A specific absorption rate of a dilute assembly of various random clusters of iron oxide nanoparticles in alternating magnetic field has been calculated using Landau–Lifshitz stochastic equation. This approach simultaneously takes into account both the presence of thermal fluctuations of the nanoparticle magnetic moments and magneto-dipole interaction between the nanoparticles of the clusters. It is shown that for usual 3D clusters, the intensity of the magneto-dipole interaction is determined mainly by the cluster packing density η = N p V/V cl, where N p is the average number of the particles in the cluster, V is the nanoparticle volume, and V cl is the cluster volume. The area of the low frequency hysteresis loop and the assembly-specific absorption rate have been found to be considerably reduced when the packing density of the clusters increases in the range of 0.005 ≤ η < 0.4. The dependence of the specific absorption rate on the mean nanoparticle diameter is retained with an increase of η, but becomes less pronounced. For fractal clusters of nanoparticles, which arise in biological media, in addition to a considerable reduction of the absorption rate, the absorption maximum is shifted to smaller particle diameters. It is found also that the specific absorption rate of fractal clusters increases appreciably with an increase of the thickness of nonmagnetic shells at the nanoparticle surfaces.

Seismo‐Electromagnetic (SEM) waves observed by low‐altitude satellites passing over seismic regions were studied. The data of the COSMOS‐1809 satellite were analysed over the earthquake region in Armenia during the period from January 20 to February 17, 1989. Intense EM radiation at frequencies below 450 Hz was observed at the L‐shells of the earthquake, during 12 orbits out of the 13 that passed within 6° in longitude from the epicenter, and during 1 out of 6 in the range of 6°–8° longitude away from this region. The other orbits, which passed 10°–12° from the epicentre, showed no effect. To complete this study, we used the emissions observed by another low‐altitude satellite (AUREOL‐3).It is shown that during the event the seismic region is permanently radiating; the intensity and the envelope shape of the wave depend on its time relatively to the time of the earthquake. Their frequency spectra are compared to the average spectrum recorded in the same geomagnetic regions. Similar wave intensities and spectral distributions were observed on the two satellites during the seismic periods.

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