What is WHI?
The Whole Heliosphere Interval is an internationally coordinated observing and modeling effort to characterize the 3-dimensional interconnected solar-heliospheric-planetary system - a.k.a. the "heliophysical" system.
WHI observing campaigns began with the 3-D solar structure from solar Carrington Rotation 2068, which ran from March 20 - April 16, 2008. Observations and models of the outer heliosphere and planetary impacts extend beyond those dates as necessary; for example, the solar wind transit time to outer planets can take months. Specific dates were determined according to each science topic.
WHI Rationale and Heritage
WHI transpired during the International Heliophysical Year, on the 50th anniversary of the International Geophysical Year (IGY). IGY included the launch of Sputnik (the first spacecraft) and Explorer I, which brought the first scientific observations of space.
Now, 50 years later, we have observations of the outer reaches of the heliosphere, and we are poised to make great advances in our understanding of our extended heliophysical domain and our relationship with interstellar space. WHI takes full advantage of the 50 years of scientific progress of IGY by coordinating state-of-the-art models and observations to address the entire interconnected heliophysical system.
One solar cycle after the first Whole Sun Month campaigns, WHI benefits from dramatic improvements in observations, including new 3-D measurements, higher temporal/spatial/spectral resolutions, and expanded synoptic observations from deep in the solar interior extending through the heliosphere to the Earth.
Making 3-D Connections
The heart of the WHI campaign is the study of the interconnected 3-D heliophysical domain, from the interior of the Sun, to the Earth, outer planets, and into interstellar space. The WHI Science Team has determined a set of scientific topics to be addressed by the observations and models.
Many participating observatories ran a continuous "synoptic" set of observations, to provide baseline measurements of the heliophysical system. These synoptic observing programs were ran throughout WHI.
There are also scientific studies of focused topics that are ideally addressed in the context of global structures. targeted observing campaigns have been identified. These campaigns involve day-to-day coordination of observations of heliospheric sub-regions, to address specific scientific questions.
Another key strength of WHI is the involvement of theoretical models and simulations in planning the observations. Models are essential to complete the 3-D picture of the heliosphere, especially in connecting magnetic structures across the heliophysical system. By understanding the needs and limitations of current models, WHI's campaigns were optimized for interpretation.
There is a comprehensive list of observatories, instruments and missions participating in WHI, and our Science Team welcome new observers and modelers when are interested in participating.