Effects of strong IMF Bz southward events on the equatorial and mid-latitude ionosphere
Other literature type
Dayside ionospheric response to five intense geomagnetic storms (<I>D<sub>st</sub></I><−120 nT)
that occurred in 2001–2005 was investigated by use of simultaneous
TEC measurements by the CHAMP, SAC-C, TOPEX/Jason-1 satellites. Since the
satellites passed over different longitudinal sectors and measured TEC in
different range of altitudes, it was possible to obtain information about
altitudinal and longitudinal ionosphere redistribution during these storms.
Severe enhancements (up to ~350%) of the equatorial and
mid-latitude TEC above ~430 km with concurrent traveling of the
equatorial anomaly crests for a distance of 10–15° of latitude were
observed during two of the five events analyzed here (6 November 2001 and 8
November 2004). This phenomenon, known as the dayside ionosphere uplift, or
the "daytime super-fountain effect", occurred after sudden drop in IMF
<I>B<sub>z</sub></I> and consequent penetration of the electric fields to the
low-latitude ionosphere. However, the same order <I>B<sub>z</sub></I> negative events
caused comparatively weak changes in the dayside TEC (up to ~80 TECU)
during the other three events of 18 June 2003, 11 February 2004 and 24
August 2005. At the main phase of these storms there were mostly observed
formation of the "typical" dual peak structure of the equatorial anomaly
rather than the reinforcement of the fountain effect and the anomaly itself.
Possible reasons and factors responsible for the development of the extreme
ionosphere effects are discussed in the paper.