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How Did UCLA Develop the Worlds Largest Ground Magnetometer Network ~ An insiders account ~ Peter Chi IGPP & ESS, UCLA Prof. Russell Symposium May 8-9, 2013 Slide 2 Once Upon a Time (circa 1992) Chris suggested me, a new graduate student from Taiwan, to study ground magnetometer data for my graduate research. At that time UCLA was not operating ground magnetometers. But a few sets of ground magnetometer data were studied with great interest (e.g. IGS data from UK; AFGL data from Howard Singer and Jeff Hughes) Research using ground magnetometer data: Ultra-low- frequency (ULF) waves; Subsurface conductivity inferred from wave amplitude Chi et al. [1996] AFGL array Slide 3 Chris Advice on Scientific Research: Path to Discovery Imagination Reality Slide 4 List of UCLA Magnetometer Projects (both space-based and ground-based) Slide 5 1995: Renewed Interest in Ground Magnetometers SMALL-type Fluxgate Magnetometers Made use of desktop PC for housing electronics, acquiring and storing data Included a GPS for accurate location and time A low-cost system that made it economically feasible for many research projects Slide 6 1995- early 2000s: SMALL & IGPP-LANL Arrays PI: Guan Le Chris organized a meeting with Chinese PIs at UCLA A dozen stations were established in China PI: V. Angelopoulos, C. T. Russell Domestic ground observations since AFGL magnetometer project, paving the way for more ground projects in North America Slide 7 Detecting Field Line Resonance (FLR) from the Ground Chi and Russell (1998) Russell et al. (1999): Using IGPP-LANL data Chi et al. (2000): Using IGPP-LANL data Slide 8 8 Field line resonance method requires close separation between ground stations in the north-south direction. The mean north-south separation between two adjacent McMAC stations is 275 Km. Joint operation with CANOPUS Churchill Line (Canada), IGPP-LANL (U.S.) and MAGDAS (Japan) provides the magnetic field data from L = 1.2 to 11 + at one local time. (2005 -): Mid-continent Magnetoseismic Chain (McMAC) Slide 9 Automated Detection of FLR Frequencies We developed an algorithm to automated detection of FLR frequencies in cross- phase/cross-power spectrograms. The algorithm is based on the criteria used by Berube et al. (2003) with additional constraints. We examined the results in cross-phase spectrograms but rarely needed to make corrections. 1.Peaks in cross phase 2.Coherence 3.t-statistic 4.Positive slope in power ratio 5.Remove isolated selections 9 Slide 10 FLR-inferred Equatorial Density: (July 2006-June 2007) Equatorial 10 Slide 11 Local Time Dependence of Density Plasmasphere: Density increases in afternoon/evening hours are not predicted by models. Thermosphere: Equatorial ionization anomaly peaks in local afternoon at low magnetic latitudes. Reason: Neutral plasma coupling 11 Equatorial Lhr et al. [2011] Plasmasphere Theremosphere Slide 12 Other UCLA-built Ground Magnetometers Since Late 1990s SAMBA PI: Eftyhia Zesta Region: South America/Antarctica PI: Martin Connors Region: Canada MEASURE PI: Mark Moldwin Region: US East Coast AMBER PI: Endawoke Yizengaw Region: Africa Slide 13 THEMIS Ground Magnetometers (2003-) System Features 72KnT dynamic range @ 0.01nT Resolution (~23 bits) Offset DAC system for 256 possible ranges per axis Sigma-delta modulator design 2 vectors per second data rate Low power < 4W Small size 22cm x 13cm x 5cm Ruggedized all weather sensor design USB interface for data retrieval and firmware upload GPS antenna and electronics Integrated into one package NTP compatible (1msec time accuracy) Slide 14 Effective Station Pairs for FLR Sounding in North America (During 23-26 October 2007) Magnetometer Arrays: McMAC Falcon THEMIS GBO/EPO USGS IGPP/LANL GIMA CARISMA AUTUMN CANMOS Slide 15 Monitoring Equatorial Density by Ground Magnetometers log 10 (n eq ) [a.m.u. cm 3 ] 2007-Oct-25 Slide 16 16 Magneto-seismology Travel-time Magneto-seismology Spacecraft Ground stations Slide 17 An international consortium for ground- based magnetometers since 2006. Provides a platform for ground-based magnetometer networks to collaborate. ULTIMA and mini-GEM have been holding joint meeting sessions on an annual basis. ULTIMA looks forward to continuing this practice that helps interact with other scientists/projects. ULTIMA kick-off meeting at UCLA (2006) Slide 18 World Map of Magnetic Observatories (for Magnetospheric Research) L 10 8 6 4 2 1 2 4 6 8 10 Slide 19 Lots of Babies (Ground Stations) to Look After Slide 20 Next Destination: Antarctica Slide 21 Conclusions Since mid-1990s, UCLA and collaborators have developed the worlds largest ground magnetometer network in 15 years What made it happen: 1.Persistent support and leadership by Prof. Russell 2.Engineering innovations and scientific quests 3.Joint ventures between UCLA Team and Collaborators 4.Unconditional love 5.Spirit of exploration