马斯克的“星链”卫星，突然开始大批坠落地球，发生了什么？

Core Insights - The "Starlink" satellite network operated by SpaceX is experiencing a significant increase in satellite re-entries due to heightened solar activity, with over 120 satellites falling back to Earth in January 2025 alone [1][5][18] Group 1: Satellite Operations and Performance - As of June 2025, Starlink has launched over 8,800 satellites, with approximately 7,600 currently operational, accounting for two-thirds of active satellites in Earth's orbit [3] - Between 2020 and 2024, 523 Starlink satellites prematurely re-entered the atmosphere, with an average of 3 satellites re-entering daily in 2024 [7][18] - The design and operational strategy of Starlink, including the planned retirement of Gen1 satellites to make way for the more advanced V2 models, has contributed to the increased rate of satellite re-entries [14][18] Group 2: Environmental and Safety Concerns - The re-entry of Starlink satellites poses environmental risks, as each Gen1 satellite generates approximately 30 kilograms of aluminum oxide nanoparticles upon re-entry, which may harm the stratospheric ozone layer [13][16] - A 2.5-kilogram piece of Starlink debris was discovered on a Canadian farm, highlighting the potential for incomplete incineration during re-entry [5][14] - NASA has indicated that the risk of debris falling to Earth increases with the frequency of satellite re-entries, although the overall probability remains low [14] Group 3: Solar Activity Impact - The primary cause of the increased satellite re-entries is attributed to the strong solar activity during Solar Cycle 25, which peaked in 2024-2025, leading to frequent solar flares and coronal mass ejections (CMEs) [9][18] - The CMEs have caused geomagnetic storms that heat and expand the upper atmosphere, increasing drag on low Earth orbit satellites, particularly those below 300 kilometers [11][18]