Infrasonic acoustic waves generated by fast air heating in sprite cores

Silva, Caitano L. da; Pasko, Victor P.

doi:10.1002/2013gl059164

Cited by 15 publications

(17 citation statements)

References 43 publications

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“…With this sprite streamer rescaling of its radius, the current flowing through the streamer channel is ≃ A and ≃1120 A at 80 km and 50 km, respectively. In this way, our current density becomes consistent with the sprite core currents estimated by da Silva and Pasko [].…”

Section: Modelsupporting

confidence: 91%

“…However, externally imposing this electric field as derived from independent microscopic simulations leads to unrealistic predictions since small differences in the rates of ionization between two models grow exponentially and often result in wildly overestimated electron densities. Following da Silva and Pasko [], we have found it more convenient to impose an electric current as input, instead of the electric field. As we will see now, this provides a certain degree of self‐consistency in the sense that an overshoot in the electron density is quickly damped by the consequent decrease in the electric field.…”

Section: Modelmentioning

confidence: 99%

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Chemical and thermal impacts of sprite streamers in the Earth's mesosphere

2015

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A one‐dimensional self‐consistent model has been developed to study the chemical and thermal effects of a single sprite streamer in the Earth's mesosphere. We have used sprite streamer profiles with three different driving current durations (5 ms, 50 ms, and 100 ms) between 50 and 80 km of altitude and considering a kinetic scheme of air with more than 90 chemical species. Our model predicts strong increases in practically all the concentrations of the species studied at the moment of the streamer head passage. Moreover, their densities remain high during the streamer afterglow phase. The concentration of electrons can reach values of up to 108 cm−3 in the three cases analyzed. The model also predicts an important enhancement, of several orders of magnitude above ambient values, of nitrogen oxides and several metastables species. On the other hand, we found that the 4.26 μm IR emission brightness of CO2 can reach 10 GR at low altitudes (< 65 km) for the cases of intermediate (50 ms) and long (100 ms) driving currents. These results suggest the possibility of detecting sprite IR emissions from space with the appropriate instrumentation. Finally, we found that the thermal impact of sprites in the Earth's mesosphere is proportional to the driving current duration. This produces variations of more than 40 K (in the extreme case of a 100 ms driving current) at low altitudes (< 55 km) and at about 10 s after the streamer head.

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Section: Modelsupporting

confidence: 91%

Section: Modelmentioning

confidence: 99%

Chemical and thermal impacts of sprite streamers in the Earth's mesosphere

2015

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“…It is unlikely that ohmic heating in the streamer zones of the lightning channel could produce the observed infrasound pulses, although there is evidence that ohmic heating can produce infrasound in sprites [ da Silva and Pasko , ]. While the scale size of the ohmic heating region is correct for producing infrasound pulses with reasonable duration, there are a number of issues with the ohmic heating mechanism.…”

Section: Discussionmentioning

confidence: 99%

Location and analysis of acoustic infrasound pulses in lightning

Arechiga

Stock

Thomas

et al. 2014

Geophysical Research Letters

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Acoustic, VHF, and electrostatic measurements throw new light onto the origin and production mechanism of the thunder infrasound signature (<10 Hz) from lightning. This signature, composed of an initial compression followed by a rarefaction pulse, has been the subject of several unconfirmed theories and models. The observations of two intracloud flashes which each produced multiple infrasound pulses were analyzed for this work. Once the variation of the speed of sound with temperature is taken into account, both the compression and rarefaction portions of the infrasound pulses are found to originate very near lightning channels mapped by the Lightning Mapping Array. We found that none of the currently proposed models can explain infrasound generation by lightning, and thus propose an alternate theory: The infrasound compression pulse is produced by electrostatic interaction of the charge deposited on the channel and in the streamer zone of the lightning channel.

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“…The coefficient η T in the first term on the rhs of equation is the fraction of electronic power (or Joule heating rate σE 2 ) that is directly transferred into random translational kinetic energy of neutrals and, thus, contributes to air heating. This quantity has been calculated to be η T ≃ 0.1 at near‐ambient temperatures (da Silva & Pasko, ; da Silva, ), largely arising from surplus energy from the quenching of excited electronic states and molecular (electron‐impact) dissociation, which consist the so‐called fast air heating mechanism (Popov, , ; da Silva & Pasko, ).Most of the remainder electronic power is spent into the excitation of vibrational energy levels of nitrogen molecules. However, as temperature increases, rates of vibrational‐translational energy relaxation quickly accelerate, effectively making η T ≈ 1 for temperatures of 2,000 K and above (provided that radiative losses are treated in a separate sink term in the rhs of the energy balance equation).…”

Section: Model Formulationmentioning

confidence: 99%

The Plasma Nature of Lightning Channels and the Resulting Nonlinear Resistance

et al. 2019

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Lightning channels are made of plasma. As a consequence, the driving electrical current changes the channel's resistance in a nonlinear fashion. The resistance has an intricate dependence on the history of Joule heating and various cooling processes, as well as on the various kinetic processes that dictate the population balance of electrons within the channel. Such dependence cannot be captured by an analytic function, as often attempted. In this paper, we introduce a minimal numerical model that can qualitatively capture the temporal dynamics of the key plasma properties of a lightning channel, including its electric field, temperature, plasma density, radius, and the resulting nonlinear resistance. Through a series of novel parameterizations, we introduce six zero‐dimensional equations that can capture both nonequilibrium/low‐temperature and local thermodynamic equilibrium/high‐temperature plasma regimes. In this manuscript, we go to great lengths to validate the model, showing that it can reproduce the finite time scale of streamer‐to‐leader transition, replicate the negative differential resistance behavior of steady‐state plasma arcs, and properly describe the temporal evolution of temperature in a return stroke channel. Finally, the model is applied to the simulation of optical emissions from rocket‐triggered lightning strikes, explaining the measured delay between the rise of current and visible light, as well as reproducing the direct relationship between peak current and peak radiated power and between charge transferred to ground and total radiated energy.

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Infrasonic acoustic waves generated by fast air heating in sprite cores

Cited by 15 publications

References 43 publications

Chemical and thermal impacts of sprite streamers in the Earth's mesosphere

Chemical and thermal impacts of sprite streamers in the Earth's mesosphere

Location and analysis of acoustic infrasound pulses in lightning

The Plasma Nature of Lightning Channels and the Resulting Nonlinear Resistance

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