We self-consistently derive the magnetic energy and relative magnetic helicity budgets of a three-dimensional linear force-free magnetic structure rooted in a lower boundary plane. For the potential magnetic energy we derive a general expression that gives results practically equivalent to those of the magnetic Virial theorem. All magnetic energy and helicity budgets are formulated in terms of ...

Antiproton proton annihilation reactions allow unique access to the moduli and phases of nucleon electromagnetic form factors in the time like region. We present the helicity amplitudes for the unequal mass single photon reaction p p̄ → l+ l− in the s channel including the lepton mass. The relative signs of these amplitudes are determined using simple invariance properties. Helicity amplitudes f...

Besides total energy, three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses two inviscid invariants, which are the magnetic helicity and the generalized helicity. Exact relations are derived for homogeneous (nonisotropic) stationary Hall MHD turbulence (and also for its inertialess electron MHD limit) with nonzero helicities and in the asymptotic limit of large Reynolds num...

The conservation of the enstrophy (L2 norm of the vorticity ω) plays an essential role in the physics and mathematics of two-dimensional (2D) Euler fluids. Generalizing to compressible ideal (inviscid and barotropic) fluids, the generalized enstrophy ∫ Σ(t) f (ω/ρ)ρd2x ( f an arbitrary smooth function, ρ the density, and Σ(t) an arbitrary 2D domain co-moving with the fluid) is a constant of mot...

The macromolecular helicity of charged poly(phenylacetylene)s induced by small chiral guests in water can be retained by the alternative deposition of achiral polyelectrolytes with opposite charges, resulting in optically active multilayer thin films with a macromolecular helicity memory.

We examine some implications of inertial range and dissipation range correlation and spectral analyses extracted from 33 intervals of Wind magnetic field data. When field polarity and signatures of cross helicity and magnetic helicity are examined, most of the data sets suggest some role of cyclotron-resonant dissipative processes involving thermal protons. We postulate that an active spectral ...

In the solar atmosphere the twist parameter α has the same sign as magnetic helicity. It has been observed using photospheric vector magnetograms that negative/positive helicity is dominant in the northern/southern hemisphere of the Sun. Chromospheric features show dextral/sinistral dominance in the northern/southern hemisphere and sigmoids observed in X-rays also have a dominant sense of rever...

We present the two-loop helicity amplitudes for the scattering of massless quarks and massless gauge bosons in QCD. We use projector techniques to compute the coefficients of the general tensor describing the two-quark two-boson amplitude in conventional dimensional regularisation and use these coefficients to derive the helicity amplitudes in the ’t Hooft-Veltman scheme. The structure of the i...

We have studied in detail the spectrum of the decay μ− → e−ν̄eνμγ as a function of the electron helicity, and verify the prediction [1] that a significant fraction of the electrons in this decay is righthanded. These “wrong-helicity” electrons persist in the limit λ = me/mμ → 0, and are connected with helicity-flip bremsstrahlung in QED. The longitudinal polarization of the electron is calculate...

Reconnection is a fundamental event in many areas of science, from the interaction of vortices in classical and quantum fluids, and magnetic flux tubes in magnetohydrodynamics and plasma physics, to the recombination in polymer physics and DNA biology. By using fundamental results in topological fluid mechanics, the helicity of a flux tube can be calculated in terms of writhe and twist contribu...