ИСТИНА

We report observational evidence for a strong impact of dust on variations of plasma parameters, in particular, the solar wind temperature at current sheets in the heliosphere from the smallest heliocentric distances of tens solar radii ever reached by a spacecraft to several AU. Despite the common knowledge that (i) dust grains are charged, (ii) current sheets represent specific sites at which there is a change of the direction and parameters of the local magnetic field, and (ii) the change of the field polarity causes variations of the spatial characteristics of small dust grains, very limited number of studies considers dust as a source of noticeable effects at current sheets in the solar wind. We analyze plasma and dust observations from the two unique spacecraft, one of which, namely recently launched Parker Solar Probe, has measured parameters of the young solar wind as close to the Sun as several tens solar radii, and the other, Ulysses, is the only spacecraft that observed heliosphere far above the ecliptic plane. It has been known from observations with the resolution of a second made at the Earth orbit and further downstream that thin current sheets (TCSs) may be observed hundreds times per day. According to recent high-scale observations from Parker Solar Probe obtained with a microsecond resolution, TCSs occur up to tens thousands times a day. We have found that the solar wind temperature drops, sometimes significantly, at the heliospheric current sheet and TCSs simultaneously with the decrease in the small-size dust grain flux associated with the TCSs crossing, while the density of larger-size dust grains increases. We suggest that, on one hand, the occurrence of the heliospheric current sheets and TCSs impacts spatial distribution of dust significantly, especially at low heliolatidues and small heliocentric distances, and, on the other hand, the presence of dust dramatically changes parameters of the solar wind plasma at current sheets and leads to poorly investigated effects such as the temperature decrease. The latter may contribute to the explanation of puzzling variations of the solar wind temperature throughout the heliosphere.