Correlation between the solar wind speed and the passage of poleward-moving auroral forms into the polar cap

Abstract

In 1961, Dungey suggested that magnetic reconnection occurs due to the solar-terrestrial interaction. The interplanetary magnetic field (IMF) is thought to merge with Earth’s geomagnetic field (GMF). After the reconnection process the newly formed magnetic flux tube, consisting of both the IMF and GMF, moves anti-sunward. Poleward-moving auroral forms (PMAFs) are believed to be the ionospheric signatures of this process, which transfers magnetic flux from the dayside to the nightside. This paper looks at the connection between the solar wind speed and the motion of the PMAF as it moves from the auroral oval, anti-sunward, into the polar cap. PMAFs are identified using both the meridian scanning photometer (MSP) and colored all-sky camera (ASC). Once the PMAFs are identified, the PMAF-SLOPE, (Formula presented.) (units of degrees per time) and the angle (αPMAF) the PMAF makes with the horizontal (Time axis), in the MSP plot are calculated. These values ((Formula presented.) and αPMAF) are individually plotted against the (Formula presented.) -component of the solar wind speed and the flow speed (total solar wind speed). The plots generate linear a relationship between PMAF-SLOPEs, (Formula presented.), [or PMAF angles (αPMAF)], and the (Formula presented.) -component of the solar wind speed (or the flow speed). A total of 57 PMAF events from 8 different days were associated with solar wind speeds ((Formula presented.) -component) ranging from 344 to 679 km/s. The first linear plot, between the PMAF-SLOPE and solar wind speed ((Formula presented.) -component), shows a high correlation: (Formula presented.). A second linear plot, between αPMAF and the solar wind speed ((Formula presented.) -component) shows a very high correlation: (Formula presented.). The conclusions obtained from this statistical study are: 1) both the PMAF-SLOPE (Formula presented.) and αPMAF are highly correlated to the (Formula presented.) -component of the solar wind, increasing when (Formula presented.) increases and vice versa, 2) PMAFs must be connected to both the IMF and GMF and are dragged anti-sunward, mostly by the (Formula presented.) -component of the solar wind, and 3) PMAFs are indeed the ionospheric footprints of a newly formed magnetic flux tube, due to dayside magnetic reconnection, being transferred from the dayside to nightside.