Abstracted/indexed

Numerical modeling is used to simulate atmospheric circulation and calculate residual mean meridional circulation (RMC) during sudden stratospheric warming event (SSW). Calculating the RMC is used to take into account wave effects on transport of atmospheric quantities and gas species in the meridional plane. The results show that RMC undergoes significant changes at different stages of SSW and also contribute to the SSW development.

Boundaries in the plasma around comet 67P separate regions with different properties. Many have been identified, including a new boundary called an infant bow shock. Here, we investigate how the plasma and fields behave at this boundary and where it can be found. The main result is that the infant bow shock occurs at intermediate activity and intermediate distances to the comet. Most plasma parameters behave as expected, however some inconsistencies indicate that the boundary is non-stationary.

Geomagnetic activity is known to exhibit semi-annual variation with larger occurrences during equinoxes. A similar seasonal feature was reported for relativistic (∼ MeV) electrons throughout the entire outer zone radiation belt. Present work, for the first time reveals that electron fluxes increase with an ∼ 6-month periodicity in a limited L-shell only with large dependence in solar activity cycle. In addition, flux enhancements are not essentially equinoctial.

We present findings of mass, velocity, and composition of 22 small-mass meteors detected optically in Arecibo, Puerto Rico. Spectral observations of these meteors showed evidence of various metals including Na, Mg, Ca, and Fe. Evidence was also found for differential ablation, the process by which more volatile elements ablate earlier in the meteor's path. These spectral observations of the smallest, faintest meteors greatly improve our understanding of the composition of this meteor population.