The results of a study on the relationship of ion upflow occurrence with upstream solar wind plasma parameters and terrestrial magnetic activity are presented. Measurements taken by the EISCAT Svalbard Radar (ESR) during the International Polar Year 2007 campaign are classified into periods of low, medium and high-flux ion upflow, based on thresholds of magnitude 1.0 × 10 13 m - 2 s - 1 ⩽ f ion < 2.5 × 10 13 m - 2 s - 1 , 2.5 × 10 13 m - 2 s - 1 ⩽ f ion < 7.5 × 10 13 m - 2 s - 1 and f ion ⩾ 7.5 × 10 13 m - 2 s - 1 , respectively. The Pearson correlation coefficient, ρ , indicates that ion upflows correlate better with IMF B mag and coupling function, as its value is above 0.9 for all classes. The value of ρ correlate better with solar wind density ( n sw ) compared to solar wind speed ( v sw ) , in the low flux category, whereas, the reverse is the case during times of high- and medium-flux upflow. In addition, our analysis reveals that the sharp decline in the occurrence frequency of ion upflows during periods when the solar wind speed exceeds 700 kms - 1 reported in previous studies is mainly due to the lack of high-flux upflow during those times. Further analysis reveals that the occurrence of ion upflows seldom exceeds 10% unless v sw ⩾ 650 kms - 1 and that there is no significant upflow occurrence in the medium and high flux unless n sw ⩾ 20 cm - 3 . However the maximum occurrence of ion upflows corresponds to times during which the solar wind dynamic pressure ( P dyn ) exceeds 10 nPa, also associated with intense disturbance of the magnetosphere. All classes of ion upflow flux occur most commonly when the IMF B z is southward, but preferentially when the cusp is in the post-noon (positive B y ) rather than the pre-noon (negative B y ) sector during low flux. The higher the magnitude of the upflowing flux, the more it depends on the reconnection rate (the latter is characterised using the coupling function), while the geomagnetic activity correlates better with the westward electrojet than with the ring current.
David et al. (Sun,) studied this question.