VHF ionospheric scintillations atL= 2.8 and formation of stable auroral red arcs by magnetospheric heat conduction

The 137-MHz amplitude scintillation data obtained from the ATS 3 satellite at a mid-latitude station (L = 2.8) are utilized to study the temporal behavior of electron density irregularities following sudden commencements of intense magnetic storms. Comparison with the equatorial Dst index shows that the onset of scintillations is controlled by the universal time of commencement of the main and rapid recovery phases of storms. Total electron content data obtained simultaneously are used to show that the plasmapause-associated ionospheric trough moves to the vicinity of the observing point during the onsets of such universal time controlled scintillations. The magnetospheric heat conduction into the ionosphere during these storms, which sometimes causes stable auroral red arcs near the plasmapause, is found to produce field-aligned irregularities. A persistence of local time dominated scintillations following such storm time onsets is noted. The results of this study indicate that mid-latitude scintillations following large magnetic storms may have a storm time component in addition to the widely known local midnight component.