Ionospheric response to the solar storm on 4th February 2011
Solar storms may cause significant perturbations in the ionosphere even under low solar activity conditions.
Enhancements, southward turning of the Bz component and obvious fluctuations of the interplanetary magnetic field, measured onboard the solar wind satellite ACE satellite, indicate the approach of a solar storm effect on 4th February 2011. As the behaviour of the Dst index shows, this assumption is confirmed by the subsequent development of the ring current in the equatorial magnetosphere of the Earth.
Perturbation induced changes of electric fields and thermospheric winds cause a significant redistribution of the ionospheric plasma. Whereas the Total Electron Content (TEC) maps on 3rd February, 21:00UT show normal behaviour, the solar storm causes considerable deviations of the plasma distribution from average behaviour over the American sector at the same time on 4th February. It seems that the Northward crest region enhances, widening and moves northward. This leads to an unusual increase of TEC over United States and Canada enhancing the vertical GPS range error by about 2 m. Small and medium scale plasma perturbations which might cause higher range errors are not resolved by global maps.
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