On May 11, 2024, between 2:00 and 8:00 (Beijing time), there was a strong geomagnetic disturbance, with the Kp index reaching the highest level (Kp=9) since November 2004.
This geomagnetic storm event was caused by multiple full-halo coronal mass ejections (CMEs) that erupted between the 8th and 9th of May. It is expected that the geomagnetic activity will remain at severe storm levels from the 11th to the 13th of May.
The solar active region AR3664, which became visible on the solar disk on May 1, rapidly grew in size. By the 8th, it reached an area of 1200 solar surface units, doubling to 2400 solar surface units by the 10th, marking its highest activity in nearly a decade.
The last time such a large active region appeared was in October 2014 with AR2192, reaching 2750 solar surface units and producing several X-class flares, albeit without causing proton events or geomagnetic storms. Its activity level was far lower compared to AR3664.
AR3664, currently located on the western side of the solar disk, is highly favorable for generating solar proton events due to its strong coronal mass ejections towards Earth. Multiple eruptions have already led to an increase in high-energy proton flux in Earth’s synchronous orbit, reaching moderate proton event levels, with peak flux reaching 207 pfu. The event is ongoing.
Since May 8, AR3664 has erupted six X-class flares and multiple M-class flares, with almost every major flare accompanied by a CME directed towards Earth.
As of 8:00 on May 11 (Beijing time), there were six hours of extremely severe geomagnetic storm levels (Kp=9), and three hours of severe storm levels (Kp=8).
During geomagnetic storms, the density of the lower orbital atmosphere increases, exacerbating the decay rate of low-orbit satellites. Disturbances in the ionosphere electron density will affect radio communication quality and navigation positioning accuracy.
Continuous CMEs into interplanetary space and the resulting interplanetary shockwaves have significantly altered the distribution of the space magnetic field, scattering high-energy cosmic rays and causing rapid attenuation of galactic cosmic rays reaching the Earth’s surface.
The Forbes decrease event was detected by China’s Sub-Muon Telescope in Siziwang Banner and Beijing Neutron Monitor, with maximum decreases of 4.6% and 6.1%, respectively.
The intensity of the geomagnetic storm has led to spectacular auroras visible in China.
Currently, the severe geomagnetic storm and solar proton event are ongoing, and are expected to last for about three more days.
AR3664 will remain visible on the solar disk for another three days, maintaining its high activity level with frequent eruptions, leading to new geomagnetic storms and solar proton events.
We are currently in the peak year of Solar Cycle 25, with frequent solar eruptive activities and an increased probability of X-class flares. Strong geomagnetic disturbances (Kp≥7) are also on the rise, and major proton events are highly likely to occur. Such eruptive events are expected to occur multiple times over the next two to three years.
