Analysis of lightning strokes associated with sprites observed by ISUAL in the vicinity of North America (original) (raw)
Related papers
Journal of Geophysical Research: Atmospheres, 2013
This study examined the meteorological characteristics of precipitation systems that produced 38 "sprite-class" negative cloud-to-ground (CG) strokes (i.e., peak currents in excess of 100 kA and charge moment changes in excess of 800 C km) as well as those that produced three confirmed negative sprites on 23 different days during 2009-2011. Within 15 km of the negative sprite-parent/class stroke, the median characteristics for these systems were to produce negative CGs as 69.2% of all CGs, and for the 30 dBZ radar reflectivity contour to reach on average 14.2 km above mean sea level (MSL), during a 25 min period encompassing the occurrence of the stroke. The median contiguous area of 30 dBZ composite radar echo (i.e., maximum value in the vertical column) for these systems was 6.73 × 10 3 km 2. All but three of the discharges occurred in intense multicellular convection, with 30 dBZ exceeding 10 km MSL in altitude, while the others occurred in the stratiform regions of mesoscale convective systems. All but six of the systems produced greater than 50% negative CG lightning, though flash rates tended to be low near the stroke (1-2 min À1 on average). The results suggest that negative sprite-parent/class lightning typically occurs in precipitation systems of similar size and intensity as those that produce positive sprites, but not necessarily the same systems, and the negative lightning normally strikes ground in the convection rather than the stratiform precipitation. However, upper-level positive charge in the convection may play an important role in sprite-class/parent lightning of either polarity.
Geophysical Research Letters, 2008
As part of a collaborative campaign to investigate Transient Luminous Events (TLEs) over South America, coordinated optical, ELF/VLF, and lightning measurements were made of a mesoscale thunderstorm observed on February 22-23, 2006 over northern Argentina that produced 445 TLEs within a $6 hour period. Here, we report comprehensive measurements of one of these events, a sprite with halo that was unambiguously associated with a large negative cloud-to-ground (CG) lightning discharge with an impulsive vertical charge moment change (DM Qv) of À503 C.km. This event was similar in its location, morphology and duration to other positive TLEs observed from this storm. However, the downward extent of the negative streamers was limited to 25 km, and their apparent brightness was lower than that of a comparable positive event. Observations of negative CG events are rare, and these measurements provide further evidence that sprites can be driven by upward as well as downward electric fields, as predicted by the conventional breakdown mechanism.
Monthly Weather Review, 2003
During the summer of 2000, the Severe Thunderstorm Electrification and Precipitation Study (STEPS) program deployed a three-dimensional Lightning Mapping Array (LMA) near Goodland, Kansas. Video confirmation of sprites triggered by lightning within storms traversing the LMA domain were coordinated with extremely low frequency (ELF) transient measurements in Rhode Island and North Carolina. Two techniques of estimating changes in vertical charge moment (M q) yielded averages of ϳ800 and ϳ950 C km for 13 sprite-parent positive polarity cloud-to-ground strokes (ϩCGs). Analyses of the LMA's very high frequency (VHF) lightning emissions within the two mesoscale convective systems (MCSs) show that ϩCGs did not produce sprites until the centroid of the maximum density of lightning radiation emissions dropped from the upper part of the storm (7-11.5 km AGL) to much lower altitudes (2-5 km AGL). The average height of charge removal (Z q) from 15 sprite-parent ϩCGs during the late mature phase of one MCS was 4.1 km AGL. Thus, the total charges lowered by spriteparent ϩCGs were on the order of 200 C. The regional 0ЊC isotherm was located at about 4.0 km AGL. This suggests a possible linkage between sprite-parent CGs and melting-layer/brightband charge production mechanisms in MCS stratiform precipitation regions. These cases are supportive of the conceptual MCS spriteproduction models previously proposed by two of the authors (Lyons and Williams).
Characteristics of lightning flashes generating sprites above storms
E3S Web of Conferences, 2016
Sprites are Transient Luminous Events (TLEs) that can extend vertically from 40 to 90 km and horizontally over several tens of km to form clusters of individual or multiple column or/and carrot-shaped luminous elements. They can even extend over more than 100 km in the form of sequential luminous emissions that are called "dancing sprites". Their optical detection and other parameters describing the storm and the lightning activity associated allow us to understand the conditions of their production and their links with the lightning activity. Our observations confirm some characteristics of the sprites and put forward others: (i) the sprites are essentially produced above the stratiform region of the Mesoscale Convective Systems after positive cloud-to-ground lightning flashes that produce large Charge Moment Change (CMC), with a shorter delay if the impulsive CMC (iCMC) is larger. (ii) The dancing sprites reflect the timing and the location of the successive lightning strokes that generate them. (iii) The sprite elements can be shifted from the stroke location when their delay is large. (iv) Bright sprites produce current signatures in ELF radiation a few milliseconds (<5 ms) after the positive strokes that generate them.
Evidence for continuing current in sprite-producing cloud-to-ground lightning
Geophysical Research Letters, 1996
Radio atmospherics launched by spriteproducing positive cloud-to-ground lightning flashes and observed at Palmer Station, Antarctica, exhibit large ELF slow tails following the initial VLF portion, indicating the presence of continuing currents in the source lightning flashes. niometry method is based on the Fourier Transform of a function whose real part is BNS and whose imaginary part is BEv\,. The phase of the transform represents the direction of arrival as a function of frequency. The arrival azimuth of a given sferic is computed over the 5.5 kHz to 9.5 kHz band, weighted by the magnitude of the signal at each frequency. This frequency range is selected as one in which multiple cycles of the waveform are available within the duration of
Polarity asymmetry of sprite-producing lightning: A paradox?
Radio Science, 2007
1] 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.
Quarterly Journal of The Royal Meteorological Society, 2010
Sprites have been detected in video camera observations in Niger over mesoscale convective systems in Nigeria during the 2006 AMMA campaign. The parent lightning flashes have been detected by multiple ELF receiving stations worldwide. The recorded charge moments of the parent lightning flashes are often in excellent agreement between different receiving sites, and are furthermore consistent with conventional dielectric breakdown in the mesosphere as the origin of the sprites. Analysis of the polarization of the horizontal magnetic field at the distant receivers provides evidence that the departure from linear magnetic polarization at ELF is caused primarily by the day-night asymmetry of the Earth-ionosphere cavity.
Implications of lightning charge moment changes for sprite initiation
Journal of Geophysical Research: Space Physics, 2005
We report impulse lightning charge moment changes (defined as occurring in the first 2 ms after return stroke onset) in all cloud-to-ground lightning strokes detected by the National Lightning Detection Network in three storms during which above-thunderstorm sprite video was recorded. After analyzing strokes that both did and did not produce sprites and carefully accounting for lightning-sprite delay times, we found that sprite initiation on all three nights is consistent with a sharp charge moment threshold; essentially, all charge moment changes above and none below this threshold produced sprites with short delays (<5 ms) from the source lightning. On two nights this threshold was approximately 600 C km and on the other it was approximately 350 C km. This internight variability is probably due to expected variability in the nighttime mesospheric conductivity, and the thresholds themselves are consistent with predictions of conventional breakdown theory. Additionally, we found only one negative polarity lightning stroke from all three storms that exceeded this threshold, indicating that the rarity of documented sprites produced by negative strokes may be largely explained by the lack of sufficiently big negative strokes in the U.S. High Plains.