Aurora
Auroras are a direct visible effect of space weather driven by the Sun.
Solar flares and coronal mass ejections (CMEs) eject charged particles
(mostly electrons and protons). These particles travel through space and
hit
Earth's magnetosphere. Earth's magnetic field guides particles toward
the
polar regions. Particles collide with oxygen and nitrogen atoms in the
upper atmosphere (~100-400 km altitude) which emit light
(Oxygen: green and red, Nitrogen: blue and purple).
Aurora is an indicator of geomagnetic storms and correlates with risks to:
satellites (charging, drag increase), GPS accuracy,
HF radio communications,
and power grids.
Ground observations of aurora (Courtesy of Prof. Sheng, UCLA, December 2025)
Auroras interfere with signals because they are a sign that the ionosphere is being strongly disturbed by energetic particles and currents. Those disturbances directly affect how radio waves and navigation signals propagate. VIIRS/DNB is one of the best spaceborne imagers for global auroral monitoring due to its Extreme low-light sensitivity (detect radiances down to ~10^-9 W-cm^-2-sr^-1), which is perfect for Auroral emissions. The DNB spectral range of ~500-900nm also overlaps key auroral lines at 557.7 nm - green oxygen (dominant), and 630.0 nm - red oxygen. In addition, VIIRS/DNB spatial resolution of 750m allows observation of fine auroral arcs, oval structure and substorm expansion. Each of the VIIRS/DNB on three JPSS satellites passes the polar regions multiple times of a day and provides unprecedented high temporal observations of aurora with high spatial resolution.
