Atmospheric Background Noise Research Articles

Performance of antenna-based and Rydberg quantum RF sensors in the electrically small regime

Rydberg atom electric field sensors are tunable quantum sensors that can perform sensitive radio frequency measurements. Their qualities have piqued interest at longer wavelengths where their small size compares favorably to impedance-matched antennas. Here, we compare the signal detection sensitivity of cm-scale Rydberg sensors to similarly sized room-temperature electrically small antennas with active and passive receiver backends. We present and analyze effective circuit models for each sensor type, facilitating a fair sensitivity comparison for cm-scale sensors. We calculate that contemporary Rydberg sensor implementations are less sensitive than unmatched antennas with active amplification. However, we find that idealized Rydberg sensors operating with a maximized atom number and at the standard quantum limit may perform well beyond the capabilities of antenna-based sensors at room temperature, the sensitivities of both lying below typical atmospheric background noise.

Efficient Methods to Detect Atmospheric Concentration with Low Signal to Noise Ratio on a Sensor Network

Accidental or malicious releases of materials into the air can occur surreptitiously and lead to low concentrations involving very limited changes in the atmospheric background noise. This may result in signal variations on sensors placed in the environment characterized by a low signal-to-noise ratio (SNR). In this work, we aim to provide a selection of efficient online detection methods adapted to low signal to noise ratio (SNR). These methods take into consideration signals that are monitored by a subset of a network of sensors and for a limited period of time. We show that it is possible to detect with a very reasonable false alarm rate only knowing the statistics of the background noise. Derived from the Cumulative Sum (CUSUM), the methods presented and tested here are generalizations to multivariate time series considering space and time sparsity of the exposure of the network of sensors. We show that the methods previously presented in a Gaussian context can easily be extended to a Poisson model which is consistent with particle counting sensors like those used in the frame of radioactivity detection. We demonstrate the validity of the different methods on toy example and then prove its interest on data from the twin experiment of a fictitious radioactive release in an urban area.

Seasonal changes in atmospheric noise levels and the annual variation in pigeon homing performance.

Repeated releases of experienced homing pigeons from single sites were conducted between 1972 and 1974 near Cornell University in upstate New York and between 1982 and 1983 near the University of Pittsburgh in western Pennsylvania, USA. No annual variation in homing performance was observed at these sites in eastern North America, in contrast to results from a number of similar experiments in Europe. Assuming pigeons home using low-frequency infrasonic signals (~0.1-0.3Hz), as has been previously proposed, the annual and geographic variability in homing performance within the northern hemisphere might be explained, to a first order, by seasonal changes in low-frequency atmospheric background noise levels related to storm activity in the North Atlantic Ocean, and by acoustic waveguides formed between the surface and seasonally reversing stratospheric winds. In addition, increased dispersion among departure bearings of test birds on some North American release days was possibly caused by infrasonic noise from severe weather events during tornado and Atlantic hurricane seasons.

Experimental Noise Reducers for an Active Microbarograph Array

Summary Brief outlines are given of the problem of identifying low frequency acoustic waves from atmospheric background noise and of the methods used by UKAEA to improve detection of these waves. An important aspect of the experimental work has been to develop devices to reduce atmospheric pressure noise, suitable for use at existing microbarograph recording sites, and to evaluate their performance in field tests. Some interim results from these experiments are given.

Interdisciplinary innovation: psychoeducational multimedia technologies

This article presents new ideas arising at the intersection of many subfields of psychology – including child, cognitive, developmental, educational, general, personality, and media psychology, – as well as education and multimedia, and leading to the creation of an innovative type of educational multimedia 1 1 Educational multimedia applications” means on-line (e.g., Internet) and off-line (e.g., CD-ROMs and CD-Is) multimedia products and services devoted to learning, teaching, and training of various knowledge domains. In turn, “multimedia” in general refers to a new generation of communication tools, which can draw on a full range of audio-visual resources – from text and data to sound and pictures – and which store and process all these diverse data in a single integrated delivery system. A general definition of multimedia describes an integrated presentation which combines at least three of: • Text (including notes, captions, subtitles and resources such as tables of contents, indexes, dictionaries and help facilities). • Data (such as tables, charts, graphs, spreadsheets, statistics and raw data of various kinds). • Audio (including speech, music, atmospheric background noise and sound effects). • Graphics (often ranging from traditional media such as drawings, prints, maps and posters to images processed or created entirely within a computer). • Photographic images, from negatives, slides, prints or even digital cameras (which record photographic images directly as computer graphics). • Animation (whether recorded on film or video, or created with a computer). • Moving pictures (specifically, digital video either converted from analogue film and video, or created entirely within a computer). technologies – psychoeducational multimedia technologies (PEMTs). The existing educational multimedia applications are critically examined. The nature of PEMTs, their basis, and specific traits are considered. One of the most developing multimedia areas, “edutainment”, is in fact transformed into “psychoedutainment”. Finally, one of the possible kinds of PEMTs – high intellectual and creative educational multimedia technologies (HICEMTs) – are discussed.

Domestic biomass combustion and associated atmospheric emissions in West Africa

Biofuel is the main source of energy for cooking and heating in Africa. In order to estimate the consumption of this resource at a regional level, a database with a spatial resolution of 1° latitude by 1° longitude of the distribution of the amounts of fuel wood and charcoal annually burned in West Africa has been derived. Chemical emission factors for fuel wood, for charcoal burning, and for charcoal fabrication measured during two field experiments are then used in conjunction with this database to produce a second 1° latitude by 1° longitude database of the emissions due to domestic fires for the region. A comparison of these emissions from domestic fires with those of savanna fires, the dominant form of biomass burning in tropical Africa, shows that the relative contribution of the wood fuel (i.e. fuel wood and charcoal) combustion is important for CH4(46%), CO (42%), and nonmethane hydrocarbons (NMHC) (44%), less so for CO2(32%). This source of biomass burning has a different spatial and temporal distribution than that of savanna fires and represents an atmospheric background noise throughout the year, whereas the savanna fires occur during a limited season.

Noise Equivalent Power of Background Limited Thermal Detectors at Submillimeter Wavelengths

With the advent of large submillimeter telescopes at high, dry sites, the atmospheric background noise in a moderate bandwidth can be low enough to challenge the ability of instrument designers to produce sufficiently low noise bolometers to be background limited. We compare the predictions for the noise power of a bolometer observing through an emissive atmosphere, considering the effect of atmospheric absorption, telescope optical efficiency, and detector optical efficiency, with measurements through the atmosphere over Mauna Kea.

Emission of electromagnetic radiation preceding the Ito seismic swarm of 1989

THERE have been several reports1–8 of electromagnetic radiation being detected in air and/or underground before large earthquakes or volcanic eruptions. Unfortunately, such measurements are often plagued by contamination from other sources of noise. We have developed an electrode system that is effective at filtering out urban and atmospheric background noise. Here we report the detection of anomalous electromagnetic signals several hours before the occurrence of large earthquakes near Ito city, Japan, about 150 km from the location of the electrodes. We have also detected anomalous signals about one day before an undersea volcanic eruption that constituted part of the same seismic swarm near Ito. Although the mechanism responsible for such signals is still unclear, these results indicate that their monitoring could be valuable for the prediction of seismic activity.

The ionospheric Alfv/'en resonator

The ionospheric Alfvén resonator (IAR) associated with peculiarities of the plasma distribution in the F-region ionosphere affects significantly the spectral form of electromagnetic noise registered on the Earth's surface and by satellites. The eigenfrequencies of the IAR are in the range from 0.1 to 10 Hz, and the Q-factor is ~ 10. This is proved experimentally by the spectral resonance structure (SRS), excited by lightning, which manifests itself as pronounced minima and maxima in the averaged spectral intensity of atmospheric background noise of a few hertz. A theory for the SRS is constructed which explains the main experimental facts. New ground-based diagnostics of the electron density profile above the F-layer maximum derived from SRS data are discussed.

Measurements of infrasound from artificial and natural sources

A quadrangle array of infrasonic detectors to monitor rocket engine noise during flight through the atmosphere and lower ionosphere monitored the atmospheric background noise, as well, for a period of two hours around the launching time. Data acquired gave a description of the rocket engine noise in the frequency range of 20–0.05 cps. It is proven that signals from rockets igniting in the upper atmosphere and ionosphere travel long distances and can be detected by the ground sensors. The atmospheric background noise consists of a great variety of sources, some of which are pressure fluctuations traveling with low velocity of approximately 5–50 m/sec. Other sources are infrasonic in nature. The data were analyzed by means of analog and mathematical bandwidth filters and power and cross spectra methods. Some studies were made by utilizing calculation of travel time and ray-tracing techniques.