Superstorm of 06.04.2000: effects of strong dynamic shocks

The analysis of maps of equivalent currents (EC) and field-aligned currents (FAC) of April 6, 2000 superstorm within the range of 15:00-20:00 UT was made. Major disturbances were caused by abrupt increase in solar wind (SW) dynamic pressure (Pd). The analogy of magnetospheric currents and wire electric circuits was used. The key property of circuits under consideration is Pedersen meridional ionospheric currents connecting FACs of one sign of zone 1 and FACs of another sign of the adjacent zone 2 or 0. We describe the empirical model in which the three currents form one of the meridional current systems (MCS). These systems are classified as MCS-0, MCS-1 and MCS-2. Within the region of each MCS, along with Pedersen current, Hall current is generated which causes well-observed auroral electrojets AEJW and AEJE, as well as Hall electrojet in the polar cap ionosphere. The conclusion of Hall origin of electrojets is valid for relieving AEJW. MCS systems replace the classic substorm current wedge (SCW) or is added to it as the main component of the general three-dimensional current system of Pd-disturbances and substorms. The electric circuits MCS-1 and MCS-0 close on the magnetospheric generator through the known partial ring current DRP-1 and previously unknown current DRP-2 in the tail lobes respectively. A prominent feature of the Pd-disturbances is predominance of daytime activity over nighttime activity which is general for typical substorms. In our opinion, this fact can explain some phenomena unusual for substorms. At the relieving phase of disturbances, the polar cap area, as well as the observed values of the magnetic flux of the tail lobes φ and of the Poynting flux ε' did not decrease but increased. These results contradict the conclusions made before for substorms and Pd-disturbances as is the fact that the relationship between the superstorm input power e' and the disturbance power consumption Q was of the form Q ε'. We suppose that the observed Pd jumping results in increase in the rate of daytime reconnection (magnetic reconnection disturbance, MRD). This increase more than compensates for simultaneous increase in rates of nighttime processes such as reconnection in the closed tail (MR1) and in the tail lobes (MR2). We conclude that Pd-disturbances under consideration reveal cardinal processes similar to those which are peculiar to typical substorms. These processes are MRD, CD (current disruption) formation, FAC SCW, MR1 and MR2. For the examined Pd-disturbances, the observed processes were characterized by significant peculiarities caused by increased compression of the magnetosphere due to SW dynamic pressure.