Solar magnetic storm
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Understanding Solar Magnetic Storms: Causes and Impacts
Introduction to Solar Magnetic Storms
Solar magnetic storms, also known as geomagnetic storms, are significant disturbances in Earth's magnetosphere caused by solar wind and interplanetary magnetic field (IMF) variations. These storms can have profound effects on satellite operations, communication systems, and power grids.
Causes of Solar Magnetic Storms
Coronal Mass Ejections (CMEs)
The primary drivers of intense geomagnetic storms are fast coronal mass ejections (CMEs) from the Sun. These CMEs release large amounts of solar wind and magnetic fields into space, which can interact with Earth's magnetosphere. The sheath region behind the CME's forward shock and the CME ejecta itself are critical for storm development, especially when they contain intense southward IMFs1. The initial phase of a storm is triggered by increased plasma ram pressure, while the main phase is driven by southward IMFs1.
High-Speed Solar Wind Streams (HSSs) and Corotating Interaction Regions (CIRs)
During solar minimum, high-speed streams from coronal holes dominate, creating CIRs when they interact with slower solar wind. These CIRs can also cause geomagnetic storms, although typically weaker and more irregular than those caused by CMEs1 4. The interaction of these high-speed streams with the heliospheric current sheet (HCS) plasma can lead to prolonged storm recovery phases, characterized by intermittent reconnection and substorm activity1.
Complex Interplanetary Structures
Occasionally, very intense magnetic storms result from complex interplanetary structures, such as multiple CMEs or a combination of CME and HSS events. These structures can lead to extremely intense storms due to the combined effects of high-speed solar wind, strong magnetic fields, and high plasma densities5 8.
Historical and Recent Examples
The St. Patrick’s Day Storm (2015)
One notable example is the St. Patrick’s Day storm on March 17, 2015, which was the first super geomagnetic storm of solar cycle 24. This storm was caused by a CME followed by a high-speed stream from a nearby coronal hole, leading to a two-step storm with significant intensification during the passage of the magnetic cloud5 8.
August 26, 2018 Geomagnetic Storm
Another example is the geomagnetic storm on August 26, 2018, initiated by a solar filament eruption. This storm was driven by weak CME transients and CIRs, highlighting the role of multiple solar wind structures in storm development2.
Predicting Geomagnetic Storms
Forecasting from Coronal Holes
Recent advancements have enabled the prediction of CIR/HSS-driven geomagnetic storms directly from solar observations. By analyzing coronal hole areas and associated magnetic field polarity, researchers can predict the strength of geomagnetic storms with reasonable accuracy, extending the forecasting lead time up to several days4.
Statistical Analysis of Solar Activity
Studies of magnetic storms during the space age (1957-2021) have shown that storm occurrence follows the slow decrease of sunspot activity and related changes in solar magnetic structure. This analysis helps in understanding the long-term trends and variability in geomagnetic storm activity7.
Conclusion
Solar magnetic storms are complex phenomena driven by various solar and interplanetary processes, primarily CMEs and high-speed solar wind streams. Understanding these drivers and improving prediction models are crucial for mitigating the impacts of geomagnetic storms on modern technological systems. Continued research and advancements in space weather forecasting will enhance our ability to prepare for and respond to these powerful natural events.
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Most relevant research papers on this topic
Interplanetary origin of geomagnetic storms
Interplanetary phenomena, such as fast coronal mass ejections and high-speed streams from coronal holes, can cause intense magnetic storms, with the main phase being driven by southward IMFs and the sheath region.
Highly CitedSolar Origins of August 26, 2018 Geomagnetic Storm: Responses of the Interplanetary Medium and Equatorial/Low‐Latitude Ionosphere to the Storm
The August 26, 2018 geomagnetic storm was driven by weak CME transients and CIR/HSSs, with the major determining factors being local time of storm onset, minimum SYM-H, and changes in thermospheric O/N2.
Great magnetic storms
Great magnetic storms are primarily caused by extreme southward interplanetary magnetic fields, rather than solar wind speeds, with shocked and draped sheath fields being as effective as strong fields within the driver gas.
Highly CitedGeomagnetic storm forecasting from solar coronal holes
Predicting CIR/HSS-driven geomagnetic storms directly from solar observations can extend forecasting lead time up to several days, improving space weather predictions.
Pileup accident hypothesis of magnetic storm on 17 March 2015
The largest magnetic storm to date was driven by a combination of fast coronal mass ejections, high-speed streams from coronal holes, and piled-up solar wind before reaching Earth.
Highly CitedWhat Is a Solar Electromagnetic Storm?
Solar storms are caused by disturbances in the Sun's magnetosphere, affecting Earth's magnetosphere and posing threats to human technological systems.
Magnetic Storms During the Space Age: Occurrence and Relation to Varying Solar Activity
Magnetic storms during the space age (1957-2021) have been influenced by weak sunspot activity, varying solar magnetic structure, and the occurrence of large and moderate high-speed solar wind streams.
The first super geomagnetic storm of solar cycle 24: “The St. Patrick’s day event (17 March 2015)”
The first super geomagnetic storm of solar cycle 24 occurred on "St. Patrick's day" (17 March 2015), driven by a magnetic cloud and a CME, with the CME being the sole solar source of the magnetic cloud.
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