1. Space weather phenomena in the ionosphere and their effect on GNSS (Presented by Japan) IPXX ICAO ISTF/4 New Delhi, India, 5th to 7th February 2014 SUMMARY This paper presents a short review of major space weather phenomena observed in mid- and low-latitude ionosphere. Their effect on GNSS also mentioned.

2. Sudden Ionospheric Disturbance (SID) GOES X-ray flux [W/m 2 ] UT [hour] SOHO/SEM EUV [count/s] GPS TEC [TECU] TIMED/GUVI O, N 2 [R] [Tsurutani et al., 2005] 10 15 0 35 [Tsugawa et al., 2007]

3. Sudden Ionospheric Disturbance (SID) Amplitude+Several 10 TECU Depending on flare class Time scaleIncrease in several minutes Enhancement lasts for several hours Spatial structureGlobal scale in the sunlit hemisphere Depending on solar zenith angle Other characteristics HF radio absorption (Dellinger phenomena) Possibility of loss-of-lock on GNSS signals due to solar radio burst Effect on GNSSAugmented GPS (due to TEC model correction error) Loss-of-lock on GPS signals

4. JST Wakkanai Okinawa foF2 [MHz] JST (UT+9h) Ionospheric Storm One-month Average Negative Storm Kp Positive Storm

5. Ionospehric Storm Amplitude±Several 10 TECU compared to quiet conditions Time scaleSeveral hours to several days Spatial structureSmall spatial TEC gradient Other characteristics Basically occurring during and/or after magnetic storms Effect on GNSSAugmented GPS (due to TEC model correction error)

6. Equatorial Ionization Anomaly 20:40 JST, 23 Jan 2002 20:40 JST, 24 Jan 2002

7. Equatorial Ionization Anomaly Amplitude±Several 10 TECU Time scale Spatial structureLarge latitudinal TEC gradient Other characteristics Day-to-day variation is not negligible (increase, disappearance, hemispheric asymmetry, etc) Affected by magnetic storms Effect on GNSSAugmented GPS (due to TEC model correction error)

8. Storm enhanced density (SED) [Foster et al., JGR, 2005]

9. Short summary of SED Amplitude+Several 10 to 100TECU Time scaleSeveral hours (?) Spatial structureSteep horizontal TEC gradient Narrow in zonal direction Extending in NW-SE direction Other characteristics Often observed from noon to sunset during the large geomagnetic storm Sometimes accompanied with ionospheric irregularity Effect on GNSSDifferential GPS Augmented GPS (due to TEC model correction error) Loss-of-lock on GPS signals

10. GPS-TEC Observations for Space Weather Absolute TECROTI (~10km scale irregularity) Loss-of-Lock (~100m scale irregularity) 12:20 UT (21:20 JST) 12:40 UT (21:40 JST) 13:00 UT (22:00 JST) 3D simulation of plasma bubble [Courtesy of Dr. T. Yokoyama (NICT) ]

11. Short summary of EPB Amplitude-Several 10 to -100TECU Time scaleSeveral 10 minutes to several hours Spatial structureSteep horizontal TEC gradient Narrow in zonal direction Extending along the magnetic field line Other characteristics Often observed mid- to low latitudes after the sunset. Almost always accompanied with ionospheric irregularity Effect on GNSSDifferential GPS Augmented GPS (due to TEC model correction error) Loss-of-lock on GPS signals

12. Traveling Ionospheric Disturbances (TID) [Tsugawa et al., GPS solut., 2007] [Tsugawa et al., JGR., 2003] Large -scale TID (LSTID) Medium -scale TID (MSTID)

13. AmplitudeA few TECU Time scaleMS: Several 10 minutes LS: Several hours Spatial structureMS: Wavelengths of several 100 km LS: Wavelengths of 1,000 – 3,000 km, Zonally extended wavefront Other characteristics MS: Southwestward and Southeastward propagations in nighttime and daytime, respectively. LS: Related with magnetic storm Effect on GNSSDifferential GPS Augmented GPS (due to TEC model correction error) Traveling Ionospheric Disturbances (TID)

14. Summary of Ionospheric Space Weather Phenomena Spatial Scale Solar Act./ Mag. Storm dependence Lower Atm. dependence 10km100km1000km Global Plasma Bubble SED Ion. Strom SID MSTID LSTID Large Med. Small Sporadic E Eq. Ion. Anomaly Amplitude