Available online at www.sciencedirect.com Planetary and Space Science 51 (2003) 613–615 www.elsevier.com/locate/pss On the problem of additional sources of microwave radiation in space plasma V.N. Malnev a , E.V. Martysh b , A.N. Kotsarenko c , V.V. Grimalsky d , R. Perez-Enriquez c , S.V. Koshevaya e ; * a Kiev National University, Ukraine b Institute for Space Research NAN Ukraine, Ukraine c UNICIT, UNAM, Campus Juriquilla, Queretaro, Mexico d National Institute of Astrophysics, Optics and Electronics (INAOE), P.O. Box 51 and 216, C.P. 72000, Puebla, Mexico e Autonomous University of Morelos, CIICAp, Av.Universidad, Cuernavaca, Morelos 62210, Mexico Received 4 July 2002; accepted 14 April 2003 Abstract We discuss possible additional mechanisms of microwave radiation in the dusty space plasma associated with the electron–ion recombination on the surface of grains that have to be taken into account in general balance of radiation. It is assumed that the Coulomb-type bound states of electrons exist on the surface of dusty particles. The recombination of plasma ions with electrons in these states forms neutral excited atoms (Rydberg atoms). Their quantum states depend on the dielectric permittivity of the grains and the quantum state of the electron on the surface. Spontaneous quantum transitions of the Rydberg atoms to the states with lower energies may be considered as an additional source of infrared radiation. The Rydberg atoms with energies closed to zero (near the ionization threshold) in a constant magnetic eld may radiate cyclotron radiation ? 2003 Published by Elsevier Ltd. Keywords: Space plasma; Microwave radiation; Dusty object 1. Introduction Recent studies of microwave radiation of star systems, es- pecially with the help of the Earth articial satellites, discov- ered some contradictions between the evaluations according to the theoretical models and the data observed (Malumyan, 2000). At present, it is accepted that the infrared radiation of normal galaxies is caused by the thermal mechanism, i.e. by radiation of dust particles heated by the ultra-violet and optical radiation of the stars. The radio radiation of galaxies is caused by the non-thermal mechanism—the synchrotron radiation of relativistic electrons in the inter- stellar magnetic elds. Modern measurements of the radiation of some dusty neb- ulas within a range of 10–100 m show that the intensities observed are much larger then numerical evaluations accord- ing to the existing theoretical models (Bogdanov, 2000). * Corresponding author. Tel./fax: +52-777-3297084. E-mail address: svetlana@uaem.mx (S.V. Koshevaya). Moreover, there were observed some space objects that ra- diate the infrared spectra with expressed maximums in some spectral domains (in particular, 1:643 m)(Dickinson et al., 2000). In this paper, we would like to bring attention to a struc- ture of the negative charge of granules of the space dusty plasma. It consists of electrons that are adsorbed by the gran- ule surface. We suggest that these electrons distributed over the so-called surface quantum levels. At low temperatures they corresponds to the bound states of electrons with gran- ules. Cole (1970) rstly discussed the electron levels near the surface of solid dielectrics, to our mind. Latter, the bound states of electron on the surface of solid hydrogen and neon were observed experimentally (Troyanovskii et al., 1979). The spontaneous quantum transitions of electrons be- tween the quantum energy levels on the surface of dusty particles have been considered as a possible source of sub-millimeter radiation (Khaikin, 1978). This type of ra- diation could appear only due transitions of electrons on high surface levels. At the same time, the experiments 0032-0633/03/$ - see front matter ? 2003 Published by Elsevier Ltd. doi:10.1016/S0032-0633(03)00073-4