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We present the long-term X-ray spectral and temporal analysis of a 'bare-typeAGN' Ark 120. We consider the observations from XMM-Newton, Suzaku, Swift, andNuSTAR from 2003 to 2018. The spectral properties of this source are studiedusing various phenomenological and physical models present in the literature.We report (a) the variations of several physical parameters, such as thetemperature and optical depth of the electron cloud, the size of the Comptoncloud, and accretion rate for the last fifteen years. The spectral variationsare explained from the change in the accretion dynamics; (b) the X-ray timedelay between 0.2-2 keV and 3-10 keV light-curves exhibited zero-delay in 2003,positive delay of 4.71 \pm 2.1 ks in 2013, and negative delay of 4.15 \pm 1.5ks in 2014. The delays are explained considering Comptonization, reflection,and light-crossing time; (c) the long term intrinsic luminosities obtainedusing nthcomp, of the soft-excess and the primary continuum show a correlationwith a Pearson Correlation Coefficient of 0.922. This indicates that thesoft-excess and the primary continuum are originated from the same physicalprocess. From a physical model fitting, we infer that the soft excess for Ark120 could be due to a small number of scatterings in the Compton cloud. UsingMonte-Carlo simulations, we show that indeed the spectra corresponding to fewerscatterings could provide a steeper soft-excess power-law in the 0.2-3 keVrange. Simulated luminosities are found to be in agreement with the observedvalues.

Long term X-Ray Observations of Seyfert 1 Galaxy Ark 120: On the origin of soft-excess