Longitudinal Structure of the Mid- and Low-Latitude Ionosphere Observed by Space-borne GPS Receivers
This study presents longitudinal structures of the mid- and low-latitude ionosphere using the GPS radio occultation observation on board the COSMIC satellite mission. The longitudinal structure seen in the equatorial and low-latitude ionospheric regions results from modification of the daily dynamo electric field by upward propagating atmospheric tides that are generated by latent heat release of the tropical rainstorms. Changes of the dynamo electric field modify the equatorial plasma fountain and thereby enhance the equatorial ionization anomaly (EIA). With capability of three-dimensional global ionospheric observation, altitudinal, local time, and monthly variations of this recent discovered fascinating feature are obtained for further understanding of the underlying physical mechanism. Through comparison between electron densities at various altitudes, the longitudinal structure is prominently seen at upper part of the ionosphere. Additionally, COSMIC observations provide three-dimensional structure of the Weddell Sea anomaly which is featured by the greater nighttime electron density than daytime. Not only occurring at the southern hemisphere near the Weddell Sea region of the Antarctica, a similar nighttime density enhancement feature is also found in the northern hemisphere during local summer by COSMIC observations. The anomalous signatures in both hemispheres share very similar characteristics in electron density structure, latitudinal distribution, and appearance time. They are, therefore, categorized as the mid-latitude summer nighttime anomaly (MSNA).
KeywordsTotal Electron Content Radio Occultation Longitudinal Structure Atmospheric Tide Equatorial Ionization Anomaly
This work is partially supported by the Taiwan National Science Council under NSC NSC 98-2111-M-006-003-MY2 and by NSPO under 98-NSPO(B)-IC-FA07-01(L) and 98-NSPO(B)-IC-FA07-01(V).
- Burns AG, Zeng Z, Wang W, Lei J, Solomon SC, Richmond AD, Killen TL, Kuo Y-H (2008) The behavior of the F 2 peak ionosphere over the South Pacific at dusk during quiet summer condition from COSMIC data. J Geophys Res 113:A12305. doi:10.1029/2008JA013308Google Scholar
- Dudeney JR, Piggot WR (1978) Antarctic ionospheric research. In: Lanzerotti LJ, Park CG (eds) Upper atmosphere research in Antarctica. Antarctic Research Series, Washington, DC, pp 200–235Google Scholar
- Hajj GA, Lee LC, Pi X, Romans LJ, Schreiner WS, Straus PR, Wang CM (2000) COSMIC GPS ionospheric sensing and space weather. Terr Atmos Oceanic Sci 11(1):235–273Google Scholar
- Lin CH, Wang WB, Hagan ME, Hsiao CC, Immel TJ, Hsu ML, Liu JY, Paxton LJ, Fang TW, Liu CH (2007b) Plausible effect of atmospheric tides on the equatorial ionosphere observed by the FORMOSAT-3/COSMIC: three-dimensional electron density structures. Geophys Res Lett 34:L11112. http://doi:10.1029/2007GL029265 CrossRefGoogle Scholar
- Lin CH, Liu JY, Cheng CZ, Chen CH, Liu CH, Wang W, Burns AG, Lei J (2009) Three-dimensional ionospheric electron density structure of the Weddell Sea Anomaly. Geophys Res Lett 114:A02312. doi:10.1029/2008JA013455Google Scholar
- Liu JY, Lin CY, Lin CH, Tsai HF, Solomon SC, Sun YY, Lee IT, Schreiner W, Kuo YH (2010) Artificial plasma cave in the low-latitude ionosphere results from the radio occultation inversion of the FORMOSAT-3/COSMIC. J Geophys Res 115:A07319. doi:10.1029/2009JA015079Google Scholar
- Penndorf R (1965) The average ionospheric conditions over the Antarctic. In: Waynick AH (ed) Geomagnetism and aeronomy, vol 4. Antarctic Research Series. AGU, Washington, DC, [pp 1–45Google Scholar
- Rishbeth H, Garriott OK (1969) Introduction to ionospheric physics. Academic, New York, NYGoogle Scholar
- Sagawa E, Immel TJ, Frey HU, Mende SB (2005), Longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by IMAGE/FUV. Geophys Res Lett 110:A11302. doi:10.1029/2004JA010848Google Scholar