The paper explains why the solar activity index F30 is more suitable for ionospheric and thermospheric long-term trends.

The manuscript reports the first observations of continuum emission at the poleward boundary of the dayside auroral oval. The unique measurements show that a number of different emission lines and bands contribute to the broadband continuum emission. Even emission structures in the near and far infrared were observed, suggesting that multiple emitting species are responsible for the observed spectral enhancements. The authors suggest that the interplay of different heating mechanisms may be an important factor in the generation of high-latitude continuum emissions.

The study is devoted to a shock auroral event that occurred on February 26, 2023, in northern Scandinavia, and represents the first time such nighttime auroral features have been captured by ground-based cameras. Shock auroras result from a very specific driving impulse in the solar wind. While the primary effects appear on the dayside of the Earth, the authors succeeded in observing the nightside signatures, which are rare and difficult to detect. The study is a successful scientific achievement as it presents newly discovered phenomena that provide new insights into solar wind interactions with the nightside ionosphere.