Received: 4 January 2019 Revised: 15 April 2019 Accepted: 15 April 2019 DOI: 10.1002/ctpp.201900001 ORIGINAL ARTICLE Non-linear absorption of an intense laser pulse propagating in wiggler-assisted underdense collisional plasma Mehdi Abedi-Varaki 1 Nasser Panahi 2 1 Young Researchers and Elite Club, Bandar Abbas Branch, Islamic Azad University, Bandar Abbas, Iran 2 Department of Physics, Bandar Abbas Branch, Islamic Azad University, Bandar Abbas, Iran Correspondence Mehdi Abedi-Varaki, Young Researchers and Elite Club, Bandar Abbas Branch, Islamic Azad University, Bandar Abbas, Iran. Email: m.abedi.varaki@gmail.com In this article, the propagation of an intense laser pulse through underdense colli- sional plasma in the presence of planar magnetostatic wiggler is studied. It is shown that the electron density distribution, in the presence of planar wiggler with increas- ing of the normalized plasma length, increases initially and then reaches a peak for different values of wiggler amplitudes. In addition, it is found that the existence of wiggler field leads to an increase in the electron density distribution and subse- quently enhancement of electric field. Moreover, it is observed that by increasing the wiggler field, as a result of the increase of the electron density distribution, the dielectric permittivity constant is reduced. It is seen that while wiggler magnetic field was applied appropriately, the total absorption coefficient in the underdense colli- sional isothermal magnetized plasma improves. In fact, increase of wiggler magnetic field causes the enhancement of the total absorption coefficient of plasma medium. KEYWORDS electron density distribution, intense laser pulse, non-linear absorption, planar magnetostatic wiggler, underdense collisional plasma 1 INTRODUCTION The propagation of intense laser pulses in plasma with a wide range of their applications is an interesting area of research. The propagation of intense laser pulse in plasma leads to numerous instabilities and non-linear effects including, Raman and Brillouin instabilities, [1,2] modulational and filamentational instabilities, [1,3–5] laser self-focusing, [6–11] and self-modulation properties. [12–14] Furthermore, these processes play a significant role in advanced physical events such as, laser fusion, [13,15–18] X-ray lasers, [19–24] laser ablation, [25,26] inertial confinement fusion (ICF), [27–30] and optical harmonic generation. [31] In the laser-plasma interaction, the fraction of laser absorption during interaction between ultrashort, ultra-intense laser pulses and dense plasma is a significant problem of ion acceleration, [32,33] high energy density matter production, [34,35] and fast ignition. [36,37] There are many mechanisms involved in the absorptions observed in different laser pulses and plasma conditions such as, resonance absorption, collisional absorption, vacuum heating, and so on. While the effect of collision is strong, a mech- anism the so-called collisional absorption (or inverse bremsstrahlung) contributes to total absorption. [38] In fact, bremsstrahlung is electromagnetic radiation produced by a high-energy electron, when an electron deflected in the Coulomb field of the atomic nucleus. Also, the scattering of hot electrons with atoms and ions of the plasma leads to the bremsstrahlung emission. In recent years, the non-linear absorption mechanism has been investigated by many authors. Xu et al. [39] studied the effect of light intensity on resonance absorption of p-polarization laser pulses in plasma with steep density gradients. In fact, they have investigated self-consistently the effects of the relativistic and ponderomotive-force non-linearities on mode conversion and resonance absorption in plasma with a density scale length of a few laser wavelengths by particle-in-cell (PIC) simulations. It was found that for a given incident angle and density scale length, the absorption rate decreases with increasing laser intensity. This can be attributed to a relativistic reduction of the local plasma frequency and consequently detuning of the driving laser Contrib. Plasma Phys. 2019;1–9. www.cpp-journal.org © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1