ИСТИНА

One of the main reasons for the occurrence of geomagnetic disturbances associated with the magnetospheric storms and substorms development are magnetic clouds of the Solar wind. In the magnetic clouds (MC) structure the sheath and the body of the cloud are distinguished [1]. The sheath in front of the cloud is a compression region that occurs when it moves in a slower Solar wind. This is a dense and hot turbulent region with strong fluctuations of the Interplanetary magnetic field (IMF) components which have MHD character. Low-frequency MHD disturbances can be transferred from the cloud sheath to the Earth's magnetosphere from the night side through the "Substorm Current Wedge" current system, which includes the magnetosphere tail currents, field-aligned currents and the westward electrojet. This current system appears in the disturbed magnetosphere during magnetosphere substorm explosive phase and connects its active regions with the high-latitude ionosphere. The resulting electrojet instability can generate low-frequency MHD disturbances in the ionosphere and geomagnetic field. This work is devoted to the search for night-time synchronous ionospheric and geomagnetic MHD disturbances on the background of significant substorm activity. The study was carried out for intense substorms intervals caused by MC turbulent sheath which follow the shock waves. In this paper we are supposed that low-frequency MHD night disturbances in geomagnetic field and ionosphere occurring on the substorm background are caused by outmagnetospheric wave agent located in the near-Earth space.