1. Status of GNSS ionospheric Study in Korea
ISTF/1 – SP/2
Jong-Kyun Chung
Korea Astronomy & Space Science Institute

2. Contents Korea GNSS Permanent Sites KASI IGS Global Data Center
GPS TEC for Ionosphere
Ionospheric Climatology in Korea
Mid-latitude Ionospheric Storm Study

3. Korea GPS Permanent Network
Korea GPS permanent network of 86 sites including of 2 IGS sites is well distributed with 20~50 km inter-spacing.
MLTL (71), KASI (9), KIGAM (6)
KASI has 1Hz GPS data.
Korea GPS data center has been planned.
From Google Earth

4. International GNSS Service
IGS is a voluntary federation of more than 200 worldwide agencies that pool resources and permanent GPS & GLONASS station data to generate precise GPS& GLONASS products.
NAVSTAR GPS Satellites
Telephone - Modem, Radio Links
INTERNET
SATELLITE LINK
16 Operational & 6 Regional
Data Centers
3 Global Data Centers
10 Analysis Centers
Analysis Center
Coordinator
Central Bureau
Management, Network Coordinator,
Central Bureau Information System
USERS
Practical, Custom,
Commercial, Governments,...
INTERNATIONAL GOVERNING BOARD
Regional Network
Associate Analysis Centers
Global Network
Reference Frame Densification
Precise Time Transfer
Low Earth Orbiters
Ionosphere
Atmosphere
Sea Level
GLONASS Pilot Service Project 4

5. KASI IGS Global Data Center
IGS GDC is the main interface to the IGS Analysis Centers and the user community.
IGS GDC receive/retrieve, archive, & provide online access to tracking data of IGS sites and to IGS products from the IGS Analysis Centers.
KASI has officially operated the IGS GDC since 1 January 2006.
USA
France
Korea
Crustal Dynamics Data Information System (NASA)
Scripps Institution of Oceanography (UC San Diego)
Institut Geographique National
Korea Astronomy and Space Science Institute
CDDIS
SIO
IGN
KASI
1 storage server (8 TB) & 1 backup server (8 TB)
Daily, hirate(15 min), hourly
ftp://nfs.kasi.re.kr

6. Korea TEC Map
In the near-real time of 10 minutes, GPS TEC map over Korea is made using KASI GNSS permanent sites.
The GPS TEC map of 1 hour resolution over the Northeast Asia is constructed using IGS GPS daily data, but number of GPS sites are rare.

7. Korea Ionospheric Tomography
F10.7=271, Kp=3, Dst=-33
F10.7=245, Kp=8+, Dst = -77
Ionospheric tomography using ground-based GPS TEC is constructed to see the vertical profile of ionopsheric electron densities at 2003 Halloween event.
Vertical grid size of 10 km between 100 km to 800 km
The main storm occurred on 29 October 2003 (left) and NmF2 increased, but electron densities in top-side ionopshere was enhaced on 31 October.
 Ionospheric electron densities are different with altitude, and can affect GPS slant TEC.

8. Korea Ionospheric Storm Events
The big ionospheric storms were occurred in the northeast asia on 8 and 10 November 2004.
GPS signal tracking loss : 110 (08/11) & 287 (10/11)
Irregularities of electron density affect GPS signal loss.
Thermospheric chemical composition affect ionospheric electron density variation.
Thermospheric O/N2 ratio during 7~12 November from GUVI/TIMED

9. GPS TEC Variation with the Sun 11-yr Period
GPS TEC variation is strongly affected with solar activity.
It is normal variation and is based to construct an local ionopspheric empirical model.

10. Annual & Semi-annual Variation
Annual and semi-annual variation of GPS TEC depend on the solar activity.

11. GPS TEC Seasonal Variation
Equinoctial asymmetry is significant at solar maximum in daytime and seasonal anomaly is only appeared at solar maximum.
Seasonal variation of GPS TEC should be considered in construction of an ionospheric empirical model.

12. Solar 27-day Period
GPS TEC can changed according to the solar rotation period of ~27 day.
It may be related with solar wind from solar coronal hole.

13. Correlation with Solar EUV radiation
Day
Night
Day
Night
The relationship with solar EUV flux has three types of linear, quadratic, and saturation.
GPS TEC has the different relationship with F10.7 and EVU fluxes

14. Summary Korea has the GNSS permanent network of 86 sites.
KASI has operated the IGS Global Data Center.
Ionopsheric storm was studied using GPS TEC map and tomography method from ground-based GPS TEC data.
Ionospheric climatology has been studied using GPS TEC. - GPS TEC variation with Solar 11-yr period - GPS TEC variation with Solar 27-day rotation period - GPS TEC annual and semi-annual variation - GPS TEC correlation with solar EUV and F10.7 fluxes

15. Thank you !