Space weather includes a variety of conditions in the solar atmosphere, the solar wind, and geospace that can affect the performance and reliability of space-borne and ground-based electronic systems. Today's technologies are increasingly vulnerable to disturbances from outside the Earth system, and in particular to those originating in explosive events on the Sun. The economic consequences of these phenomena can be enormous. Our ability to understand and predict such events is crucial for the success of space exploration, exploitation of space resources, and the stability of our social and economic infrastructure.
The phenomena of space weather are controlled by several non-linearly coupled fundamental cosmo-physical processes. These include solar flares, coronal mass ejections (CMEs), substorms, magnetic storms, and bursty bulk flows, as well as the release of magnetic energy, manifested by magnetic reconnection and particle acceleration and heating. These processes are not yet fully understood. Studying space weather events in the Sun-Earth system (SES) will help us gain a deeper understanding of these basic processes.
Space weather research on previous space missions focused mainly on the study of localized regions of the SES. However, the flow of energy and material from the Sun to Earth is complex, characterized predominantly by the interaction of simultaneous processes with different spatiotemporal scales. The photosphere, chromosphere, and corona are connected by the Sun's magnetic field. Around Earth, the magnetospheric plasma, energetic particles in the radiation belts, the ionosphere, and the thermosphere are also connected through the geomagnetic field.
A qualitative leap in space weather research can be accomplished only through shifting our focus to simultaneous observations of different spatiotemporal scales in the SES and the use of a system-science approach in the exploration of solar-terrestrial phenomena. Imperative to this new emphasis are a variety of advanced technologies, such as imaging technologies, that can track the evolution of eruptive events in the SES. In order, to drive further progress in this research area, a new kind of space weather observation mission is urgently needed.
The Space Weather Explorer-KuaFu project aims to obtain a full range of observations of the entire cause-and-effect chain of space weather from its origin in the solar atmosphere to its arrival in geospace.1 The project has four broad, related objectives. The first is to concentrate on the observation of continuous systemic changes in solar-terrestrial storms. The project will also investigate flows of energy and solar material and their interactions in the SES. Finally, KuaFu aims to improve the quality of space hazard forecasts and create opportunities to advance solar-terrestrial physics. Events and objects of interest include solar flares, CMEs, interplanetary magnetic clouds, shocks, and geospace responses, such as magnetic storms and substorms. The data provided by the KuaFu mission will fully support three-day forecasts, one-hour alarms, 10-hour alarms, and real-time reporting.
Figure 1. The proposed location for KuaFu-A is at the first Lagrange point, L1. KuaFu-B1 and KuaFu-B2 will be located in polar Earth orbit.
The KuaFu Project consists of three satellites. Their locations relative to the Sun and Earth are shown in Figure 1. KuaFu-A will be located at the first Lagrange point (L1) between the Earth and the Sun, and will be used primarily for observing solar extreme UV (EUV) and far UV (FUV) emission, white-light CMEs, radio bursts, and local plasma and particle distributions. KuaFu-B1 and B2 will be placed in a polar elliptical orbit around Earth, with a phase difference equivalent to half an orbital period, in order to collect continuous images of the aurora borealis and inner magnetosphere. KuaFu-B1 and B2 will carry an identical set of imaging instruments that will examine auroral electrons and protons at high resolution, observe the southern auroral oval with a wide-angle imager, identify neutral atoms of different species, and study the plasmasphere in EUV. They will also carry other instruments for in situ observations of the magnetic field, particles, and waves.
An international working team was formed in 20041 for the preliminary assessment of the KuaFu project with 30-plus scientists from more than 10 countries. In 2005, this team completed a report, which has been rated between ‘very good’ and ‘excellent’ by reviewers from the International Living With a Star program. The ‘Feasibility Study of the Global System for KuaFu Project,’ sponsored by the China National Space Administration (CNSA), was completed in April 2008. The ‘Report on Scientific Objectives and Measurement Requirements’ and the ‘Payload Definition Document’ have been given positive evaluations by two reviewing groups in China.
The project is now waiting for an order from the CNSA to begin the second phase. In the meantime, project scientists are developing a new mission scenario for coordinating with other missions in the next decade and helping to organize international collaborations on providing scientific payloads, satellite platforms, and launch vehicles for the KuaFu project.
The KuaFu preliminary assessment has been supported by the CNSA and the National Science Foundation of China (Key Project 40436015). We would also like to thank all the scientists and agencies that have given their support to the KuaFu Project.
Chuanyi Tu is a full professor whose research interests include solar wind turbulence in the heliosphere and the origin of the solar wind in the solar atmosphere. Tu was chosen as an academician of Chinese Academic Sciences in 2001, and as an academician of the Third World Academic Sciences in 2006.
1. C.-Y. Tu, R. Schwenn, E. Donovan, E. Marsch, J.-S. Wang d, L.-D. Xia e, Y.-W. Zhang f, on behalf of the KuaFu working team, Space weather explorer—The KuaFu mission, Adv. Space Res. 41, pp. 190-209, 2008.doi:10.1016/j.asr.2007.04.049