Studies of ionospheric variations during geomagnetic activities at the low-latitude station, Ile-Ife, Nigeria

The dual frequency SCINDA NovAtel GSV 4004B GPS receiver installed at the Ile-Ife (low-latitude station) has been in operation since December 2009. Data records for the year 2010 were processed to obtain Total Electron Content (TEC) and S4 index. These were interpreted to analyze the ionospheric condition during low geomagnetic activity period (when Dst is from −40 to 0 nT) and during geomagnetic storm events (with Dst about −100 nT). Seasonal variations of the TEC and S4 index were also investigated. The occurrence of scintillations is closely linked to the peak value of TEC during the daytime; this is very evident during the equinox months when TEC ≥ 30 TECu. When the maximum TEC value is below 30 TECu, as shown by most of the days in the summer months, the scintillation phenomenon does not occur. During geomagnetic storms, the daytime segment of the TEC plot experiences fluctuations (even bifurcations) in values with the peak TEC value of about 40 TECu. From the interpreted data, the occurrence of geomagnetic storm does not necessarily suggest an increase in the level of scintillations at a low-latitude region. Also, there is a remarkable difference between the IRI 2007 model and the observed TEC values, as the daytime TEC peak differs in magnitude and time of occurrence from the observed TEC.

[1]  A. Coster,et al.  Diurnal Variation of TEC and S4 Index During the Period of Low Geomagnetic Activity at Ile-Ife, Nigeria , 2013 .

[2]  S. Alex,et al.  Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone , 2009 .

[3]  Mala S. Bagiya,et al.  TEC variations during low solar activity period (2005–2007) near the Equatorial Ionospheric Anomaly Crest region in India , 2009 .

[4]  Libo Liu,et al.  A study of the ionogram derived effective scale height around the ionospheric hm F2 , 2006 .

[5]  Junru Shi,et al.  Seasonal variations of the ionospheric effects of geomagnetic storms at different latitudes of East Asia , 2006 .

[6]  N. Dashora,et al.  Observations in equatorial anomaly region of total electron content enhancements and depletions , 2005 .

[7]  Libo Liu,et al.  Responses of equatorial anomaly to the October-November 2003 superstorms , 2005 .

[8]  R. Langley,et al.  Study of the March 31, 2001 magnetic storm effects on the ionosphere using GPS data , 2005 .

[9]  I. Batistaa,et al.  Study of the March 31 , 2001 magnetic storm effects on the ionosphere using GPS data , 2005 .

[10]  Takashi Maruyama,et al.  Signature of TEC storm on 6 November 2001 derived from dense GPS receiver network and ionosonde chain over Japan , 2004 .

[11]  Cesar E. Valladares,et al.  Latitudinal extension of low-latitude scintillations measured with a network of GPS receivers , 2004 .

[12]  S. Basu,et al.  Ionospheric effects of major magnetic storms during the International Space Weather Period of September and October 1999: GPS observations, VHF/UHF scintillations, and in situ density structures at middle and equatorial latitudes , 2001 .

[13]  J. Lastovicka,et al.  Eects of geomagnetic storms on the ionosphere and atmosphere , 2001 .

[14]  Richard B. Langley,et al.  GPS, the Ionosphere, and the Solar Maximum , 2000 .

[15]  M. Buonsanto.  Ionospheric Storms — A Review , 1999 .

[16]  S. Schlüter,et al.  Total electron content of the ionosphere during thegeomagnetic storm on 10 January 1997 , 1999 .

[17]  Jules Aarons,et al.  GPS phase fluctuations in the equatorial region during sunspot minimum , 1997 .

[18]  Timothy Fuller-Rowell,et al.  On the seasonal response of the thermosphere and ionosphere to geomagnetic storms , 1996 .

[19]  I. Batista,et al.  Equatorial ionospheric electric fields during magnetospheric disturbances: local time/longitude dependences from recent EITS campaigns , 1995 .

[20]  John A. Klobuchar,et al.  Design and characteristics of the GPS ionospheric time delay algorithm for single frequency users , 1986 .