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1. Proton Helicity GPDs from Lattice QCD

   https://doi.org/10.22323/1.453.0310  

   Miller, Joshua; Bhattacharya, Shohini; Cichy, Krzysztof; Constantinou, Martha; Gao, Xiang; Metz, Andreas; Mukherjee, Swagato; Petreczky, Peter; Steffens, Fernanda; Zhao, Yong (May 2024, Sissa Medialab)
2. On Galilean invariance of mean kinetic helicity

   https://doi.org/10.1063/5.0178926  

   Soltani_Tehrani, Dina; Aluie, H (December 2023, Physics of Fluids)

   While kinetic helicity is not Galilean invariant locally, it is known [Moffatt, J. Fluid Mech. 35, 117 (1969)] that its spatial integral quantifies the degree of knottedness of vorticity field lines. Being a topological property of the flow, mean kinetic helicity is Galilean invariant. Here, we provide a direct mathematical proof that kinetic helicity is Galilean invariant when spatially integrated over regions enclosed by vorticity surfaces, i.e., surfaces of zero vorticity flux. We also discuss so-called relative kinetic helicity, which is Galilean invariant when integrated over any region in the flow. 

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3. Magnetic helicity and eruptivity in active region 12673

   https://doi.org/10.1051/0004-6361/201935870  

   Moraitis, K.; Sun, X.; Pariat, É.; Linan, L. (August 2019, Astronomy & Astrophysics)

   Context . In September 2017, the largest X-class flare of solar cycle 24 occurred from the most active region (AR) of this cycle, AR 12673. This AR attracted much interest because of its unique morphological and evolution characteristics. Among the parameters that were examined in the AR was magnetic helicity, but either only approximately, or intermittently, or both. Aims . We here study the evolution of the relative magnetic helicity and of the two components of its decomposition, the non-potential, and the volume-threading one, in the time interval around the highest activity of AR 12673. We especially focus on the ratio of the non-potential to total helicity, which has recently been proposed as an indicator of AR eruptivity. Methods . We first approximated the coronal magnetic field of the AR with two different optimization-based extrapolation procedures, and chose the method that produced the most reliable helicity value at each instant. Moreover, in one of these methods, we weighted the optimization by the uncertainty estimates derived from the Helioseismic and Magnetic Imager (HMI) instrument for the first time. We then followed an accurate method to compute all quantities of interest. Results . The first observational determination of the evolution of the non-potential to total helicity ratio seems to confirm the quality it has in indicating eruptivity. This ratio increased before the major flares of AR 12673 and afterwards relaxed to lower values. Additionally, we discuss the evolution patterns of the various helicity and energy budgets of AR 12673 and compare them with results from other works. 

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4. Helicity-conservative finite element discretization for incompressible MHD systems

   https://doi.org/10.1016/j.jcp.2021.110284  

   Hu, Kaibo; Lee, Young-Ju; Xu, Jinchao (July 2021, Journal of Computational Physics)

   null (Ed.)
5. Controlling the helicity of light by electrical magnetization switching

   https://doi.org/10.1038/s41586-024-07125-5  

   Dainone, Pambiang Abel; Prestes, Nicholas Figueiredo; Renucci, Pierre; Bouché, Alexandre; Morassi, Martina; Devaux, Xavier; Lindemann, Markus; George, Jean-Marie; Jaffrès, Henri; Lemaitre, Aristide; et al (March 2024, Nature)