Portal de Periódicos da CAPES

Theories and simulations of elves, sprites and blue jets

1998; Elsevier BV; Volume: 60; Issue: 7-9 Linguagem: Inglês

10.1016/s1364-6826(98)00034-0

1879-1824

H. L. Rowland,

Fire effects on ecosystems

This review considers the different models that have been developed to explain a class of phenomena that occur above lightning storms. These phenomena have been named elves, red sprites and blue jets. The elves appear between 90 and 70 km altitude and extend over several 100 km horizontally. They are visible for less than 0.1 ms. Red sprites cover a range of altitudes from 80 to 55 km with narrow tendrils extending below 55 km. Horizontally they are 20–30 km wide. Their visible lifetime is from a few to some tens of ms. Blue jets propagate from cloud tops (15 km) to an altitude of 40 km with a velocity of 100 km/s which gives a lifetime of 300 ms. In all of the models, the energy source is the electric fields associated with the lightning—the quasistatic fields due to the original charge distribution, the electromagnetic pulse due to the propagation of the return stroke or the quasistatic fields due to the charge redistribution by the currents. There are two different models to explain the heating of the neutral atmosphere by these electric fields. These models accelerate either the ambient thermal electrons (<eV) or high-energy, cosmic-ray-generated MeV electrons. These electrons in turn collisionally heat the neutrals and produce the heating, ionization and optical emissions.