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Satellite Observations of Lightning-Induced Hard X-Ray Flux

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Satellite Observations of Lightning-Induced Hard X-Ray Flux Ann. Geophys., 24, 1969–1976, 2006 www.ann-geophys.net/24/1969/2006/ Annales © European Geosciences Union 2006 Geophysicae Satellite observations of lightning-induced hard X-ray flux enhancements in the conjugate region R. Bucˇ´ık1, K. Kudela1, and S. N. Kuznetsov2 1Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Kosice,ˇ Slovakia 2Institute of Nuclear Physics, Moscow State University, Vorob’evy Gory, 119899 Moscow, Russia Received: 14 February 2006 – Revised: 10 May 2006 – Accepted: 24 May 2006 – Published: 9 August 2006 Abstract. Preliminary examination of October-December Observations of hard X-rays associated with electron pre- 2002 SONG (SOlar Neutron and Gamma rays) data aboard cipitation due to lightning flashes are rare. A one-to- the Russian CORONAS-F (Complex Orbital Near-Earth Ob- one correspondence between balloon X-ray (>30 keV) data servations of the Activity of the Sun) low-altitude satellite and ground VLF emissions, triggered by whistlers from has revealed many X-ray enhanced emissions (30–500 keV) lightning, was for the first time, presented by Rosenberg in the slot region (L∼2–3) between the Earth’s radiation et al. (1971) from an experiment conducted at Siple Station, belts. In one case, CORONAS-F data were analyzed when Antarctica (L∼4.1). In a rocket experiment made at Wallops the intense hard X-ray emissions were seen westward of Island, Virginia (L∼2.6), Goldberg et al. (1987) observed the South Atlantic Anomaly in a rather wide L shell range (with X-ray detectors) electron bursts (>80 keV) that were from 1.7 to 2.6. Enhanced fluxes observed on day 316 coincident with lightning detected by nearby ground stations. (12 November) were most likely associated with a Major Se- Geographic intensity maps of hard X-rays (up to 750 keV) vere Weather Outbreak in Eastern USA, producing extensive from a low-Earth orbit over mid-latitudes within ±43.3◦ and lightning flashes, as was documented by simultaneous opti- their possible origin in lightning, due to electron precipita- cal observations from space. We propose that whistler mode tion and/or acceleration, has been discussed by Feldman et al. signals from these lightning discharges cause precipitation (1996). of energetic electrons from terrestrial trapped radiation belts, There is extensive experimental evidence on the associa- which, in turn, produce atmospheric X-rays in the Southern tion of individual lightning events with the precipitation of Hemisphere. energetic electrons (e.g. Voss et al., 1998, and references therein). The electromagnetic energy originating in light- Keywords. Magnetospheric physics (Energetic particles, ning discharges escapes into the magnetosphere and prop- precipitating; Magnetosphere-ionosphere interactions) agates as a whistler mode wave, and pitch angle scatters (and thus precipitates) energetic electrons, thereby generat- ing bremsstrahlung hard X-rays. 1 Introduction In the present paper we report on new satellite obser- vations of hard X-rays from the CORONAS-F experiment, Hard X-rays from the bremsstrahlung emissions of ∼ MeV which, by association with simultaneous optical observations electrons precipitating into the atmosphere have been ob- made on TRMM, may be related to lightning in the geomag- served both over the auroral zones (Smith et al., 1995; Foat netically conjugate region. et al., 1998; Millan et al., 2002) during low geomagnetic ac- tivity and in the South Atlantic Anomaly (Martin et al., 1974) during a magnetic disturbance. Scattering by the substorm- 2 Instrumentation excited electromagnetic ion cyclotron waves has been sug- gested as a mechanism for the auroral electron precipitation The CORONAS-F satellite was launched on 31 July 2001 ◦ (e.g. Lorentzen et al., 2000). into a Sun-synchronous polar orbit (inclination ∼83 ) with a period of ∼95 min at 500 km nominal altitude. The Correspondence to: R. Bucˇ´ık SONG experiment on CORONAS-F contained a large area ([email protected]) CsI(Tl) scintillator (20 cm diameter × 10 cm length) for the Published by Copernicus GmbH on behalf of the European Geosciences Union. 1970 R. Bucˇ´ık et al.: Lightning induced hard X-rays 90 10 8 60 3.0 2.6 3.0 2.42.2 2.6 2.0 6 2.42.2 1.8 2.0 1.8 1.6 4 1.6 1.4 30 1.4 2 0 0 0 2 4 6 8 10 1.4 1.6 -30 1.4 1.6 1.8 1.8 2.0 2.0 2.2 2.42.2 2.4 2.6 3.0 2.6 3.0 -60 -90 -180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180 1 10 100 1 10 100 Counts / s.keV Fig. 1. The colored geographical map of average counts for 60–150 keV X-rays measured by CORONAS-F throughout October–December, 2002 in the altitude range of 440–490 km. Note in the South Atlantic Anomaly the SONG instrument was saturated by high fluxes of energetic (>50 MeV) protons (purple and blue). The footprints of several L shells between 1.4 and 3.0 and the region of stable trapping (crosshatched) at 500 km are shown for reference. The location of the stable trapping area at an altitude of 500 km is adopted from Bucˇ´ık et al. (2005). It consists of set of L, B values (determined by IGRF 1990), for which the minimum longitude traced altitude is above 100 km. Small white strips in the Eastern Europe mean no data available for these regions, due to operative controls when the satellite passed over Moscow. Note that the adjacent region is characterized by a reduction in the amount of data. There are less than 10 records per bin in the area clustered at longitudes 20◦–30◦ and latitudes 40◦–60◦. measurement of energetic neutral radiation from the Sun reduced. According to the approach given in Bucˇ´ık et al. (Kuznetsov et al., 2002, 2004). The crystal scintillator (2002), an estimate of the detector field of view is 1.7π sr was viewed by three photomultipliers and was entirely for 100 keV and 2.3π sr for 1000 keV X-ray energies. The surrounded by a 2-cm thick plastic anticoincidence shield calculation is based on a model of the distribution of mat- against charged particles. It was viewed by three other pho- ter near the CsI crystal in a similar experimental setup as for tomultiplier tubes. the preceding CORONAS-I experiment (Bucˇ´ık and Kudela, During calibration the efficiency of the active anticoinci- 2003). dence shield was tested by using atmospheric muons as test Energy losses in the scintillation crystal were pulse- particles. The measured rejection efficiency was about 95% height-discriminated into twelve differential channels from at muons peak (∼55 MeV) (Ryumin et al., 1996). For low 30 keV to 200 MeV, and one integral channel above energies, the efficiency of the active veto is higher, since at 200 MeV. The SONG instrument provided high time res- these energies charged particles produce a smaller amount olution measurements of 1 s in the burst mode and 4 s in of light in the CsI(Tl) and the anticoincidence plastic scin- monitoring mode. For the present analysis we selected the tillator makes a passive barrier for electrons with energies four lowest energy channels (30–60, 60–150, 150–500, and <4 MeV and protons with energies <48 MeV. 500–1500 keV). The instrument’s maximum effective area (at vertical incidence) for gamma-ray photons is 270 cm2; the The scintillation crystal had no collimator and its axis was effective photopeak area at 100 keV is 200 cm2, and 140 cm2 parallel to the longitudinal axis of the satellite which was di- at 1 MeV. More details of SONG aboard CORONAS-I are rected towards the Sun. Due to attenuation in the instrumen- given in Bala´zˇ et al. (1994). tal and spacecraft matter around the main detector, the nom- inal omnidirectional response for incoming X-rays would be Ann. Geophys., 24, 1969–1976, 2006 www.ann-geophys.net/24/1969/2006/ R. Bucˇ´ık et al.: Lightning induced hard X-rays 1971 Nov-09-2002 Nov-10/11-2002 Nov-12-2002 45 NAA 45 NAA 45 NAA 3.0 3.0 3.0 3.0 3.0 12:29 3.0 2.6 2.6 2.6 2.6 2.6 2.6 2.4 10 2.4 2.4 10 2.4 2.4 10 2.4 2.2 2.2 2.2 2.2 2.2 2.2 2.0 2.0 2.0 2.0 2.0 2.0 30 1.8 12:39 30 1.8 30 1.8 8 1.8 8 1.8 8 1.8 1.6 1.6 1.6 12:33 1.6 11/ 1:36 1.6 1.6 1.4 6 1.4 6 1.4 6 15 1.4 15 1.4 15 1.4 4 4 4 14:19 12:45 0 0 0 2 2 11/ 1:29 2 12:40 0 0 0 -15 0 2 4 6 8 10 -15 0 2 4 6 8 10 -15 0 2 4 6 8 10 14:26 12:52 11/ 1:22 14:21 12:47 -30 -30 -30 1.4 1.4 1.4 1.4 1.4 1.4 1.6 14:32 1.6 1.6 -45 12:591.6 -45 1.6 -45 1.6 1.8 1.8 1.8 12:53 2.0 1.8 2.0 11/ 1:16 10/23:421.8 2.0 14:28 1.8 2.2 2.0 2.2 2.0 2.2 2.0 -60 2.4 2.2 -60 2.4 2.2 -60 2.4 2.2 2.6 2.4 PA 2.6 2.4 PA 2.6 2.4 PA 3.0 2.6 3.0 2.6 3.0 2.6 3.0 3.0 3.0 -105 -90 -75 -60 -105 -90 -75 -60 -105 -90 -75 -60 1000 10000 1000 10000 1000 10000 1000 10000 1000 10000 1000 10000 Counts, s Counts, s Counts, s Fig.
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