On the characteristic parameters of magnetic storms during two solar cycles

• Published in: Journal of atmospheric and solar-terrestrial physics Vol. 114; pp. 66 - 72
• Main Authors: Monreal MacMahon, R., LLop-Romero, C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-07-2014
• Subjects: Correlation; Interplanetary magnetic fields; Magnetic storms; Phases; Solar cycles; Solar wind; Solar wind-magnetosphere interactions; Storms; Storms and substorms; Solar wind-magnetosphere interactions; Storms and substorms
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2014.04.007

Relationships between characteristic parameters of geomagnetic storms like the pressure corrected Dst index (Dst⁎), the solar wind speed, the southward component of the interplanetary magnetic field BS, and their associated times were studied during two solar cycles and for approximately 300 storm events extracted from the OMNI database (1974–1996) to further analyze what drives Dst⁎ not only during storms but also during non-storm times.
Analyzing the whole data set, that is considering storm time and the less disturbed (nonstorm) times, we infer that outside the storm phases the dominant driver role is played by the solar wind speed and that its role during storms is usually not negligible. However, as expected, during the main and recovery phases of magnetic storms the driving parameter is the dawn-dusk component of the interplanetary electric field vBS, where the main role is played by BS. We found that the Dst⁎ peak grows monotonically with the peak of BS. The duration time tBs that BS remains over a certain threshold value grows linearly with the peak of Dst⁎ for weak, moderate and some intense storms. For more intense events the growth rate diminishes and probably vanishes. Significant differences appear when the correlation between the peaks of Dst⁎ and BS is analyzed during the different solar cycle phases. That correlation and also the recurrence of our chosen storms have a periodic behavior, similar to the solar cycle. The most of storms are registered during the ascending phases of the solar cycle and sunspot maxima, however the higher correlations between the peaks of BS and Dst⁎ are found during minima and ascending phases of the solar cycle.
•Main role of the solar wind velocity on the Dst behavior for the full data set.•The role of solar wind speed on the Dst behavior is enhanced reducing storm events.•Storm intensity depends on the Bs strength and duration over a threshold value.•Recurrence of storms has a periodic behavior with maxima on solar cycle maxima.•Higher correlation between the peaks of Bs and Dst was found on solar cycle minima.