@Article{RodriguesIHRKJRDT:2004:MuInSt,
               author = "Rodrigues, Eurico de Paula. and Iyer, K. N. and Hysell, D. L. and 
                         Rodrigues, F. S. and Kherani, E. A. and Jardim, A. C. and Rezende, 
                         L. F. C. and Dutra, S. G. and Trivedi, Nalin Babulal",
          affiliation = "Instituto Nacional de Pesquisas Espaciais, Divis{\~a}o de 
                         Geofisica Espacial(INPE,DGE) and Cornell Univ, Ithaca, NY 14853 
                         USA and Saurashtra Univ, Dept Phys, Rajkot, Gujarat",
                title = "Multi-technique investigations of storm-time ionospheric 
                         irregularities over the S{\~a}o Luis equatorial station in 
                         Brazil",
              journal = "Annales Geophysicae",
                 year = "2004",
               volume = "22",
               number = "10",
                pages = "3513--3522",
             keywords = "ionosphere, ionospheric irregularities/GLOBAL POSITIONING SYSTEM, 
                         SPREAD-F, ELECTRIC-FIELDS, RADAR OBSERVATIONS, LOW-LATITUDE, 
                         MAGNETOSPHERIC DISTURBANCES, BACKSCATTER RADAR, GPS OBSERVATIONS, 
                         MAGNETIC STORMS, JULIA RADAR.",
             abstract = "On 11 April 2001, a large magnetic storm occurred with SSC at 
                         13:43 UT, and D-st reached below -200nT after two southward B-z 
                         excursions. The K-p index during this storm reached 8 and remained 
                         high (>4) for about 21 h, and the Sao Luis magnetometer H 
                         component presented simultaneous oscillations and decreased 
                         substantially relative to the previous magnetically quiet days. 
                         This storm triggered strong ionospheric irregularities, as 
                         observed by a recently installed 30 MHz coherent scatter radar, a 
                         digisonde, and a GPS scintillation receiver, all operating at the 
                         Sao Luis equatorial station (2.33degrees S, 44degrees W, dip 
                         latitude 1.3degrees S). The ionospheric conditions and the 
                         characteristics of the ionospheric irregularities observed by 
                         these instruments are presented and discussed. The VHF radar RTI 
                         (Range Time Intensity) echoes and their power spectra and spectral 
                         width for the storm night 11-12 April 2001, were used to analyse 
                         the nature and dynamics of the plasma irregularities and revealed 
                         the coexistence of many structures in the altitudinal range of 
                         400-1200 km, some locally generated and others that drifted from 
                         other longitudinal sectors. The radar data also revealed that the 
                         plumes had periodic eastward and westward zonal velocities after 
                         22:20 UT, when well-developed quiet-time plumes typically drift 
                         eastward. Another interesting new observation is that the F-layer 
                         remained anomalously high throughout the 11-12 April 2001 storm 
                         night (21:00 UT to 09:00 UT next day) (the LT at Sao Luis is UT -3 
                         h), as indicated by the digisonde parameters hmF2 and h'F, which 
                         is a condition favourable for spread F generation and maintenance. 
                         The AE auroral index showed enhancements (followed by decreases) 
                         that are indicative of magnetospheric convection enhancements at 
                         about 15:00 UT, 20:00 UT and 22:00 UT on 11 April 2001 and at 
                         00:20 UT (small amplitude) on 12 April 2001, associated with many 
                         B-z fluctuations, including clear two southward incursions that 
                         gave rise to large and long lasting K-p values and large negative 
                         D-st values. This intense auroral activity generated disturbance 
                         dynamo and prompt penetration electric fields that were 
                         responsible for the maintenance of the F-layer at a high altitude 
                         along the night of 11-12 April 2001. The short-lived F-region 
                         height rise seen between 16:00 to 18:00 UT on 11 April 2001 is 
                         probably due to the prompt penetration eastward electric fields of 
                         magnetospheric origin during the first IMF B-z turning to south 
                         around 15:00 UT.",
                 issn = "0992-7689",
             language = "en",
        urlaccessdate = "15 jun. 2024"
}