The effect of external magnetic field on the density distributions and electromagnetic fields in the interaction of high-intensity short laser pulse with collisionless underdense plasma

Laser absorption in the interaction betweenultra-intense femtosecond laser and solid density plasma isstudied theoretically here in the intensity rangeIk2 ’ 1014 1016 W cm 2 lm2. The collisionless effect isfound to be significant when the incident laser intensity isless than 1016 W cm 2 lm2. In the current work, thepropagation of a high-frequency electromagnetic wave, forunderdense collisionless plasma in the presence of anexternal magnetic field is investigated. When a constantmagnetic field parallel to the laser pulse propagationdirection is applied, the electrons rotate along the magneticfield lines and generate the electromagnetic part in thewake with a nonzero group velocity. Here, by consideringthe ponderomotive force in attendance of the externalmagnetic field and assuming the isothermal collisionlessplasma, the nonlinear permittivity of the plasma medium isobtained and the equation of electromagnetic wave propagationin plasma is solved. Here, by considering the effectof the ponderomotive force in isothermal collisionlessmagnetized plasma, it is shown that by increasing the laserpulse intensity, the electrons density profile leads tosteepening and the electron bunches of plasma becomenarrower. Moreover, it is found that the wavelength ofelectric and magnetic field oscillations increases byincreasing the external magnetic field and the density distributionof electrons also grows in comparison to theunmagnetized collisionless plasma.