Sprite beads and glows arising from the attachment instability in streamer channels

Luque, Alejandro; Stenbaek‐Nielsen, H. C.; McHarg, M. G.; Haaland, R. K.

doi:10.1002/2015ja022234

Cited by 35 publications

(95 citation statements)

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“…Our results thus stress the role in maintaining the corona played by poorly understood processes such as the inception of counterpropagating streamers Luque et al, 2016) or the propagation of successive ionization waves along preexisting channels (Babich et al, 2015;Nijdam et al, 2014;Phelps, 1974;Rison et al, 2016). However, at around 100 ns, the overall conductivity of a streamer channel decays, stalling 10.1029/2019GL082063 the increase in temperature.…”

Section: Discussionmentioning

confidence: 53%

“…As sketched in Figure 1B, where we plot the effective ionization rate of air, this enhanced field triggers an attachment instability (Luque et al, 2016): The higher field increases the rate of associative electron attachment, decreasing further the conductance per unit length and increasing Figure 1. As the streamer emerges from the leader, it goes through a narrowing phase where the conductance per unit length decreases.…”

Section: Resultsmentioning

confidence: 98%

“…A number of processes may reduce the channel conductance per unit length and trigger the instability, among them a jittering of the leader potential during the streamer propagation or preexisting conductivity or gas-density perturbations along the streamer path (Luque & Gordillo-Vázquez, 2011;Luque et al, 2016). A number of processes may reduce the channel conductance per unit length and trigger the instability, among them a jittering of the leader potential during the streamer propagation or preexisting conductivity or gas-density perturbations along the streamer path (Luque & Gordillo-Vázquez, 2011;Luque et al, 2016).…”

Section: Formation Of the Space Stemmentioning

confidence: 99%

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Spontaneous Emergence of Space Stems Ahead of Negative Leaders in Lightning and Long Sparks

Malagón-Romero¹,

Luque²

2019

Geophysical Research Letters

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We investigate the emergence of space stems ahead of negative leaders. These are luminous spots that appear ahead of an advancing leader mediating the leader's stepped propagation. We show that space stems start as regions of locally depleted conductivity that form in the streamers of the corona around the leader. An attachment instability enhances the electric field leading to strongly inhomogeneous, bright, and locally warmer regions ahead of the leader that explain the existing observations. Since the attachment instability is only triggered by fields above 10 kV/cm and internal electric fields are lower in positive than in negative streamers, our results explain why, although common in negative leaders, space stems, and stepping are hardly observed if not absent in positive leaders. Further work is required to fully explain the streamer to leader transition, which requires an electric current persisting for timescales longer than the typical attachment time of electrons, around 100 ns.

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Section: Discussionmentioning

confidence: 53%

Section: Resultsmentioning

confidence: 98%

Section: Formation Of the Space Stemmentioning

confidence: 99%

See 1 more Smart Citation

Spontaneous Emergence of Space Stems Ahead of Negative Leaders in Lightning and Long Sparks

Malagón-Romero¹,

Luque²

2019

Geophysical Research Letters

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“…Regarding the chemistry, we have tested two kinetic schemes. The first one (Luque et al, ) includes electrons,

{normalN}_{2}

{normalO}_{2}

{normalO}_{2}^{+}

{normalN}_{2}^{+}

, and

{normalO}^{-}

and accounts for impact ionization and dissociative attachment. The second one is an extended version with more species and some other processes such as electron detachment.…”

Section: Sprite Streamer Modelmentioning

confidence: 99%

“…To model this we add neutral electron‐ion densities in the shape of a truncated funnel attached to the bottom of the column. Then, the initial electron density reads (Luque et al, )

n_{e, c h} false(r, z false) = ({, \begin{matrix} left left \\ array n_{e 0, c h} (z) \frac{a_{0}^{2}}{a {(z)}^{2}} \max (0, 1 - \frac{r^{2}}{a {(z)}^{2}}), \forall r & array 50 km < z < 80 km \\ array 0 & array elsewhere, \end{matrix})

where

n_{e 0, c h} false(z false) = C n_{air} false(z false)

is the electron density at the axis of the column,

n_{air} false(z false) = n_{a i r, 0} e^{()(, - z false/ 7.2 km)}

is the air density scaled at altitude

z

from the ground air density

n_{air, 0} = 2.5 \times 1 0^{25}

^{- 3}

and

C = 3.33 \times 1 0^{- 11}

. The value of

C

is determined from the equality

n_{e 0, c h} ()(, 60 km) = 2 \times 1 0^{11} {normalm}^{- 3}

.…”

Section: Sprite Streamer Modelmentioning

confidence: 99%

On the Emergence Mechanism of Carrot Sprites

Malagón-Romero¹,

Teunissen

Stenbaek‐Nielsen

et al. 2020

Geophysical Research Letters

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We investigate the launch of negative upward streamers from sprite glows. This phenomenon is readily observed in high‐speed observations of sprites and underlies the classification of sprites into carrot or column types. First, we describe how an attachment instability leads to a sharply defined region in the upper part of the streamer channel. This region has an enhanced electric field, low conductivity and strongly emits in the first positive system of molecular nitrogen. We identify it as the sprite glow. We then show how, in the most common configuration of a carrot sprite, several upward streamers emerge close to the lower boundary of the glow, where negative charge gets trapped and the lateral electric field is high enough. These streamers cut off the current flowing toward the glow and lead to the optical deactivation of the glow above. Finally, we discuss how our results naturally explain angel sprites.

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Radio Frequency Electromagnetic Radiation From Streamer Collisions

Luque

2017

JGR Atmospheres

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We present a full electromagnetic model of streamer propagation where the Maxwell equations are solved self‐consistently together with electron transport and reactions including photoionization. We apply this model to the collision of counter‐propagating streamers in gaps tens of centimeters wide and with large potential differences of hundreds of kilovolts. Our results show that streamer collisions emit electromagnetic pulses that, at atmospheric pressure, dominate the radio frequency spectrum of an extended corona in the range from about 100 MHz to a few gigahertz. We also investigate the fast penetration, after a collision, of electromagnetic fields into the streamer heads and show that these fields are capable of accelerating electrons up to about 100 keV. By substantiating the link between X‐rays and high‐frequency radio emissions and by describing a mechanism for the early acceleration of runaway electrons, our results support the hypothesis that streamer collisions are essential precursors of high‐energy processes in electric discharges.

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Sprite beads and glows arising from the attachment instability in streamer channels

Cited by 35 publications

References 50 publications

Spontaneous Emergence of Space Stems Ahead of Negative Leaders in Lightning and Long Sparks

Spontaneous Emergence of Space Stems Ahead of Negative Leaders in Lightning and Long Sparks

On the Emergence Mechanism of Carrot Sprites

Radio Frequency Electromagnetic Radiation From Streamer Collisions

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