Some Properties of Dust Outside the Galactic Disk
  The joint use of accurate near- and mid-infrared photometry from the 2MASS
and WISE catalogues has allowed the variations of the extinction law and the
dust grain size distribution in high Galactic latitudes (|b|>50) at distances
up to 3 kpc from the Galactic midplane to be analyzed. The modified method of
extrapolation of the extinction law applied to clump giants has turned out to
be efficient for separating the spatial variations of the sample composition,
metallicity, reddening, and properties of the medium. The detected spatial
variations of the coefficients E(H-W1)/E(H-Ks), E(H-W2)/E(H-Ks), and
E(H-W3)/E(H-Ks) are similar for all high latitudes and depend only on the
distance from the Galactic midplane. The ratio of short-wavelength extinction
to long-wavelength one everywhere outside the Galactic disk has been found to
be smaller than that in the disk and, accordingly, the mean dust grain size is
larger, while the grain size distribution in the range 0.5-11 microns is
shifted toward coarse dust. Specifically, the mean grain size initially
increases sharply with distance from the Galactic midplane, then decreases
gradually, approaching a value typical of the disk at $|Z|\approx2.4$ kpc, and,
further out, stabilizes or may increase again. The coefficients under
consideration change with coordinate $Z$ with a period of about 1312\pm40 pc,
coinciding every 656\pm20 pc to the south and the north and showing a
significant anticorrelation between their values in the southern and northern
hemispheres at intermediate Z. Thus, there exists a unified large-scale
periodic structure of the interstellar medium at high latitudes within at least
5 kpc. The same periodic variations have also been found for the extinction
coefficient Rv within 600 pc of the Galactic midplane through the reduction of
different photometric data for stars of different classes.
