ИСТИНА

We present a brief review of large scale distortions observed in the size and shape of the dayside magnetopause. It was found that during geomagnetic storms and periods of strong southward IMF, the magnetopause size and shape change dramatically. The magnetopause shrinks by several earth radii (Re) and becomes skewed toward dusk by several tens of Re. In addition, a trench of a few Re is formed at the equator in the afternoon sector. These features are accompanied by saturation of reconnection at the magnetopause when the increasing southward IMF does not result in further shrinking of the magnetopause. Under undisturbed conditions, the magnetopause can expand by several Re during prolonged periods of quasi-radial IMF lasting for tens of minutes. However, it is still not clear how the magnetopause shape changes under such conditions. Interaction of interplanetary discontinuities with the bow shock results in generation of fast and dense plasma streams in the magnetosheath, so called plasma jets, whose spatial scale and duration can reach tens of Re and several minutes respectively. Most of large-scale plasma jets interact with the magnetopause and produce strong local distortions of the magnetopause shape of several Re scale. Hence these magnetopause distortions can be successfully observed with spatial resolution of a portion of Re and temporal resolution of 5 min.