Spectro-photometric variability of quasars caused by lensing of diffuse
  massive substructure: Consequences on flux anomaly and precise astrometric
  measurements
  We investigate the spectro-photometric variability of quasars due to lensing
of small mass substructure (from several tens to several hundreds solar
masses). The aim of this paper is to explore the milli/microlensing influence
on the flux anomaly observed between images of a lensed quasar in different
spectral bands and possible influence of small mass structure lensing of
non-macrolensed quasars.We find that spectro-photometric variability may be
also caused by lensing of small mass diffuse structure and can produce the flux
anomaly which is sometimes seen in different images of a lensed quasar.
Additionally, we found that the lensing by small mass diffuse structure may
produce significant changes in photo-center position of a quasar, and sometimes
can split or deviate images of one source that can be detected as separate from
the scale from 0.1 to several milliarcseconds. This can be measured ith
Gaialike space astrometric missions. We point out a special case where a low
redshifted deflector zd = 0.01 is lensing a high redshifted source, for which
the variability in the flux and photocenter (several milliarcseconds) may be
detected on a relatively short time scale.
