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Short-time Variations in Gamma-Ray and Relativistic Electron Flux Observed in Vernov and Lomonosov Missions

This study focuses on the observation and analysis of short-term variations in gamma-ray and relativistic electron flux using the Vernov and Lomonosov missions. The data collected provides valuable insights into electron precipitations, electromagnetic phenomena in nearby space, and transient phenomena in the atmosphere.

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Short-time Variations in Gamma-Ray and Relativistic Electron Flux Observed in Vernov and Lomonosov Missions

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  1. Gamma-Ray and Relativistic Electron Flux Short-time Variations Observed in Vernov and Lomonosov Missions M.I. Panasyuk, S.I. Svertilov, V.V. Bogomolov, G.K. Garipov, V.O. Barinova, A.V. Bogomolov, A.F. Iyudin, V.V. Kalegaev, M.A. Kaznacheeva, V.S. Morozenko, I.N. Myagkova, P.A. Klimov, V.L. Petrov, A.V. Prokhorov, I.V. Yashin Skobeltsyn Institute of Nuclear Physics, Moscow State University. Moscow, Russia Physical Department of Moscow State University. Moscow, Russia

  2. Space experiment “Vernov” small satellite (M=283 kg) with “RELEC” experiment on-board was launched on 2014 July, 8 into a polar solar-synchronous orbit with perigee ~600 km, apogee~800 km • Scientific goals of the mission: • Electron precipitations • Electromagnetic phenomena in nearby space • Transient phenomena in atmosphere

  3. Instrumentation: • DRGE-1 and DRGE-2 – two identical detector boxes for x-ray and gamma-ray measurements with high sensitivity and good temporal resolution • DRGE-3 – contains three axe directed detectors of electrons, protons and gammas. • Telescope-T (MTEL-2) – optical imager. • DUV – detector of UV and optical flashes • NChA – low-frequency analyzer • RChA – radiofrequency analyzer • BE – information unit ~50Gb of scientific data from “RELEC” complex were obtained during the period from 25.07.2014 to 10.12 2015

  4. DRGE-1 and DRGE-2 gamma-ray detectors There are two identical detector boxes named DRGE-1 and DRGE-2. Each of them consists of two identical detector units. These units made in one case work independently. Total area is ~500 cm2 Detector consists of optically coupled thin (3mm) NaI(Tl) and considerably thick (17mm) CsI(Tl) crystals. Thickness of NaI(Tl) is optimized for soft part of energy range. CsI(Tl) plays a role of active shield for soft radiation being the main detector for hard one. Working ranges are 0.01-0.5 MeV for NaI(Tl) and 0.05-3 MeV for CsI(Tl) one.

  5. Structure of output data 1. Monitoring frames Contain number of events detected in wide energy channels separately for NaI(Tl) and for CsI(Tl) 2. Event frames Contain detailed data: (timer value at the moment of detection, fast and slow ADC codes) for each of gammas detected during the frame time but not more than some fixed value (default is 800 for equator, 200 for regions of trapped particles) 3. Telemetric frames Contain a number of health parameters including total rate, number of timer counts, energy thresholds etc.

  6. Methods of TGF search in “RELEC” data - Since atmospheric gamma-ray flashes are characterized by small durations (<1 ms) “event” frame data were used for their search. It should be noted that in Equatorial regions the record of all the events in the detector was made, while at high latitudes only about ~20% of events was passed in event mode for reasons of reducing the amount of data. - Since the spectra of TGFs are hard only the events with energy over 400 keV were considered in the search algorithm. - The requirement of coincident flash in two or more detectors was used as an additional criterion of significance (see below)

  7. Imitations caused by cosmic rays The most of short increases satisfying the criterion were related to the registration of heavy charged particles of galactic cosmic rays which cause a significant flare of scintillators, PMTS and overloading sensitive input elements of electronic circuits.In this case, the device records the sequence of noise pulses of decreasing amplitude at intervals of ~10 μs (time event processing electronics) and a total duration of several milliseconds. To suppress imitations of bursts by particles an additional requirement was added to the criterion. The cases when a sequence of points on the graph of "energy – duration" shows a monotonous decline of the amplitude (no less than 5 such points in a row) were excluded. Example of TGF imitation by cosmic-ray proton with energy ~15 GeV

  8. Criterion used for TGF search • The candidate must satisfy one of two conditions: • registration at least 5 energetic gamma-quanta in a time interval of 1 ms by at least two detectors • registration at least 3 energetic gamma-quanta in a time interval of 1 ms by at least two detectors. • These criteria are consistent with: • On the equator: the simultaneous registration of event by two detectors at 12 level or by three detectors at 7 level. • At high lattitudes: the simultaneous registration of event by two detectors a 8.5 level or by three detectors at 5 level. • In order to exclude the registration of increases caused by intense variations of background in the areas of trapped radiation an additional condition was used: average background rate should not exceed 1500 Hz.

  9. The results of TGF search

  10. TGF 2014-09-18-10-15-34 Electrons inDRGE-3 Gamma-radiation in DRGE-1(2) Sum for 50mcs Energy loss spectrum in DRGE-1(2)

  11. Time profiles of TGF candidates 2014-08-08, 00:31:07 2014-08-07, 22:20:55

  12. Time profiles of TGF candidates 2014-08-16, 13:06:55 2014-11-02, 03:34:14

  13. Comparison with the lightning activity according to the global network WWLLN A list of the closest lightning in a radius of 15 degrees from the subsatellite point (1500 km) WWLLN detects reliably only the stormy areas. If there is a thunderstorm then the distance between adjacent lightning is within a couple of seconds. The average duration of a thunderstorm is about 30 minutes, and the average size is of order 100 km. For this reason, on the area of several thousand square miles some storm is usually present and the distance between the lightning is within a couple of seconds

  14. Next step of TGF search - New method of cleaning data from TGF imitations by particles, based on more accurate analysis of the time profile of candidate was realized. It allows to conduct a search of TGF according to the individual detectors (without coincidence). This will increase the analyzed observation period of almost 2 times - We plan to search with shorter times (~500 mcs) at the equator and at high latitudes at the level defined statistical confidence - We plan to compare both the previous and newly selected candidates with RFA data with ~100ms temporal resolution , WWLLN, and other ground-based lightning networks. Some candidates obtained as a preliminary result of selection of 6 events for 600 μs from the detector DRGE-1 without coincidences

  15. Map of 111 new TGF candidates from detector DRGE1-1 for 294.5 h out of ERBs and polar caps

  16. Expected number of random events for all time of observation The figure shows the dependence of the expected number of random candidates on the selection parameter, expressed by the number of counts detected over 0.4 ms. This dependence is calculated by multiplying the probability of accidental imitation on single interval (defined by Poisson distribution for taken background level), at the observation time.

  17. Comparison with UV flashes UV data are obtained by DUV for 42 of TGF candidates, 2 events were accompanied by UV flashes

  18. Distribution on time interval between TGF-candidate and previous/next lightning detected by the global network WWLLN

  19. “LOMONOSOV” SPACE MISSION Was launched 28/04/2016 Scientific objectives: • Study of ultra-high energy cosmic rays • phenomena in hard x-rays and soft gamma-rays (0.01-3.0 MeV) • Search and detection of optical transients accompanying gamma-ray bursts • study of transient luminosity events in the Earth atmosphere • magnetosphere physics research

  20. Parameters of “Lomonosov” mission: Orbit: ~500 km, polar Mass: spacecraft ~600kg, payload ~150kg Total power ~ 300W Data amount ~3Gb/day Launch date – 28/04/2016 Complex of instruments: • BDRG – gamma spectrometer • SHOK – wide field optical camera • UFFO – coding mask x-ray telescope + UV telescope • TUS – Telescope for detecting flashes in atmosphere produced by cosmic rays with E>5*10^19 eV and TLEs • DEPRON, ELFIN-L – particle detectors

  21. Instrument BDRG onboard “Lomonosov” BDRG instrument consists of 3 similar detector boxes, connected to data analysis box. Parameters of each BDRG box: Detector: 3mm NaI(Tl) /17 mm CsI(Tl) Sensitive area: 130mm Energy range: 0.01 – 3 MeV Mass: 5.5 kg Power consumption of detector box: <3W Power consumption of data analysis box ~15W Sensitivity for GRBs 10-7erg/sm2 GRB localization- ~2оfor bright GRBs Goals of BDRG: 1. Production of GRB trigger 2. Spectral measurements and timing of GRB in hard x-ray and gamma range 3. Estimation of GRB coordinates 4. X-ray and gamma-ray monitoring 5. Study of TGFs

  22. Accuracy of GRB localization from BDRG data: Dependence on fluence, kT and background rate (the results of Geant numeric modeling) Standard formula for cosine shape of FOV: Here cos 1 ,, cos 2and cos 3 are cosines of the angles between the axis of correspondent BDRG box and the GRB direction. kT=100keV

  23. Structure and amount of information from BDRG 3 detector boxes Now the day portion of BDRG data is about 500-1000 Mb

  24. BDRG flightmonitoring data More than 85% of time all 3 detectors of BDRG are operating More than 90% of time all types of data frames are collected

  25. BDRG flight test: detailed spectral data

  26. BDRG flight test: data for GRBs noted in GCN

  27. List of GCN notices and BDRG events (5 SGRs, 11 GRBs)

  28. BDRG: examples of light curves GRB 2016-07-05 SGR2016-06-23 GRB 2016-07-20

  29. SGRs in monitoring data with time resolution 0.1s

  30. SGR LIGHTCURVES (“Monitoring”, time resolution 0.1s)

  31. SGR LIGHTCURVES (“Monitoring”, time resolution 0.1s) The

  32. SGR LIGHTCURVES (“Monitoring”, time resolution 0.1s) The

  33. SGR LIGHTCURVES (“Monitoring”, time resolution 0.1s)

  34. SGR LIGHTCURVES (“Monitoring”, time resolution 0.1s)

  35. Light curve of SGR outburst measured 2016-06-20 by BDRG onboard “Lomonosov”

  36. SGR JUNE 20, 2016 LIGHTCURVES (“Events”, time resolution 0.01s) Events in NaI(Tl) in different energy ranges

  37. FOURIER ANALYSIS OF SGR JUNE 20, 2016 To be discussed…

  38. Detailed study of GRB 2016-07-20

  39. Detailed study of GRB 2016-07-20 BDRG-2/Lomonosov GBM/Fermi

  40. Observation of Solar Flare 19-06-2016 (C1.7 class)

  41. BDRG monitoring data in RB and polar region

  42. Detailed BDRG monitoring data near the RB

  43. Detailed BDRG monitoring data: structure of RB

  44. BDRG monitoring data: variations in the Equatorian region

  45. Detailed BDRG monitoring data: variations in the equator region

  46. Search of TGFs in BDRG/Lomonosov data 1) Triggering for TGFs – 10 ms trigger, coincidence of at least 2 detectors, energy range E>300 keV at the level >5 events, 10 sigma. Detailed event-moda data and 1 ms monitoring are formed 2) Off-line search in recorded event-mode data – will be realized soon. The instrument must be reconfigured for data amount optimization. Now some amount of event-mode data from triggers is collected to start the search

  47. Thank You!

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