author = "Sripathi, S. and Abdu, Mangalathayil Ali and Patra, A. K. and 
                         Ghodpage, R. N.",
          affiliation = "{Indian Institute of Geomagnetism} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and National Atmospheric Research 
                         Laboratory, ISRO and {Indian Institute of Geomagnetism}",
                title = "Unusual Generation of Localized EPB in the Dawn SectorTriggered by 
                         a Moderate Geomagnetic Storm",
              journal = "Journal of Geophysical Research: Space Physics",
                 year = "2018",
               volume = "123",
               number = "11",
                pages = "9697--9710",
                month = "Nov.",
             abstract = "An interesting piece of observation related to the equatorial 
                         plasma bubble (EPB) that is triggered by a geomagnetic storm at 
                         dawn sector on 4-5 February 2011 is presented. The storm activity 
                         was initiated at 17 UT when interplanetary magnetic field (IMF) Bz 
                         turned southward and the Dst index started decreasing (accompanied 
                         by AE intensifications) attaining its minimum at -70 nT. The IMF 
                         Bz presented large fluctuations marked by southward/northward 
                         transitions at slow and rapid rates and eventually returning to 
                         normal in the morning of 5 February. Observations from the very 
                         high frequency radar located at Gadanki, an off-equatorial 
                         station; an all-sky imager located at Kolhapur, a low-latitude 
                         station; and an ionosonde at Tirunelveli, an equatorial station, 
                         are analyzed to study the impact of this storm on the postmidnight 
                         to presunrise equatorial spread F. The results demonstrate that 
                         EPB irregularities can be generated by penetration electric field 
                         during what can be characterized as a moderate storm event. In 
                         contrast to prevailing belief, the present results show that 
                         EPB/equatorial spread F can be generated by undershielding 
                         electric field in the dawn sector, caused by an unusually delayed 
                         polarity reversal of the penetration electric field. The results 
                         further reveal oscillatory behavior in the height of F layer 
                         topside irregularities in association with IMF Bz oscillations. 
                         Observation of radar echoes from nighttime E layer irregularity 
                         structures and their Doppler velocities representing the 
                         penetration electric field polarity and intensity are also a 
                         notable finding of this paper.",
                  doi = "10.1029/2018JA025642",
                  url = "http://dx.doi.org/10.1029/2018JA025642",
                 issn = "2169-9402",
             language = "en",
           targetfile = "sripathi_unusual.pdf",
        urlaccessdate = "05 dez. 2020"