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  1. Article: In-Flight Observation of Positron Annihilation by ILDAS.

    Kochkin, P / Sarria, D / Skeie, C / van Deursen, A P J / de Boer, A I / Bardet, M / Allasia, C / Flourens, F / Østgaard, N

    Journal of geophysical research. Atmospheres : JGR

    2018  Volume 123, Issue 15, Page(s) 8074–8090

    Abstract: We report a 511-keV photon flux enhancement that was observed inside a thundercloud and is a result of positron annihilation. The observation was made with the In-flight Lightning Damage Assessment System (ILDAS) on board of an A340 test aircraft. The ... ...

    Abstract We report a 511-keV photon flux enhancement that was observed inside a thundercloud and is a result of positron annihilation. The observation was made with the In-flight Lightning Damage Assessment System (ILDAS) on board of an A340 test aircraft. The aircraft was intentionally flying through a thunderstorm at 12-km altitude over Northern Australia in January 2016. Two gamma ray detectors showed a significant count rate increase synchronously with fast electromagnetic field variations registered by an on-board antenna. A sequence of 10 gamma ray enhancements was detected, each lasted for about 1 s. Their spectrum mainly consists of 511-keV photons and their Compton component. The local electric activity during the emission was identified as a series of static discharges of the aircraft. A full-scale Geant4 model of the aircraft was created to estimate the emission area. Monte Carlo simulation indicated that the positrons annihilated in direct vicinity or in the aircraft body.
    Language English
    Publishing date 2018-08-03
    Publishing country United States
    Document type Journal Article
    ZDB-ID 710256-2
    ISSN 2169-8996 ; 2169-897X ; 0148-0227
    ISSN (online) 2169-8996
    ISSN 2169-897X ; 0148-0227
    DOI 10.1029/2018JD028337
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Meter-scale spark X-ray spectrum statistics.

    Carlson, B E / Østgaard, N / Kochkin, P / Grondahl, Ø / Nisi, R / Weber, K / Scherrer, Z / LeCaptain, K

    Journal of geophysical research. Atmospheres : JGR

    2015  Volume 120, Issue 21, Page(s) 11191–11202

    Abstract: X-ray emission by sparks implies bremsstrahlung from a population of energetic electrons, but the details of this process remain a mystery. We present detailed statistical analysis of X-ray spectra detected by multiple detectors during sparks produced by ...

    Abstract X-ray emission by sparks implies bremsstrahlung from a population of energetic electrons, but the details of this process remain a mystery. We present detailed statistical analysis of X-ray spectra detected by multiple detectors during sparks produced by 1 MV negative high-voltage pulses with 1 μs risetime. With over 900 shots, we statistically analyze the signals, assuming that the distribution of spark X-ray fluence behaves as a power law and that the energy spectrum of X-rays detectable after traversing ∼2 m of air and a thin aluminum shield is exponential. We then determine the parameters of those distributions by fitting cumulative distribution functions to the observations. The fit results match the observations very well if the mean of the exponential X-ray energy distribution is 86 ± 7 keV and the spark X-ray fluence power law distribution has index -1.29 ± 0.04 and spans at least 3 orders of magnitude in fluence.
    Language English
    Publishing date 2015-11-13
    Publishing country United States
    Document type Journal Article
    ZDB-ID 710256-2
    ISSN 2169-8996 ; 2169-897X ; 0148-0227
    ISSN (online) 2169-8996
    ISSN 2169-897X ; 0148-0227
    DOI 10.1002/2015JD023849
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Gamma Ray Glow Observations at 20-km Altitude.

    Østgaard, N / Christian, H J / Grove, J E / Sarria, D / Mezentsev, A / Kochkin, P / Lehtinen, N / Quick, M / Al-Nussirat, S / Wulf, E / Genov, G / Ullaland, K / Marisaldi, M / Yang, S / Blakeslee, R J

    Journal of geophysical research. Atmospheres : JGR

    2019  Volume 124, Issue 13, Page(s) 7236–7254

    Abstract: In the spring of 2017 an ER-2 aircraft campaign was undertaken over continental United States to observe energetic radiation from thunderstorms and lightning. The payload consisted of a suite of instruments designed to detect optical signals, electric ... ...

    Abstract In the spring of 2017 an ER-2 aircraft campaign was undertaken over continental United States to observe energetic radiation from thunderstorms and lightning. The payload consisted of a suite of instruments designed to detect optical signals, electric fields, and gamma rays from lightning. Starting from Georgia, USA, 16 flights were performed, for a total of about 70 flight hours at a cruise altitude of 20 km. Of these, 45 flight hours were over thunderstorm regions. An analysis of two gamma ray glow events that were observed over Colorado at 21:47 UT on 8 May 2017 is presented. We explore the charge structure of the cloud system, as well as possible mechanisms that can produce the gamma ray glows. The thundercloud system we passed during the gamma ray glow observation had strong convection in the core of the cloud system. Electric field measurements combined with radar and radio measurements suggest an inverted charge structure, with an upper negative charge layer and a lower positive charge layer. Based on modeling results, we were not able to unambiguously determine the production mechanism. Possible mechanisms are either an enhancement of cosmic background locally (above or below 20 km) by an electric field below the local threshold or an enhancement of the cosmic background inside the cloud but then with normal polarity and an electric field well above the Relativistic Runaway Electron Avalanche threshold.
    Language English
    Publishing date 2019-07-08
    Publishing country United States
    Document type Journal Article
    ZDB-ID 710256-2
    ISSN 2169-8996 ; 2169-897X ; 0148-0227
    ISSN (online) 2169-8996
    ISSN 2169-897X ; 0148-0227
    DOI 10.1029/2019JD030312
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Relativistic electrons from sparks in the laboratory.

    Østgaard, N / Carlson, B E / Nisi, R S / Gjesteland, T / Grøndahl, Ø / Skeltved, A / Lehtinen, N G / Mezentsev, A / Marisaldi, M / Kochkin, P

    Journal of geophysical research. Atmospheres : JGR

    2016  Volume 121, Issue 6, Page(s) 2939–2954

    Abstract: Discharge experiments were carried out at the Eindhoven University of Technology in 2013. The experimental setup was designed to search for electrons produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage was applied to the high ... ...

    Abstract Discharge experiments were carried out at the Eindhoven University of Technology in 2013. The experimental setup was designed to search for electrons produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage was applied to the high voltage (HV) electrode. Five thin (1 mm) plastic detectors (5 cm
    Language English
    Publishing date 2016-03-18
    Publishing country United States
    Document type Journal Article
    ZDB-ID 710256-2
    ISSN 2169-8996 ; 2169-897X ; 0148-0227
    ISSN (online) 2169-8996
    ISSN 2169-897X ; 0148-0227
    DOI 10.1002/2015JD024394
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Book ; Online: In-flight measurements of energetic radiation from lightning and thunderclouds

    Kochkin, P. O. / van Deursen, A. P. J. / de Boer, A. / Bardet, M. / Boissin, J. -F.

    2015  

    Abstract: In the certification procedure aircraft builders carry out so-called icing tests flights, where the zero degree Celsius altitude is deliberately sought and crossed in or under thunderstorms. Airbus also used these flights to test ILDAS, a system aimed to ...

    Abstract In the certification procedure aircraft builders carry out so-called icing tests flights, where the zero degree Celsius altitude is deliberately sought and crossed in or under thunderstorms. Airbus also used these flights to test ILDAS, a system aimed to determine lightning severity and attachment points during flight from high speed data on the electric and magnetic field at the aircraft surface. We used this unique opportunity to enhance the ILDAS systems with two x-ray detectors coupled to high speed data recorders in an attempt to determine the x-rays produced by lightning in-situ, with synchronous determination of the lightning current distribution and electric field at the aircraft. Such data are of interest in a study of lightning physics. In addition, the data may provide clues to the x-ray dose for personnel and equipment during flights. The icing campaign ran in April 2014; in six flights we collected data of 61 lightning strikes on an Airbus test aircraft. In this communication we briefly describe ILDAS and present selected results on three strikes, two aircraft initiated and one intercepted. Most of the x-rays have been observed synchronous with initiating negative leader steps, and as bursts immediately preceding the current of the recoil process. Those processes include the return stroke. The bursts last one to four micro-second and attain x-ray energies up to 10 MeV. Intensity and spectral distribution of the x-rays and the association with the current distribution are discussed. ILDAS also continuously records x-rays at low resolution in time and amplitude.

    Comment: 28 pages, 9 figures
    Keywords Physics - Atmospheric and Oceanic Physics ; Physics - Instrumentation and Detectors
    Subject code 551
    Publishing date 2015-09-03
    Publishing country us
    Document type Book ; Online
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  6. Article ; Online: A terrestrial gamma-ray flash and ionospheric ultraviolet emissions powered by lightning.

    Neubert, Torsten / Østgaard, Nikolai / Reglero, Victor / Chanrion, Olivier / Heumesser, Matthias / Dimitriadou, Krystallia / Christiansen, Freddy / Budtz-Jørgensen, Carl / Kuvvetli, Irfan / Rasmussen, Ib Lundgaard / Mezentsev, Andrey / Marisaldi, Martino / Ullaland, Kjetil / Genov, Georgi / Yang, Shiming / Kochkin, Pavlo / Navarro-Gonzalez, Javier / Connell, Paul H / Eyles, Chris J

    Science (New York, N.Y.)

    2019  Volume 367, Issue 6474, Page(s) 183–186

    Abstract: Terrestrial gamma-ray flashes (TGFs) are transient gamma-ray emissions from thunderstorms, generated by electrons accelerated to relativistic energies in electric fields. Elves are ultraviolet and optical emissions excited in the lower ionosphere by ... ...

    Abstract Terrestrial gamma-ray flashes (TGFs) are transient gamma-ray emissions from thunderstorms, generated by electrons accelerated to relativistic energies in electric fields. Elves are ultraviolet and optical emissions excited in the lower ionosphere by electromagnetic waves radiated from lightning current pulses. We observed a TGF and an associated elve using the Atmosphere-Space Interactions Monitor on the International Space Station. The TGF occurred at the onset of a lightning current pulse that generated an elve, in the early stage of a lightning flash. Our measurements suggest that the current onset is fast and has a high amplitude-a prerequisite for elves-and that the TGF is generated in the electric fields associated with the lightning leader.
    Language English
    Publishing date 2019-12-11
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 128410-1
    ISSN 1095-9203 ; 0036-8075
    ISSN (online) 1095-9203
    ISSN 0036-8075
    DOI 10.1126/science.aax3872
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  7. Article: In-Flight Observation of Gamma Ray Glows by ILDAS.

    Kochkin, Pavlo / van Deursen, A P J / Marisaldi, M / Ursi, A / de Boer, A I / Bardet, M / Allasia, C / Boissin, J-F / Flourens, F / Østgaard, N

    Journal of geophysical research. Atmospheres : JGR

    2017  Volume 122, Issue 23, Page(s) 12801–12811

    Abstract: An Airbus A340 aircraft flew over Northern Australia with the In-Flight Lightning Damage Assessment System (ILDAS) installed onboard. A long-duration gamma ray emission was detected. The most intense emission was observed at 12 km altitude and lasted for ...

    Abstract An Airbus A340 aircraft flew over Northern Australia with the In-Flight Lightning Damage Assessment System (ILDAS) installed onboard. A long-duration gamma ray emission was detected. The most intense emission was observed at 12 km altitude and lasted for 20 s. Its intensity was 20 times the background counts, and it was abruptly terminated by a distant lightning flash. In this work we reconstruct the aircraft path and event timeline. The glow-terminating flash triggered a discharge from the aircraft wing that was recorded by a video camera operating onboard. Another count rate increase was observed 6 min later and lasted for 30 s. The lightning activity as reported by ground networks in this region was analyzed. The measured spectra characteristics of the emission were estimated.
    Language English
    Publishing date 2017-12-04
    Publishing country United States
    Document type Journal Article
    ZDB-ID 710256-2
    ISSN 2169-8996 ; 2169-897X ; 0148-0227
    ISSN (online) 2169-8996
    ISSN 2169-897X ; 0148-0227
    DOI 10.1002/2017JD027405
    Database MEDical Literature Analysis and Retrieval System OnLINE

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