  We present results from multi-wavelength study of intense flaring activity
from a high frequency peaked BL Lac object Mrk 421. The source was observed in
its flaring state on February 16, 2010 with the $TACTIC$ at energies above 1.5
TeV. Near simultaneous multi-wavelength data were obtained from high energy
(MeV-GeV) $\gamma$--ray observations with \emph{Fermi}--LAT, X--ray
observations by the \emph{Swift} and \emph{MAXI} satellites, optical V-band
observation by SPOL at \emph{Steward Observatory} and radio 15 GHz observation
at OVRO 40 meter-telescope. We have performed a detailed spectral and temporal
analysis of $TACTIC$, \emph{Fermi}--LAT and \emph{Swift}--XRT observations of
Mrk 421 during February 10--23, 2010 (MJD 55237-55250). The flaring activity of
the source is studied by investigating the properties of daily light curves
from radio to $TeV$ energy range and we present the correlation and variability
analysis in each energy band. The $TeV$ flare detected by $TACTIC$ on February
16, 2010 is well correlated with the activity in lower energy bands. The
differential energy spectrum of the source, in the energy range 1.5-11 TeV, as
measured by $TACTIC$ on this night is described by a power law ($dN/dE \propto
E^{-\Gamma}$) with spectral index $\Gamma = 2.6\pm0.3$. After accounting for
absorption of $TeV$ photons by low energy extragalactic background light
photons via pair production, the intrinsic $TeV$ spectrum reveals a power law
index of $2.3\pm0.3$. Finally the broad band spectral energy distribution of
the source in flaring state is reproduced using a simple emission model
involving synchrotron and synchrotron self Compton processes. The obtained
parameters are then used to understand the energetics of the source during the
flaring episode.

High Energy Astrophysical Phenomena