  Dayside magnetosphere of Mars is a thin layer with usually increased magnetic
field and heated planetary ions between the magnetosheath and the ionosphere.
The Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft provided,
for the first time, high temporal and spatial resolution measurements enabling
to study the structure of this region. The region was given several names
including the boundary layer, the plasma mantle, and magnetosphere. The outer
boundary of this region was called magnetopause, ionopause, ion composition
boundary and pile-up boundary (see Espley, 2018). We analyze the properties and
plasma populations in the layer between the magnetosheath flow and ionosphere
on the day side of Mars. The region with the Solar-Zenith Angle (SZA) between
40{\deg} and the subsolar point is considered. It was found that the region
between magnetopause and ionosphere filled with the heated diluted ionospheric
ions and the heavy pick-up ions is formed in magnetosheath. So, it is found
that this region of heated ionospheric ion is collocated with another heavy
ions component which has magnetosheath origin. This magnetosheath component was
eluded from identification due to two reasons. First one is that the second
component looked like the high-energy tail of the heated ionospheric component
on energy-time spectrograms. Second one is that STATIC energy-mass analyzer's
energy range was shortened in the ionosphere diminishing observations of the
higher energy ions. It appears that the magnetosheath ion component is
important factor of formation of dayside magnetosphere and the source of energy
in upper ionosphere and atmosphere.
