Linking solar minimum, space weather, and night sky brightness

Area of Science:

• Geophysics and Space Physics
• Atmospheric Science
• Astronomy

Background:

• Night sky airglow intensity exhibits variations.
• Understanding these variations is crucial for various scientific and recreational applications.
• Previous studies have not fully characterized broadband night sky brightness during deep solar minimum.

Purpose of the Study:

• To analyze time-series observations of broadband night sky airglow intensity from September 2018 to April 2020.
• To identify previously unrecognized sources of night sky brightness variations during solar minimum.
• To investigate the relationship between night sky brightness, solar activity, and Earth's magnetosphere.

Main Methods:

• Collected time-series data of broadband night sky airglow intensity at five geographically dispersed sites.
• Analyzed data spanning the minimum of Solar Cycle 24 and the beginning of Solar Cycle 25.
• Correlated airglow variations with solar flux, solar wind streams, and geomagnetic field orientation.

Main Results:

• Observed significant, previously unrecognized sources of broadband night sky brightness variations unrelated to solar flux during deep solar minimum.
• Documented continuous variations in night sky brightness on multiple timescales (minutes to months).
• Found semi-annual brightness variations linked to Earth's magnetic field orientation and solar wind streams causing brightness increases.

Conclusions:

• The natural night sky is dynamic, even during solar minimum, with brightness influenced by factors beyond solar flux.
• Night airglow and geomagnetic indices may respond similarly to solar energy input into Earth's magnetosphere.
• These findings provide a quantitative basis for predicting night sky brightness variations relevant to astronomy, space weather, and light pollution studies.