Status of GNSS ionospheric Study

in Korea

Jong-Kyun Chung

Korea Astronomy & Space Science Institute

ISTF/1 – SP/2

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

From Google Earth

• Korea GPS perma-nent 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.

International GNSS Service

NAVSTAR GPS Satellites

Telephone - Modem, Radio Links

INTERNET

SATELLITE LINK

16 Operational & 6 Regional Data Centers

3 Global Data Centers

10 Analysis Centers

Analysis Cen-ter

Coordinator

Central BureauManagement, Network Coordinator,Central Bureau Information System

USERSPractical, Custom,

Commercial, Govern-ments,...

INTERNATIONAL GOVERNING BOARD

Regional Network Associate Analysis Centers

Global Network Associate Analysis Centers

Reference Frame Densi-fication

Precise Time TransferLow Earth Orbiters

IonosphereAtmosphereSea Level

GLONASS Pilot Service Project

4

• 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.

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.USAUSA

FranceKorea

Crustal Dynamics Data Information System (NASA)Scripps Institution of Oceanography (UC San Diego)Institut Geographique NationalKorea Astronomy and Space Science Institute

CDDISSIOIGNKASI

• 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 con-structed to see the vertical profile of ionopsheric electron den-sities 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 elec-tron density affect GPS signal loss.

• Thermospheric chemi-cal composition affect ionospheric electron density variation.

Thermospheric O/N2 ratio during 7~12 November from GUVI/TIMED

GPS TEC Variationwith the Sun 11-yr Period

• GPS TEC variation is strongly affected with solar activity.

• It is normal varia-tion and is based to construct an local ionopspheric em-pirical 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 radia-tion

Day

Day

Night

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

Thank you !