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"space physics"
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Detection and modeling of Rayleigh wave induced patterns in the ionosphere
Global Positioning System (GPS) allows the detection of ionospheric disturbances associated with the vertical displacements of most of the major shallow seismic events. We describe a method to model the time and space distributions of Rayleigh wave induced total electron content (TEC) patterns detected by a dense GPS array. We highlight the conditions for which a part of the ionospheric pattern can be directly measured, at teleseismic distance and above the epicenter. In particular, a satellite elevation angle lower than 40° is a favorable condition to detect Rayleigh wave induced ionospheric waves. The coupling between the solid Earth and its atmosphere is modeled by computing the normal modes of the solid Earth–atmosphere system. We show the dependency of the coupling efficiency on various atmospheric conditions. By summation of the normal modes we model the atmospheric perturbation triggered by a given earthquake. This shows that a part of the observation is a Rayleigh‐induced radiation pattern and therefore characteristic of the seismic rupture. Through atmosphere‐ionosphere coupling, we model the ionospheric perturbation. After the description of the local geomagnetic field anisotropic effects, we show how the observation geometry is strongly affecting the radiation pattern. This study deals with the related data for two earthquakes with far‐field and near‐field observations using the Japanese GPS network GEONET: after the 12 May 2008 Wenchuan earthquake (China) and after the 25 September 2003 Tokachi‐Oki earthquake (Japan), respectively. Waveforms and patterns are compared with the observed TEC perturbations, providing a new step toward the use of ionospheric data in seismological applications. Key Points We describe how Rayleigh‐wave‐induced ionospheric TEC disturbances are observed We propose a model for the observations at near and far field We compare the synthetics with the GPS‐TEC observations
Journal Article
Six not-so-easy pieces : Einstein's relativity, symmetry, and space-time
\"...In the challenging 'Six Not-So-Easy Pieces', Feynman delves into one of the most revolutionary discoveries in twentieth-century physics: Einstein's Theory of Relativity...\"--P. [4] of cover.
Book
The resonant response of the ionosphere imaged after the 2011 off the Pacific coast of Tohoku Earthquake
We provide here a preliminary analysis of the ionospheric perturbations observed after the 11 March 2011 Tohoku Earthquake using a GPS-derived Total Electron Content (TEC) technique. Such anomalies are routinely observed after seismic events of magnitude
M
w
= 6 and more. Here, we use the high density and the wide coverage of the Japanese Global Positioning System (GPS) network GEONET to image the ionosphere just after the main shock. We describe ionospheric perturbations with exceptional extension in amplitude and duration. As already seen in earlier events, a first intense signal is observed about 10 minutes after the seismic rupture; the first response consists in two modes: one propagating beyond 3 km/s and the other at nearly 1 km/s. A further analysis of TEC time series of the latter mode near the source shows the typical frequencies of acoustic resonance. Beyond 400 km from the source, both the tsunami induced gravity wave and a third mode are imaged, the latter for the first time. We show that the pattern of this slow (225 m/s ± 10 m/s) and long period gravity wave (1.8 ± 0.2 mHz) is most visible in the North-West of the epicentral area. This description is corroborated by a computation of the normal modes of the solid Earth-atmosphere system.
Journal Article
Void : the strange physics of nothing
James Owen Weatherall's previous book, The Physics of Wall Street, was a New York Times best-seller and named one of Physics Today's five most intriguing books of 2013. In his newest volume, he takes on a fundamental concept of modern physics: nothing. The physics of stuff--protons, neutrons, electrons, and even quarks and gluons--is at least somewhat familiar to most of us. But what about the physics of nothing? Isaac Newton thought of empty space as nothingness extended in all directions, a kind of theater in which physics could unfold. But both quantum theory and relativity tell us that Newton's picture can't be right. Nothing, it turns out, is an awful lot like something, with a structure and properties every bit as complex and mysterious as matter. In his signature lively prose, Weatherall explores the very nature of empty space--and solidifies his reputation as a science writer to watch.-- Source other than the Library of Congress.
Book
A sublimated water atmosphere on Ganymede detected from Hubble Space Telescope observations
Ganymede’s atmosphere is produced by charged particle sputtering and sublimation of its icy surface. Previous far-ultraviolet observations of the O
i
1,356 Å and O
i
1,304 Å oxygen emissions were used to infer sputtered molecular oxygen (O
2
) as an atmospheric constituent, but an expected sublimated water (H
2
O) component remained undetected. Here we present an analysis of high-sensitivity spectra and spectral images acquired by the Hubble Space Telescope revealing H
2
O in Ganymede’s atmosphere. The relative intensity of the oxygen emissions requires contributions from the dissociative excitation of water vapour, indicating that H
2
O is more abundant than O
2
around the subsolar point. Away from the subsolar region, the emissions are consistent with a pure O
2
atmosphere. Eclipse observations constrain atomic oxygen to be at least two orders of magnitude less abundant than these other species. The higher H
2
O/O
2
ratio above the warmer trailing hemisphere compared with the colder leading hemisphere, the spatial concentration in the subsolar region and the estimated abundance of ~10
15
molecules of H
2
O per cm
2
are consistent with sublimation of the icy surface as source.
Far-UV observations from the Hubble Space Telescope provide evidence of water vapour in the tenuous atmosphere of Ganymede. Atmospheric water originates from surface ice sublimation, with an enrichment in the subsolar region and substantial asymmetry between the leading and trailing hemispheres.
Journal Article
The speed of starlight
Explores the topics of physics, light and color, sound, and space, covering such topics as sonar sound, the speed of light, exploding stars, and the basics of quantum physics.
Book
Turbulence Heating ObserveR – satellite mission proposal
The Universe is permeated by hot, turbulent, magnetized plasmas. Turbulent plasma is a major constituent of active galactic nuclei, supernova remnants, the intergalactic and interstellar medium, the solar corona, the solar wind and the Earth’s magnetosphere, just to mention a few examples. Energy dissipation of turbulent fluctuations plays a key role in plasma heating and energization, yet we still do not understand the underlying physical mechanisms involved. THOR is a mission designed to answer the questions of how turbulent plasma is heated and particles accelerated, how the dissipated energy is partitioned and how dissipation operates in different regimes of turbulence. THOR is a single-spacecraft mission with an orbit tuned to maximize data return from regions in near-Earth space – magnetosheath, shock, foreshock and pristine solar wind – featuring different kinds of turbulence. Here we summarize the THOR proposal submitted on 15 January 2015 to the ‘Call for a Medium-size mission opportunity in ESAs Science Programme for a launch in 2025 (M4)’. THOR has been selected by European Space Agency (ESA) for the study phase.
Journal Article
The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter
The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm
−1
. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described.
Journal Article