Three Decades of Global Oscillation Network Group (GONG): From Helioseismology to Magnetic Field and Space Weather (Invited Review)

The U.S. National Science Foundation’s (NSF) Global Oscillation Network Group (GONG) began observing the Sun in 1995, focusing initially on helioseismic full-disk Doppler measurements over a planned three-year period. The network utilizes six strategically located sites around the world. GONG has undergone significant upgrades and remains operational after three decades. It continues to deliver near-continuous, high-cadence observations of various solar observables. These observations have been pivotal in advancing numerous scientific and space-weather studies, unveiling details about the Sun’s internal dynamics, structural properties, and surface magnetic activity. We provide an overview of the instrumentation, data products, and key findings derived from GONG observations, highlighting their contributions to understanding the solar interior and its interactions with the atmosphere and heliosphere. Additionally, we will discuss the implications of these findings for theoretical models, summarize space-weather applications, and outline the network’s future plans.