Effects on SuperDARN HF radar echoes of sudden impulses of solar wind dynamic pressure
Résumé
As for the I events, a latitudinal analysis shows that the MRS increase for Quiet conditions is seen both at low latitudes (60°–70° ?) and at high latitudes (70°–80° ?); for Disturbed Is the MRS decrease is stronger at high latitudes. We suggest that the MRS increase for Quiet Is can be due to two different mechanisms: 1) a soft electron precipitation induced by Field Line Resonances (FLR) or loss cone instability at lower latitudes; 2) an enlargement of the cusp at higher latitudes, which in turn may induce enhanced particle precipitation.
For what concerns Disturbed Is, the MRS decrease can be produced by a higher energy electron precipitation (>1 keV), that enhances the electron density in the E and D regions. This provokes a strong absorbtion of the radio waves in the D region and a higher refraction in the E region, leading to a decrease in MRS, especially at higher latitudes.
For I events a further classification has been made on the basis of IMF orientation: this suggests that the effects summarized above are due to the SI itself.
Keywords. Ionosphere (Ionospheric irregularities) – Magnetospheric physics (Magnetosphere-ionosphere interactions; Solar wind-magnetosphere interactions)