solar cycle effects on gnss-derived ionospheric total electron content ...

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ionosphere, transport and communications, environmental management and space weathermonitoring (e.g. Lui et al., 2007; Skone and Yousuf, 2007).2.8.2 SOHO CELIAS/SEMThe Solar and Heliospheric Observatory (SOHO) spacecraft, launched on 2 December 1995 andinjected in 1996 into its halo orbit around the first Lagrangian point of the Sun-Earth System,performs global investigations of the Sun and Heliosphere. Since then, the Charge, Element, andIsotope Analysis System/Solar Extreme Ultraviolet Monitor (CELIAS/SEM) instrument onboard thespacecraft has continuously been monitoring <strong>solar</strong> X-Ray and EUV fluxes up to date. A detaileddescription of the instrument is given in Hovestadt et al. (1995) and Judge et al. (1998).Figure 2.7: Image of SOHO Charge, Element, and Isotope Analysis System/Solar ExtremeUltraviolet Monitor instrument (http:///.www.usc.edu/dept/space_science/intrument_pages ).The SOHO CELIAS/SEM instrument is a transmission grating spectrometer, as shown in Figure2.7, which utilises highly stable photodiode detectors designed and fabricated for high efficiencyand stability especially in EUV wavelength ranges. This spectrometer continuously measures thefull disk absolute <strong>solar</strong> flux at the prominent and important HeII 30.4 nm line as well as the absolute39
<strong>solar</strong> flux between 0.1 to 50 nm. The dispersing element is a freestanding 5000 bar/mm goldtransmission grating. Two thin film aluminium filters are utilized to reduce out of band stray light,resulting in a background diode current. This instrument has been at a near temperature of 3 ° Cthroughout the mission (Judge et al., 2002). The precision of the SEM is ~0.5% and is primarily tolog compression of the CELIAS database. Integration period for CELIAS is 15s and data values arecontinuously transmitted.The CELIAS/SEM EUV data have provided scientists with a wealth of information to betterunderstand the connections within the <strong>solar</strong>-magnetosphere-ionosphere system (e.g.Tsurutani et al.,2005), and used in this study to investigate <strong>effects</strong> of <strong>solar</strong> flares on TEC over South Africa.2.8.3 GOES Satellite Solar Environment MonitorA geostationary satellite experiment began in 1966 with the launch of the first satellite of theApplications Technology Satellite (ATS) series. These satellites carried an instrument capable ofproviding continuous images of the Earth, and instrumentation that enabled the transmission of datato and from ground stations. The Geostationary Operational Environmental Satellite (GOES)program formally began in 1975 as a joint effort of the National Oceanic and AtmosphericAdministration (NOAA) and NASA with the launch of SMS-1 and SMS-2 satellites. Thereafter, aseries of generations of GOES satellites were launched. The recent launch included GOES 8, GOES10 and GOES 12 which carried the Space Environment Monitor (SEM). The GOES 12 satellite wasthe first to carry Solar X-ray Imager (SXI) type instruments.The SEM consists of three instrument groups: an energetic particle sensor (EPS), two magnetometersensors and a <strong>solar</strong> X-ray sensor which monitors space weather at ~35,000 km altitude. Theseinstruments provide the real-time data to the Space Environment Center (SEC) in Boulder,Colorado. The SEC is the USA’s space weather center and receives, monitors, and interprets a widevariety of <strong>solar</strong> terrestrial data and issues reports, alerts, warnings, and forecasts for special events40
Page 1 and 2: SOLAR CYCLE EFFECTS ON GNSS-DERIVED
Page 3 and 4: ACKNOWLEDGEMENTSI would like to ack
Page 5 and 6: SOHOSXITECVLBIVTECVTMUNB-IMTULMCARU
Page 7 and 8: 2.6.3 Ionospheric group delay and p
Page 9 and 10: 7.2 Recommendation for future work
Page 11 and 12: Figure 4.4: The scatter plot of mid
Page 13 and 14: Figure 6.5: Panel (a) depicts the c
Page 15 and 16: Chapter 1INTRODUCTION1.1 Background
Page 17 and 18: station using stochastic parameters
Page 19 and 20: (GTEC) computed using UNB-IMT with
Page 21 and 22: Chapter 2THE SUN, EARTH`S IONOSPHER
Page 23 and 24: that the solar mat
Page 25 and 26: charged ion is created, and the neg
Page 27 and 28: 2.3.1 The D layerThe D layer is the
Page 29 and 30: Figure 2.4: Major geographic region
Page 31 and 32: latitude of 78 to 80 near local n
Page 33 and 34: with different propagation velociti
Page 35 and 36: 2.6 Ionospheric effects</st
Page 37 and 38: where ω (radian.cωCZ = ,(2.5)ω1s
Page 39 and 40: nwhich is the group refractive inde
Page 41 and 42: (e.g. McKinnell, 2002). The ionogra
Page 43: GPS is a satellite-based system for
Page 47 and 48: Chapter 3THE IONOSPHERIC TOTAL ELEC
Page 49 and 50: although efforts are continuously i
Page 51 and 52: side of the equation, which is slow
Page 53 and 54: TECcombi= TEC −ϕin2∑nj=−2p
Page 55 and 56: this reference frame compared to th
Page 57 and 58: 1997). For more information about t
Page 59 and 60: As first validation, Figure 3.2 ill
Page 61 and 62: Chapter 4VALIDATION OF UNB-IMT USIN
Page 63 and 64: esults using ITEC measurements as o
Page 65 and 66: code described in Chapter 3 to comp
Page 67 and 68: Figure 4.2: Comparison of daily mid
Page 69 and 70: (b) Main phase: the TEC is expected
Page 71 and 72: (Fedrizzi, et al., 2005). Further i
Page 73 and 74: Figure 4.5: Computed difference ∆
Page 75 and 76: The seasonal variation is difficult
Page 77 and 78: Figure 4.7 (a)-(c) depicts the midd
Page 79 and 80: 5. Summary and ConclusionsThis work
Page 81 and 82: Chapter 5MAPPING GNSS-DERIVED TEC O
Page 83 and 84: A detailed description of CELIAS/SE
Page 85 and 86: 30 ° W 0 ° 30 ° E 60 ° E 90 °
Page 87 and 88: latitudes is not associated with ge
Page 89 and 90: However, a further investigation wa
Page 91 and 92: Figure 5.6: The day 301, 2003 <stro
Page 93 and 94: who reported that the largest TEC e
Page 95 and 96:
Figures 5.7 and 5.8 depict examples
Page 97 and 98:
dramatically to the X - ray and Ext
Page 99 and 100:
the X9 flare, (e) shows the TEC map
Page 101 and 102:
solar cycl
Page 103 and 104:
chapter demonstrated the capabiliti
Page 105 and 106:
(Hobiger et al., 2006). The main pu
Page 107 and 108:
(d) Based on (a), (b) and (c), VTEC
Page 109 and 110:
Figure 6.3: Comparison of VTEC (dar
Page 111 and 112:
However, for days in which data wer
Page 113 and 114:
1994) and the follow-up to CONT95 (
Page 115 and 116:
6.4.2 CONT05 CampaignCONT05 was a t
Page 117 and 118:
To further investigate the capabili
Page 119 and 120:
space geodetic techniques during th
Page 121 and 122:
(2) Short-term variations of TEC (p
Page 123 and 124:
conducted for the year 2002 (near <
Page 125 and 126:
REFERENCESBartels, J., Heck, N. H.,
Page 127 and 128:
Precision Geodesy using the Mark-II
Page 129 and 130:
Fuller-Rowell, T. J., Codrescu, M.
Page 131 and 132:
Jakowski, N., Heise, S., Wehrenpfen
Page 133 and 134:
Langley, R. B., The GPS observables
Page 135 and 136:
McNamara, L. F. Radio amateur guide
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Prölss, G. W. On explaining the lo
Page 139 and 140:
Stubbe, P. The ionosphere as a Plas
Page 141:
Zhang, D. H., Xiao, Z. Study of ion
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