Correlating the interplanetary factors to distinguish extreme and major geomagnetic storms

Abstract

We investigate the correlation between Disturbance Storm Time (Dst) characteristics and solar wind conditions for the main phase of geomagnetic storms, seeking possible factors that distinguish extreme storms (minimum Dst <−250 nT) and major storms (minimum Dst <−100 nT). In our analysis of 170 storms, there is a marked correlation between the average rate of change of Dst during a storm's main phase (ΔDst/Δt) and the storm's minimum Dst, indicating a faster ΔDst/Δt as storm intensity increases. Extreme events add a new regime to ΔDst/Δt, the hourly time derivative of Dst (dDst/dt), and sustained periods of large amplitudes for southward interplanetary magnetic field Bz and solar wind convection electric field Ey. We find that Ey is a less efficient driver of dDst/dt for extreme storms compared to major storms, even after incorporating the effects of solar wind pressure and ring current decay. When minimum Dst is correlated with minimum Bz, we observe a similar divergence, with extreme storms tending to have more negative Dst than the trend predicted on the basis of major storms. Our results enable further improvements in existing models for storm predictions, including extreme events, based on interplanetary measurements.

Responses of the field-aligned currents in the plasma sheet boundary layer to a geomagnetic storm

“…Considerable momentum and energy can penetrate into the magnetosphere and ionosphere from the solar wind during geomagnetic storms, which can then result in large magnetic field disturbances and geomagnetic-induced currents on the ground (Gonzalez et al, 1994;Milan et al, 2017;Zong QG and Zhang H, 2018;Ma X et al, 2020;Otsuka et al, 2021;Wang YB et al, 2023). One important medium for the momentum and energy transport among the solar wind, magnetosphere, and ionosphere is fieldaligned currents (FACs), which can become very intense during storms, substorms, or both (Milan et al, 2017;McPherron et al, 2018;Cowley, 2000;Balachandran et al, 2021). At an ionospheric altitude, large-scale FAC systems have been termed Region 1 and Region 2 current systems, which are generally around the auroral region (Iijima and Potemra, 1978).…”

Properties of the Geomagnetic Storm Main Phase and the Corresponding Solar Wind Parameters on 21–22 October 1999

“…Many researchers hold the concept that the intensity of a geomagnetic storm depends on the peak value of some kind of solar wind parameter. Therefore, they usually calculate the correlation coefficients (CCs) between the intensities of geomagnetic storms and the peak values of various solar wind parameters [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Because only the peak value of B s (hereafter B smax ), or the peak value of the solar wind's dawn-to-dusk electric field (hereafter the largest solar wind electric field E ymax ) has good correlation with the intensity of the corresponding storm, many researchers insist that the intensity of a geomagnetic storm mainly depends on B smax or E ymax , with the solar wind density or dynamic pressure making a minor or even no contribution.…”