High time-resolution sprite imaging: observations and implications

Stenbaek‐Nielsen, H. C.; McHarg, M. G.

doi:10.1088/0022-3727/41/23/234009

Cited by 107 publications

(179 citation statements)

References 53 publications

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“…Here sprite channels propagating downwards seem to connect to each other, often accompanied by a bright spot. Sprite discharges have been established to be large versions of streamers at low gas densities, related to each other by similarity laws [16][17][18]. This phenomenon looks quite similar to the reconnection described above, however, the sprite streamers do not reach any electrodes to change the channel polarity.…”

Section: Introductionmentioning

confidence: 72%

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Reconnection and merging of positive streamers in air

Nijdam¹,

Geurts²,

Veldhuizen³

et al. 2009

J. Phys. D: Appl. Phys.

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Pictures show that streamer or sprite discharge channels emerging from the same electrode sometimes seem to reconnect or merge though their heads carry electric charge of the same polarity; one might therefore suspect that reconnections are an artefact of the two-dimensional projection in the pictures. Here we use stereo photography to investigate the full three-dimensional structure of such events. We analyse reconnection, possibly an electrostatic effect in which a late thin streamer reconnects to an earlier thick streamer channel, and merging, a suggested photoionization effect in which two simultaneously propagating streamer heads merge into one new streamer. We use four different anode geometries (one tip, two tips, two asymmetric protrusions in a plate and a wire), placed 40 mm above a flat cathode plate in ambient air. A positive high voltage pulse is applied to the anode, creating a positive corona discharge. This discharge is studied with a fast ICCD camera, in many cases combined with optics to enable stereoscopic imaging. We find that reconnections as defined above occur frequently. Merging on the other hand was only observed at a pressure of 25 mbar and a tip separation of 2 mm, i.e. for a reduced tip distance of p · d = 50 µm bar. In this case the full width at half maximum of the streamer channel is more than 10 times as large as the tip separation. At higher pressures or with a wire anode, merging was not observed.

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Section: Introductionmentioning

confidence: 72%

“…The similarity of sprites and streamers by now is well established, see [16][17][18]. However, there is another important difference, namely the early attracting sprite channel is not connected to some electrode to explain its polarity change.…”

Section: Discussionmentioning

confidence: 99%

Reconnection and merging of positive streamers in air

Nijdam¹,

Geurts²,

Veldhuizen³

et al. 2009

J. Phys. D: Appl. Phys.

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“…These data are tabulated in Table 2. From sprite observations reported by Stenbaek-Nielsen et al [2007] and Stenbaek-Nielsen and McHarg [2008], the measured brightness of sprites is 4 × 10 8 -3 × 10 11 Rayleigh in an ICCD camera with exposure time of 50 ms. Thus, the corresponding photon emission rate in the streamer head is 10 21 -3 × 10 24 photons s −1 .…”

Section: Comparison Of the Model And The Observed Streamer Emissionsmentioning

confidence: 97%

The 762 nm emissions of sprites

et al. 2011

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[1] We report the 762 nm emissions in sprites recorded by the ISUAL experiment onboard the FORMOSAT-2 satellite. The 762 nm imager filter is centered at 763.3 nm with a 7 nm bandwidth at 50% transmittance. Sprite emissions in this passband include the N 2 first positive (1PN 2 ) bands, (2, 0) and (3, 1), the O 2 atmospheric (atm) band (0, 0), and the hydroxyl (4, 0) emissions. Because these mixed emissions cannot be resolved in the 762 nm narrowband filter, a zero-dimensional plasma chemistry model is used to estimate the expected relative intensities of these emission bands in sprites. The computed 1PN 2 brightness in a single streamer is 1.4 MR and 2.6 kR for the O 2 atm band emissions at frame integration times of 30 ms. In the 762 nm passband, the 1PN 2 emissions are the dominant emissions in sprites, and the ratio of 1PN 2 to O 2 atmospheric emissions is ∼500, while the hydroxyl emissions can be neglected. In this ISUAL 762 nm campaign, the brightest sprite out of the four recorded events has possible O 2 atm band emissions that lasted more than 90 ms, and its observed brightness is consistent with the model prediction. Even though the lightning 762 nm emissions are strongly absorbed by O 2 below 60 km, the ISUAL observed parent lightning emissions in this passband are still more than a factor of two brighter than those from ISUAL observed sprites. Hence for spacecraft nadir TLE detection missions, 762 nm bands may not be used as the sole signature to identify sprites, and auxiliary emission bands are needed.

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“…This model assumes that most of the chemical activity due to sprites begins in their brightest regions, that is, in their initial and very short living streamer heads. The duration of the sprite streamer heads have not yet been completely resolved in time but recent sprite imaging at 10000 frames per second (with 50 ms exposure time) Stenbaek-Nielsen et al, 2007;Stenbaek-Nielsen and McHarg, 2008] shows the expected point-like structure of the streamer heads. Thus, faster recordings at 20000 or perhaps even 50000 frames per second would be needed to completely resolve the time scale of sprite streamer heads.…”

Section: Kinetic Modelmentioning

confidence: 99%

Vibrational kinetics of air plasmas induced by sprites

Gordillo‐Vázquez

2010

J. Geophys. Res.

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[1] The vibrational kinetics of air plasmas produced by the presence of sprites in the mesosphere of the Earth is studied in detail. The present model solves the coupled electron Boltzmann equation and rate equations for electrons, neutrals (ground and excited), and ions. Special attention is paid to the vibrational kinetics of N 2 (X 1 S g + ) and to that of the N 2 triplet states (A 3 S u + , B 3 P g , C 3 P u , W 3 D u , and B′ 3 S u + ). The results presented are for an altitude of 78 km over sea level where the model-predicted vibrational distribution function (VDF) of N 2 (B 3 P g ) is in agreement with available VDF derived from sprite spectra (640-820 nm) obtained using spectrographs coupled to high-speed video cameras (300 frames per second (fps)). In addition, the model predictions indicate that the sprite plasma VDFs of N 2 (B 3 P g ) and N 2 (C 3 P u ) are almost in thermal equilibrium and exhibit a maximum at v = 0 followed by lower values for v = 1 and v = 2. Finally, it is also predicted that the N 2 (B 3 P g ) and N 2 (C 3 P u ) VDFs recorded with very high speed video cameras (up to 10000 fps) should not differ much from the N 2 (B 3 P g ) and N 2 (C 3 P u ) VDFs obtained with cameras working at lower speeds (30 and 300 fps).

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High time-resolution sprite imaging: observations and implications

Cited by 107 publications

References 53 publications

Reconnection and merging of positive streamers in air

Reconnection and merging of positive streamers in air

The 762 nm emissions of sprites

Vibrational kinetics of air plasmas induced by sprites

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