NSF’s Inouye Solar Telescope’s Cryo-NIRSP instrument offers unprecedented look at Alfvén waves

image with 4 sections — The top left and right panels are images from SDO/AIA taken in the 171 Å and 193 Å passbands, respectively. The bottom left panel shows a composite SUVI image processed with multi-Gaussian normalization to bring out the details of the coronal structure. The data at the limb are in the 195 Å passband, and the disk image is from the 171 Å passband. The bottom right panel is the SDO/AIA 193 Å passband image filtered with multi-Gaussian normalization (H. Morgan & M. Druckmüller 2014). The circular DKIST field of view, the Cryo-NIRSP raster region, and the Cryo-NIRSP slit position for the sit-and-stare observations are overplotted on the images. The SDO/AIA images also indicate the location of data extracted for time−distance analysis (“TD slit”). Richard J. Morton et al 2025 ApJ 982 104

Over the last decade, scientists have confirmed the presence of a an important type of magnetized waves called Alfvén waves in the Sun’s outer atmosphere – i.e., the corona. These waves, specific to plasma environments like those in the Sun, can transport energy from the lower atmosphere into the hot corona and solar wind.

Recently, the Cryo-NIRSP instrument at the National Science Foundation (NSF) Daniel K. Inouye Solar Telescope, built and operated by the NSF National Solar Observatory (NSO), has changed our ability to study them, and has started collecting sharper and faster data than ever before – the Inouye’s data is 9 times clearer, 30 times faster, and less noisy than previous observations.

Using these unprecedented data, researchers from Northumbria University, Southwest Research Institute, NSF High Altitude Observatory, CU Boulder, and NSO have closely examined these waves. Their results not only confirm what we already knew about them, but also show that higher-frequency waves (faster oscillations) are also present – something advanced models suggest we should not really see because those waves were expected to get absorbed before reaching the corona.

Interestingly, although these high-frequency waves exist, they likely carry less energy than the lower-frequency ones. The study also confirms that these waves do not compress the material they move through, which is another important property of Alfvén waves.

The unique capabilities of Cryo-NIRSP and the Inouye are affording the solar physics community to investigate our home star like never before, and furthering our understanding of solar physics as well as fundamental plasma interactions.