ILWS WORKSHOP 2006, GOA, FEBRUARY 19-24, 2006

MAGDAS project and its application for space weather
K. Yumoto and the MAGDAS GroupSpace Environment Research Center, Kyushu University, Japan
Abstract. We introduce a real-time MAGnetic Data Acquisition System of Circum-pan Pacific Magnetometer Network,
i.e. MAGDAS/CPMN for space weather study and application, and its preliminary results. By using this system, we willconduct real-time monitoring and modeling of (1) global 3-dimensional current system, (2) plasma mass density, and (3)penetrating process of polar electric fields into the equatorial ionosphere, in order to understand electromagnetic andplasma environment changes in the geospace during the period of ILWS/CAWSES/IHY.
Index Terms. Space weather, MAGDAS, electromagnetic and plasma environment, geospace.

_____________________________________________________________________________________________________
1. Introduction
One purpose of the Solar Terrestrial Physics (STP)
research in the twenty-first century is to support humanactivities from an aspect of fundamental study. The
scientific new aim for the STP society is a creation of new
physics; (1) couplings of the complex and composite
systems and (2) multi-scale couplings in the Sun-Earthsystem. The goals for the attainment of the purpose are toconstruct Network Stations for observations and Modeling
Stations for simulation/ empirical modeling. In order tounderstand the Sun-Earth system and its effects to human
lives, the international LWS (Living With a Star) andCAWSES (Climate and Weather of Sun-Earth System)
programs started from 2004.
The International
Heliophysical Year (IHY) program is also planned to startin 2007.
For space weather study on the complexity in the SunEarth system, the Space Environment Research Center(SERC), Kyushu University started to construct a new
ground-based magnetometer network, in cooperation with
about 30 organizations in the world from 2004. The SERC
will conduct the MAGDAS (MAGnetic Data Acqusition
System) observations at 50 stations in the CPMN (Circumpan Pacific Magnetometer Network) region, and the FMCW radar observations along the 210°magnetic meridian(see Fig. 1), in order to understand dynamics ofplasmaspheric changes during space storms, responses ofmagnetosphere-ionosphere-thermosphere to various solar
wind changes, and penetration mechanisms of DP2-ULF
range disturbances from the solar wind region into theequatorial ionosphere.
On the other hand, electromagnetic phenomena, e.g.,
ULF, ELF and VLF waves are recognized as usefuldiagnostic probes of the solar wind-magnetosphere-

ionosphere-atmosphere coupled system for space weather
studies. These waves convey information about the
dynamics and morphology of the coupled system.
In the present paper, at the first we will introduce ourreal-time data acquisition and analysis system of
MAGDAS/CPMN, and preliminary results obtained by thissystem; (1) monitoring of the global 3-dimensional current
system to know the electromagnetic coupling of highlatitude and Sq current systems, and (2) monitoring of theplasma mass density in geo-space to understand plasma
environment change during storms. In the second, we willshow the FM-CW radar system at L=1.26 to deduce
electric field from the ionospheric plasma Doppler
velocity. From 24hr monitoring of the ionospheric drift
velocity with 10-sec sampling rate by the FM-CW radarobservation, (3) we can understand how the polar electricfield penetrates into the equatorial ionosphere.
2. MAGDAS/CPMN system
The Circum-pan Pacific Magnetometer Network (CPMN)
was constructed by Kyushu University in collaborations
with about 30 international organizations along the210゜magnetic meridian and the magnetic equator during
the international Solar Terrestrial Energy Program (STEP)
period (1990-1997) (see Yumoto and CPMN group, 2001).
The 1-sec magnetic field data from the coordinatedground-based network made it possible to (1) study
magnetospheric processes by distinguishing between
temporal changes and spatial variations in the phenomena,(2) clarify global structures and propagation characteristics
of magnetospheric variations from higher to equatorial
latitudes, and (3) understand global generation
mechanisms of the Solar-Terrestrial phenomena (seeYumoto, 2004, Yumoto and 210゜MM group, 1995 and1996).

2

Fig. 1. MAGDAS/CPMN (MAGnetic Data Acquisition System/Circum-pan
Pacific Magnetometer Network) system of the SERC, Kyushu University.

For space weather study and application, the Kyushu
University group is now re-constructing a new realtime MAGDAS (MAGnetic Data Acquisition System) in the
CPMN region, and the FM-CW radar network along the
210°magnetic meridian. New 50 fluxgate-type magnetometers as shown in Fig. 2 and their data acquisition systemfrom overseas sites to Japan are being deployed by the
SERC, Kyushu University from 2005.
The new
magnetometer system consists of 3-axial ring-core(amorphous metallic alloys) sensors, fluxgate-typemagnetometer, data logging/transferring unit, and power unit.
Magnetic field digital data (H+δH, D+δD, Z+δZ, F+δF)
are obtained with the sampling rate of 1/16 seconds, and thenthe averaged data are transferred from the overseas stations to
the SERC, Japan in real time. The ambient magnetic field,
expressed by horizontal (H), declination (D), and vertical (Z)components, are digitized by using the field-canceling coils
for the dynamic range of ±64,000nT/16bit. The magnetic
variations (δH, δD, δZ) subtracted from the ambient fieldcomponents (H, D, Z) are further digitized by a 16-bit A/Dconverter. Three observation ranges of ±2,000nT, ±1,000
nT, and ± 300 nT can be selected for high, middle, andlow-latitude stations, respectively. The total field (F + δF) isestimated from the H+δH, D+δD, and Z+δZ components.
The resolutions of MAGDAS data are 0.061 nT/LSB, 0.031
nT/LSB, and 0.0091 nT/LSB for ±2,000 nT, ±1,000 nT,
and ±300 nT range, respectively. The estimated noise levelof the MAGDAS magnetometers is 0.02 nTp-p. The longterm inclinations (I) of the sensor axes can be measured by
two tiltmeters with 0.2 arc-sec resolution. The temperature(T) inside the sensor bloc is also measured. The GPS signals
are received to adjust the standard time inside the datalogger/transfer unit. These data are logging in the Compact
Flash Memory Card of 1 GB. The total weight of theMAGDAS magnetometer system is less than 15 kg. The
sensitivity, efficiency, capacity, and performance of theMAGDAS systems are tested until the end of March, 2005.
After April, 2005, 20 of the new MAGDAS magnetometers
were installed at (and/or near) the CPMN stations in 2005.

Yumoto et al: MAGDAS Project for Space Weather

Fig. 2. The component of MAGDAS/CPMN magneto-meter system for realtime data acquisition.

Every day, the data logger at an overseas site generates a filecontaining averaged 1-sec magnetic data (H, D, Z, F) and afile containing the averaged 1-min magnetic data andinclination andtemperature data
(I, T)
ofthemagnetometer sensor. The file size of the 1-sec data is lessthan 1MB. The file size of the 1-min data is less than 50KB.
If the communication line at the site does not allow a fastenough connection, the data logger sends only the 1-min fileto the SERC every day; if the connection is fast enough, thedata logger sends both the 1-min file and the 1-sec file to the
SERC every day. In fact, the data transfer does not have to
be on a daily basis: That is, the data-transfer interval can be
set to any value between 10 minutes and 1 day, depending on
the condition of the following communication lines. The
MAGDAS data can be transferred from the overseas stations
to the SERC, Japan, by using three possible ways;A) Special line for INTERNET
If the data logger of MAGDAS at overseas sites can beconnected to a special line for INTERNET (via a Switch,
HUB, or Router of INTERNET), the data logger uses
software called “SSH client” or “FTP client” to automatically establish an INTERNET connection to the SERC,
Kyushu University, Japan. Then, the data logger at thesites
automaticallytransfers
theMAGDAS
magnetometer data to the SERC.
B) Telephone line
If the above A) is impossible but if the data logger of
MAGDAS at overseas sites can be connected to atelephone line, the data logger uses it, automatically dials
up to a PPP server at the SERC, establishes a connection,and sends the data to the SERC.
C) Satellite telephone line
If the above A) and B) are both impossible, the datalogger of MAGDAS at overseas sites uses a satellitemobile-phone system, automatically dials up to a PPP
server at the SERC, establishes a connection, and sends
the data to the SERC.

ILWS WORKSHOP 2006, GOA, FEBRUARY 19-24, 2006

3. Scientific objectives and preliminary results
In order to establish the space weather studies, we have toclarify dynamics of geospace plasma changes during
magnetic storms and auroral substorms, the electro-magnetic
response of iono-magnetosphere to various solar windchanges, and the penetration and propagation mechanisms of
DP2-ULF range disturbances from the solar wind region into
the equatorial ionosphere. Figure 3 shows one example ofamplitude-time records of 3-component ordinary (upper) and
induction-type (bottom) magnetograms observed at the Kujyu
station in Oita, Japan, during 24 hrs. The ordinary data (i.e.
MAGDAS data (1)) can be used for studies of long-term
variations, e.g. magnetic storm, auroral substorms, Sq, etc.,
while the induction-type data (i.e. MAGDAS data (2)) will be
useful for studies of ULF waves, transient and impulsive
phenomena. By using these new MAGDAS data, we canconduct a real-time monitoring and modeling of (1) the
global 3-dimensional current system and (2) the ambient
plasma density for understanding the electromagnetic andplasma environment changes in the geospace.

Fig. 3. An example of amplitude-time records of ordinary (upper; MAGDAS
data (1)) and induction-type (bottom; MAGDAS data (2)) variations
observed at the Kujyu station.

In 2005, MAGDAS magnetometers were installed at 20
stations along the 210゜magnetic meridian. After 2005, 30
MAGDAS magnetometers will be installed along themagnetic equator and in Siberia. Figure 4 shows one
example of H-component amplitude-time records observed at
the MAGDAS stations (ASB, ONW KUJ, AMA in Japan,
HLN in Taiwan, MUT, CEB, DAV in Philippines, MND, and
PRP in Indonesia, DAW, CGR, CMD, HOB in Australia)
during two days of November 10-11, 2005. We can see clear
equatorial enhancements near the magnetic equator at DAV,and global nature of si—, DP-2, and substorm-associatedvariations.
3.1. Global 3-D current system
The left panel of Figure 5 indicates the ionosphericequivalent current pattern obtained from the CPMN stations
along the 210°magnetic meridian during a northernsummer. Each ionospheric current vector was estimated by
the horizontal magnetic fields observed at each CPMN
station at every hour. We will make the ionosphericequivalent current pattern every day using the MAGDAS
data (1) as shown in Figs. 3

Fig. 4. H-component amplitude-time records observed at the MAGDAS
stations (ASB, ONW KUJ, AMA in Japan, HLN in Taiwan, MUT, CEB,DAV in Philippines, MND, and PRP in Indonesia, DAW, CGR, CMD, HOB
in Australia) during two days of November 10-11, 2005.

and 4. The right panel of Fig. 5 shows the global 3dimensional currents and electric potential, with the currents
illustrated by ribbons and the potential with + and –(Richmond and Thayer, 2000). At high latitudes theionospheric currents are joined with field-aligned currents(FAC) from the solar wind region into the magnetosphere,
and the electro-dynamics is dominated by the influences ofsolar wind-magnetosphere interaction processes. The total
current flows is of the order of 107 A. On the other hand, theionospheric current at middle and low latitudes is generated
by the ionospheric wind dynamo, which produces global
current vortices on the dayside ionosphere, i.e.,counterclockwise in the northern hemisphere and clockwisein the southern hemisphere. The total current flow in eachvortex is order of 105 A.

Fig. 5. (Left) The ionospheric equivalent current pattern obtained from the
MAGDAS/CPMN data. (Right) Global 3-dimensional current system casedby magneto-spheric field-aligned currents at high latitude and the ionospheric
dynamo at middle and low latitudes.

There are strong electric fields at high latitudes, on theorder of several tens of millivolts per meter or more
depending on the magnetic activity. At middle and low
latitudes electric fields are considerably smaller, typically a

4
few millivolts per meter during magnetically quiet periods.
During magnetic active periods the part of strong electricfields at high latitude can penetrate into middle and low
latitudes, and then the global ionospheric current pattern must
be re-organized strongly. In reality the current and electricfields at all latitudes are coupled, although those at high, andmiddle and low latitudes have been often consideredseparately. By using the MAGDAS ionospheric current
pattern as shown in the left panel of Figure 5, the global
electromagnetic coupling processes at all latitudes will beclarified during the ILWS/CAWSES/ IHY period (seeYoshikawa et al., 2003).
Fig. 6(A) shows equivalent ionospheric current patterns
obtained from the MAGDAS Data (1) on September 25,
2005 (Kohta et al., 2005). The vertical axis indicatesmagnetic latitudes of the MAGDAS stations, and thehorizontal axis is the local time of the 210o magnetic
meridian stations. The arrows indicate the current vectors
obtained from the H and D components, and the color code
indicates the negative and positive magnetic Z component.
The equatorial electrojet can be seen at the dayside dip
equator. There are twin vortices of Sq current, i.e., counterclockwise and clockwise in the northern and southernhemisphere, respectively. The centers of Sq current patterns
are sometime not consistent with the maximum and minimum
points of the Z component. Fig. 6(B) is one example of Sq
equivalent current pattern obtained by the CPMN data on
July 15, 2000, during a disturbed day. The vertical axis
indicates geographic latitudes of the CPMN stations, and thehorizontal axis is the local time of the 210o magnetic
meridian stations. A clear Sq current vortex, equatorial
electrojet, auroral electrojet, and ring current patterns can be
identified in the figure. It is newly found a current flowing
from the northern hemisphere into the southern hemispherearound 06 hr local time during magnetic storm.
3.2. Plasma mass density
The field line resonance (FLR) oscillations in the Earth's
magnetosphere are excited by external source waves, and areso-called as ultra low frequency (ULF) waves (cf. Yumoto,1988). The amplitude of H-component magnetic variations
observed at the ground stations reaches a maximum at theresonant point, and that its phase jumps by 180 degrees
across the resonant point (see Yumoto, 1985). The eigenfrequency of FLR oscillations is dependent upon the ambient
plasma density and the magnetic field intensity in the regionof geospace threaded by the field line, and the length of theline of force as shown in Figure 7. When we observe theeigen-frequency of FLR and assume models for the latitude
profiles of the magnetic field and the plasma density (withthe equatorial density as a free parameter), we can estimate
the plasma mass density in the magnetosphere. Therefore,
the FLR oscillations are useful for monitoring temporal andspatial variations in the magnetospheric plasma density. By
using ground-based network observations, we can identify
the FLR phenomena and measure the fundamental field-line
eigen-frequency by applying the dual-station H-power
ratio method (Baransky et al., 1985) and the cross-phase

Yumoto et al: MAGDAS Project for Space Weather

method (Baransky et al., 1989, Waters et al., 1991), whichhave been established to identify the FLR properties.

Fig. 6 (A) & (B). MAGDAS Sq current pattern on September 5, 2005 during
magnetic quiet day (top), while CPMN Sq current pattern on July 15, 2000
during magnetic disturbed day (bottom) (Kohta et al., 2005).

We will install new MAGDAS magnetometers at several
pair stations along the 210°magnetic meridian, and observe
magnetic FLR pulsations. Each pair stations are separated inlatitude by ~100 km. The MAGDAS data (2) as shown in
Fig. 3 will be analyzed by using the two methods, i.e., theamplitude-ratio method and the cross-phase method. As aresult, we can identify the FLR events and measure theireigen-frequencies, providing the plasma mass density varying
with time.
By using these methods, Takasaki et al. (2006) discussed
temporary variations of the plasma mass density during
magnetic storm. From ground-based observations at L~1.4
they found a significant decrease in the FLR frequency atduring a large magnetic storm as shown in Fig. 8. During 28 31 October, 2003, a series of coronal mass ejections hit themagnetosphere and triggered two consecutive large storms.
Three ground magnetometers at L = 1.32~1.41 recorded
field-line resonances (FLRs) during this interval. The FLR
frequencies decreased from 0600 LT on 31 October 2003
during in the main phase of the second storm until 12 LT

ILWS WORKSHOP 2006, GOA, FEBRUARY 19-24, 2006

when the recovery phase of this storm began. After thedecrease, the FLR frequencies increased to its value before
the storm started at 0600 LT on 31 October in a few hours.

Abe et al. (2006) have applied the dual-station Hcomponent power ratio method, which identifies the fieldline eigen-frequency, to eleven-months magnetometer dataobtained at two ground stations TIK (L=5.98) and CHD(L=5.55)
thatbelong to the Circum-pan Pacific
Magnetometer Network (CPMN). As a result, they haveidentified two patterns in the frequency dependence of thepower ratio (TIK/CHD); one is an increase-then-decrease
pattern (named Type 1), and the other is a decrease-thenincrease pattern (named Type 2). Type 1 is observed where
the Alfvén velocity (VA) decreases with increasing L, and it
has often been reported in literature. In the paper, theymainly studied the Type 2 events which have rarely beenreported for the area near L=5.7 (midpoint of TIK and CHD);

Fig. 7. Plasma mass density (ρ=Σnimi) can be estimated from the eigenfrequency（T=2L/VA）of the field-line resonance (FLR) oscillations
identified by using the gradient methods of amplitude-ratio and cross-phase oat dual stations.

The measured decrease in FLR frequency might indicate a
relative increase in mass density along the field lines during
the magnetic storm. On the other hand, the plasma number
density in the ionosphere estimated from TEC values was
similar in magnitude taken during quiet time. A possible
explanation for the increase in mass density would be an
outflow of the heavy ions (e.g., O+) from the ionosphere to
the plasmasphere.

Fig. 8. (From top to bottom) Dst index, FLR frequencies derived fromground observations at L~1.4, ρeq estimated from data in the second panel,and the total electron content (TEC). The dashed vertical line marks the
beginning of the second magnetic storm (Takasaki et al., 2006).

Fig. 9. Schematic picture of the plasmapause location (view from above thenorth pole). The place where mant Type 2 FLR events were observed isshown by the thick line, and the estimated plasmapause is shown by the black
ellipse (Abe et al., 2006).

Type 2 is expected to be observed where VA drasticallyincreases with increasing L. Their statistical analysis showsthat the Type 2 events were observed more frequently in theafternoon sector (especially in 15~18 hr LT) than in themorning sector as shown in Fig. 9. The geomagnetic
condition was usually quiet when the Type 2 events wereobserved. These features are consistent with theinterpretation that their Type 2 events were observed at thefootpoint of the plasmapause layer, as follows. The
plasmapause is the only location around L=5.7 where VA
drastically increases with increasing L, leading to Type 2. Lof the plasmapause is smaller than 5.7 at all LT during
geomagnetically active times (meaning Type 1 at L=5.7)
while it is larger than 5.7 only on the late-afternoon sector
during quiet times.
3.3. Ionospheric electric fields
Geomagnetic variations generated by DP2 type current
systems coherently appear at the auroral and equatorial
latitudes in daytime, and these amplitudes sharply decrease
with decrease of latitudes but were enhanced at the dip
equator. Equatorial enhancement had been understood as
manifestation of Cowling effect for penetration of electricfield from polar to the equatorial ionosphere. Furthermore,
preliminary reverse impulse (PRI) and main impulse (MI) of
geomagnetic sudden commencement (SC) are caused by the6
DP2 type current systems, and some type of Pc5 magnetic
pulsations are also generated by this current system.
In order to investigate penetration mechanisms of theionospheric electric fields from the polar to the equatorial
ionosphere, we have built a FM-CW radar (HF radar of 2~42
MHz) system at Sasaguri, Fukuoka (geomagnetic latitude
θ=23.2°, geomagnetic longitude λ=199.6°) as shown in Fig.
10. The height of dipole antenna is 26 m. HF radio wave of
2~30 MHz is emitted in the vertical direction with 20 W
power for ionosonde mode, while radio waves of central
frequencies (f0; 2.5 and 8 MHz) for Doppler mode are
emitted during night (09 – 21 UT=18 – 06 LT) and day time,
respectively. The speed of sweep frequency and the sampling
frequency are 100~1000 kHz/sec and 2000~20,000Hz/sec,
respectively. This system can measure the Doppler frequency(Δf) of reflected radio wave from the ionized layer and

Yumoto et al: MAGDAS Project for Space Weather

At the onset time of SC preceded by PRI on November 4,
2003, the initial change in the ionosphere was observed
simultaneous with the geomagnetic initial change in theaccuracy of ±6.4s at 0625UT as shown in Figure 11. This
result is in agreement with the event at 0519UT on May 9,
2003. Simultaneous observations of the initial changes are
not contradictory to the result of the past report, and approveof the instantaneous penetration of the electric fields to theequatorial latitude. At the same time, it proves the quality of
the FM-CW radar as an useful tool for detection ofionospheric electric fields.
The electric field variations (period of about 5 min)associated with Pc5 magnetic pulsations were also observedat the low-latitude ionosphere at Sasaguri (geomagnetic
latitude θ=23.2°) during the recovery phase of severemagnetic storm on October 30 - 31, 2003 as shown in Figure
l2. The top and bottom panel show amplitude-time records

Fig. 10. FM-CW radar system at Sasaguri. 26m dipole antenna (left) andcontrol system including network server, radar control, radio-wave
transmitter and receiver (right).

the height of reflection layer with 10-sec sampling rate.
From the observed vertical plasma drift velocity (v = cΔf/2f0), we can deduce east-west component of electric field(E) in the ionosphere, i.e. E = - v x Bo, where Bo is theambient magnetic field at Sasaguri.
We have performed correlation analysis between
ionospheric Doppler data obtained at the Sasaguri station andgeomagnetic variations observed at the CPMN stations, andfocus on DP2 type current systems associated with SC and Pc
5, which show equatorial enhancements of magnetic field
variations at the dip equator. The ionospheric electric field
and its intensity during at the time of SC are estimated asshown in Figure 11. From top to bottom, the number density
measured by the ACE satellite in the solar wind region, theH-component magnetic field variations at the CPMN station
at Cebu near the magnetic equator, and the Doppler
frequency of FM-CW radar at Sasaguri are shown as afunction of amplitude-time records during 90 minute on
November 4, 2003. The intensity of PI electric field was
0.16mV/m (westward) and MI was 0.54mV/m (eastward) in
dayside on November 4, 2003, while MI was 1.01mV/m(westward) in night-side at January 21, 2005, respectively.

Fig. 11. From top to bottom, the number density measured by the ACE
satellite in the solar wind region, the H-component magnetic field variations
at the CPMN station at Cebu near magnetic equator, and the Doppler
frequency of FM-CW radar at Sasaguri during 90 minute on November 4,
2003.

H-component magnetic field observed at the CPMN station at
Yap near the magnetic equator, and the Doppler shiftedfrequency of HF radio wave measured by FM-CW radar at
Sasaguri, respectively, during the period of 00:30-03:30 UT
on October 30, 2003. This is the evidence of Pc5 magnetic
pulsations produced by DP2-type current system in the low
latitude ionosphere. In this case, the phase delay ofgeomagnetic variations was found to be about 10-40 second
to the ionospheric variations. We can not ignore the selfinductance effect of enhanced ionospheric current caused by
the Cowling conductivity to understand the phase delay ofgeomagnetic variations observed at the dip equator in
daytime (Shinohara et al., 1997).

ILWS WORKSHOP 2006, GOA, FEBRUARY 19-24, 2006

Fig. 12. Amplitude-time records of H-component magnetic field observed at
the CPMN station at Yap near the magnetic equator (top), and the Doppler
shifted frequency of HF radio wave measured by FM-CW radar at Sasaguri(bottom) during the period of 00:30-03:30 UT on October 30, 2003.

4. Conclusion
Until the end of December, 2005, the SERC, Kyushu
University have deployed a new real-time MAGDAS/ CPMN
system at 20 stations along the 210°magnetic meridian forspace weather study and application. In 2006-07, 30
MAGDAS magnetometers will be installed along themagnetic equator and in the Siberian region. By using theMAGDAS/CPMN system, we will conduct the real-timemonitoring and modeling of (1) the global 3-dimensional
current system and (2) the plasma mass density variations forunderstanding electromagnetic and plasma environmentchanges in the geospace, especially, during the solar flare,
coronal mass ejection, magnetic storms, and auroral
substorms. Using FM-CW radar chain, we also investigate(3) how solar-wind electric fields and polar electric fields ofSC, DP-2, Pc 5 and other disturbances can penetrate into theequatorial ionosphere.
A group of several organizations for geospaceenvironment science in Japan will conduct a coordination ofsimulation/modeling, ground-based observations and satellite
observations to understand couplings of complex, compound
Sun-Earth system and generation mechanisms of highenergetic particles in the inner magnetosphere during
magnetic.
Acknowledgements. Our sincere thanks go to all members of
the MAGDAS/CPMN project for their ceaseless support.
The MAGDAS/CPMN project is financially supported by the
Ministry of Education, Science and Culture of Japan (andJapan Society for the Promotion of science) as the Grant-in
Aid for Overseas Scientific Survey (15253005, 18253005).
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