Finding: The highest-level objectives and research focus areas in the NASA Heliophysics Roadmap align with the decadal survey science challenges. However, there are several science questions in the decadal survey—most notably, coronal heating, the magnetospheres and ionospheres of other planets, and interaction with the interstellar medium—that receive little or no attention in the Roadmap.
Background: At the top level, the Roadmap’s three objectives and 12 research focus areas (RFAs) align with the five science challenges in the decadal survey. Many of the survey’s science challenges are purposely framed as broad, cross-cutting, and multidecadal. The survey implies that significant progress should be made in the time frame of a decade on representative questions that are part of the broader challenges. Thus, the committee looked for correspondence between the Roadmap’s RFAs and the key science questions in the decadal survey. It is not expected that the Heliophysics Roadmap would cover all of the questions in the survey. Rather, the committee looked for trends in the Roadmap RFAs that might indicate exclusion or poor coverage of subsets of questions dealing with similar topics.
This challenge focuses on understanding the Sun from its interior out through its atmosphere and solar wind. The science questions focus on the solar cycle and solar dynamo, the solar corona, the fast and slow solar wind, and explosive energy releases like coronal mass ejections (CMEs).
For the solar cycle and solar dynamo, there is a Heliophysics Roadmap RFA that is directed at the solar dynamo question (RFA F4.1). This focus area and related questions in the decadal survey should be addressed with the Solar Dynamics Observatory (SDO) mission as well as ongoing research using existing space assets like the Solar and Heliospheric Observatory (SOHO).
For the solar corona, there is only indirect overlap between the decadal science questions and RFAs concerning fundamental processes (e.g., RFA F1.1 and F1.2). Although coronal heating is included in the science objectives of NASA missions like Hinode, SDO, SOHO, and Transition Region and Coronal Explorer (TRACE), the Heliophysics Roadmap does not adequately emphasize important topics related to coronal heating and coronal characteristics.
For the fast and slow solar wind, RFA F2.3 is directed at related decadal science questions. The origin of the fast and slow solar wind has been the focus of recent study of the solar atmosphere by the Hinode spacecraft. It will also be a focus of the SDO mission and is a prime objective of Solar Probe.
For explosive energy releases, there are several RFAs (for example, fundamental processes such as particle acceleration, precursors to solar disturbances and CMEs, and consequences for the near-Earth environment) that correspond directly to decadal survey questions. The evolution of CMEs and other disturbances is a prime focus of the Solar Terrestrial Relations Observatory (STEREO) mission and existing space assets like the Advanced Composition Explorer (ACE) and Wind missions. Precursor studies and evolution of disturbances are included also in the Hinode mission as well as the future SDO mission.
This challenge focuses on understanding the heliosphere as a single, dynamic structure immersed in and interacting with the local interstellar medium. Science questions focus on the propagation of solar events throughout the heliosphere, the nature of the interaction between the interstellar medium and the heliosphere, the location and characteristics of heliospheric boundaries, and the nature of the local interstellar medium.
For propagation of solar events through the heliosphere, there are several Roadmap RFAs that are directly related to these decadal survey questions. The RFAs span all three Roadmap objectives. The propagation of solar events in the heliosphere continues to be researched with an unprecedented fleet of spacecraft, including those located at several longitudes at L1, at Mars, Saturn, and out to the edge of the heliosphere.