NASA’s Heliophysics Great Observatory and the Decadal Survey’s Integrated Research Strategy
The investigation of solar system plasmas as coupled nonlinear systems requires synergy between observational and theoretical initiatives and between basic research and targeted research programs. NASA recognized this in establishing a fleet of 12 missions—consisting of the Advanced Composition Explorer (ACE), Solar and Heliospheric Observatory (SOHO), and Wind in L1 orbit; Cluster, Transition Region and Coronal Explorer (TRACE), Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), Geotail, Fast Auroral Snapshot Explorer (FAST), Polar, and Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) in Earth orbit; and Ulysses and the Voyager probes—that NASA’s Heliophysics Division would later call its Heliophysics Great Observatory. SOHO, TRACE, and RHESSI observe the variable outputs of the Sun; ACE and Wind provide advance information on the disturbances traveling to Earth; Cluster, Geotail, FAST, POLAR, and TIMED observe the resulting space weather responses in the geospace environment; and Ulysses and Voyager measure responses in the heliosphere. The Heliophysics Great Observatory enabled the coordinated investigation of space plasmas as complex coupled systems driven from the Sun to Earth and into the heliosphere, as demonstrated by the observation and analysis of the famous “Halloween” solar storms of 2003.
The decadal survey clearly recognized the mission synergies and balance that underpin the Heliophysics Great Observatory approach: mission selections and priorities in the Integrated Research Strategy were chosen in order to most efficiently maintain and augment such a research approach. The decadal survey anticipated a midterm period where Solar-B, Solar Terrestrial Relations Observatory (STEREO), and Solar Dynamics Observatory (SDO) would be providing more detailed information on the propagation of solar disturbances to Earth, while the Magnetospheric Multiscale (MMS) mission, the Geospace Network, and the Geospace Electrodynamic Connections (GEC) mission would be providing the information needed to understand how the disturbances were processed within the geospace system. Throughout this period the Explorer Program was expected to play a pivotal role in addressing new inquiries and strategic initiatives that would emerge during the conduct of the program. A revitalized sounding rocket program would also continue to provide unique capabilities associated with access to critical regions and diagnosis of small-scale features. However, as of this writing, the only two strategic missions to have been successfully implemented are Solar-B (Hinode) and STEREO. SDO and MMS are in development, and the Geospace Network and GEC have not received starts. Only one of the 10 large and moderate missions called for in the decadal survey (see Table 1.1), Jupiter Polar Mission, will be launched by 2013, the end of the 10-year period covered by the strategy. Thus, one of the foremost findings of this report is that the status of the Integrated Research Strategy is in jeopardy and that the loss of synergistic capabilities in space will seriously impede progress in the Heliophysics Division.
Hinode, SOHO, and STEREO Missions Identify Origins of the Solar Wind. The solar atmosphere consists of closed magnetic loops anchored to the solar surface at both ends, and also of open flux tubes extending from the Sun into space. Early models proposed that the solar wind was heated and accelerated strictly within the regions of open magnetic field. An unprecedented complement of spacecraft instrumentation, including NASA’s SOHO and its STEREO and the Japanese Hinode mission, has recently revealed that some jets originate from the interfaces between the open and closed magnetic fields, driven by a process called magnetic reconnection (see Figure 1.1).
CINDI Mission Maps Baseline for Earth’s Equatorial Ionosphere. CINDI is a NASA mission of opportunity flown on the DOD’s Communication/Navigation Outage Forecast System (C/NOFS) satellite, which launched in 2008. The CINDI instruments measure neutral wind and ion drift vectors along with total ion density, composition, and temperature. Initial data were taken during a time of extremely low solar activity when most of the atmosphere lay below the satellite’s altitude. Measurements made by CINDI during that time have revealed the daily expansion