Moderate Magnetic Storm Expected as a Typical Space Weather Event in the Era of the Decreased Solar Activity

The 25 th cycle of solar activity (SA) is the second one in the epoch of decreased SA when the geomagnetic activity become lower year by year.Really, the number of intense magnetic storms in the 23 rd , 24 th , and approaching its maximum in the 25 th SA cycle is decreased.Thus, moderate magnetic storms (50 < |SymH| <100 nT or G2-storms) become the most expected events of the space weather.Here we discuss the behavior of the magnetic storm on September 12, 2023 as an example of a typical moderate magnetic storm.Our study was based on the analysis of the global maps of ionospheric and field-aligned currents obtained from magnetic measurements on 66 low-orbit AMPERE project satellites and electrons and ions data from DMSP satellites as well as the ground-based magnetic data from the Scandinavian IMAGE profile and Intermagnet.It was shown that the initial phase of the magnetic storm was characterized by daytime polar-latitude geomagnetic disturbances and the storm main phase was associated with nighttime substorms in auroral latitudes accompanied by positive magnetic bays at the middle latitudes.It was supposed that such magnetic storms caused by both magnetic clouds or high-speed streams from coronal holes, could be the most expected phenomena in the near future.