Middle Latitude Geomagnetic Disturbances Caused by Hall and Pedersen Current Circuits Driven by Prompt Penetration Electric Fields

The prompt penetration electric field (PPEF) drives the DP2 currents composed of the two-cell Hall current vortices surrounding the Region-1 field-aligned currents (R1FACs), and the zonal equatorial electrojet (EEJ, Cowling current) at the dayside equator, which is connected to the R1FACs by the Pedersen currents at middle latitudes. The midlatitude H- and D-components of the disturbance magnetic field are caused by the DP2 currents, as well as by the magnetospheric currents, such as magnetopause currents, FACs, ring currents, and so on. If the DP2 current is the major source for the midlatitude geomagnetic disturbances, H and D are supposed to be caused by the Hall and Pedersen currents, respectively. The H-D correlation would be negative in both morning and afternoon sectors, and H/D-EEJ correlation would be negative/positive in the morning and positive/negative in the afternoon. We picked out 39 DP2 events in the morning and 34 events in the afternoon from magnetometer data at Paratunka, Russia (PTK, 45.58 degrees N geomagnetic latitude (GML)), which are characterized by negative H-D correlation with correlation coefficient (cc) < -0.8. We show that the midlatitude H/D is highly correlated with EEJ at Yap, Micronesia (0.38 degrees S GML) in the same local time zone, meeting the Pedersen-Cowling current circuit between midlatitude and equator in the DP2 current system. Using the global simulation, we confirmed that the ionospheric currents with north-south direction at midlatitude is the Pedersen currents developing concurrently with the Cowling current. We suggest that the negative H-D correlation provides a clue to detect the PPEF when magnetometers are available at middle latitudes.