Chanrion, Olivier Arnaud

Cohen, Morris B.

Gokani, Sneha A.

Maurya, Ajeet K.

Neubert, Torsten

Selvakumaran, R.

Singh, Rajesh

Veenadhari, B.

The article offers information on the initial observations of flashes of lightning discharge observed above thunderstorms. It mentions that the transient luminous events (TLE) are classified on the basis of their geometrical shape and luminosity into Sprites, Halos and Blue Starters. It also focuses on the first sprite observed in the Indian subcontinent on April 11, 2012, whose optical measurements were conducted at Allahabad, India using the charge-coupled device camera system

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Downloaded from orbit.dtu.dk on: Dec 20, 2017First observations of transient luminous events in Indian sub-continentSingh, Rajesh; Maurya, Ajeet K.; Veenadhari, B.; Gokani, Sneha A.; Selvakumaran, R.; Cohen, Morris B.;Chanrion, Olivier; Neubert, TorstenPublished in:Current SciencePublication date:2014Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Singh, R., Maurya, A. K., Veenadhari, B., Gokani, S. A., Selvakumaran, R., Cohen, M. B., ... Neubert, T. (2014).First observations of transient luminous events in Indian sub-continent. Current Science, 107(7), 1107-1108.SCIENTIFIC CORRESPONDENCE  CURRENT SCIENCE, VOL. 107, NO. 7, 10 OCTOBER 2014 1107 First observations of transient luminous events in Indian sub-continent  Initial observations of optical flashes above thunderstorms were sparsely re-ported in the late 19th century. But it was in the beginning of 20th century that possibility of discharges above a thun-dercloud at high altitudes was postulated by Wilson1 based on electric field com-putations due to the residual charges of the cloud just after a positive cloud-to-ground (+CG) lightning discharge. But it was after 65 years, Wilson’s proposition was confirmed with the observations of spectacular optical flashes above  thundercloud accidentally by Winckler group2 while testing experimental low-light television camera (LLTV) on one dark night. The observation attracted global attention and initiated experimen-tal and theoretical studies in this area as these discharges electrically connected lower atmosphere to ionosphere and were considered as important contributor to global electric circuit (GEC).   Transient luminous events (TLEs) are short-lived flashes of lightning discharge observed above large thunderstorms in the stratosphere and mesosphere regions of Earth’s atmosphere. TLEs depending on their geometrical shape and lumino-sity are mainly classified as: Sprites,  Halos, Blue Starters, Blue Jets, Gigantic Jets, Elves, etc. These optical emissions above thunderstorms are considered very energetic and more powerful than terres-trial lightning discharges. Studies in this filed are being carried out since the last two decades but despite much advance-ment in technology and scientific under-standing many questions still remain unanswered. During the last two decades ground and aircraft campaigns were car-ried out across the globe especially in USA, Australia, Japan, Taiwan and Europe and a large number of events concerning TLEs have been identified and studied. On the global scale the In-dian subcontinent is the part of tropical regions in the world, where two of every three lightning flashes occur and make this region an important location for TLEs observations. But studies on TLEs generated by Indian thundercloud system are lacking mainly because of two  reasons: (1) Belief that thunder clouds over Indian subcontinent do not form Mesoscale Convective Systems (MCSs) which are proposed to produce TLEs and (2) absence of proper TLEs observation facilities in India. To fill this gap under the collaboration between the Indian  Institute of Geomagnetism (IIG) and DTU Space Denmark, the first TLEs monitoring camera system was setup in 2011 by IIG. The setup is also an integral part of global facility to provide simulta-neous ground-based observations support to DTU Space led Atmosphere–Space In-teractions Monitor (ASIM) payload for the International Space Station and French microsatellite Tool for the Analy-sis of RAdiation from lightNIng and Sprites (TARANIS) scheduled to be launched in 2016.   Here we report the first ‘Sprites’ ob-served in the Indian subcontinent on 11 April 2012. The optical measurements were conducted at Allahabad (lat. 25.4N, long. 81.9E) over the thunder clouds of Indo-Gangatic plain. The TLEs camera system uses two low-light sensi-tive charge-coupled device (CCD) cam-era systems3. Two monochromatic CCD cameras are used: one with 16 mm F/1.4 wide angle, horizontal field of view (FOV) of 26.5 and the vertical field of view: 15 for event detection and re-cording. The second camera consists of a 25 mm F/0.95 narrow angle: horizontal FOV of 7.25, vertical field of view: 4.8 for high resolution event recording. The cameras are mounted in weather proof housing on top of a QuickSet 20 motor-ized Pan-Tilt unit which allows for the pointing of the cameras within 360 of azimuth (also known as pan) and from −35 to +35 degrees of elevation (tilt). The camera frame rate is 250 frames/sec. Both camera systems can be remotely controlled via the internet and also in-cludes trigger software for automatic op-tical event detection and an automatic event detection algorithm to reduce the amount of data. The digitized video files are time-stamped using GPS unit provid-ing 1-pulse-per-second (PPS) signal was used to ensure high precision time stamping of the data. More details about the TLE observation setup can be found in ref. 3.  On the night of 11 April 2012 at 22:48:53.823 UT, the first ‘Sprite’ events were recorded in Indian region above the thunderstorm (~35 km above the ground in the stratosphere) (Figure 1) located around (87E, 24.5N) ~220 km south east of Allahabad (25.4N, 81.9E)  (Figure 2). The lightning activity (red dots)  5 min at 22:48:53.823 UT which produced the sprites is shown in Figure 2. This observation is important as it opens new questions about the genera-tion of sprite and related phenomena as well as characteristics of Indian thunder clouds; previously it was thought that because of low energy associated with lightning discharges and absence of MCSs in Indian thunder clouds TLEs cannot be generated and observed. The lightning dataset used in the present ob-servation to understand the characteristic   Figure 1. First optical image of sprites observed on 11 April 2012 at 22:48:53.823 UT.  SCIENTIFIC CORRESPONDENCE  CURRENT SCIENCE, VOL. 107, NO. 7, 10 OCTOBER 2014 1108 of sprite associated lightning discharge is from Global Lightning Detection 360 (GLD360) network. GLD360 is a net-work of VLF receivers across the globe, measuring both time of arrival and direc-tion of incoming sferics4.  Sprites are widely observed/studied phenomena among the TLEs originating in the stratosphere/mesosphere (∼40 to 80 km altitude) and extending upwards towards the lower edge of the ionosphere and sometimes downwards into the stratosphere below. They appear like pinkish red luminous columns, more of-ten in carrot-shaped with bundle of fila-ments, stretching from ~40 to 80 km altitude having width less than one km with duration of 5–500 ms (ref. 5). TLEs are usually generated over thunderstorms with MCSs. MCSs are characterized by laterally extensive regions of stratiform precipitation with a total area larger than 104 sq. km, which is usually more than an order of magnitude greater than the area of an ordinary thunderstorm6 such as over Indian regions. Sprites are pre-dominantly generated by electric field pulse traveling up-ward towards the ionosphere from a +CG lightning strokes possessing large charge moment changes. Sprite resembles closely with the lightning return stroke as both have energies of few electron volts; hence sprites are also known as high altitude lightnings5.   TLEs research has forced scientist to revise the present understanding of elec-trical process in the atmosphere. Scien-tists now suggest towards possible connection of TLEs with weather and cli-mate, as the lightning discharges produc-ing TLEs may also cause heating and ionization by depositing significant amount of energy into the overlying  neutral atmosphere/ionosphere, therefore leading to conductivity enhancements. TLEs induced perturbation in the iono-sphere is widely studied with the use of VLF transmitter generated narrowband VLF signals propagating in the earth–ionosphere wave guide (EIWG)7. IIG  operates network of three VLF stations in India8 which are serving as comple-mentary supporting observations for the studies of TLEs in Indian region. TLEs are also thought of affecting GEC and may be responsible for maintaining it up to certain extent. Possible contribution of TLEs in GEC is the subject of ongoing studies.  TLEs have special significance in  Indian scenario, their observation and  detailed study will help in characterizing Indian thunderstorms, contribution to GEC and other related meteorological phenomenon. The observed sprite has open new window for TLEs research in India and quest for observing other TLEs such as Elves, Blue Jets, Gigantic Jets, etc. Since the observation of first TLE on 11 April 2012, continuous observations have been made on more sprites events in India. The results will be reported  elsewhere.   1. Wilson, C. T. R., Proc. R. Soc. London, 1925, 37, 32D. 2. Franz, R. C., Nemzek, R. J. and Winckler, J. R., Science, 1990, 249, 48–51. 3. Chanrion, O. et al., Adv. Geosci., 2007, 13, 3–9. 4. Said, R. K., Inan, U. S. and Cummins, K. L., J. Geophys. Res., 2010, 115, D23108, doi:10.1029/2010JD013863. 5. Neubert, T., Science, 2003, 300, 747– 749. 6. Lyons, W. A., Cummer, S. A., Stanley, M. A., Huffiness, G. R., Wiens, K. C. and Nelson, T. E., Am. Meteorol. Soc., 2008, 89, 1165–1174. 7. Haldoupis, C., Cohen, M., Cotts, B.,  Arnone, E. and Inan, U., Geophys. Res. Lett., 2012, 39, L16801; doi:10.1029/ 2012GL052765 8. Singh, R. et al., Curr. Sci., 2010, 98(3), 398–405.  Received 28 March 2014; accepted 9 August 2014  RAJESH SINGH1,* AJEET K. MAURYA1 B. VEENADHARI2 SNEHA A. GOKANI2 R. SELVAKUMARAN2 MORRIS B. COHEN3 OLIVIER CHANRION3 TORSTEN NEUBERT3  1KSK Geomagnetic Research   Laboratory,  IIG, Chamanganj,  Allahabad 221 505, India 2Indian Institute of Geomagnetism,  New Panvel,  Navi Mumbai 410 218, India 3School of Electrical and Computer   Engineering,  Georgia Institute of Technology, USA 4Department of Solar System Physics, DTU Space, Denmark *For correspondence. e-mail: rajeshsing03@gmail.com      Figure 2. TLE ground observing station at Allahabad (green star) and lightning discharge loca-tions using GLD 360 data (red dots) at  5 min of 22:48:53.823 UT which produced the sprites of 11 April 2012.   

First observations of transient luminous events in Indian sub-continent

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First observations of transient luminous events in Indian sub-continent

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