"Magnetic" components of gravitational waves and response functions of interferometers

Recently, arising from an enlighting analysis of Baskaran and Grishchuk in Class. Quant. Grav. 21, 4041-4061 (2004), some papers in the literature have shown the presence and importance of the so-called "magnetic" components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. In Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) and Int. J. Mod. Phys. D 16, 9, 1497-1517 (2007) accurate response functions for the Virgo and LIGO interferometers have been analysed. However, some results which have been shown in Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) look in contrast with the results which have been shown in Int. J. Mod. Phys. D 16, 9, 1497-1517 (2007). In fact, in Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) it was claimed that the "magnetic" component of GWs could, in principle, extend the frequency range of Earth based interferometers, while in Int. J. Mod. Phys. D 16, 9, 1497-1517 (2007) such a possibility has been banned. This contrast has been partially solved in the Proceedings of the XLIInd Rencontres de Moriond, Gravitational Waves and Experimental Gravity, La Thuile, Val d'Aosta Italy (March 12-18 2007). The aim of this review paper is to re-analyse all the framework of the "magnetic" components of GWs with the goal of solving the mentioned contrast in definitive way. Accurate response funtions for the Virgo and LIGO interferometers will be also re-discussed in detail.