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Doppler Shift (doppler + shift)

Distribution by Scientific Domains
Physics and Astronomy80%

Selected Abstracts

Measurements of Directional Flow Using a Directional Langmuir Probe in Weakly Magnetized Plasmas

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2006
T. Shikama
Abstract Measurement of flow directed with respect to the magnetic field is performed using a directional Langmuir probe (DLP). A previously proposed practical formula for measurement of the Mach number under a weakly magnetized condition is modified for application to the directional flow field which consists of parallel and azimuthal flow components. The effect of density gradient caused by the rotational DLP measurement in the measurement of the radial profile of ion current angular distribution is modified. For the verification of the DLP measurement, parallel flow velocity is measured from the Doppler shift of HeII emission, while azimuthal flow velocity is calculated from E × B and diamagnetic drifts. It is revealed that this method provides plausible Mach numbers in the parallel and azimuthal directions with inclusion of the effect of density gradient. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Fractionally spaced spatial adaptive equalization of S-UMTS mobile terminals,

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2002
Jörgen Nordberg
Abstract In this paper we present fractionally spaced adaptive equalization techniques and space diversity combined receiver and evaluate their performance for the downlink of S-UMTS system. The conventional ,training' (or non-blind) and the ,unsupervised' (or blind) adaptive equalization algorithms are both investigated. Simulation results show that the equalizers are robust to Doppler shift and non-linearity effects due to TWT amplifiers aboard the satellite. It is also shown that even with a moderate array size of two antenna elements, a significant improvement in terminal performance is achieved. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Can variable meridional flows lead to false exoplanet detections?

ASTRONOMISCHE NACHRICHTEN, Issue 10 2007
J.M. Beckers
Abstract The search for habitable exoplanets centers on planets with Earth-like conditions around late type stars. Radial velocity searches for these planets require precisions of 1 m/s and better. That is now being achieved. At these precisions stellar surface motions might lead to false detections. Of particular interest are variable meridional flows on stellar surfaces. I review the available observations of solar surface meridional flows using both Doppler shift and local helioseismology techniques. Interpretation in terms of Doppler shifts in integrated starlight leads to estimates of the likelihood of false detections. It is unlikely that these false detections occur in the habitability zones of exoplanets. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

IR spectroscopy of COmosphere dynamics with the CO ?rst overtone band

ASTRONOMISCHE NACHRICHTEN, Issue 6 2010
T.A. Schad
Abstract We discuss observations of the weak ?rst overtone (,, = 2) CO absorption band near 2300 nm with the U.S. National Solar Observatory Array Camera (NAC), a modern mid-infrared detector. This molecular band provides a thermal diagnostic that forms lower in the atmosphere than the stronger fundamental band near 4600 nm. The observed center-to-limb increase in CO line width qualitatively agrees with the proposed higher temperature shocks or faster plasma motions higher in the COmosphere. The spatial extent of chromospheric shock waves is currently at or below the diffraction limit of the available CO lines at existing telescopes. Five minute period oscillations in line strength and measured Doppler shifts are consistent with the p-mode excitation of the photospheric gas. We also show recent efforts at direct imaging at 4600 nm. We stress that future large-aperture solar telescopes must be teamed with improved, dynamic mid-infrared instruments, like the NAC, to capitalize on the features that motivate such facilities (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Can variable meridional flows lead to false exoplanet detections?

ASTRONOMISCHE NACHRICHTEN, Issue 10 2007
J.M. Beckers
Abstract The search for habitable exoplanets centers on planets with Earth-like conditions around late type stars. Radial velocity searches for these planets require precisions of 1 m/s and better. That is now being achieved. At these precisions stellar surface motions might lead to false detections. Of particular interest are variable meridional flows on stellar surfaces. I review the available observations of solar surface meridional flows using both Doppler shift and local helioseismology techniques. Interpretation in terms of Doppler shifts in integrated starlight leads to estimates of the likelihood of false detections. It is unlikely that these false detections occur in the habitability zones of exoplanets. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]