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Electromagnetic waves traveling through the ionosphere undergo a Faraday rotation of the polarization vector which modifies the polarization and phase characteristics of the electromagnetic signal.
Magnetic fields of radio sources - spectral and Faraday effect observations
Saturation induced optical nonreciprocity in He-Ne ring laser plasma, eliminating frequency locking by using Faraday effect
Ionospheric electron content at temperature latitudes during declining phase of sunspot cycle determined by observation of Faraday effect
Wave propagation in anisotropic plasma in presence of electron density irregularities, noting Faraday effect
Ionospheric electron density during declining phase of sunspot cycle by Faraday effect observations
We report that the gyrotropic properties of a rotating magnetized plasma are derived analytically. Mechanical rotation leads to a new cutoff for wave propagation along the magnetic field, and polarization rotation above this cutoff is the sum of the classical magneto-optical Faraday effect and the mechanico-optical polarization drag. Exploiting the very large effective group index near the cutoff, we expose here that polarization drag can be 10 4 larger than Faraday rotation at GHz frequency. The rotation leads to weak absorption while allowing direct frequency control, demonstrating the unique potential of rotating plasmas for nonreciprocal elements. The very large rotation frequency of a dense non-neutral plasma could enable unprecedented gyrotropy in the THz regime.
Total ionospheric electron density at magnetic equator from observations of faraday effect on satellite transmissions
Measurement of electron content by faraday effect on satellite beacon transmitters located on magnetic equator
A new read gate design for the vertical Bloch line (VBL) memory is disclosed which offers larger operating margin than the existing read gate designs. In the existing read gate designs, a current is applied to all the stripes. The stripes that contain a VBL pair are chopped, while the stripes that do not contain a VBL pair are not chopped. The information is then detected by inspecting the presence or absence of the bubble. The margin of the chopping current amplitude is very small, and sometimes non-existent. A new method of reading Vertical Bloch Line memory is also disclosed. Instead of using the wall chirality to separate the two binary states, the spatial deflection of the stripe head is used. Also disclosed herein is a compact memory which uses vertical Bloch line (VBL) memory technology for providing data storage. A three-dimensional arrangement in the form of stacks of VBL memory layers is used to achieve high volumetric storage density. High data transfer rate is achieved by operating all the layers in parallel. Using Hall effect sensing, and optical sensing via the Faraday effect to access the data from within the three-dimensional packages, an even higher data transfer rate can be achieved due to parallel operation within each layer.
Magnetic turbulence is directly observed internally in the pedestal of ELMy H-mode tokamak plasmas using a newly developed Faraday-effect polarimetry measurement. Fluctuation amplitude is δb r ≥ 15 G (150–500 kHz), with a ratio of magnetic to density fluctuation |δb r /B|/|δn/n|≥0.15. Here, magnetic turbulence is identified as resulting from micro-tearing-instability and mode growth accompanied by degraded plasma confinement is observed.
Internal fluctuation measurements with Faraday-effect polarimetry in the DIII-D tokamak reveal the onset of a tearing mode with toroidal mode number n = 3 well before it is detected by the sensing coils external to the plasma. This mode appears before the n = 2, 1 modes and is first detected with internal measurements at a lower value of the ideal-wall kink beta limit than is indicated at the time of first detection by the sensing coils. When the mode is first detected, the linear resistive stability parameter, Δ′, indicates marginal stability and continues to do so until later when the mode amplitude begins increasing linearly with time—together suggesting a neoclassical origin for this mode.
A Faraday-effect radial interferometer–polarimeter is designed for the National Spherical Torus Experiment-Upgrade (NSTX-U) to measure multiscale magnetic and density fluctuations critical to understanding fusion plasma confinement and stability, including those originating from magnetohydrodynamic instabilities, energetic particle-driven modes, and turbulence. The diagnostic will utilize the three-wave technique with 5 MHz bandwidth to simultaneously measure line-integrated magnetic and density fluctuations up to the ion-cyclotron frequency. Probe beams will be launched radially from the low-field side at the NSTX-U midplane, where the measured Faraday fluctuations mainly correspond to radial magnetic fluctuations that directly link to magnetic transport. A correlation technique will be employed to reduce the measurement noise to below 0.01° enabling detection of small amplitude fluctuations. Two toroidally displaced chords with 7° separation will be installed to measure toroidal mode numbers up to n = 25 for mode identification. Finally, solid-state microwave sources operating at 321 μm (935 GHz) will be used to minimize the impact of the Cotton–Mouton effect.
We demonstrate the detection of phase-resolved magnetization dynamics with combinatorial magneto-optic Kerr and Faraday effects. The method uses a continuous-wave laser that is amplitude-modulated at the spin dynamic frequencies, and thus allows for coherent tracking of the spin dynamics, akin a “lock-in” type measurement. In particular, our method, using a single 1550-nmwavelength, probes simultaneously the ferromagnetic resonance of Y 3 Fe 5 O 12 (YIG) and Permalloy (Py = Ni 80 Fe 20 ) in a YIG-Pyhetero structure. The fiber-based magneto-optic components also have the advantage of being made into a compact, tabletop or even portable system with yet robust measurement performances. We believe that our method will be found useful in studying hybrid quantum magnonic systems and/or investigating phase-resolved spin dynamics in nanomagnet structures involving both ferromagnetic insulators and metals.
Observational results on Jupiter's high-frequency radiation, for the range 1-35 MHz (10 to 100 m), obtained over the past six years with the aid of orbited telescopes, are surveyed. Spectral distributions, periodic effects, burst waveforms and dynamic spectra of storms, polarization effects, high-resolution interferometry, and possible correlations with solar activity are discussed. Related spacecraft experiments are described. Close attention is given to long-term accumulation of occurrence probability data as functions of time and frequency (synoptic monitoring) on Jovian HF emission, and to dominating effects of the Jovian satellite Io, as well as modulation of periodicities by the 11.9-year orbital motion period of Jupiter. Possible effects of the other four Jovian satellites immersed in the Jovian magnetosphere are also taken into consideration. Absence of a Jovian Faraday effect and polarization of fine burst structure are discussed.
Understanding the emergence of magnetic flux from the solar interior through the photosphere and its global impact on the inner heliosphere is a key scientific goal of the heliophysics community. This white paper outlines the concept of the Multiview Observatory for Solar Terrestrial Science (MOST) mission, which will make measurements of solar variability from the solar interior, atmosphere, and the interplanetary (IP) medium. MOST will be a 4- spacecraft mission with one each at L4 (MOST1) and L5 (MOST2) and the other two (MOST3 and MOST4) at variable locations along Earth orbit. MOST1 and MOST2 will each carry seven remote-sensing and 3 in-situ instruments. All four spacecraft will carry a novel radio package known as the Faraday Effect Tracker of Coronal and Heliospheric structures (FETCH) that will systematically probe the magnetic content of transient IP structures including coronal mass ejections (CMEs) and stream interaction regions (SIRs). The Faraday rotation measurements will provide magnetic content of these structures at various heliocentric distances from the outer corona to Earth’s vicinity. Photospheric and/or chromospheric magnetograms will cover >70% of the solar surface providing synchronic maps needed for accurately modeling the corona and solar wind. EUV, coronagraph, radio spectrograph, and heliospheric imager (HI) observations from multiple viewpoints provide 3-d information on CMEs/CME-driven shocks, SIRs, and other solar wind structures. Hard X-ray imagers will provide the flare aspects of solar eruptions to complement the CME aspects. MOST, a 10-year mission, is well aligned with NASA’s Heliophysics objectives and will provide an unprecedented opportunity to achieve these objectives with broad participation from the heliophysics community.
The effects of the ionospheric retardation of satellite-emitted timing signals was presented. The retardation at the navigation frequencies, which is proportional to the total ionospheric electron content (TEC), was determined by Faraday polarization measurements of VHF emissions of a geostationary satellite. The polarization data yielded TEC up to approximately 1200 km only, since the measurement technique is based on the Faraday effect which is weighted by the terrestrial magnetic field.
A 2015 NASA Aeronautics Mission "Seedling" Proposal is described for a Severe-Environment UAV (SE-UAV) that can perform in-situ measurements in hazardous atmospheric conditions like lightning, volcanic ash and radiation. Specifically, this paper describes the design of a proof-of-concept vehicle and measurement system that can survive lightning attachment during flight operations into thunderstorms. Elements from three NASA centers draw together for the SE-UAV concept. 1) The NASA KSC Genesis UAV was developed in collaboration with the DARPA Nimbus program to measure electric field and X-rays present within thunderstorms. 2) A novel NASA LaRC fiber-optic sensor uses Faraday-effect polarization rotation to measure total lightning electric current on an air vehicle fuselage. 3) NASA AFRC's state-of-the-art Fiber Optics and Systems Integration Laboratory is envisioned to transition the Faraday system to a compact, light-weight, all-fiber design. The SE-UAV will provide in-flight lightning electric-current return stroke and recoil leader data, and serve as a platform for development of emerging sensors and new missions into hazardous environments. NASA's Aeronautics and Science Missions are interested in a capability to perform in-situ volcanic plume measurements and long-endurance UAV operations in various weather conditions. (Figure 1 shows an artist concept of a SE-UAV flying near a volcano.) This paper concludes with an overview of the NASA Aeronautics Strategic Vision, Programs, and how a SE-UAV is envisioned to impact them. The SE-UAV concept leverages high-value legacy research products into a new capability for NASA to fly a pathfinder UAV into hazardous conditions, and is presented in the SPIE DSS venue to explore teaming, collaboration and advocacy opportunities outside NASA.