Abstract
Whistler and Alfvén waves are known to scatter mirror-trapped electrons and protons into the loss cone of the earth's dipole magnetic field. An array of satellites with properly phased antennas can be used to artificially reduce the flux of energetic particles from regions where their flux has been naturally or artificially pumped. In any space based system, the power required to drive antennas is at a premium. We present here experimental evidence that the efficiency of an antenna can be greatly enhanced with the use of ferrite cores with high relative magnetic permeability μ. Ferrite-based antennas were constructed to launch Alfvén waves in a magnetized plasma. The wave magnetic field of shear Alfvén waves launched with a ferrite core was by the magnetization factor μ larger than that of a similar antenna without a ferrite. Combining multiple ferrite antennas allowed control of the injected perpendicular wavelength. This novel technique can be used to efficiently launch low frequency waves with amplitude above the threshold required for nonlinear triggering.
Highlights
Understanding the wave-particle interactions that lead to electron and proton loss and acceleration in the radiation belts is a critical issue in space physics and in the development of space weather models
In this paper, following the description of the experimental setup, we describe experiments that address and verify the coupling efficiency and control of the perpendicular wavelength of the ferrite antenna injected in a magnetoplasma in the Alfven/Electromagnetic Ion Cyclotron (EMIC) range
By combining several antennas driven in or out of phase, shear Alfvén waves with large perpendicular wavenumber were excited
Summary
Understanding the wave-particle interactions that lead to electron and proton loss and acceleration in the radiation belts is a critical issue in space physics and in the development of space weather models. While theoretical work was successful in reproducing many of the observed features of chorus and triggered EMIC as well as determining the threshold amplitude required to trigger the emissions, there is lack of cause-and-effect understanding due to absence of in situ space experiments Such an understanding is required in order to incorporate the physics of triggered emission in space weather Radiation Belt (RB) codes and is especially true for Radiation Belt Remediation (RBR) concepts intended to precipitate trapped “MeV” satellite “killer” electrons following intentional or accidental high altitude nuclear detonation.. Since the equivalent current due to the magnetization M is given by Ieq = MI, the injected power will be given by P = I2μ2N2R(r, f ) This means that the radiation resistance of the SDMN antenna increases by a factor of μ2 as compared to the conventional multi-turn loop. The paper concludes by discussing the implication of the results in exploring wave-particle interactions using space-based ferrite or MNT transmitters
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