Lightning and electrical activity during the Shiveluch volcano eruption on 16 November 2014

According to World Wide Lightning Location Network (WWLLN) data, a sequence of lightning discharges was detected which occurred in the area of the explosive eruption of Shiveluch volcano on 16 November 2014 in Kamchatka. Information on the ash cloud motion was confirmed by the measurements of atmospheric electricity, satellite observations and meteorological and seismic data. It was concluded that WWLLN resolution is enough to detect the earlier stage of volcanic explosive eruption when electrification processes develop the most intensively. The lightning method has the undeniable advantage for the fast remote sensing of volcanic electric activity anywhere in the world. There is a good opportunity for the development of WWLLN technology to observe explosive volcanic eruptions.


Introduction
Observations of atmospheric electricity variations during volcano explosive eruptions indicate the development of electrification processes of eruptive clouds which may be the result of magma (ash) fragmentation and formation of an eruptive column (James et al., 1998(James et al., , 2003Mather and Harrison, 2006), or may involve ice-ice interactions 15 from the rapidly expanding and cooling water vapor of the volcano (McNutt and Williams, 2010). Whatever the detailed cause of volcanic ash cloud charge separation, volcano explosive eruptions are powerful sources of lightning. Thus, ash clouds, posing a threats to air transport and to the adjacent area, may be identified within seconds by a lightning location system even in conditions of poor visibility.

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At present, the World Wide Lightning Location Network (WWLLN) is capable to register lightning discharges with the timing accuracy of a few microseconds (Hutchins et al., 2012a), which makes it possible to determine the location of discharges with the accuracy of a few kilometers anywhere in the world.
Eruptive cloud electrification also affects the atmospheric electric field variations Shiveluch volcano eruption, a fluxmeter was used to measure atmospheric electric field variations, and WWLLN was used for locating the lightning. Moreover, to determine the beginning of the eruption, seismic data were drawn, and to observe the eruptive cloud motion, satellite images were applied. Cloud motion velocity and direction were compared with meteorological data.

2 Observation means
Data on the location of lightning discharges accompanying the eruption are available on the site http://wwlln.net. Kamchatka WWLLN site is installed in Paratunka (Fig. 1). EF-4 fluxmeter and Vasiala wxt520 weather station are located about 120 km to the south-west from Shiveluch volcano at Kozyrevsk (KZY) seismic station of Kamchatka Branch of Geophysical Service of RAS (KB GS RAS). The closest seismic station, Baidarnaya (BDR), is located at the distance of 10 km from Shiveluch volcano crater.
Kluchi meteorological observatory of Kamchatka Department on hydrometeorology and environment control is located 48 km from Shiveluch volcano. Its data (atmospheric pressure, air temperature, humidity and height radio sounding of the atmosphere twice 15 a day) is available on the site http://www.esrl.noaa.gov/raobs/intl/intl2000.wmo.
According to the height sounding on 16 November 2014 at 12:00 (UT), Fig. 2 illustrates temperature and wind stratification up to the height of 25 km. It had two inversions at the heights of 9-10 and 12 km where wind velocities were 17 and 11 m s −1 , correspondingly. The height of the lower inversion corresponded to the 20 tropopause height characteristic for the autumn-winter period in Kamchatka. For these heights, south-south western wind direction is typical (azimuth is 50 and 80 • , Fig. 2b).
The direction is opposite to the azimuth.

Development of eruptive plume
Motion of the eruptive plume from volcano eruption is traced by lightning discharges occurring during ash cloud passage at the initial stage of its formation. The WWLLN network registered seven discharges, the time of which is shown in the Table and the location is illustrated in Fig. 1. Within the interval of 25-40 s after the beginning 5 of the eruption, three discharges were registered near the eruption center. These discharges, may have, accompanied the rise and formation of the eruptive column. The subsequent three discharges occurred almost simultaneously in 8.4 min, supposedly, at the background of the eruptive cloud carried by wind and possibly involving iceice charge separation. The last discharge was registered in 17 min at the distance of 10 20.5 km from the eruption center. A satellite image (Landsat 8), made 22 min after the beginning of the eruption (Fig. 3) represents the character of cloud propagation. At that time, the head part of the plume is still loaded with ash (dark area).
In 19 min after the eruption, a disturbance with the duration of 1.5 h (Fig. 4a)

Conclusions
The Kamchatka volcano group is located near international air routes. Due to that, explosive eruptions are serious threats for communication security. To decrease the risks, effective systems for detection of eruptions are necessary. WWLLN resolution is enough to trace ash clouds at the stage of their fragmentation when electrification 5 processes develop the most intensively. During the development of regional WWLLN segment, the observation resolution may be increased. The undeniable advantage of WWLLN method is its efficiency and the possibility to use in the conditions of poor visibility. Moreover, during the analysis not only of arrival times but also of the signal structure and its comparison with electric, acoustic and meteorological data, it is possible to obtain information on the characteristics and tendencies of development of ash cloud fragmentation process. This publication is based on work supported by a grant from the US Civilian Research and Development Foundation (RUG1-7084-PA-13) with funding from the United States Department of State and FEB RAS and CRDF Grant (CRDF-14-007 no.16983