The National Science Foundation’s National Solar Observatory’s SOLIS instrument is one step closer to restarting Sun observing with the pouring of a concrete foundation at the Big Bear Solar Observatory (BBSO) site in California recently. The new construction provides a new permanent home to one of the NSO’s primary instruments.
“This is exciting news that we have been waiting for several years now,” said Dr. Alexei Pevtsov, the Program Director for NSO Integrated Synoptic Program (NISP). “Bringing SOLIS back on-line will enable us to continue exploring how our nearest star evolves and how its changing activity affects Earth. SOLIS also will provide context observations to support the Daniel K. Inouye Solar Telescope operations.”
SOLIS, or the Synoptic Optical Long-term Investigations of the Sun facility was originally installed at Kitt Peak in 2003. The project then moved to Tucson, Arizona in 2014 and where it operated until 2017. The Big Bear Solar Observatory, operated by the Center for Solar-Terrestrial Research (CSTR) of  New Jersey Institute of Technology (NJIT), will become SOLIS’s permanent base and provide the first year’s operational support.
“The SOLIS relocation project represents the ongoing successful collaboration between NSO and BBSO/NJIT that has lasted for more than 30 years,” explains Dr. Wenda Cao, BBSO Director and NJIT professor. “Thanks to the long periods of steady, excellent seeing at the BBSO lake-site, SOLIS will supply comprehensive observations for solar synoptic research.”
SOLIS contains the Vector Spectromagnetograph, or VSM, Integrated Sunlight Spectrometer, or ISS, and the Full-Disk Patrol, or the FDP. The VSM records the Sun’s magnetic field strength and direction. The ISS collects different wavelengths of light or spectra from the entire disk of the Sun, treating it as if it was a far-away star. The FDP takes rapid sequences of full-disk Sun images in a variety of different wavelengths to record dynamic processes, such as flares, in the solar atmosphere.
“We are excited that the SOLIS construction project has begun,” said Carrie Black, NSF Program Director for NSO. “SOLIS measurements are used to address the most pressing questions of the day about the complex magnetic fields of the Sun and are an important complement to NSO’s other instrument suites. The location at Big Bear Solar Observatory is an excellent site for SOLIS science and greatly enhances NSO’s collaboration with the New Jersey Institute of Technology.”
Full-disk magnetograms from SOLIS/VSM will continue a historical, 50-year record of magnetic activity started at NSO in early 1970s. The world’s first full-disk vector magnetograms from the VSM enabled systematic observations of the corkscrew winding of the magnetic fields on the Sun. These observations were key in understanding how magnetic fields on our star are created and how they erupt as solar flares.
VSM has the valuable capability to observe the direction of magnetic fields at two different levels in the solar atmosphere: the photosphere (surface) and the chromosphere (low atmosphere). Measuring magnetic fields in these regions is critical for understanding the impact of solar eruptions on Earth, known as space weather. The combination of data from VSM and ISS bridges solar and stellar astrophysics creating a better understanding of other sun-like stars. Researchers also use measurements of our own Sun to model the effects of space weather on planets orbiting other stars.
Construction of the SOLIS site should be complete by mid-October 2021, and SOLIS is expected to be fully operational in 2022.