Peter Chi IGPP & ESS, UCLA Prof. Russell Symposium May 8-9, 2013 How Did UCLA Develop the World’s Largest Ground Magnetometer Network ~ An insider’s account ~ Peter Chi IGPP & ESS, UCLA Prof. Russell Symposium May 8-9, 2013

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 AFGL array Chi et al. [1996]

Chris’ Advice on Scientific Research: Path to Discovery Imagination Reality

List of UCLA Magnetometer Projects (both space-based and ground-based)

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

1995- early 2000s: SMALL & IGPP-LANL Arrays Get maps (check IGPP website) PI: V. Angelopoulos, C. T. Russell Domestic ground observations since AFGL magnetometer project, paving the way for more ground projects in North America PI: Guan Le Chris organized a meeting with Chinese PIs at UCLA A dozen stations were established in China

Detecting Field Line Resonance (FLR) from the Ground Russell et al. (1999): Using IGPP-LANL data Chi et al. (2000): Using IGPP-LANL data Chi and Russell (1998)

(2005 -): Mid-continent Magnetoseismic Chain (McMAC) ● 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.

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. Peaks in cross phase Coherence t-statistic Positive slope in power ratio Remove isolated selections

FLR-inferred Equatorial Density: (July 2006-June 2007)

Local Time Dependence of Density Plasmasphere Theremosphere Equatorial Lühr et al. [2011] 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

Other UCLA-built Ground Magnetometers Since Late 1990s MEASURE PI: Mark Moldwin Region: US East Coast PI: Martin Connors Region: Canada AMBER PI: Endawoke Yizengaw Region: Africa SAMBA PI: Eftyhia Zesta Region: South America/Antarctica

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) Add image of THEMIS Add PI and Co-I names

Effective Station Pairs for FLR Sounding in North America Magnetometer Arrays: McMAC Falcon THEMIS GBO/EPO USGS IGPP/LANL GIMA CARISMA AUTUMN CANMOS (During 23-26 October 2007)

Monitoring Equatorial Density by Ground Magnetometers 2007-Oct-25 log10 (neq) [a.m.u. cm3] (movie) 2-D FLR sounding

Travel-time Magneto-seismology Spacecraft Ground stations Imagine an impulse propagating in the magnetosphere observed by satellite and ground stations at different locations Two critical things to know: Travel speed Travel path These two pieces of information lead to travel time

Terrestrial International Magnetometer Array Ultra Large Terrestrial International Magnetometer Array 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. Count # of stations involved ULTIMA kick-off meeting at UCLA (2006)

World Map of Magnetic Observatories (for Magnetospheric Research) 10 8 6 4 2 1

Lots of Babies (Ground Stations) to Look After A photo of ~100 babies

Next Destination: Antarctica

Conclusions Since mid-1990s, UCLA and collaborators have developed the world’s largest ground magnetometer network in 15 years What made it happen: Persistent support and leadership by Prof. Russell Engineering innovations and scientific quests Joint ventures between UCLA Team and Collaborators Unconditional love Spirit of exploration