Open AccessStrong postmidnight equatorial ionospheric anomaly observations during magnetically quiet periods
Author(s) -
Yizengaw Endawoke,
Moldwin Mark B.,
Sahai Yogeshwar,
de Jesus Rodolfo
Publication year - 2009
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009ja014603
Subject(s) - ionosonde , ionosphere , tec , quiet , total electron content , geophysics , geodesy , anomaly (physics) , f region , physics , thermosphere , local time , satellite , geology , atmospheric sciences , plasma , electron density , astronomy , mathematics , statistics , condensed matter physics , quantum mechanics
We have examined the quiet time equatorial electrodynamics of the ionosphere in the postmidnight sector using satellite, GPS total electron content (TEC) and ionosonde data. ROCSAT‐1 vertical drift data are used to estimate the equatorial ionosphere electrodynamics, TOPEX altimeter and GPS TEC are used to obtain the density structure of the ionosphere. Ionosonde data measure the postmidnight F layer height as function of local time. We analyzed 4 years (2001–2004) of quiet time ( Kp ≤ 3) observations in the postmidnight sector. We found that very strong equatorial ionospheric anomalies (EIAs) in the postmidnight (0100–0500 LT) sector during magnetically quiet periods are common and are capable of disrupting satellite communication and navigation systems. The coordinated multi‐instrument observations clearly demonstrate that these strong EIAs are not simply the EIAs observed in earlier local time sectors that have corotated into the postmidnight sector as has been suggested by previous studies. We demonstrate that they are triggered by a reversed vertically upward drift, which is suggested to be generated by thermospheric neutral wind through F region dynamo. This clearly demonstrates that the Earth's postmidnight ionosphere is dynamic even in magnetically quiet periods contrary to simple theoretical model predictions.