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-lowfrequency (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
• 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
Detecting Field Line Resonance (FLR)
from the Ground
Russell et al. (1999):
Using IGPP-LANL data
Chi and Russell (1998)
Chi et al. (2000):
Using IGPP-LANL
data
(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.
8
Automated Detection of FLR Frequencies
100
100
50
Frequency [mHz]
• We developed an
algorithm to automated
detection of FLR
frequencies in crossphase/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.
X-Phase: - (WRTH)+  (BENN) 2006 Jul 31
120
80
0
60
40
-50
20
-100
2
4
6
8
10
12
14
16
18
20
22
Universal Time [hours]
1.
2.
3.
4.
5.
Peaks in cross phase
Coherence
t-statistic
Positive slope in power ratio
Remove isolated selections
9
FLR-inferred Equatorial Density:
(July 2006-June 2007)
Equatorial
Mass Density [amu/cm-3]
10
10
4
L=1.77
L=2.15
L=2.73
L=3.06
3
0
6
12
Local Time [hours]
18
24
10
Local Time Dependence of Density
Theremosphere
Plasmasphere
Equatorial
Mass Density [amu/cm-3]
10
10
4
L=1.77
L=2.15
L=2.73
L=3.06
3
0
6
12
18
24
Lühr et al. [2011]
Local Time [hours]
•
Plasmasphere: Density increases in
afternoon/evening hours are not
predicted by models.
•
•
Thermosphere: Equatorial ionization
anomaly peaks in local afternoon at
low magnetic latitudes.
11
Reason: Neutral plasma coupling
Other UCLA-built Ground Magnetometers Since
Late 1990s
MEASURE
PI: Martin Connors
Region: Canada
SAMBA
PI: Eftyhia Zesta
Region: South America/Antarctica
PI: Mark Moldwin
Region: US East Coast
AMBER
PI: Endawoke Yizengaw
Region: Africa
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)
Effective Station Pairs for FLR Sounding in
North America
72oN
o
60 N
48oN
36oN
24oN
Magnetometer Arrays:
• McMAC
• Falcon
• THEMIS GBO/EPO
• USGS
• IGPP/LANL
• GIMA
• CARISMA
• AUTUMN
• CANMOS
12oN
175oW
150oW
125oW
100oW
(During 23-26 October 2007)
75oW
50oW
Monitoring Equatorial Density by
Ground Magnetometers
2007-Oct-25
log10 (neq)
[a.m.u. cm3]
4
3.5
3
2.5
2
1.5
1
1
Travel-time Magneto-seismology
Spacecraft
Ground stations
16
• An international
consortium for groundbased 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)
World Map of Magnetic Observatories
(for Magnetospheric Research)
80oN
MACCS
Svalbard
GIMA
MAGDAS
Meridian
AAMN
L
10
8
6
4
o
40 N
0o
40oS
2
CARISMA
NRCan
AUTUMN
McMAC
Falcon
THEMIS
IGPP-LANL
MEASURE
SAMBA
AMBER
IMAGE
SAMNET
Greenland
MAGIC
SEGMA
Finnish
USGS
Geo. Australia
IPGP
BGS
INTERMAGNET-others
1
2
4
AGO
South-Pole (VT)
6
8
10
o
80 S
Copyright © 2012 Peter J. Chi
180oW
120oW
60oW
0o
60oE
120oE
180oW
Lots of Babies (Ground Stations) to
Look After
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:

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