One of the central research tasks of the experiment conducted with the help of the Electron M PESCA instrument onboard the Coronas Photon satellite, the.
ISSN 00380946, Solar System Research, 2011, Vol. 45, No. 3, pp. 206–211. © Pleiades Publishing, Inc., 2011. Original Russian Text © Yu.I. Denisov, V.V. Kalegaev, I.N. Myagkova, M.I. Panasyuk, 2011, published in Astronomicheskii Vestnik, 2011, Vol. 45, No. 3, pp. 213–218.
Experiment on the Measurement of Charged Particle Flows with ELECTRONMPESCA Onboard the CORONASPHOTON Solar Research Satellite Yu. I. Denisov†, V. V. Kalegaev, I. N. Myagkova, and M. I. Panasyuk D.V. Skobel’tsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia Received April 13, 2010
Abstract—This paper describes the design and principles of operation of the ElectronMPESCA instru ment, provides a specification of the information system to store and access the measurement results regis tered with ElectronMPESCA, and evaluates the prospects of applying this system to assess the radiation conditions in the nearEarth space. It presents an analysis of the increase in relativistic electron flows with energies of 1–4 MeV registered in Earth’s outer radiation belt in the middle of March 2009 after weak mag netic disturbances caused by the approach of a highspeed solar wind flow as an example of online analysis of research information obtained with ElectronMPESCA. DOI: 10.1134/S0038094611020031 †
INTRODUCTION
EXPERIMENT
Information on the radiation conditions in near Earth space (NES) is necessary both for fundamental research and applied tasks. Despite a large number of spacecraft providing information on charged particle flows in the near space—ACE (Advanced Composi tion Explorer), GOES (Geostationary Operational Environmental Satellite), and POES (PolarOrbiting Operational Environmental Satellites)—the problem of monitoring relativistic electron flows at low alti tudes is still a hot issue. The reason for this is, in par ticular, the possible failures in the spacecraft operation during upsurges in relativistic electron flows caused by geomagnetic disturbances (e.g., Reeves et al., 2003, and the references cited in this work).
The ElectronMPESCA onboard CoronasPho ton is intended to register proton, electron, αparticle and CNO nuclei flows. These measurements provide important information on the patterns of cosmic ray particles and radiation belts and enable ongoing monitoring of the radiation conditions in the near Earth space.
One of the central research tasks of the experiment conducted with the help of the ElectronMPESCA instrument onboard the CoronasPhoton satellite, the third satellite in the Coronas Program (Complex Orbital Observations NearEarth of Activity of the Sun), is to investigate the patterns of relativistic elec tron flows in the Earth’s magnetosphere. This task is now coming out on top since the other two—monitor ing of solar cosmic rays (SCR) and exploration of the region where SCR penetrate the Earth’s magneto sphere during geomagnetic disturbances—are irrele vant in the period of a deep minimum of solar activity, because of the absence of SCR events. Fortunately, CoronasPhoton’s round polar orbit allows one to effectively explore the Earth’s outer radiation belt (ORB) at low altitudes.
The instrument consists of two blocks: the Elec tronMDPESCA detector block and the Electron ME PESCA electronic block. A view of the detector block is given in Fig. 1. The ElectronMDPESCA detector block is a fourelement semiconductor tele scope designed to register proton, electron, α particle and CNO nuclei flows in the nearEarth space by the range–energy relation. The instrument contains two parallel telescopes consisting of ~6 cm2 detectors. All the detectors have a 0.375mmthick body and 0.6mmthick mounting plate. The first detector is protected with a 0.1mmthick aluminum filter. The
† Deceased.
Fig. 1. View of the detector block of ElectronMPESCA.
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EXPERIMENT ON THE MEASUREMENT OF CHARGED PARTICLE FLOWS Table 1. Energy ranges of particles registered by the detector block of ElectronMPESCA Registered parameters Proton spectra and fluxes Electron spectra and fluxes αparticle fluxes C, N, O nuclei fluxes
ME PESCA, 2.3 ± 0.2 kg. A list of the output param eters of ElectronMPESCA is given in Table 2.
Energy ranges 4–16, 16–28, 41–55, >80 MeV 0.2–1, 1–4, >4.0 MeV 5–16, 16–24 MeV/nucleon 6–15 MeV/nucleon
second detector is positioned directly below the first one. Between the second and third detector, there is a 4.5mmthick aluminum filter; between the third and the fourth, a 7mmthick brass filter. The effective area of each of the four detectors is 6 cm2. Electrons are registered by the first three detectors in the energy release range of 0.1–0.8 MeV against the background of protons with energies >80 MeV. The first two detectors identify protons as particles releas ing energy of >2 MeV. The third detector has a 1.5 MeV threshold for proton registration. The fourth detector has a threshold of ~0.1 MeV for registration of relativistic particles. The flow of electrons with energies of >14 MeV in the radiation belts and solar cosmic rays can be neglected as compared to the flow of protons with energies >80 MeV. The α particle flows are registered by the first and second detectors in the case of energy release >12 MeV. CNO nuclei flows are registered by the first detector in the case of energy release >40 MeV. The energy ranges of the particles registered by the detector blocks of ElectronM PESCA are given in Table 1. The flow chart of the detector block and the principle of producing the out put parameters are shown in Fig. 2. The dimensions of the blocks of ElectronMD PESCA are 200 × 186 × 140 mm; ElectronME PESCA, 258 × 150 × 150 mm; the masses of the blocks of ElectronMDPESCA are 2.2 ± 0.2 kg; Electron
INFORMATION SYSTEM FOR PROCESSING AND STORAGE OF THE DATA OBTAINED WITH ELECTRONMPESCA The Skobeltsyn Institute of Nuclear Physics of Moscow State University (SINP MSU) has developed an automated information system to work with the data from ElectronMPESCA. The system operates on a software platform that consists of a computing cluster run by HP Proliant servers (32 Opteron proces sor cores) and an Oracle database server. The data are managed and accessed via the web portal of the Space Monitoring Data Center (SMDC) of SINP MSU, at http://smdc.sinp.msu.ru (Parunakian et al., 2008). The software package includes: —a telemetry data download system; —a telemetry deciphering system; —an orbit parameter download system; —a satellite orbit calculation system; —a system to upload data to the FTP server and Oracle database; —a system to access the data in the Oracle data base; —a data visualization system; —and a real time system to analyze the radiation conditions in the space environment. The source data come to the FTP site of the Mos cow Engineering Physics Institute (MEPhI). The SINP MSU server sends periodic queries against the telemetry file storage at MEPhI for new information on the ElectronMPESCA. When relevant data appear on the MEPhI site, the files are copied to the SIMP server, and a deciphering program is instantly launched. The processed file with the data on the mea surements of charged particle flows and the source telemetry file are uploaded to the FTP server of the
Table 2. Output parameters of ElectronMPESCA No.
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Registered particles, MeV
Registration logic
Note
P1
е—0.2–1.0 MeV
D1 D2 D5
D—coincidence
P2
р—4–16 MeV
D2
D—anticoincidence
P3 P4
α—5–16 MeV/nucleon CNO nuclei—6–15 MeV/nucleon
D3 D4
P5
е—1.0–4.0 MeV
P6 P7
р—16–28 MeV α—16–24 MeV/nucleon
D5 D6 D8 D6 D7
P8
е—>4.0 MeV
P9 P10
р—41–55 MeV р—>80 MeV
SOLAR SYSTEM RESEARCH
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DENISOV et al. 0.1 D1 P1
L1
2.0 D2 Dt11
PA11
AI11
P2 12.0
D3
P3 40.0 P4
D4
D5
0.1 2.0
Dt21
PA21
P5
L2
P6
D6
AI21
12.0 P7
D7 0.1 D8 Dt31
PA31
AI31
L3
1.5 D9
P8 P9
0.1 Dt41
PA41
D10
AI41
L4 Dt12
PA12
Dt22
PA22
P10
Backup telescope Dt32
PA32
Dt42
PA42
Fig. 2. The flow chart of the detector block and the principle of producing the output parameters of ElectronMPESCA (the designations used: Dt is the silicon detector, PA is the preamplifier, AI is the amplifier inverter, D is the discriminator, L is the logical pattern of coincidence/anticoincidence, P is the output parameter; the figures above the connecting lines show the energy release thresholds).
Space Monitoring Data Center (SMDC) of SINP MSU (http://smdc.sinp.msu.ru) in Sections L1 and L0 of the file system, respectively. At the same time, the current files with the orbit parameters of the CORONASPHOTON satellite (.tle files) are downloaded from the site http://celestrak. com/. The satellite’s path is calculated in an automatic mode: the system calculates the geodetic, geographi cal, solarmagnetic, and McIlvain coordinates (L–B). The measurement data and satellite coordinates are uploaded to the Oracle database. The current mea
surements of particle flows registered by the instru ment during the last 2 h and the last 12 h are placed to the homepage of the SMDC portal as diagrams for preliminary review in the Section “Cosmic Weather” (two channels are presented: 4–16 MeV protons and 1–4 MeV electrons). The images are hypertext links to the archives with all the images of the flux profiles for the time intervals 2 and 12 h, which show, apart from the above two channels, the data on the flows of pro tons Е > 80 MeV and electrons Е < 1 MeV; geographi cal, spherical, and Cartesian coordinates; and local SOLAR SYSTEM RESEARCH
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Particle fluxes
Data available from 20090304 and arriving in quasi real time. Time interval 4 March 4 March Output type Table
2009 2009
Graphic
19 23
0 0
File
Data channels Ee 0.2–1.0 MeV Ee 1–4 MeV Ee >4 MeV Ep 4–16 MeV Ep 41–55 MeV Ep >80 MeV Ea 5–16 MeV/nucleon Ea 16–24 MeV/nucleon CNO 6–15 MeV/nucleon X [km] Y [km] Z [km] Latitude [deg]
Copyright © 2007 Skobeltsyn Institute of Nuclear Physics Moscow State University Abaut Done
Fig. 3. Web form for access to the measurement data of CoronasPhoton (ElectronMPESCA) on the site of the Space Moni toring Data Center of SINP MSU.
magnetic time. The data are accessed via special web forms on the SMDC Internet portal (http://smdc. sinp.msu.ru) in the section DATA/CoronasPhoton. To get the information, the user should select a presen tation format (table on the screen, graphic file, or text file), and specify the time intervals and channels. Fig ure 3 is a screenshot of the access form to retrieve the data on CORONASPHOTON measurements (Elec tronMPESCA) on the site of SMDC SINP MSU. The user fills out the fields in the web form, and the server generates an SQL query against the Oracle data base. The images are plotted using the QLOOK graphic software (Barinova et al., 2007). An important characteristic feature of the system is public access, portability, and scalability. The mea surement data can be obtained by anyone interested via the web interfaces without any access restrictions. The system architecture provides for its possible deployment at other space centers, including on other platforms and operating systems. New disk arrays and computational modules can be added to the system as the data are accumulated and computing resources are used up. SOLAR SYSTEM RESEARCH
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ELECTRON FLUX VARIATIONS IN THE OUTER ERB IN 2009 DURING MINOR GEOMAGNETIC DISTURBANCES The data obtained with ElectronMPESCA was used to investigate variations in relativistic electron fluxes in the outer ERB at a 550 km altitude in the first half of 2009. Thus, according to the data of Goddard Space Flight Center (http://cdaweb.gsfc.nasa.gov/) on variations of the parameters of the interplanetary magnetic field (IMF), solar wind (SW), and geomag netic indices, in the night from March 12 to 13, 2009, there was a minor (Dst = –28 nT, Кр = 5) magnetic dis turbance connected with an approach of a highspeed solar wind flow toward the Earth (maximum plasma velocity Vsw = 550 km/s). The auroral activity in the period under consideration was also relatively low. According to the data of the World Data Center for Geomagnetism in Kyoto, Japan (http://wdc.kugi. kyotou.ac.jp/), the AE index reached its maximum 800 nT only at about 7 a.m. on March 13 (at the max imum of the magnetic disturbance main phase) and about noon on March 21. And, according to Interma gnet, a number of highlatitude stations, such as
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DENISOV et al. (а) 1000 10 1000
Electron counting rate (1–4 MeV), 1/s
100 Electron counting rate, 1/s
(b) 1000
12.03.2009 13.03.2009 14.03.2009
15.03.2009 17.03.2009
100 10 1000
18.03.2009 19.03.2009
100 10 1000 100 10
20.03.2009 21.03.2009
3
4
5 L
6
7 8 9 10
L = 3–4 L = 4–5 L = 5–6
100
10 4
6
8 10 12 14 16 18 20 22 24 26 Days of March 2009
Fig. 4. Dependences of the counting rates of electrons with energies of 1–4 MeV on the Lshell for nine events of CoronasPhoton pass ing through the outer ERB obtained from March 12 to 21, 2009 (a); the time dependence of the maximum counting rates of relativistic electrons at a 550km altitude from the ElectronMPESCA data in March 2009 in three ranges L = 3–4, 4–5, 5–6 (b).
Sodankyla and Narsarsuaq, registered an increase in wave activity from March 15 to 20, 2009. Figure 4a shows the counting rate profiles for elec trons with energies of 1–4 MeV by L for nine events of CoronasPhoton passing through the outer ERB with the same values of the geographical coordinates and local magnetic time before, during and after the geo magnetic disturbance on March 12–13. The dashed lines in all four panels show the data on the electron counting rates obtained early in the morning on March 12, before the disturbance began; these rates were selected as background conditions. Figure 4a shows that, on March 13 (the main phase of the storm), the counting rates of the registered electrons are observed to decline (the boldface curve in the upper panel). This does not contradict the results obtained by CoronasF, the previous satellite of the Coronas Program; during strong geomagnetic storms, there was a sharp fall in the intensity of relativistic electrons in the outer ERB, practically to null (Kuz netsov et al., 2007). On March 14, (the thin solid curve in the upper panel), the electron flux near the “pre storm” maximum at L = 4 did not change, and, at higher L, there was an additional peak with the maxi mum at L = 5.2. On March 17 (the thin solid curve in the second panel from the top), the aforementioned new maximum moved a little closer to the Earth (approximately to L = 5), and its intensity grew by almost an order of magnitude. On March 18–19, the intensity of the electron fluxes in the outer ERB kept on growing. The maximum in the counting rate of rel ativistic electrons was registered on March 19. Figure 4b shows the pattern of the maximum counting rates of relativistic electrons at a 550km altitude in the ranges:
L = 3–4, 4–5, and 5–6. It is easy to see from the figure that the maximum growth of the electron fluxes was observed at the maximum distance from the Earth, i.e., at L = 5–6, and there was practically no increase at L = 3–4. The maximum flows at L = 5–6 were reg istered one day earlier than at L = 4–5, four days after the disturbance event caused by an approach of a high speed SW flow. The obtained time lag is consistent with the results of the study (Li et al., 2005) carried out from the data of the SAMPEX (Solar Anomalous and Magnetospheric Particle Explorer) satellite. Relativistic electron fluxes (with energies higher than 1 MeV) have been also found to correlate with the solar wind velocity at a geostationary orbit (LANL (Los Alamos National Laboratory) satellite) (Li et al., 1997), with the measurements being carried out, as in our case, near a minimum of solar activity (1995). This work argued that the factors that make relativistic elec tron fluxes vary may be either radial diffusion, or VLF wave “heating”; however, the relative contribution of these factors is still unclear. Experimental studies on electron flow variations in the outer ERB have been carried out both in Russia and abroad by various research teams from the discovery of the Earth’s radi ation belts up to the present (e.g., Williams et al., 1968; Vakulov et al., 1975; Bezrodnykh et al., 1987; Baker et al., 1997; Li and Temerin, 2001; Reeves et al., 2003; and the references cited in these works). Many of these works have convincingly demonstrated a connection between relativistic electron flow variations and solar wind parameters, in particular, the speed of the latter. However, a significant feature of 2009 was the extremely quiet geomagnetic situation; the approach of highspeed SW flows did not cause any significant SOLAR SYSTEM RESEARCH
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magnetic storms in the Earth’s magnetosphere. Thus, in the case under study, the geomagnetic disturbance on March 12–13, 2009, which caused all the above relativistic electron flux variations, was neither strong, nor can it, in fact, be considered a magnetic storm at all, in the common sense. Neither there were any sig nificant substorms in this period; however, a number of highlatitude stations registered an increase in wave activity, which might have caused the observed increase in the relativistic electron fluxes. CONCLUSIONS Construction of instruments for new experiments in the nearEarth space environment and develop ment of information systems for storage of space related information and online processing of research data are necessary elements of space experiments. The space monitoring data on charged particle flows in the nearEarth space and their analysis based on the mod els of space environment and modern information technologies allow one to analyze the radiation condi tions in the inner magnetosphere at low altitudes. This monitoring will make it possible to clarify the relevant issues of the solar activity influence on the radiation processes in the near space. The increases in the relativistic electron fluxes in the outer ERB registered in 2009 with ElectronM PESCA clearly demonstrate that even weak geomag netic disturbances in combination with wave activity may have a significant effect on the radiation condi tions in the nearEarth space. ACKNOWLEDGMENTS The authors thank L.I. Starostin and A.V. Bogo molov for their help in processing the data. This work was supported in part by the Russian Foundation for Basic Research, project nos. 070292004NNS_a and 090500798.
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