A research team from the Yunnan Observatories of the Chinese Academy of Sciences (CAS) has detailed the physical characteristics of chromospheric jets in and around a sunspot, using high-resolution observations from the New Vacuum Solar Telescope (NVST). Their findings were published in The Astrophysical Journal.

The study focused on active region NOAA 13386, which the NVST observed on July 31, 2023. By analyzing high-resolution Hα data alongside extreme ultraviolet and magnetic field observations from NASA's Solar Dynamics Observatory (SDO), the team conducted a systematic analysis of the chromospheric jets' physical properties in and around the sunspot.

Inside the sunspot, the jets have projected velocities of 4–14 km/s, lengths of 1–4 megameters (Mm), widths of 0.2–0.6 Mm, and lifetimes of 135–450 seconds. In contrast, jets outside the sunspot exhibit faster projected velocities (8–50 km/s), greater lengths (1–20 Mm), slightly wider profiles (0.3–0.8 Mm), and longer lifetimes (135–630 seconds), indicating that the outside jets have larger spatial and temporal scales than the inside jets.

Multiwavelength observations reveal clear brightenings in the solar corona for both jet types, signaling high-temperature signatures. This suggests the jets may contribute to chromospheric and coronal heating. Further analysis shows inside jets are driven by partial magnetic reconnection between intersecting filaments, while line-of-sight magnetograms indicate outside jets typically form in regions of opposite magnetic polarities, closely tied to magnetic flux emergence.

This study provides new observational evidence for understanding the formation mechanisms of active-region jets and their roles in energy transport in the solar atmosphere, the researchers noted. It also underscores the ability of NVST's high spatiotemporal resolution data to investigate small-scale activities in the solar chromosphere.

This work was supported by the CAS Strategic Priority Research Program, and the National Science Foundation of China, among other sources.

Figure 1. (a) Distribution of the sunspot and the jets analyzed in this study. The umbra is marked in black and the penumbra in white. The colors of the jets indicate the projected velocities. (b)–(e) Histograms comparing the velocity, length, width, and lifetime of the jets. Inside jets are shown in red, while outside jets are shown in blue. The dashed lines mark the mean values of each group. (Image by WU Guotang)