May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects Penetration Characteristics of the Interplanetary Electric Field to the Day-time Equatorial Ionosphere C. Manoj*, S. Maus and Patrick Alken NGDC/CIRES, Boulder, Colorado, USA (* On leave from, NGRI-Hyderabad, India) H. Lhr GeoForschungsZentrum-Potsdam, Germany May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects The ionospheric equatorial electric field (EEF) exhibits large day-to-day variability. Wind forced diurnal variations (~50% of the variance) Influence of interplanetary variations on EEF Wind forced (disturbance dynamo) Prompt penetration Other May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects Prompt penetration, some questions -Frequency dependence of the prompt penetrating electric field? -Coherence, phase relation -Does the prompt penetration depend on local time, solar flux, season, polarity of IMF Bz, etc ? -What is the period range of prompt penetration effect on EEF? May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects 1.Advance Composition Explorer (ACE) satellite at L1 point 2.Time-shifted to the magnetospheres bow-shock nose by OMNI 1.Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) radar, Peru days Data during 2001 to 2008 Interplanetary electric field (IEF) data Equatorial ionospheric electric field (EEF) data May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects 1.Diurnal variation of JULIA data is removed using the model by *Alken (2008) 2.Eastward electric field at JULIA is calculated as, 3.The ionospheric field variations are correlated with the interplanetary E-field (IEF). * manuscript in preparation Example of data processing May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects Average power spectra of IEF and JULIA electric fields Spectra are estimated from pairs of daily EEF and IEF data, each 6 hours long. 265 pairs of data. The power spectra and cross spectra are computed by Welch's averaged periodogram method (Welch, 1967). Both power spectra show monotonous increase in power with period. Dependence on activity level (Ap). Power is higher by factor of 3. May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects Coherence between IEF and EEF Coherence is significant for periods above 20 minutes. It peaks around 2 hours (0.5 cycles / hour). Coherence is slightly higher during active days Significance level (Thompson, 1979) ||-> | | 120). May 23, :45ISEA, Crete, Greece. S10 Ionospheric storms and space weather effects Ratio of EEF/IEF Signal Transfer Function ||-> |