SAR-Arc viewed from 4000ft at Thunder Ridge on the Blue Ridge Parkway in Virginia.

A SAR arc is a phenomenon related to the Earth's magnetosphere and ionosphere. SAR stands for "Stable Auroral Red" arc. Here's a simple explanation:

Auroras: These are natural light displays in the sky, usually seen in high latitude regions (around the Arctic and Antarctic). They are caused by the interaction between the Earth's magnetosphere and solar wind—a stream of charged particles emanating from the Sun.

Geomagnetic Storms: These are disturbances in the Earth's magnetosphere caused by a solar wind shock wave or cloud of magnetic field that interacts with the Earth's magnetic field. This interaction can enhance auroral activity.

Stable Auroral Red (SAR) Arc: During geomagnetic storms, a SAR arc can form. It is a specific type of aurora that appears at lower latitudes than typical auroras. Unlike the more common green auroras, SAR arcs are characterized by their red color, which is due to their emission of light at specific red wavelengths. This red light comes primarily from atomic oxygen at higher altitudes in the Earth's atmosphere.

Stability and Location: The term "stable" in SAR arc refers to its relatively steady and long-lasting nature compared to other auroral phenomena, which can be quite dynamic and rapidly changing. SAR arcs are typically observed in the sub-auroral zone, which is the region between the usual auroral oval and lower latitude areas.


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Make:	NIKON CORPORATION
Model:	NIKON D750
Exposure:	20
Aperture:	f/2.8
ISO Speed:	400
Focal Length:	16 mm
Lens:	Tokina opera 16-28mm F2.8 FF