A rare ‘reversed’ sunspot may spark bright auroras tonight

A rare ‘reversed’ sunspot may spark bright auroras tonight

The Aurora Borealis could stretch down over much of Canada and the northern United States on Thursday night.

On Tuesday, a rare ‘reversed-polarity’ sunspot blasted out yet another solar flare. The solar storm that erupted along with it could cause the auroras to shine brighter and extend farther south than usual on Thursday night.

On the afternoon of May 9, sunspot AR3296, which has been crackling with activity for days, blasted out two moderate-strength solar flares in quick succession. At the same time, the release of energy caused a coronal mass ejection to erupt into space. This follows two other smaller CMEs that erupted toward Earth on Sunday.

May10-Flare-CME

The flare from sunspot AR3296 on May 9 is shown here (left panel), as seen by NASA’s Solar Dynamics Observatory (SOHO). On the right, the bright ‘cloud’ towards the top right of the panel, is the CME expanding away from the solar flare, as captured by the coronagraph instrument on the NASA/ESA Solar and Heliospheric Observatory (SOHO). Credit: NASA/ESA/Scott Sutherland

Coronal mass ejections, aka solar storms, are immense clouds of charged solar particles that expand away from the Sun, typically following a solar flare. If a solar storm sweeps past us, the magnetic field carried by the cloud interacts with Earth’s magnetic field, causing a disturbance known as a geomagnetic storm. Space weather forecasters rank these storms on a five-point scale, from G1 (minor) to G5 (extreme). The stronger the geomagnetic storm, the more likely we’ll see bright displays of the Northern Lights, the farther south those displays will extend, and the greater the possibility that we could see impacts to orbiting spacecraft or power grids on the ground.

According to NOAA’s Space Weather Prediction Center, there is already a chance for a G2 (moderate) geomagnetic storm to develop Wednesday night due to the effects of the solar storms from Sunday.

10 May G2-3 Watches SWPC

This graphic shows NOAA’s space weather model that predicts the progress of solar storms as they expand away from the Sun, along with the expected impacts over the next two days due to the edge of the incoming solar storms affecting Earth as they pass by. Credit: NOAA SWPC

When the CME from Tuesday arrives, its effects could combine with the residual impacts from the previous solar storms to produce an even stronger, G3 (strong) geomagnetic storm on Thursday.

“Forecasters predict a component of this CME will arrive at Earth by midday on 11 May as a G3 (Strong) geomagnetic storm while the bulk of the eruptive material passes ahead and north of Earth’s orbit,” SWPC wrote. “G2 (Moderate) storming is likely into 12 May with ongoing CME influences.”

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