1. 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

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
AFGL array
Chi et al. [1996]

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

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

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

6. 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

7. 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)

8. (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.

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

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

11. 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

12. 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

13. THEMIS Ground Magnetometers (2003-)
System Features
• ±72KnT dynamic 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

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

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

16. 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

17. 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)

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

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

20. Next Destination:
Antarctica

21. 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