph A.A differential absorption lidar (DIAL) instrument for automated profiling of water vapor in the lower troposphere has been designed, tested, and is in routine operation at Montana State University. The laser transmitter for the DIAL instrument uses a widely tunable external cavity diode laser (ECDL) to injection seed two cascaded semiconductor optical amplifiers (SOAs) to produce a laser transmitter that accesses the 824–841-nm spectral range. The DIAL receiver utilizes a 28-cm-diameter Schmidt–Cassegrain telescope; an avalanche photodiode (APD) detector; and a narrowband optical filter to collect, discriminate, and measure the scattered light. A technique of correcting for the wavelength-dependent incident angle upon the narrowband optical filter as a function of range has been developed to allow accurate water vapor profiles to be measured down to 225 m above the surface. Data comparisons using the DIAL instrument and collocated radiosonde measurements are presented demonstrating the capabilities of the DIAL instrument.