Publications

2025

• Phase transition from turbulence to zonal flows in the Hasegawa–Wakatani system
  
  • Guillon P L
  • Gürcan Ö D
  Physics of Plasmas, American Institute of Physics, 2025, 32 (1). The transition between two-dimensional hydrodynamic turbulence and quasi-one-dimensional zonostrophic turbulence is examined in the modified Hasegawa–Wakatani system, which is considered as a minimal model of β-plane-like drift-wave turbulence with an intrinsic instability. Extensive parameter scans were performed across a wide range of values for the adiabaticity parameter C describing the strength of coupling between the two equations. A sharp transition from 2D isotropic turbulence to a quasi-1D system, dominated by zonal flows, is observed using the fraction of the kinetic energy of the zonal modes as the order parameter, at C≈0.1. It is shown that this transition exhibits a hysteresis loop around the transition point, where the adiabaticity parameter plays the role of the control parameter of its nonlinear self-organization. It was also observed that the radial particle flux scales with the adiabaticity parameter following two different power law dependencies in the two regimes. A simple quasi-linear saturation rule which accounts for the presence of zonal flows is proposed, and is shown to agree very well with the observed nonlinear fluxes. Motivated by the phenomenon of quasi-one dimensionalisation of the system at high C, a number of reduction schemes based on a limited number of modes were investigated and the results were compared to direct numerical simulations. In particular, it was observed that a minimal reduced model consisting of 2 poloidal and 2 radial modes was able to replicate the phase transition behavior, while any further reduction failed to capture it. (10.1063/5.0242282)
  DOI : 10.1063/5.0242282
• Nutritional and growth enhancement of alfalfa sprouts through cold plasma and UV seed treatments
  
  • Benabderrahim Mohamed Ali
  • Hannachi Hédia
  • Elfalleh Walid
  • Dufour Thierry
  Italian Journal of Food Science, Codon Publications, 2025, 37 (3), pp.160-173. Employing eco-friendly techniques like cold plasma (CP) and ultraviolet (UV) radiation provides innovative approaches to enhance the sprout quality and productivity of alfalfa. This study explores the effects of CP and UV radiation on the germination, growth, and phytochemical profiles of alfalfa sprouts. CP significantly accelerated germination time, reducing median germination time by 8 hours compared to the control, and enhanced photosynthetic pigments, leading to higher biomass (25.87 mg/sprout fresh weight and 1.45 mg/sprout dry weight). UV treatments, particularly UV-C, increased chlorophyll and total flavonoid content. Overall, CP effectively promotes alfalfa germination and growth, while UV treatments improve specific phytochemicals. (10.15586/ijfs.v37i3.2982)
  DOI : 10.15586/ijfs.v37i3.2982
• The Solar Orbiter merged magnetic field
  
  • Kretzschmar M.
  • Brochot J.-Y.
  • Horbury T. S.
  • Rackovic K.
  • Maksimovic M.
  • Alexandrova O.
  • Bonnin X.
  • Jannet G.
  • O’brien H.
  • Crabtree A.
  • Morris J.
  • Krasnoselskikh Vladimir
  • Dudok de Wit Thierry
  • Le Contel O.
  • Chust T.
  • de Gelis P.-M.
  • da Silva Gonçalves L.
  • Fauchon-Jones E.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2025, 699, pp.A236. Context. In situ studies of the solar wind require precise magnetic field measurements at all frequencies. The Solar Orbiter mission carries two magnetometers to measure the solar wind magnetic field: the fluxgate magnetometer (MAG), which is best suited for frequencies from DC to a few Hertz, and the search coil magnetometer (SCM), which is best suited for frequencies above a few Hertz. Aims: The aim of this paper is to produce a merged magnetic field data product that takes the best of both instruments and provides the community with high quality, easy to use magnetic field data over a wide range of frequencies. Methods: We first compared the two instruments in their overlapping frequency range, then we performed the merging in Fourier space using a weighted function determined by the sensitivity of the two sensors. Results: The two instruments are found to give consistent results in their overlapping frequency range. SCM has a lower gain than MAG by 14% around 1 Hz and MAG is delayed by about 20 ms with respect to SCM, and the merged magnetic field takes care of these discrepancies. It is basically identical to MAG data below 2 Hz and to SCM data above about 15 Hz (with amplitude increased by 14%). We show that the merged magnetic field is suitable to analyse waves and turbulence over a broad frequency range, in particular by confirming that ion cyclotron waves can lower the level of energy at the sub ionic scales. The merged magnetic field is distributed as daily files containing the magnetic field at either 256 or 4096 Hz, and either in the radial-tangential-normal co-ordinates or in the spacecraft reference frame co-ordinates. (10.1051/0004-6361/202554731)
  DOI : 10.1051/0004-6361/202554731