L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere

In the Earth’s inner magnetosphere, there exist regions like plasmasphere, ring current, and radiation belts, where the population of charged particles trapped along the magnetic field lines is more. These particles keep performing gyration, bounce and drift motions until they enter the loss cone and get precipitated to the neutral atmosphere. Theoretically, the mirror point latitude of a particle performing bounce motion is decided only by its equatorial pitch angle. This theoretical manifestation is based on the conservation of the first adiabatic invariant, which assumes that the magnetic field varies slowly relative to the gyro-period and gyro-radius. However, the effects of gyro-motion cannot be neglected when gyro-period and gyro-radius are large. In such a scenario, the theoretically estimated mirror point latitudes of electrons are likely to be in agreement with the actual trajectories due to their small gyro-radius. Nevertheless, for protons and other heavier charged particles like oxygen, the gyro-radius is relatively large, and the actual latitude of the mirror point may not be the same as estimated from the theory. In this context, we have carried out test particle simulations and found that the L-shell, energy, and gyro-phase of the particles do affect their mirror points. Our simulations demonstrate that the existing theoretical expression sometimes overestimates or underestimates the magnetic mirror point latitude depending on the value of L-shell, energy and gyro-phase due to underlying guiding centre approximation. For heavier particles like proton and oxygen, the location of the mirror point obtained from the simulation deviates considerably (∼ 10°–16°) from their theoretical values when energy and L-shell of the particle are higher. Furthermore, the simulations show that the particles with lower equatorial pitch angles have their mirror points inside the high or mid-latitude ionosphere.

Off-Shell Quantum Fields to Connect Dressed Photons with Cosmology

The anomalous nanoscale electromagnetic field arising from light–matter interactions in a nanometric space is called a dressed photon. While the generic technology realized by utilizing dressed photons has demolished the conventional wisdom of optics, for example, the unexpectedly high-power light emission from indirect-transition type semiconductors, dressed photons are still considered to be too elusive to justify because conventional optical theory has never explained the mechanism causing them. The situation seems to be quite similar to that of the dark energy/matter issue in cosmology. Regarding these riddles in different disciplines, we find a common important clue for their resolution in the form of the relevance of space-like momentum support, without which quantum fields cannot interact with each other according to a mathematical result of axiomatic quantum field theory. Here, we show that a dressed photon, as well as dark energy, can be explained in terms of newly identified space-like momenta of the electromagnetic field and dark matter can be explained as the off-shell energy of the Weyl tensor field.

A New Method to Lightweight Magnesium Using Syntactic Composite Core

Light weighting of magnesium-based materials is crucial for its extensive use in transportation applications. Hybrid processing of these materials in a shell-core pattern can substantially improve the specific properties of magnesium. In the present study, the Mg/Mg-20GMB (glass microballoon) hybrid composite was prepared using a disintegrated melt deposition technique. Microstructural characterization and mechanical properties of the developed as-cast Mg/Mg-20GMB hybrid composite were investigated. Results revealed that a unified metallurgical interface was formed between the Mg-20GMB core material and the pure Mg shell. Energy dispersive X-ray spectroscopy (EDX) results confirmed the existence of Mg2Si as the secondary phase in the Mg-20GMB core material. The hybrid Mg/Mg-20GMB composite exhibited much superior compressive yield strength (↑71.6%), lower ultimate compressive strength (↓23.25%), and enhanced ductility (↑186.48%) when compared to as-cast pure magnesium.