GEOMAGNETIC STORM WATCH (G2): NOAA forcasters say there is a chance of G2–class geomagnetic storms today, Nov. 7th, when the subsiding effects of Sunday’s CME might overlap with an incoming solar wind stream. Earth’s magnetosphere is already humming with G1–class activity, and it won’t take much to push it across the threshold to G2. Aurora alerts: SMS Text
EARTH’S RING CURRENT JUST SPRANG A LEAK: During this weekend’s strong G3-class geomagnetic storm, low-latitude auroras spread as far south as Texas and Arizona. Upon further review, most of those lights were not auroras at all. Everything red in these photos is an “SAR”:
Credits: Texas (Anita Oakley); Missouri (Dan Bush); New York (James Perez-Rogers); Arizona (Jeremy Perez)
“This was a new phenomenon to me,” says Jeremy Perez, who took the Arizona photo. “I had never heard of SARs before, but I kept shooting anyway.”
SARs were discovered in 1956 at the beginning of the Space Age. Researchers didn’t know what they were and unwittingly gave them a misleading name: “Stable Auroral Red arcs” or SARs. In fact, SARs are neither stable nor auroras.
Auroras appear when charged particles rain down from space, hitting the atmosphere and causing it to glow. SARs form differently. They are a sign of heat energy leaking into the upper atmosphere from Earth’s ring current system– a donut-shaped circuit carrying millions of amps around our planet.
“On Nov. 5th, the ring current was pumped up for hours by the geomagnetic storm, with energy dissipating into these SAR arcs,” says Jeff Baumgardner of Boston University’s Center for Space Physics. “It was a global event. Our cameras registered SAR activity from Italy to New Zealand.”
Recent research has linked SARs to another phenomenon that is not an aurora: STEVE . The mauve ribbon in the sky was not originally thought to have anything to do with Earth’s ring current. Yet in 2015, observers in New Zealand caught a bright red SAR transforming itself into STEVE .
Mark Savage may have seen the same thing happen on Nov 5th when an SAR apparently gave birth to STEVE over of Northumberland, UK:
“The entire process took about 10 minutes,” says Savage. This roughly matches the timescale of an SAR-to-STEVE transition observed over Canada in April 2022.
“The connection between STEVE and SARs is still elusive,” cautions Carlos Martinis, a leading researcher in the field at Boston University. “Sometimes SARs evolve into STEVE–but not always. This is a very active field of research, involving citizen scientists and researchers.”
More SAR images: from Chris Cook of Borrego Springs, California; from Todd Bush of Banner Elk, North Carolina; from Ronnie Sherrill of Troutman, North Carolina; from George Preoteasa of Milford, PA; from David Blanchard of Wupatki National Monument, Arizona; from Hunter Outten of Laurel, Delaware; from Caryl Bohn of West Oak, Nebraska
The SAR arcs or Stable Auroral Red arcs were discovered in 1956. The reason that SAR arcs were discovered so late compared to polar aurora is that SAR arcs aren’t usually visible. So, humans have to use instruments to tell that they are there (see image to left). SAR arcs can stretch across the entire sky.
Scientists have only known that SAR arcs existed for last 50 years. So, there are still debates as to exactly what produces SAR arcs. It is likely that this faint red glow is caused by the release of energy by the Earth’s ring current system…
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