Geomagnetically Induced Currents over Iznik associated with Geomagnetic Storms

Geomagnetic storms are major disturbances in the near-Earth magnetic environment.  A geomagnetic storm can cause electrical power outages on the ground known as the geomagnetically induced currents (GICs). The GICs are directly related to the changes in the geomagnetic field over time and thus, they can be approximated by the time derivative of the geomagnetic field (dH/dt). A geomagnetic storm has three phases: initial phase, main phase and recovery phase. The initial phase of a geomagnetic storm is identified by a strong increase in the positive direction in the magnetic index Dst, known as the Sudden Commencement (SC) following the solar wind compression at the magnetopause. When there is no main phase following the solar wind compression, it is called Sudden Impulse (SI). In this project, it is aimed to study the variations in the geomagnetically induced currents determined by using the ground level magnetic field measurements from Iznik geomagnetic observatory (40.43 N, 29.72 E).  The focus is given on the GICs that occur on the ground at different phases of the geomagnetic storm in order to understand the solar wind-magnetosphere connection at these latitudes.  Iznik ground level magnetic field data corresponding to 70 magnetic storm events, with 41 SC and 29 SI, were analyzed along with WIND measurements at L1 distance. GICs were calculated using the time derivatives of the ground magnetic field data through Faraday’s induction law.  First, statistical properties of the GICs associated with the magnetic storms were determined such as storm phase dependence. Following this, search on the correlation between GICs and solar wind plasma, magnetic field strength and southward IMF Bz were investigated. It was determined that the GICs are stronger and occur more dominantly during the initial phase of the storm corresponding to SC and SI events while those occurring during main phase of the storm are weaker. It was also shown that the GICs during the recovery phase occurred strong and as frequent as the initial phase of the storm.  Initial results showed positive correlation with the solar wind plasma pressure, indicating that the GICs recorded over Iznik are mostly associated with the SC/SI events.  For selected cases, CalcdeltaB model at NASA/CCMC were used in order to further investigate the occurrence of GICs over Iznik as associated with geomagnetic storms, especially to understand the cause of the Iznik GICs.  Comparisons with the model results were made and it was seen that the model results vary from event to event.  In this presentation, typical characteristics of the GICs over Iznik, Türkiye and their source of occurrence and initial results from the model comparisons will be discussed in the frame of solar wind-magnetosphere-ground interaction.