Zhong Shan photometer
email@example.com - last update: 8 May 1996, 0825 UT (RR)
The Space Physics Group of Oulu has
developed an auroral
photometer to be operated in the Chinese Zhong Shan station in Antarctic. This station is
closely conjugated with the Svalbard area.
|Important note: This message was received on 8 May 1996 from China:
trip to Zhongshan of the Chinese Antactic Research Expedition had met some trouble in the
way. The ice breaker "Snow Dragon" was already arrived the Great Wall station in
the end of 1995. Some part of the ship was gone wrong. Most of the expedition members have
to back with the ship. The photometer and other instruments including Japanese instruments
have been returned to China too. We and the photometer have to wait next trip to
Of the two Chinese scientific stations in Antarctic, the one in Zhong Shan is closely
conjugated with the Svalbard area in the northern hemisphere. This makes it a valuable
place for coordinated measurements both with the EISCAT Svalbard Radar (ESR) and the Polar satellite. In 1991 a cooperation agreement
was signed between the Ionospheric Laboratory of the China Research Institute of Radiowave
Propagation (CRIRP) in Xinxiang, China, and the Department of Physical Sciences,
University of Oulu, Finland, to build an auroral photometer system for the Zhong Shan
station (Kaila et al, 1997). The multichannel scanning photometer agreed upon was
constructed in Oulu by April 1995, and delivered to China in May. Measurements were
supposed to start in March 1997, to be continued during the local winter time until
October (the same schedule of measurements is planned for every year). However, due to
problems mentioned above, the current status of the system is unknown!
The Zhong Shan station
Figure 1. Locations of Zhong Shan station (ZHO), South Pole (SP) and Magnetic South
Pole (MSP). The line drawn over the station shows the scanning area at the altitude of 250
The Zhong Shan station is located at 69.4°S, 76.4°E (Figure 1). Table 1 lists the
most important figures related to this location. Note that the Zhong Shan station is at
high enough latitude to be, most of the time, inside the polar cap or at the
polarward edge of the auroral oval.
|Table 1: The Zhong Shan station
||Geomagnetic latitude, MLT midnight,
and geographic conjugate point
are calculated with geocgm
s/w from NSSDCA
B field azimuth is calculated
towards west from south
|B elevation and azimuth
|Geogr. conjugate point
Figure 2a shows the height of the sun in Zhong Shan as a function of
time of year and UT in isocontour lines of constant elevation angles of 0°, 6°, 12°,
and 18° below horizon. The best conditions for optical measurements are when the sun is
lower than -18° from the horizon, i.e., during the nights between March and September. In
mid-winter this makes over 13 hours of measurements per night. By extending the
measurements to cover elevations up to -12° during winter daytime one reaches the
cusp/LLBL region in the afternoon hours (11:00 UT = 16:00 LT = 13:30 MLT).
Figure 2. Degrees of light and darkness in a) Zhong Shan and b) Kilpisjärvi during
a year as indicated by the height of the sun from the horizon.
The Zhong Shan station is magnetically conjugated with the Svalbard area, the conjugate
point being about 400 km west of the island (Figure 3). Note that, with increasing
magnetic activity, this point moves southward by few degrees. The EISCAT Svalbard Radar
(ESR) can cover approximately the same area. Several groups will also provide, e.g.,
CCD-based all-sky cameras on Svalbard and in Greenlands east coast covering the
conjugate area of Zhong Shan.
Figure 3. EISCAT Svalbard Radar (ESR), Kilpisjärvi (KIL) and the Zhong Shan
It is interesting to check if there are common periods of darkness between Northern
Scandinavia and Zhong Shan. The map of suns height for Kilpisjärvi, Finland, is
drawn in Figure 2b in the same format as was done for Zhong Shan. It can be seen that
there are two periods, one in spring (March) and one in fall (September), when the
stations can make simultaneous optical measurements. These periods occur around the local
magnetic midnights, and can be several hours long when allowing measurements in the not
optimal -12° sun elevation angles. The common periods get shorter closer to the modelled
The photometer constructed in Oulu will not be the only instrument to be operated in
Zhong Shan. In addition to normal magnetic measurements made by the Chinese, the National
Institute of Polar Research (NIPR) in Japan has, in cooperation with the Polar Research
Institute in Shanghai, China, a TV-camera, an all-sky-camera, a photometer, and an imaging
riometer in Zhong Shan.
The instrument installed in Zhong Shan is a scanning, five channel auroral photometer
with the possibility to measure the background light by tilting the individual filters at
preset intervals. The wavelengths measured are listed in Table 2.
|Table 2: Photometer channels
||N2+ 1NG (0-1) R-band
||N2+ 1NG (0-1) R-band
||N2+ 1NG (0-1) P-band
The basic lines are the blue nitrogen line 427.8 nm and the red oxygen
line 630.0 nm, an often used combination to measure the energy characteristics of the
precitating electrons (Rees and Luckey, 1974; Rees and Roble, 1986). The proton line 486.1
nm can be used to study the proton precipitation. In addition, the N2+ 1 NG band shape
depends on the rotational temperature of neutral molecules in the emission source region.
By measuring the P-branch and two parts of the R-branch we can determine this temperature
and use it to define yet another energy parameter for the precipitating electrons. The
field of views of the channels are 3° for the proton line, and 2° for the others. The
proton precipitation is typically much more diffuse than the electron precipitation, and
we can thus improve the sensitivity of the channel by using wider spatial integration.
The photometer is operating in pulse counting mode and it is controlled from a standard
386 PC. The accumulated pulses are read from the counter card with a sampling frequency
that can be as high as 100 samples/second. The absolute time is kept correct with a GPS
clock, and the elevation angle (measurement direction) with an absolute angle encoder.
Data is written into a hard disk in a binary format.
The photometer will be measuring continuously during the dark periods.
This will total up to about 2210 hours of measurements per year from March the 2nd to
October the 13th (full moon periods are also included). Measurements will be made either
at fixed direction towards the magnetic zenith or with a scanning angle of 160° (higher
than 10° above the horizon). The scanning plane, determined by the magnetic field
direction and realized by proper orientation of the instrument, is drawn in Figure 1 as a
line at the altitude of 250 km, which is typical height for the 630.0 nm emission. For the
N2+ lines the region covered is about half of this. Several different modes in which the
instrument can be run are listed in Table 3.
|Table 3: Measurement modes
||Normal mode; fixed direction or scan
||Fast mode with individual integrationon times
for different channels; fixed direction
||Midex mode; both fixed direction and scan
||Mode 1 with fast scanning speed
||Mode 3 with fast scanning speed
The instrument will be operated mostly in modes 1 and 11, either with
a fixed direction or with a scan. Sometimes the photometer will be operated in the mixed
modes 3 and 13, in which 800 seconds of field aligned measurements alternate with a full
back and forth scan of 160°. Mode 2 will be used only in special events.
Since it is not possible to get the data from Zhong Shan during the Antarctic winter
time, the related satellite studies will suffer from a considerable time delay. However,
it is planned that the raw data products, e.g., in the form of quick-look-plots, will be
made publicly available as soon as possible, and interested parties with complementing
data sets are invited to take part in the subsequent data analysis.
As already mentioned, the Zhong Shan station will be most of the time in the polar cap
region or at the polarward edge of the auroral oval. Also the optical cusp/LLBL region can
be accessed in the afternoon sector. Accordingly, different optical phenomena can be
studied as the photometer measures several important emission lines simultaneously with
high temporal resolution. In the dayside these include, e.g., dayside auroral breakups and
their relation to reconnection
processes (e.g. Farrugia et al., 1995), cusp related Pc 3 range optical pulsations
(Engebretson et al., 1990), and the 1400-1600 MLT sector bright spots (e.g., Vo and
Murphree, 1995). The ability of the instrument to measure the background light makes the
measurements more reliable also during these less optimal dayside hours. Because of the
GPS timing the data can be compared with satellite and other measurements without timing
The Zhong Shan measurements have a value of their own. However, together with other
measurements, either by ground-based instruments in the conjugate northern hemisphere or
by satellites, they are even more important. For example, the EISCAT Svalbard Radar
measurements may obtain optical support from the Zhong Shan station during the light
Arctic summer, when similar measurements are not possible in the northern hemisphere. One
may also try to study conjugate optical phenomena during the short periods of common
darkness in Zhong Shan and Northern Scandinavia. The Oulu group plans coordinated optical
measurements between Zhong Shan and Kilpisjärvi in March and September each year.
Finally, the Cluster and other satellite projects will provide possibilities for further
The financial support of the University of Oulu for the photometer hardware is
gratefully acknowledged. Collaboration between the University of Oulu and CRIRP, China,
has been possible due to the grants for visiting scientists from the Academy of Finland.
- Engebretson, M. J., B. J. Anderson, J. L. J. Cahill, R. L. Arnoldy, T. J. Rosenberg, D.
L. Carpenter, W. B. Gail, and R. H. Eather, Ionospheric signatures of cusp latitude Pc 3
pulsations, J. Geophys. Res., 95, 2447-2456, 1990.
- Farrugia, C. J., P. E. Sandholt, S. W. H. Cowley, D. J. Southwood, A. Egeland, P.
Stauning, R. P. Lepping, A. J. Lazarus, T. Hansen, and E. Friis-Christensen,
Reconnection-associated auroral activity stimulated by two types of upstream dynamic
pressure variations: interplanetary magnetic field Bz~0, By, J. Geophys. Res., 100,
- Kaila, K.U., C. Chong, Z. Qunshan, H. Holma, R. Rasinkangas, and J. Kangas: Auroral
photometer measurements in Antarctic: The Zhong Shan station. Satellite-Ground Based
Coordination Sourcebook, edited by M. Lockwood, H.J. Opgenoorth, M.N. Wild, and R.
Stamper, 183-191, 1997.
- Rees, M. H. and D. Luckey, Auroral electron energy derived from ratio of spectroscopic
emissions. 1. Model computations, J. Geophys. Res., 79, 5181-5186, 1974.
- Rees, M. H. and R. G. Roble, Exitation of O(1D) atoms in aurorae and emission of the
[OI] 6300 - Å line, Can. J. Phys., 64, 1608-1613, 1986.
- Vo, H. B. and J. S. Murphree, A study of dayside auroral bright spots seen by the Viking
auroral imager, J. Geophys. Res., 100, 3649-3655, 1995.