Status of GNSS ionospheric Study in Korea

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 Den-sification

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 !