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Based on both static (extended Köhler) and dynamic modelling, we investigate the influence of temperature, humidity, HNO3 initial concentration, as well as of the particle concentration, on the efficiency of HNO3-mediated laser-induced condensation. This mechanism is most efficient for low temperatures, high HNO3 concentration, and relative humidities. It is, however, still active up to 30 °C, down to 70% relative humidity, and below the ppm level of HNO3. Furthermore, lower particle concentration minimizing the depletion of both HNO3 and water vapor is more favourable to particle growth. [ABSTRACT FROM AUTHOR]

We experimentally and numerically investigate the effect of wind forcing on the spectral dynamics of Akhmediev breathers, a wave-type known to model the modulation instability. We develop the wind model to the same order in wave steepness as the higher order modification of the nonlinear Schrödinger equation, also referred to as the Dysthe equation. This results in an asymmetric wind term in the higher order, in addition to the leading order wind forcing term. The derived model is in good agreement with laboratory experiments within the range of the facility's length. We show that the leading order forcing term amplifies all frequencies equally and therefore induces only a broadening of the spectrum, while the asymmetric higher order term in the model enhances the higher frequencies more than the lower ones. Thus, the latter term induces a permanent upshift in the spectral mean. On the other hand, in contrast to the direct effect of wind forcing, wind can indirectly lead to frequency downshifts, due to dissipative effects such aswave breaking, or through the amplification of the intrinsic spectral asymmetry of the Dysthe equation. Furthermore, the definitions of the up- and downshift in terms of peak frequency and mean frequency, which are critical to relate our work to previous results, are highlighted and discussed. [ABSTRACT FROM AUTHOR]

We compare laser-induced condensation by UV laser pulses of femtosecond, sub-picosecond, and nanosecond duration between each other, as well as with respect to near-infrared (NIR) (800 nm) ultrashort laser pulses. Particle nucleation by UV pulses is so efficient that their growth beyond several hundreds of nm is limited by the local concentration of water vapour molecules. Furthermore, we evidence a dual mechanism: While condensation induced by ultrashort UV pulses rely on nitrogen photo-oxidative chemistry like in the NIR, nanosecond laser-induced condensation occurs without NO2 production, evidencing the domination of a mechanism distinct from that previously identified in the femtosecond regime. [ABSTRACT FROM AUTHOR]

Using 100 TW laser pulses, we demonstrate that laser-induced nanometric particle generation in air increases much faster than the beam-averaged incident intensity. This increase is due to a contribution from the photon bath, which adds up with the previously identified one from the filaments and becomes dominant above 550 GW/cm2. It appears related to ozone formation via multiphoton dissociation of the oxygen molecules and demonstrates the critical need for further increasing the laser energy in view of macroscopic effects in laser-induced condensation. [ABSTRACT FROM AUTHOR]

We investigate the influence of laser parameters on laser-assisted water condensation in the atmosphere. Pulse energy is the most critical parameter. Nanoparticle generation depends linearly on energy beyond the filamentation threshold. Shorter pulses are more efficient than longer ones with saturation at ∼1.5 ps. Multifilamenting beams appear more efficient than strongly focused ones in triggering the condensation and growth of submicronic particles, while polarization has a negligible influence on the process. The data suggest that the initiation of laser-assisted condensation relies on the photodissociation of the air molecules rather than on their photoionization. [ABSTRACT FROM AUTHOR]

Distortions of ultrashort laser pulses propagating through turbulence are investigated both experimentally and numerically. As expected, a strong correlation is found between temporal distortions and local intensity on the speckle pattern. We suggest that the localization of distortions in low-intensity regions may favor remote control strategies based on nonlinear interactions with respect to those based on linear schemes. [ABSTRACT FROM AUTHOR]

We show that laser filamentation can be initiated and propagate through strong extended turbulence well above the typical atmospheric values. We suggest that the effect of turbulence on filamentation is characterized by the product of the structure parameter for the refractive index Cn2 and the length L of the turbulence region. Half of the filaments are transmitted for Cn2L≤4.4×10-10 m1/3. Moreover, the surviving filaments keep their key spectral properties including correlations inside the white-light continuum. [ABSTRACT FROM AUTHOR]

Ultrahigh power laser pulses delivered by the Alisé beamline (26 J, 32 TW pulses) have been sent vertically into the atmosphere. The highly nonlinear propagation of the beam in the air gives rise to more than 400 self-guided filaments. This extremely powerful bundle of laser filaments generates a supercontinuum propagating up to the stratosphere, beyond 20 km. This constitutes the highest power “atmospheric white-light laser” to date. [ABSTRACT FROM AUTHOR]

We demonstrate laser control of high-voltage discharges over a gap of 1.2 m filled with a dense water cloud. Self-guided filaments generated by ultrashort laser pulses are transmitted through the cloud and ionize a continuous plasma channel. The cloud typically reduces the discharge probability in given experimental conditions by 30%, but has almost no influence on the threshold required to trigger single discharge events, both in electrical field and laser energy. This result is favorable for real-scale lightning control applications. [ABSTRACT FROM AUTHOR]

We demonstrate the cooperative effect of near infrared (NIR) and ultraviolet (UV) beams on laser-induced condensation. Launching a UV laser after a NIR pulse yields up to a 5-fold increase in the production of nanoparticles (25-300 nm) as compared to a single NIR beam. This cooperative effect exceeds the sum of those from the individual beams and occurs for delays up to 1 μs. We attribute it to the UV photolysis of ozone created by the NIR pulses. The resulting OH radicals oxidize NO2 and volatile organic compounds, producing condensable species. [ABSTRACT FROM AUTHOR]

The development of robust Early Warning Signals (EWSs) is necessary to quantify the risk of crossing tipping points in the present-day climate change. Classically, EWSs are statistical measures based on time series of climate state variables, without exploiting their spatial distribution. However, spatial information is crucial to identify the starting location of a transition process and can be directly inferred by satellite observations. By using complex networks constructed from several climate variables on the numerical grid of climate simulations, we seek for network properties that can serve as EWSs when approaching a state transition. We show that network indicators such as the normalized degree, the average length distance, and the betweenness centrality are capable of detecting tipping points at the global scale, as obtained by the MIT general circulation model in a coupled-aquaplanet configuration for CO2 concentration-driven simulations. The applicability of such indicators as EWSs is assessed and compared to traditional methods. We also analyze the ability of climate networks to identify nonlinear dynamical patterns., (© 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).)