Temperature of Dust in Hot Plasmas

The thermal regime and emission characteristics of dust in hot plasmas (T=10 ⁶ -10 ⁷ K) in outer space are studied. These plasmas are encountered everywhere in the galactic interstellar medium, as well as in circumgalactic and intergalactic space. Despite the hostile environment, dust particles can survive in them for a limited time, ~0.3n ^-1 million years, where n is the plasma density, and can be studied in the infrared. This provides an additional possibility for diagnostics of the hot plasma. The distinctive feature of the thermal regime of dust particles imbedded in a rarefied hot plasma is that they experience temperature fluctuations over a wide range. The temperature distribution function depends on the radius of the dust grains and on the plasma parameters. Here the temperature distribution functions for dust particles with radii from 30-3000 Å and an array of plasma parameters are described, along with the resulting emission spectra. It is shown that over a wide range of plasma temperatures and densities, the dust emission spectrum has a “bimodal” shape (with two peaks) that could resemble the spectrum of a dust population with two temperatures. Possible errors in determining the mass of dust from observations of its thermal emission based on the assumption that it has an “equilibrium” temperature are discussed.