Relation between Dst* and interplanetary parameters during single-step geomagnetic storms

Abstract

In this work, the relation between Dst* (solar wind pressure corrected Dst) and solar wind parameters (north–south component of the interplanetary magnetic field Bz and east–west component of the electric field Ey) in the main phase of the single-step geomagnetic storms was analyzed on their peak (Dst*p and Bzp/Eyp) and difference values (ΔDst*p and ΔBz/ΔEy). From 1995 to 2019, 133 storms with peak Dst* ≤ −50 nT were selected. It was found that the correlations between Dst*p and Bzp/Eyp (r = 0.60 and −0.69) were higher than those between Dst*p and ΔBz/ΔEy (r = −0.49 and −0.45, respectively). The correlation between the variations of ΔDst* and ΔBz/ΔEy were intermediate between those ranges (r = 0.52 and 0.45, respectively). Multiple linear correlation of Dst*p with Bzp/ΔBz and Eyp/ΔEy explains 38 and 48% of the variance of Dst*p, respectively, with a larger effect of peak values of solar wind parameters. There were twice more single-step storms in cycle 23 than in cycle 24, but the average values of peaks and variations did not show significant differences. In terms of Eyp criteria for moderate (−100 nT < Dst*p ≤ −50 nT) and intense (Dst*p ≤ 100 nT) geomagnetic storms, >93% of the moderate storms had Eyp > 3 mV·m−1, while 96% of intense storms had Eyp > 5 mV·m−1. On ΔEy , 87% of the moderate storms had ΔEy ≤ 10 mV·m−1, while 72% of the intense storms had ΔEy > 10 mV·m−1. Thus it may be concluded that Bzp and Eyp were important for Dst*p of the single-step storms and that Eyp and ΔEy values could be interplanetary criteria for the moderate and intense storms.