Detection Of Electromagnetic Waves Research Articles

Electrostatic noise in non‐Maxwellian plasmas: Generic properties and “kappa” distributions

We study the generic properties of the electrostatic noise spectrum measured by an antenna immersed in a plasma with an isotropic electron velocity distribution function, at frequencies of the order of magnitude of the plasma frequency. We find that at high frequencies the noise level is proportional to the electron pressure for long wire antennae and to the electron flux for long double‐sphere antennae. At low frequencies it depends mostly on the low‐energy electrons. We also study the shape of the peak near the plasma frequency, for distribution functions with Maxwellian or power law high‐energy tails. We calculate the noise produced with a generalized Lorenzian (“kappa”) distribution function and compare the results with those obtained with different distributions having the same density and equivalent temperature. We deduce some practical consequences for plasma wave measurements in space.

Photoacoustic and photothermal detection of ferromagnetic resonance and correlation with conventionally recorded signals

The ferromagnetic resonance signals of metallic foils have been measured by conventional techniques and by photothermal methods to prove the correspondence of the electromagnetic and thermal wave detection. The magnetic permeabilities determined by the different methods are found in agreement if variations of the radiation Q-value in the course of the resonance are taken into consideration.

Detection of surface electromagnetic waves by reflected intensity distribution measurements

The complex dielectric constant of silver films at optical frequencies has been measured by detecting the reflected intensity distribution (RID) of the light leaked by free surface electromagnetic waves (SEW). This new detection technique offers in the optical range a number of advantages with respect to more traditional methods as attenuated total reflection or scattered light measurements.

The magnetospheric plasma as a source of energy for space instrumentation

It is proposed to convert the thermal motion of a plasma into electrical power: energetic electrons collected by a plate dissipate their energy into a load, and are re-injected into the medium by means of an electron source. This concept may find applications in the magnetospheres of the outer planets, but present knowledge does not allow one to assess whether the energy fluxes are sufficient for practical applications. It is therefore neccessary to perform in situ preliminary investigations with electron emitters. It is pointed out that electron sources can be simultaneously used for additional tasks: spacecraft potential clamping, plasma diagnostics and detection of electromagnetic and electrostatic waves.

Omnidirectional detectors of microwaves

Two isotropic antenna systems for detection of electromagnetic waves have been developed, and graphs of sensitivity versus angle of rotation of antennas about three mutually perpendicular axes have been recorded. The two types of antenna systems had approximately constant sensitivity for incident waves with arbitrary linear polarization. These antenna systems consist of 12 crystal-diode detectors on the surface of a sphere and six crystal-diode detectors on six edges of a tetrahedron. The spherical antenna system is the more omnidirectional of the two when the antenna system is approximately one-third wavelength in diameter or resonant. When the dimensions were reduced to less than one-tenth wavelength, the pyramidal antenna system was most omnidirectional. The immediate concern was to design detectors for the safety of workers near high-power microwave sources and probes for detection of excessive leakage from microwave ovens in the home.

Detection of electromagnetic and electrostatic waves on OV3-3

Magnetospheric electromagnetic and electrostatic waves detection by electric field sensing equipment onboard OV3-3 spacecraft