The nonlinear interaction of an ultra-short intense frequency-chirped laser pulse with an underdense plasma is studied. The effects of plasma inhomogeneity and laser parameters such as chirp, pulse duration, and intensity on plasma density and wakefield evolutions, and electron acceleration are examined. It is found that a properly chirped laser pulse could induce a stronger laser wakefield in an inhomogeneous plasma and result in higher electron acceleration energy. It is also shown that the wakefield amplitude is enhanced by increasing the slope of density in the inhomogeneous plasma.

We investigate the generation of terahertz (THz) radiation from laser-wakefield acceleration (LWFA) in a helium gas jet. We consider a three-dimensional setup incorporating a realistic gas density distribution and use particle-in-cell simulations to study the interaction of a femtosecond intense laser pulse with the gas medium. Our results show that LWFA can efficiently produce THz radiation. In the simulations, we use multiple probes to record the electric and magnetic fields arising from the interaction. In addition, we compare the results of fixed and moving window simulation boxes used to capture electromagnetic fields in the THz range. We demonstrate that a moving window with a 600 μm width can be significantly useful for THz studies. We further analyze the spectrum of spatially and temporally resolved electromagnetic radiation and its emission angle. Our results are consistent with experimental data. Our findings provide valuable insights into the potential of LWFA as a strong source of THz radiation.

The effect of laser polarization on the laser wakefield acceleration (LWFA) of electrons has been investigated in the bubble regime, in particular when assisted by ionization injection. By utilizing linear and circular laser polarizations, we discover that circular polarization leads to a dramatic increase in the electron reproducibility rate and also increases the electron charge and beam divergence, while linear polarization yields higher electron peak energy and more stable beam pointing. Our experimental findings are also supported by three-dimensional particle-in-cell simulations. Our study highlights the potential of laser polarization as a simple and effective tool in controlling LWFA and electron-beam properties depending on applications.

Women are disadvantaged across all stages of academic publishing. In science, contribution to editorial boards of journals is evidence of a high reputation within a specialty or field. Therefore, the low presence of women on editorial boards can be considered a disadvantage indicator for women in academia. This study aims to highlight the gap in women’s contributions in land science journals. We assessed the gender composition of editorial boards in 60 peer-reviewed journals using systematic reviews and meta-analyses, and we obtained data on current and past editorial boards of these journals. The result shows that the current number of editorial board members is 5197 of which only 25.47 percent are women. Gender inequality is very evident in this group of journals to the extent that journals with a high impact factor indicate inequality that is even more than 75 percent. The results of the time series analysis have also shown that the presence of women on editorial boards has increased over the last decade, although this increase has been more in the Nordic countries. The geographical distribution of editorial board members is also quite unequal in the North and South, 83 percent of female editorial board members are from northern countries, while only 12 percent are from the global South. According to the results, there is still a long way to go to achieve gender equality, especially in the field of land science. Our results also support previous findings of a considerable gender difference in urban land science, geoscience community, biodiversity conservation, and veterinary sciences. Thus, the academic community, editors, and journals must take proactive measures to achieve gender balance.

Laser wakefield acceleration offers ultra-high accelerating gradients, enabling compact sources of multi-GeV electron beams with femtosecond durations and quasi-monoenergetic spectra. In this work, we investigated the nonlinear evolution of plasma bubbles and their effect on electron injection and energy gain, using high-fidelity, multi-dimensional particle-in-cell (PIC) simulations performed with the open-source code SMILEI. A relativistically intense laser pulse ( a 0 =7.7, λ 0 =0.8 μ m, w 0 =20 μ m, E = 30 J, and τ = 30 fs) propagated through a helium gaseous medium with a plateau density of n e =7 × 10 ¹⁸ cm ⁻³ after complete ionization. The simulations revealed complex bubble dynamics, including initial formation, disruption, destruction, and bubble merging, strongly influenced by local longitudinal electric field E x approaching or exceeding the cold wave-breaking limit E WB . Exceeding the wave-breaking field E WB triggered bubble destabilization, while the bubble merging at the end of the plateau plasma density region extended the acceleration length, sustaining high longitudinal fields on the order of 1 TV m ⁻¹ and boosting continuous electron injection. This mechanism produced a dense, quasi-monoenergetic electron bunch with a charge of 1 nC, a peak energy of ∼1 GeV, femtosecond-scale duration, energy spread below 10%, rms angular divergence θ y of 7 mrad , and a longitudinal rms beam size of σ x = 10 μ m . Comprehensive analysis of the wakefield evolution demonstrated that exploiting nonlinear bubble evolution and interactions near the wave-breaking limit can enhance both energy gain and electron beam quality, providing actionable strategies for next-generation compact LPAs.