Hysteresis cycles and invariance of the Dst index form during geomagnetic storm development
We have studied the relationship between the Dst index and heliospheric parameters during 933 isolated geomagnetic storms observed over the period from 1964 to 2010. The storms were classified by their onset type (sudden or gradual) and intensity (weak, moderate, and strong). We have analyzed the Ds...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
INFRA-M
2025-06-01
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| Series: | Solar-Terrestrial Physics |
| Subjects: | |
| Online Access: | http://doi.org/10.12737/stp-112202504 |
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| Summary: | We have studied the relationship between the Dst index and heliospheric parameters during 933 isolated geomagnetic storms observed over the period from 1964 to 2010. The storms were classified by their onset type (sudden or gradual) and intensity (weak, moderate, and strong). We have analyzed the Dst index, solar wind, and interplanetary magnetic field (IMF) data accumulated using the epoch superposition method. It is shown that over the time interval of development of varying intensity storms with sudden and gradual onset the trajectory of Dst change depending on heliospheric parameters during the main phase of the storms does not coincide with its trajectory during the recovery phase, which is typical of the hysteresis phenomenon. During the storms, Dst forms hysteresis cycles with all analyzed solar wind and IMF parameters. The obtained dependences Dst(B), Dst(Bz), Dst(Ey), Dst(V), Dst(Pdyn), and Dst() have the shape of a hysteresis loop during the excitation of weak, moderate, and strong storms. The shape and area of hysteresis loops was found to change depending on heliospheric parameters and storm intensity. It is shown that the shape of the average Dst dynamics during the storms does not depend on their intensity, i.e. it is invariant. Invariant behavior is also characteristic of the shape of the average dynamics of heliospheric parameters during the magnetic storms of different intensities. Based on the nonlinear relationship of the Dst index with interplanetary parameters and the invariance of the shape of its dynamics, an integral equation of the Volterra type is proposed to describe the Dst dependence on solar wind and IMF parameters. The proposed model is suitable for interpreting the results obtained from the experimental study of hysteresis effects associated with phase shifts between changes in Dst and heliospheric parameters. |
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| ISSN: | 2500-0535 |