On May 11, 2024, from 2 to 8 a.m. Beijing time, a strong disturbance in the geomagnetic field occurred, with the Kp index reaching the highest geomagnetic storm level (Kp=9) for six consecutive hours. This is the strongest geomagnetic storm since November 2004.
This geomagnetic storm event was caused by multiple full-halo coronal mass ejections that erupted on the 8th and 9th, collectively impacting Earth. It is expected that the geomagnetic activity will remain at severe storm levels from the 11th to the 13th.
Comparison of geomagnetic storms Dst index and Kp index between 2024 and 2004.
Sunspot region AR3664, after becoming visible on the solar disk on May 1st, rapidly grew in size, reaching 1200 solar area units on the 8th and doubling to 2400 units on the 10th, marking the largest in nearly a decade.
The last time such a large active region appeared was in October 2014 with AR2192, reaching 2750 solar area units and producing several X-class flares, but without causing proton events or geomagnetic storms. Its activity pales in comparison to AR3664.
AR3664 is currently located on the western side of the solar disk, and strong CMEs generated at this position are highly conducive to producing solar proton events. Multiple eruptions have led to an increase in high-energy proton flux in Earth's synchronous orbit, reaching a moderate proton event level with a peak flux of 207 pfu, and the event is ongoing.
May 9-11, Earth's synchronous orbit experienced high-energy proton flux (GOES satellite, Coordinated Universal Time).
Since May 8, AR3664 has erupted 6 X-class flares and multiple M-class flares, with almost every major flare accompanied by a CME directed towards Earth.
As of 8:00 AM Beijing time on May 11, there have been 6 hours of severe geomagnetic storm levels (Kp=9) and 3 hours of major geomagnetic storm levels (Kp=8).
During geomagnetic storms, the low Earth orbit's atmospheric density will increase, exacerbating the decay rate of satellites in low orbits. Disturbances in the ionosphere electron density will impact radio wave communication quality and the precision of navigation systems.
Multiple full-halo coronal mass ejections (CMEs) were observed on May 8-9, as seen by the SOHO satellite (in Universal Time).
May 9-10 Solar Wind Parameters and Geomagnetic Indices (ACE Satellite, Universal Time)
May 8-10, Noon Engineering Autonomous Magnetometer Station Monitoring Data
Coronal Mass Ejections (CMEs) erupting into interplanetary space, along with the resulting interstellar shocks, have significantly altered the distribution of space magnetic fields. They have scattered high-energy cosmic rays, leading to a rapid attenuation of galactic cosmic rays reaching the Earth's surface.
The Four Sub-King Banners μ-ray Telescope of the China Noon Engineering and the Beijing Neutron Stack for Cosmic Rays both detected a Forbes descent event, with maximum decreases of 4.6% and 6.1%, respectively.
Forbes Decline Chart (Sub-Meridian Project Siziwang Banner and Beijing Station)
This geomagnetic storm has brought about a magnificent display of the beautiful aurora phenomenon in the Chinese region!
A stunning aurora was captured in Altay, Xinjiang (from photographer's Weibo @Jeff's Starry Journey).
Currently, a severe geomagnetic storm and solar proton event are unfolding, expected to last around 3 days.
The active region AR3664 will only rotate out of view of the visible solar disk in three days. It remains highly active, with frequent eruptions causing new geomagnetic storms and solar proton events.
We are currently in the peak year of Solar Cycle 25, with frequent solar eruptions and an increased probability of X-class flares. Strong geomagnetic disturbances (Kp≥7) are also on the rise, with a high likelihood of significant proton events. Such eruptions are expected to occur multiple times in the next two to three years.
