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Papers by Olivier Chanrion
Journal of Geophysical Research, 2010
1] On the night of 15/16 November 2007, cameras in southern France detected 30 transient luminous... more 1] On the night of 15/16 November 2007, cameras in southern France detected 30 transient luminous events (TLEs) over a storm located in the Corsican region (France). Among these TLEs, 19 were sprites, 6 were halos, and 5 were elves. For 26 of them, a positive "parent" cloud-to-ground lightning (P+CG) flash was identified. The peak current of the P+CG flashes for the sprites had an average value of 63 kA and had a maximum value of 125 kA. The flashes for the halos and the elves had average values of 272 and 351 kA, respectively, and they had maximum values of 312 and 384 kA, respectively. No TLEs were detected after negative CG flashes with very large peak currents. Among the 26 P+CG flashes, 23 were located in a stratiform region with reflectivity values lower than 45 dBZ. The CG flashes in this region were classified into two groups according to the time interval separating them from the following flash: one group with values less than 2 s and one with values greater than 2 s. About 79% of all CGs were produced in a sequence of at least two flashes less than 2 s apart. For 65.5% of the sequences, the first flash was positive with an average peak current of 73 kA, while the later +CG flashes in a sequence had much lower peak currents. Several triangulated sprites were found to be shifted from their P+CG flashes by about 10 to 50 km and preferentially downstream. The observations suggest that the P+CG flashes can initiate both sprites and other CG flashes in a storm.
Journal of Geophysical Research, 2010
1] Past studies have shown a correlation between sprites and early VLF perturbations, but the rep... more 1] Past studies have shown a correlation between sprites and early VLF perturbations, but the reported correlation varies widely from ∼50% to 100%. The present study resolves these large discrepancies by analyzing several case studies of sprite and narrowband VLF observations, in which multiple transmitter-receiver VLF pairs with great circle paths (GCPs) passing near a sprite-producing thunderstorm were available. In this setup, the multiple paths act in a complementary way that makes the detection of early VLF perturbations much more probable compared to a single VLF path that can miss several of them, a fact that was overlooked in past studies. The evidence shows that visible sprite occurrences are accompanied by early VLF perturbations in a one-to-one correspondence. This implies that the sprite generation mechanism may cause also sub-ionospheric conductivity disturbances that produce early VLF events. However, the one-to-one visible sprite to early VLF event correspondence, if viewed conversely, appears not to be always reciprocal. This is because the number of early events detected in some case studies was considerably larger than the number of visible sprites. Since the great majority of the early events not accompanied by visible sprites appeared to be caused by positive cloud to ground (+CG) lightning discharges, it is possible that sprites or sprite halos were concurrently present in these events as well but were missed by the sprite-watch camera detection system. In order for this option to be resolved we need more studies using highly sensitive optical systems capable of detecting weaker sprites, sprite halos and elves.
Journal of Geophysical Research, 2010
1] In this paper we estimate the probability that cold electrons can be accelerated by an ambient... more 1] In this paper we estimate the probability that cold electrons can be accelerated by an ambient electric field into the runaway regime, and discuss the implications for negative streamer formation. The study is motivated by the discovery of ms duration bursts of g-rays from the atmosphere above thunderstorms, the so-called Terrestrial Gamma-Ray Flashes. The radiation is thought to be bremsstrahlung from energetic (MeV) electrons accelerated in a thunderstorm discharge. The observation goes against conventional wisdom that discharges in air are carried by electrons with energies below a few tens of eV. Instead the relativistic runaway electron discharge has been proposed which requires a lower threshold electric field; however, seed electrons must be born with energies in the runaway regime. In this work we study the fundamental problem of electron acceleration in a conventional discharge and the conditions on the electric field for the acceleration of electrons into the runaway regime. We use particle codes to describe the process of stochastic acceleration and introduce a novel technique that improves the statistics of the relatively few electrons that reach high energies. The calculation of probabilities for electrons to reach energies in the runaway regime shows that even with modest fields, electrons can be energized in negative streamer tips into the runaway regime, creating a beamed distribution in front of the streamer that affects its propagation. The results reported here suggest that theories of negative streamers and spark propagation should be reexamined with an improved characterization of the kinetic effects of electrons.
Journal of Geophysical Research, 2010
1] The electromagnetic radiation emitted by an electron avalanche beam resulting from relativisti... more 1] The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from 10to300kHzatadistanceof10 to 300 kHz at a distance of 10to300kHzatadistanceof800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of 550km.Themeasuredbroadbandpulsesoccur550 km. The measured broadband pulses occur 550km.Themeasuredbroadbandpulsesoccur4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from 50to350kHz,andtheyexhibitcomplexwaveformswithoutthetypicalionosphericreflectionofthefirsthopskywave.Twoconsecutivepulsesoccur50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur 50to350kHz,andtheyexhibitcomplexwaveformswithoutthetypicalionosphericreflectionofthefirsthopskywave.Twoconsecutivepulsesoccur4.5 ms and $3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory. Citation: Füllekrug, M., R. Roussel-Dupré, E. M. D. Symbalisty, O. Chanrion, A. Odzimek, O. van der Velde, and T. Neubert (2010), Relativistic runaway breakdown in low-frequency radio,
Journal of Geophysical Research, 2010
Journal of Atmospheric and Solar-Terrestrial Physics, 2009
During the summer of 2005, transient luminous events were optically imaged from the French Pyré n... more During the summer of 2005, transient luminous events were optically imaged from the French Pyré né es as part of the EuroSprite campaign. Simultaneously, extremely low frequency (ELF: 3-3000 Hz) and broadband very low frequency (VLF: 3-30 kHz) data were recorded continuously at two separate receivers in Israel, located about 3300 km from the area of the parent lightning discharges responsible for the generation of sprites. Additionally, narrowband VLF data were collected in Crete, at about 2300 km away from the region of sprites.
Geophysical Research Letters, 2006
We propose a new formula to calculate the planetary rate of sprite events, based on observations ... more We propose a new formula to calculate the planetary rate of sprite events, based on observations with sprite detectors. This formula uses the number of detected sprites, the detection efficiency and the false alarm rate of the detector and spatial and temporal ...
Title: First satellite measurements of chemical changes in coincidence with sprite activity. Auth... more Title: First satellite measurements of chemical changes in coincidence with sprite activity. Authors: Arnone, Enrico; São Sabbas, Fernanda; Kero, Antti; Soula, Serge; Carlotti, Massimo; Chanrion,Olivier; Dinelli, Bianca Maria; Papandrea, Enzo; Castelli, Elisa; Neubert, Torsten. ...
Atmospheric Research, 2009
During the summers of 2003 to 2006 sprites were observed over thunderstorms in France by cameras ... more During the summers of 2003 to 2006 sprites were observed over thunderstorms in France by cameras on mountain tops in Southern France. The observations were part of a larger coordinated effort, the EuroSprite campaigns, with data collected simultaneously from other sources including the French radar network for precipitation structure, Meteosat with images of cloud top temperature and the Météorage network for detection of cloud-to-ground (CG) flash activity. In this paper two storms are analyzed, each producing 27 sprite events. Both storms were identified as Mesoscale Convective Systems (MCS) with a trailing stratiform configuration (ST) and reaching a maximum cloud area of ~120,000 km2. Most of the sprites were produced while the stratiform area was clearly developed and during periods of substantial increase of rainfall in regions with radar reflectivity between 30 and 40 dBZ. The sprite-producing periods followed a maximum in the CG lightning activity and were characterized by a low CG flash rate with a high proportion of +CG flashes, typically around 50%. All sprites were associated with +CGs except one which was observed after a −CG as detected by the Météorage network. This −CG was estimated to have −800 C km charge moment change. The peak current of sprite-producing +CG (SP+CG) flashes was twice the average value of +CGs and close to 60 kA with little variation between the periods of sprite activity. The SP+CG flashes were further characterized by short time intervals before a subsequent CG flash (median value <0.5 s) and with clusters of several CG flashes which suggest that SP+CG flashes often are part of multi-CG flash processes. One case of a lightning process associated with a sprite consisted of 7 CG flashes.
Atmospheric Chemistry and Physics, 2011
Non-luminous relativistic electron beams above thunderclouds are detected by radio remote sensing... more Non-luminous relativistic electron beams above thunderclouds are detected by radio remote sensing with low frequency radio signals from ∼40-400 kHz. The electron beams occur ∼2-9 ms after positive cloud-to-ground lightning discharges at heights between ∼22-72 km above thunderclouds. The positive lightning discharges also cause 5 sprites which occur either above or before the electron beam. One electron beam was detected without any luminous sprite occurrence which suggests that electron beams may also occur independently. Numerical simulations show that the beamed electrons partially discharge the lightning electric field above thunderclouds and thereby gain a mean energy of ∼7 MeV to transport a total charge of ∼10 mC upwards. The impul-10 sive current associated with relativistic electron beams above thunderclouds is directed downwards and needs to be considered as a novel element of the global atmospheric electric circuit. ulation of energetic seed particles to initiate an electromagnetically radiating non-linear 15553 ACPD Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al.
Annales Geophysicae, 2008
Transient luminous events, such as red sprites, occur in the middle atmosphere in the electric fi... more Transient luminous events, such as red sprites, occur in the middle atmosphere in the electric field above thunderstorms. We here address the question whether these processes may be a significant source of odd nitrogen and affect ozone or other important trace species. A well-established coupled ion-neutral chemical model has been extended for this purpose and applied together with estimated rates
Journal of Geophysical Research, 2010
1] On the night of 15/16 November 2007, cameras in southern France detected 30 transient luminous... more 1] On the night of 15/16 November 2007, cameras in southern France detected 30 transient luminous events (TLEs) over a storm located in the Corsican region (France). Among these TLEs, 19 were sprites, 6 were halos, and 5 were elves. For 26 of them, a positive "parent" cloud-to-ground lightning (P+CG) flash was identified. The peak current of the P+CG flashes for the sprites had an average value of 63 kA and had a maximum value of 125 kA. The flashes for the halos and the elves had average values of 272 and 351 kA, respectively, and they had maximum values of 312 and 384 kA, respectively. No TLEs were detected after negative CG flashes with very large peak currents. Among the 26 P+CG flashes, 23 were located in a stratiform region with reflectivity values lower than 45 dBZ. The CG flashes in this region were classified into two groups according to the time interval separating them from the following flash: one group with values less than 2 s and one with values greater than 2 s. About 79% of all CGs were produced in a sequence of at least two flashes less than 2 s apart. For 65.5% of the sequences, the first flash was positive with an average peak current of 73 kA, while the later +CG flashes in a sequence had much lower peak currents. Several triangulated sprites were found to be shifted from their P+CG flashes by about 10 to 50 km and preferentially downstream. The observations suggest that the P+CG flashes can initiate both sprites and other CG flashes in a storm.
Journal of Geophysical Research, 2010
1] Past studies have shown a correlation between sprites and early VLF perturbations, but the rep... more 1] Past studies have shown a correlation between sprites and early VLF perturbations, but the reported correlation varies widely from ∼50% to 100%. The present study resolves these large discrepancies by analyzing several case studies of sprite and narrowband VLF observations, in which multiple transmitter-receiver VLF pairs with great circle paths (GCPs) passing near a sprite-producing thunderstorm were available. In this setup, the multiple paths act in a complementary way that makes the detection of early VLF perturbations much more probable compared to a single VLF path that can miss several of them, a fact that was overlooked in past studies. The evidence shows that visible sprite occurrences are accompanied by early VLF perturbations in a one-to-one correspondence. This implies that the sprite generation mechanism may cause also sub-ionospheric conductivity disturbances that produce early VLF events. However, the one-to-one visible sprite to early VLF event correspondence, if viewed conversely, appears not to be always reciprocal. This is because the number of early events detected in some case studies was considerably larger than the number of visible sprites. Since the great majority of the early events not accompanied by visible sprites appeared to be caused by positive cloud to ground (+CG) lightning discharges, it is possible that sprites or sprite halos were concurrently present in these events as well but were missed by the sprite-watch camera detection system. In order for this option to be resolved we need more studies using highly sensitive optical systems capable of detecting weaker sprites, sprite halos and elves.
Journal of Geophysical Research, 2010
1] In this paper we estimate the probability that cold electrons can be accelerated by an ambient... more 1] In this paper we estimate the probability that cold electrons can be accelerated by an ambient electric field into the runaway regime, and discuss the implications for negative streamer formation. The study is motivated by the discovery of ms duration bursts of g-rays from the atmosphere above thunderstorms, the so-called Terrestrial Gamma-Ray Flashes. The radiation is thought to be bremsstrahlung from energetic (MeV) electrons accelerated in a thunderstorm discharge. The observation goes against conventional wisdom that discharges in air are carried by electrons with energies below a few tens of eV. Instead the relativistic runaway electron discharge has been proposed which requires a lower threshold electric field; however, seed electrons must be born with energies in the runaway regime. In this work we study the fundamental problem of electron acceleration in a conventional discharge and the conditions on the electric field for the acceleration of electrons into the runaway regime. We use particle codes to describe the process of stochastic acceleration and introduce a novel technique that improves the statistics of the relatively few electrons that reach high energies. The calculation of probabilities for electrons to reach energies in the runaway regime shows that even with modest fields, electrons can be energized in negative streamer tips into the runaway regime, creating a beamed distribution in front of the streamer that affects its propagation. The results reported here suggest that theories of negative streamers and spark propagation should be reexamined with an improved characterization of the kinetic effects of electrons.
Journal of Geophysical Research, 2010
1] The electromagnetic radiation emitted by an electron avalanche beam resulting from relativisti... more 1] The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from 10to300kHzatadistanceof10 to 300 kHz at a distance of 10to300kHzatadistanceof800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of 550km.Themeasuredbroadbandpulsesoccur550 km. The measured broadband pulses occur 550km.Themeasuredbroadbandpulsesoccur4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from 50to350kHz,andtheyexhibitcomplexwaveformswithoutthetypicalionosphericreflectionofthefirsthopskywave.Twoconsecutivepulsesoccur50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur 50to350kHz,andtheyexhibitcomplexwaveformswithoutthetypicalionosphericreflectionofthefirsthopskywave.Twoconsecutivepulsesoccur4.5 ms and $3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory. Citation: Füllekrug, M., R. Roussel-Dupré, E. M. D. Symbalisty, O. Chanrion, A. Odzimek, O. van der Velde, and T. Neubert (2010), Relativistic runaway breakdown in low-frequency radio,
Journal of Geophysical Research, 2010
Journal of Atmospheric and Solar-Terrestrial Physics, 2009
During the summer of 2005, transient luminous events were optically imaged from the French Pyré n... more During the summer of 2005, transient luminous events were optically imaged from the French Pyré né es as part of the EuroSprite campaign. Simultaneously, extremely low frequency (ELF: 3-3000 Hz) and broadband very low frequency (VLF: 3-30 kHz) data were recorded continuously at two separate receivers in Israel, located about 3300 km from the area of the parent lightning discharges responsible for the generation of sprites. Additionally, narrowband VLF data were collected in Crete, at about 2300 km away from the region of sprites.
Geophysical Research Letters, 2006
We propose a new formula to calculate the planetary rate of sprite events, based on observations ... more We propose a new formula to calculate the planetary rate of sprite events, based on observations with sprite detectors. This formula uses the number of detected sprites, the detection efficiency and the false alarm rate of the detector and spatial and temporal ...
Title: First satellite measurements of chemical changes in coincidence with sprite activity. Auth... more Title: First satellite measurements of chemical changes in coincidence with sprite activity. Authors: Arnone, Enrico; São Sabbas, Fernanda; Kero, Antti; Soula, Serge; Carlotti, Massimo; Chanrion,Olivier; Dinelli, Bianca Maria; Papandrea, Enzo; Castelli, Elisa; Neubert, Torsten. ...
Atmospheric Research, 2009
During the summers of 2003 to 2006 sprites were observed over thunderstorms in France by cameras ... more During the summers of 2003 to 2006 sprites were observed over thunderstorms in France by cameras on mountain tops in Southern France. The observations were part of a larger coordinated effort, the EuroSprite campaigns, with data collected simultaneously from other sources including the French radar network for precipitation structure, Meteosat with images of cloud top temperature and the Météorage network for detection of cloud-to-ground (CG) flash activity. In this paper two storms are analyzed, each producing 27 sprite events. Both storms were identified as Mesoscale Convective Systems (MCS) with a trailing stratiform configuration (ST) and reaching a maximum cloud area of ~120,000 km2. Most of the sprites were produced while the stratiform area was clearly developed and during periods of substantial increase of rainfall in regions with radar reflectivity between 30 and 40 dBZ. The sprite-producing periods followed a maximum in the CG lightning activity and were characterized by a low CG flash rate with a high proportion of +CG flashes, typically around 50%. All sprites were associated with +CGs except one which was observed after a −CG as detected by the Météorage network. This −CG was estimated to have −800 C km charge moment change. The peak current of sprite-producing +CG (SP+CG) flashes was twice the average value of +CGs and close to 60 kA with little variation between the periods of sprite activity. The SP+CG flashes were further characterized by short time intervals before a subsequent CG flash (median value <0.5 s) and with clusters of several CG flashes which suggest that SP+CG flashes often are part of multi-CG flash processes. One case of a lightning process associated with a sprite consisted of 7 CG flashes.
Atmospheric Chemistry and Physics, 2011
Non-luminous relativistic electron beams above thunderclouds are detected by radio remote sensing... more Non-luminous relativistic electron beams above thunderclouds are detected by radio remote sensing with low frequency radio signals from ∼40-400 kHz. The electron beams occur ∼2-9 ms after positive cloud-to-ground lightning discharges at heights between ∼22-72 km above thunderclouds. The positive lightning discharges also cause 5 sprites which occur either above or before the electron beam. One electron beam was detected without any luminous sprite occurrence which suggests that electron beams may also occur independently. Numerical simulations show that the beamed electrons partially discharge the lightning electric field above thunderclouds and thereby gain a mean energy of ∼7 MeV to transport a total charge of ∼10 mC upwards. The impul-10 sive current associated with relativistic electron beams above thunderclouds is directed downwards and needs to be considered as a novel element of the global atmospheric electric circuit. ulation of energetic seed particles to initiate an electromagnetically radiating non-linear 15553 ACPD Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al.
Annales Geophysicae, 2008
Transient luminous events, such as red sprites, occur in the middle atmosphere in the electric fi... more Transient luminous events, such as red sprites, occur in the middle atmosphere in the electric field above thunderstorms. We here address the question whether these processes may be a significant source of odd nitrogen and affect ozone or other important trace species. A well-established coupled ion-neutral chemical model has been extended for this purpose and applied together with estimated rates