  Using MHD seismology by observed kink waves, the magnetic field profile of a
coronal streamer has been investigated. STEREO-B/EUVI temporal image data on 7
March 2012 shows an evolution of two consecutive EUV waves that interact with
the footpoint of a coronal streamer evident in the co-spatial and co-temporal
STEREO-B/COR-I observations. The evolution of EUV waves is clearly evident in
STEREO-B/EUVI, and its energy exchange with coronal streamer generates kink
oscillations. We estimate the phase velocities of the kink wave perturbations
by tracking it at different heights of the coronal streamer. We also estimate
the electron densities inside and outside the streamer using SSI of polarized
brightness images in STEREO-B/COR-1 observations. Taking into account the MHD
theory of kink waves in a cylindrical waveguide, their observed properties at
various heights, and density contrast of the streamer, we estimate the radial
profile of magnetic field within this magnetic structure. Both the kink waves
diagnose the exponentially decaying radial profiles of the magnetic field in
coronal steamer upto 3 solar radii. Within the limit of uncertainties in the
measurements, it is indicated that coronal magnetic field of the streamer
varies slowly in time at various heights, although its nature always remains
exponentially decaying. It is seen that during the evolution of second kink
motion in the streamer, it increases in brightness, and also in areal extent
slightly, which may be associated with the decreased photospheric magnetic flux
at its footpoint. As a result, the magnetic field profile produced by the
second kink wave is reduced within the streamer compared to the one diagnosed
by the first one. The precisely estimated magnetic field profiles with the
uncertainty less than 10% match well with the empirical profile and various
observational estimations of the outer coronal magnetic field.
