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					Physics of Neutron Stars – 2008                                                            1


         Second harmonic generation of electromagnetic
             radiation by electron-positron vacuum
                                        N. E. Vigdorchik ∗

,           Saint-Petersburg Technological Institute, Moskovsky pr.26, Saint-Petersburg,
              Russia
    Investigation of the gamma-ray burst GB 870303, observed by the Ginga satellite,
confirms the existence of spectral features at 20 kev and 40 kev. These are interpreted
as the fundamental and the second cyclotron harmonics [1, 2]. This leads to the
problem of determining the source of radiation at the second harmonic. In the present
work, we show that a nonlinear dependence of electric and magnetic permeabilities
on the strength of an electromagnetic wave, which propagates in magnetized electron-
positron vacuum, can result in the generation of the second harmonic in gamma-ray
emission. It is well known, that electron-positron vacuum in the presence of a constant
magnetic field behaves as an anisotropic medium with double refracting characteristics.
Then the equations of electromagnetic wave propagation in a magnetic field become
nonlinear at B ≥ Bc = m2 c3 /e = 4.4·1013 G. As a result, vacuum polarization leads
to an extra nonlinear term in a Lagrange function for an electromagnetic field [3].
The dependence of polarization and magnetization of electron-positron vacuum on the
strength of electromagnetic wave is examined up to the square terms. The nonlinear
equation for electromagnetic waves propagating in the medium “vacuum plus rarefied
plasma” is obtained. The problem of the second harmonic generation by electron-
positron vacuum is analogous to the same problem in nonlinear optics of single-axis
crystals [4]. A simplified system of equations for fundamental and second harmonics is
derived using the method of a slowly changing profile. In the case of “pure” magnetized
vacuum, phase synchronism occurs between an ordinary electromagnetic wave and a
nonlinear medium polarization. It leads to an absolute conversion of the first harmonic
energy to the second harmonic. In the presence of a very rarefied plasma, where
magnetized vacuum dominates, wave disorder appears between the first harmonic and
square polarization, which leads to spatial periodic beatings of amplitudes.


References
    [1] T. Murakami et al., Nature 335,234 (1988)
    [2] V. V. Zheleznyakov. Radiation in Astrophysical plasmas (Dordrecht: Kluwer,
        1996)
    [3] V. L. Ginzburg. Theretical Physics and Astrophysics (Moscow: Nauka, 1981)
    [4] J.A. Armstrong, N. Bloembergen, J. Ducuing et al., Phys. Rev. 127, 1918 (1962)




     ∗
         E-mail: nevig@lti-gti.ru

				
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Description: Electromagnetic radiation is transferred from the common space of electric energy and magnetic energy of the composition, and the energy generated by the mobility of charge; example, the antenna is transmitting RF signals emitted by mobile charges, it will produce electromagnetic energy. Electromagnetic "spectrum"includes all forms of electromagnetic radiation, extremely low frequency electromagnetic radiation from extremely high frequency electromagnetic radiation. There are between radio waves, microwaves, infrared, visible and ultraviolet light and so on. Part of the electromagnetic spectrum in the general definition of the RF, is the frequency of about 3 kHz to 300 GHz radiation.