The day-to-day longitudinal variability of the global ionospheric

density distribution: Preliminary results

E.E. Pacheco and E. Yizengaw

Institute for Scientific Research, Boston College, Boston, USA

LISN WORKSHOP, São José dos Campos, SP, Brazil, Nov 7-10, 2011

Outline

• Introduction• Instruments and methodology• Observations• Conclusions

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Introduction

• Ionospheric density is a important parameter• The low latitude ionospherIc density changes

can affect communication and navigation signals

• Electrodynamics that controls the ionospheric density distribution is not yet fully understood

• Wind driven electric field systems modify the density structure of the ionosphere.

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INSTRUMENTS

• GPS RECEIVERS NETWORKMadrigal• CHAMP – topside TECAlt ~ 340 km, orbit~98 degree, period~100min• TIMED-TIDI- Zonal wind in the E regionAlt~600 km

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METHODOLOGY

• Geomagnetic quiet time conditions, 2008.• Global TEC map as a function of longitude and

latitude at fix local times (bins: 10 longitude by 2 latitude)

• Day-to-day variability of TEC which includes the wavenumber four structures during day and nightside

• TIDI’s global zonal wind maps ~ 60 days average

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Motivation

• What causes the longitudinal density variability, including the formation of wavenumber-4, during geomagnetic quiet period?

• Does zonal or meridional wind play a vital role for the formation of wavenumber-4 structure?

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Dayside

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Dayside

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Nightside

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ZONAL WIND FROM TIDI INSTRUMENT

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MERIDIONAL WIND FROM TIDI INSTRUMENT

C/NOFS and ROCSAT-1 ION DRIFTS

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Conclusions

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• The ionospheric density is longitudinal dependent• Wavenumber-4 is detected on the TEC

measurements• Wavenumber-4 structure can extend to post-

midnight hours• It seems the zonal wind has more impact on the

formation of wavenumber-4 structure than the meridional wind, but more studies are needed to understand the electrodynamics that controls the longitudinal variability.

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Thank you