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

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

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

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

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

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.

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.

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

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.

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

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.

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.

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

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

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