On the multifaceted role played by the Neutral Wind in the Equatorial Electrodynamics during Magnetically Disturbed times
Abstract
A disturbance dynamo was observed in the magnetic equatorial region of the Asian subcontinent on May 31, 2005, one day after an intense magnetic storm of relatively short duration. At first sight, there was nothing unusual about the event on that particular day as the ground-based magnetograms revealed very strong reduction in the normal mid-day electrojet with the essential disappearance of the Equatorial Ionization Anomaly, as revealed by the Total Electron Content (TEC) data. A closer look at the ionosonde data however revealed that, contrary to conventional thinking, the zonal electric field had remained eastward for most of the day in spite of the evidence for westward currents. There was, in addition, a clear mid afternoon amplification of the eastward zonal field followed by a westward turning field after 1600 IST. This electric field oscillation triggered a depletion in the equatorial TEC, but without an accompanying modulation of the TEC in the anomaly crest region. Interestingly, the equatorial TEC returned to its pre-depletion value when the plasma came through the downward phase of its oscillation. We argue that these observations can be explained by two important disturbed dynamo neutral wind properties that have not been emphasized before, namely,(1) the neutral wind circulation cell due to Joule heating did not reach the magnetic equator but came close enough to it to essentially kill the equatorial fountain effect while maintaining an eastward zonal field; (2) a weakening of the high latitude-driven Hadley cell circulation in the mid-afternoon hours could have easily produced the observed equatorial F region zonal electric field oscillation creating a situation that was highly reminiscent of the equatorial `Pre-Reversal-Enhancement' signature normally observed near the terminator instead of the mid-afternoon
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39..337C