Millimeter Wavelength Brightness Fluctuations of the Atmosphere Above the South Pole

We report measurements of the millimeter wavelength brightness fluctuations produced by the atmosphere above the South Pole made with the Arcminute Cosmology Bolometer Array Receiver (ACBAR). The data span the 2002 Austral winter during which ACBAR was mounted on the Viper telescope at the South Pole. We recover the atmospheric signal in the presence of instrument noise by calculating the correlation between signals from distinct elements of the ACBAR bolometer array. With this method, it is possible to measure atmospheric brightness fluctuations with high SNR even under the most stable atmospheric conditions. The observed atmospheric signal is characterized by the parameters of the Komolgorov-Taylor (KT) model, which are the amplitude and power law exponent describing the atmospheric power spectrum, and the two components of the wind angular velocity at the time of the observation. The KT model is typically a good description of the observed fluctuations, and fits to the data produce values of the Komolgorov exponent that are consistent with theoretical expectations. By combining the wind angular velocity results with measurements of the wind linear velocity, we find that the altitude of the observed atmospheric fluctuations is consistent with the distribution of water vapor determined from radiosonde data. For data corresponding to frequency passbands centered on 150, 219, and 274 GHz, we obtain median fluctuation power amplitudes of [10, 38, 74] mK^{2} rad^{-5/3} in Rayleigh-Jeans temperature units. Comparing with previous work, we find that these median amplitudes are approximately an order of magnitude smaller than those found at the South Pole during the Austral summer and at least 30 times lower than found at the ALMA site in the Atacama desert.Comment: 13 pages, 15 figures, submitted to ApJ, vertical margins fixe

In Solidarity

This edition of Next Page is a departure from our usual question and answer format with a featured campus reader. Instead, we asked speakers who participated in the College’s recent Student Solidarity Rally (March 1, 2017) to recommend readings that might further our understanding of the topics on which they spoke

Extreme Ultraviolet Variability Experiment (EVE) Multiple EUV Grating Spectrographs (MEGS): Radiometric Calibrations and Results

The NASA Solar Dynamics Observatory (SDO), scheduled for launch in early 2010, incorporates a suite of instruments including the Extreme Ultraviolet Variability Experiment (EVE). EVE has multiple instruments including the Multiple Extreme ultraviolet Grating Spectrographs (MEGS) A, B, and P instruments, the Solar Aspect Monitor (SAM), and the Extreme ultraviolet SpectroPhotometer (ESP). The radiometric calibration of EVE, necessary to convert the instrument counts to physical units, was performed at the National Institute of Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF III) located in Gaithersburg, Maryland. This paper presents the results and derived accuracy of this radiometric calibration for the MEGS A, B, P, and SAM instruments, while the calibration of the ESP instrument is addressed by Didkovsky et al. . In addition, solar measurements that were taken on 14 April 2008, during the NASA 36.240 sounding-rocket flight, are shown for the prototype EVE instruments

Correlations Between Variations in Solar EUV and Soft X-Ray Irradiance and Photoelectron Energy Spectra Observed on Mars and Earth

Solar extreme ultraviolet (EUV; 10-120 nm) and soft X-ray (XUV; 0-10 nm) radiation are major heat sources for the Mars thermosphere as well as the primary source of ionization that creates the ionosphere. In investigations of Mars thermospheric chemistry and dynamics, solar irradiance models are used to account for variations in this radiation. Because of limited proxies, irradiance models do a poor job of tracking the significant variations in irradiance intensity in the EUV and XUV ranges over solar rotation time scales when the Mars-Sun-Earth angle is large. Recent results from Earth observations show that variations in photoelectron energy spectra are useful monitors of EUV and XUV irradiance variability. Here we investigate photoelectron energy spectra observed by the Mars Global Surveyor (MGS) Electron Reflectometer (ER) and the FAST satellite during the interval in 2005 when Earth, Mars, and the Sun were aligned. The Earth photoelectron data in selected bands correlate well with calculations based on 1 nm resolution observations above 27 nm supplemented by broadband observations and a solar model in the 0-27 nm range. At Mars, we find that instrumental and orbital limitations to the identifications of photoelectron energy spectra in MGS/ER data preclude their use as a monitor of solar EUV and XUV variability. However, observations with higher temporal and energy resolution obtained at lower altitudes on Mars might allow the separation of the solar wind and ionospheric components of electron energy spectra so that they could be used as reliable monitors of variations in solar EUV and XUV irradiance than the time shifted, Earth-based, F(10.7) index currently used

Spicules in IRIS Mg II Observations: Automated Identification

We have developed an algorithm to identify solar spicules in the first-ever systematic survey of on-disk spicules using exclusively Mg II spectral observations. Using this algorithm we identify 2219 events in three IRIS datasets with unique solar feature targets spanning a total of 300 minutes: 1) an active region, 2) decayed active region/active network, and 3) a coronal hole. We present event statistics and relate occurrence rates to underlying photospheric magnetic field strength. This method identifies spicule event densities and occurrence rates similar to previous studies performed using H{\alpha} and Ca II observations of active regions. Additionally, this study identifies spicule-like events at very low rates at magnetic field intensities below 20 Gauss and increasing significantly between 100-200 Gauss in active regions and above 20 Gauss in coronal holes, which can be used to inform future observation campaigns. This information can be be used to help characterize spicules over their full lifetime, and compliments existing H-{\alpha} spectral capabilities and upcoming Ly-{\alpha} spectral observations on the SNIFS Sounding Rocket. In total, this study presents a method for detecting solar spicules using exclusively Mg II spectra, and provides statistics for spicule occurrence in Mg II wavelengths with respect to magnetic field strength for the purpose of predicting spicule occurrences.Comment: 17 pages, 9 figures, presented at the AGU Fall 2022 conference, Submitted to AAS Journa

Validity of the second law in nonextensive quantum thermodynamics

The second law of thermodynamics in nonextensive statistical mechanics is discussed in the quantum regime. Making use of the convexity property of the generalized relative entropy associated with the Tsallis entropy indexed by q, Clausius' inequality is shown to hold in the range of q between zero and two. This restriction on the range of the entropic index, q, is purely quantum mechanical and there exists no upper bound of q for validity of the second law in classical theory.Comment: 12 pages, no figure

Children's understandings of obesity, a thematic analysis

Childhood obesity is a major concern in today’s society. Research suggests the inclusion of the views and understandings of a target group facilitates strategies that have better efficacy. The objective of this study was to explore the concepts and themes that make up children’s understandings of the causes and consequences of obesity. Participants were selected from Reception (4-5 years old) and Year 6 (10-11 years old), and attended a school in an area of Sunderland, in North East England. Participants were separated according to age and gender, resulting in four focus groups, run across two sessions. A thematic analysis (Braun & Clarke, 2006) identified overarching themes evident across all groups, suggesting the key concepts that contribute to children’s understandings of obesity are ‘‘Knowledge through Education,’’ ‘‘Role Models,’’ ‘‘Fat is Bad,’’ and ‘‘Mixed Messages.’’ The implications of these findings and considerations of the methodology are discussed in full

Solidity of Viscous Liquids

Recent NMR experiments on supercooled toluene and glycerol by Hinze and Bohmer show that small rotation angles dominate with only few large molecular rotations. These results are here interpreted by assuming that viscous liquids are solid-like on short length scales. A characteristic length, the "solidity length", separates solid-like behavior from liquid-like behavior.Comment: Plain RevTex file, no figure

Destruction of density-wave states by a pseudo-gap in high magnetic fields: application to (TMTSF)2_2ClO4_4

A model is presented for the destruction of density-wave states in quasi-one-dimensional crystals by high magnetic fields. The model is consistent with previously unexplained properties of the organic conductors (TMTSF)$_2$ClO$_4$ and (BEDT-TTF)$_2$MHg(SCN)$_4$ (M=K,Rb,Tl). As the magnetic field increases quasi-one-dimensional density-wave fluctuations increase, producing a pseudo-gap in the electronic density of states near the transition temperature. When the pseudo-gap becomes larger than the mean-field transition temperature formation of a density-wave state is not possible.Comment: 4 pages, RevTeX, 2 figures in uuencoded compressed tar file. Small changes to text and Figure 1. Final version to appear in Physical Review Letter

Time decay of the remanent magnetization in the ±J\pm J spin glass model at T=0

Using the zero-temperature Metropolis dynamics, the time decay of the remanent magnetization in the $\pm J$ Edward-Anderson spin glass model with a uniform random distribution of ferromagnetic and antiferromagnetic interactions has been investigated. Starting from the saturation, the magnetization per spin $m$ reveals a slow decrease with time, which can be approximated by a power law:$m(t)=m_{\infty}+ ({t\over a_{0}})^{a_{1}}$, $a_{1} < 0$. Moreover, its relaxation does not lead it into one of the ground states, and therefore the system is trapped in metastable isoenergetic microstates remaining magnetized. Such behaviour is discussed in terms of a random walk the system performs on its available configuration space.Comment: 9 pages, 3 figure