This study revisits the sprite polarity paradox, first manifest by observations that exceptional cloud‐to‐ground flashes with negative polarity generally did not produce detectable sprites. The paradox is here resolved by the Transient Luminous Event (TLE) known as the halo, which on account of its inferior brightness (0.3 MR versus 1.5 MR) and substantially shorter duration (1 ms versus 10–100 ms) in comparison with the sprite, is not readily detectable in ground‐based video cameras with standard field duration (16.7–20 ms). Observations with improved temporal resolution (ISUAL (Imager of Sprites and Upper Atmospheric Lightnings) from space and PIPER (Photometric Imager of Precipitated Electron Radiation) observations from the ground) provide evidence that flashes with negative polarity dominate the global halo population, and that the halo numbers are more than sufficient to account for the previously missing TLEs. The evidence for lightning polarity‐dependent TLEs (sprites, positive and halos, negative) is attributable to the well established but incompletely understood contrast in the behavior of negative and positive lightning flashes to ground.

Sprites and halos in the mesosphere are produced electrostatically by lightning ground flashes whose polarity is positive, by a margin of at least 1000 to 1 in collected observations. The initiation of these events is controlled by the vertical charge moment change of the flash. Schumann resonance ELF methods have been used to measure the charge moments of millions of flashes worldwide. The bipolar distributions of these events show stronger positive than negative tails, consistent with the predominance of “positive” sprites, but the negative tail of supercritical events is still of the order of 10% of the total supercritical population, more than 1 order of magnitude larger than the observed fraction of “negative” sprites. This juxtaposition constitutes a paradox. The suggested resolution of the paradox is that the more impulsive population of supercritical negative flashes is producing dim halos that are not readily detected in conventional video imagery. Additional sensitive, high‐resolution, and high‐speed imager (<1 ms) studies of halos and their lightning parents are needed to verify this hypothesis.

Recently discovered TLEs (Transient Luminous Events) such as red sprites and elves provided a great opportunity to revisit the electromagnetic waves in the lower ELF (Extremely Low Frequency) region known as the Schumann resonances (SR). The resonance behavior is afforded by the low attenuation experienced by electromagnetic waves in this frequency range. Since TLEs are caused by energetic lightning with abundant energy in this range, these so-called ELF transients can be analyzed on a global basis from single measurement stations. In particular, the geographical location and the vertical charge moment of the lightning flash may be determined remotely. In this chapter, we aim at providing readers with an overview of electromagnetic waves from lightning in the SR frequency band. Then we introduce the technique to determine the location and demonstrate the global mapping of lightning for different thresholds of charge moment change based on the ELF transient observations in Rhode Island, USA. Meteorological interpretations of the global maps are also provided. Furthermore the sprite-producing winter lightning activity is characterized in Hokuriku by using the ELF field site in Moshiri, Japan. The generation condition for winter sprites and their coupling to the tropospheric lightning and to the ionosphere are also presented.