Studies of Ionospheric Plasma Structuring at Low Latitudes

Studies of Ionospheric Plasma Structuring at Low Latitudes from Space and Ground, their Modeling and Relationship to Scintillations Sunanda Basu Center for Space Physics, Boston University • GUVI has provided a tool for global mapping of the equatorial anomaly as shown in Figures 1 and 2 • GUVI images at dusk demonstrate the great variability of the anomaly over narrow swaths of longitude even on magnetically quiet days • Combining GUVI images with scintillation and satellite in-situ data have provided insights into day-to-day variability of equatorial irregularity generation • Attempts are being made to reproduce the observed longitudinal variability by introducing longitudinally dependent instability “drivers” in the SAMI 3 model • The ultimate goal is to determine the underlying electrodynamics that cause such longitudinally varying equatorial anomaly structure at dusk.

Day–to-Day Variability 0 f Equatorial Day-to Day Variability of Equatorial Scintillation: TIMED/GUVI and DMSP § Anomaly crest separation & asymmetry related to E-field & neutral wind § Electric field strength controls vertical drift correlated with instability onset and subsequent irregularity generation § Large meridional separation corresponds to favorable conditions for scintillation § Intense L-band scint. seen at Calcutta under anomaly crest § Coordinated DMSP data show bubbles at 840 km

Day-to-day Variability of Equatorial Scintillation: TIMED/GUVI and DMSP § Collapse of anomaly in Indian sector on day 33 is correlated with absence of VHF scintillations at both Calcutta and Singapore § Coordinated DMSP data show lack of bubbles and single density peak over magnetic equator § Initial attempt made to model the longitudinal confinement of collapse region by SAMI 3