Browsing by Author "Balan, N."
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Item Restricted F3 layer during penetration electric field(American Geophysical Union, 2008-09-04) Balan, N.; Thampi, S. V.; Lynn, K.; Otsuka, Y.; Alleyne, H.; Watanabe, S.; Abdu, M. A.; Fejer, B. G.The occurrence of an additional layer, called F3 layer, in the equatorial ionosphere at American, Indian, and Australian longitudes during the super double geomagnetic storm of 7–11 November 2004 is presented using observations and modeling. The observations show the occurrence, reoccurrence, and quick ascent to the topside ionosphere of unusually strong F3 layer in Australian longitude during the first super storm (8 November) and in Indian longitude during the second super storm (10 November), all with large reductions in peak electron density (Nmax) and total electron content (GPS‐TEC). The unusual F3 layers can arise mainly from unusually strong fluctuations in the daytime vertical E × B drift as indicated by the observations and modeling in American longitude. The strongest upward E × B drift (or eastward prompt penetration electric field, PPEF) ever recorded (at Jicamarca) produces unusually strong F3 layer in the afternoon hours (≈1400–1600 LT) of PPEF, with large reductions in Nmax and TEC; the layer also reappears in the following evening (≈1700–1800 LT) owing to an unusually large downward drift. At night, when the drift is unusually upward and strong, the F region splits into two layers.Item Restricted Relative effects of electric field and neutral wind on positive ionospheric storms(SpringerOpen, 2009-05-14) Balan, N.; Alleyne, H.; Otsuka, Y.; Vijaya Lekshmi, D.; Fejer, B. J.; McCrea, I.The paper studies the relative importance of penetrating eastward electric field (PEEF) and direct effects of equatorward neutral wind in leading to positive ionospheric storms at low-mid latitudes using observations and modeling. The observations show strong positive ionospheric storms in total electron content (TEC) and peak electron density (Nmax) at low-mid latitudes in Japan longitudes (≈125°E-145°E) during the first main phase (started at sunrise on 08 November) of a super double geomagnetic storm during 07-11 November 2004. The model results obtained using the Sheffield University Plasmashpere Ionosphere Model (SUPIM) show that the direct effects of storm-time equatorward neutral wind (that reduce poleward plasma flow and raise the ionosphere to high altitudes of reduced chemical loss) can be the main driver of positive ionospheric storms at low-mid latitudes except in Nmax around the equator. The equatorward wind without PEEF can also result in stronger positive ionospheric storms than with PEEF. Though PEEF on its own is unlikely to cause positive ionospheric storms, it can lead to positive ionospheric storms in the presence of an equatorward wind.