Tuesday, May 21, 2024

Severe Geogmagnetic Storm Has Arrived! Auroral Blast Expected Friday Night – Sky & Telescope

AstronomySevere Geogmagnetic Storm Has Arrived! Auroral Blast Expected Friday Night - Sky & Telescope

The show has already started! On Thursday night, May 9, the first salvo arrived at Earth to spark a modest but colorful aurora. Here it meets its reflection in a lake north of Duluth, Minnesota around 11:30 p.m. CDT. The W of Cassiopeia and Perseus Double Cluster appear at upper left.
Bob King

Better plan on getting a nap this afternoon, because if it’s clear tonight (May 10th), you may not get to bed until the birds sing again at dawn. The National Oceanic and Atmospheric Administration’s Space Weather Prediction Center (SWPC) expects a powerful G4 storm to hit, which could bring the aurora as far south as California and Alabama in the U.S. and as far north as Sydney, Australia in the Southern Hemisphere. Folks in the northern U.S. will see the aurora expand well beyond the zenith deep into the southern sky.

During the climax of one of the more recent G4 events on April 23, 2023, intensely bright rays from every corner of the heavens converged near the zenith and flashed and twisted about like kid’s kaleidoscope. I nearly died of amazement.

Giant sunspot region 3664
This past week sunspot region 3664 (lower right) rapidly grew into a behemoth some 15 times the diameter of the Earth. Seen here on May 8th, the region was easily visible through a safe solar filter with the naked eye. The highly volatile region, one of the largest of the current solar cycle, possesses a complex magnetic field that has spawned multiple M– and X-class flares.
Bob King

All the excitement stems from a volley of flares that erupted from the gigantic sunspot region 3664, which has hurled no fewer than five coronal mass ejections (CMEs) in our humble planet’s direction. Some of the blasts have overtaken and merged with earlier ones to create a so-called “cannibal” CME, possessed of even greater power.

CME animation
This animation, compiled from images taken by the Solar and Heliospheric Observatory’s coronagraph, show the eruption of one of the early CMEs from sunspot region 3664 on May 8th.

A high-octane storm can touch more than the human heart and soul; it can potentially affect power grids on Earth and cause disruptions in radio signals and communications systems. Satellites can experience surface charging that could potentially damage sensitive electronics.

Even astronauts aboard space stations have to take precautions. Even though the planet’s magnetic field protects them to an extent, solar protons in geomagnetic storms may breach the hull, so to speak. To minimize risk, astronauts retreat to areas in the station where the surrounding mass of material offers further protection.

H-alpha solar flare
Region 3664 (center right) blew off a large flare on May 8th, as seen in this hydrogen-alpha image through a Lunt 60 mm telescope.
Bob King

Aurora Q&A

To address some of the many questions that inevitably arise when a major auroral storm is imminent, let’s do a quick Q&A. Keep in mind that despite the best forecasts the aurora can still play tricks and arrive earlier or later than expected, or heaven forbid, not at all.

When should I look?
Even as I write this, the blast has already arrived. The latest SWPC forecast indicates the storm should continue into Friday night, May 10-11, as twilight descends over the U.S. and Canada. Sunsets are late this time of year so the sky won’t get dark until after 9:30 p.m. local time. Generally, the closer to local midnight (1 a.m. when Daylight Saving Time is in effect) the stronger and more intense the aurora. A G3-rated (strong) storm is expected from 11 p.m. to 2 a.m. EDT which should ramp up to a G4 from 2 a.m. through dawn. Yes, the show goes on all night! It will fire up again to a G2 (moderate) level on Saturday night, May 11-12, between 10 p.m. and 1 a.m. EDT. That’s great news if clouds get in your way Friday.

Where should I go to see it?
The best place to view the aurora is the most obvious one — as far as possible from city lights. If you can, drive north from your city to a location with the least amount of light pollution. Use the interactive map at lightpollutionmap.info to explore your region for potential sites. Color-coding shows where light overkill is worst — lilac, red and yellow — and where it’s suitably dark — green, blue and gray. Use your mouse (or fingers) to zoom in and out of the map and change your location. If possible, scout out your chosen spot during the daytime so you’re comfortable there at night. Importantly, make sure you have an open view of the northern sky (or southern sky in the Southern Hemisphere). Fields, lake shores, and hilltops are ideal.

What equipment do I need?
Good news — none! Your eyes will take it all in especially as they become increasingly dark-adapted with time spent outdoors. Other helpful items include a chair so you can sit and rest your legs if you’re out a long time. A beverage and snack will be very welcome as the clock ticks toward midnight. Warm clothing is essential because you’ll be standing or sitting still, frozen in awe, much of the time.

Corona aurora April 23, 2023
A dazzling coronal aurora pivots high in the sky during the G4 storm on April 23, 2023.
Bob King

Will it look like the colorful photos I see in books and online?
Generally, no. Most auroras appear pale green or white with hints of pink. Our eyes see in real time, while a camera accumulates light during a time-exposure, revealing the aurora’s subtle colors more vividly. However, during powerful storms, you’ll see brief bouts of intense color — purples, reds, pinks, and greens. Colors are caused by particles from the Sun spiraling down Earth’s magnetic field lines and striking atoms and molecules of oxygen and nitrogen in the atmosphere. Temporarily energized by the collisions, the atoms release tiny bursts of light when they settle back to their rest states.

What causes the aurora?
In a nutshell, the magnetic field that comes along for a ride in the blast of particles released in a CME, couples with Earth’s magnetic field. This creates a conduit that funnels those particles — electrons and protons — at high speed into the atmosphere over the planet’s polar regions.

iPhone aurora
This is a 3-second, handheld image of the coronal aurora with an iPhone 13 made on March 23, 2023, from northern Minnesota.
Bob King

How can I photograph the aurora?
You can use your smartphone. Hold it up to the sky, and the phone will set itself to night mode, allowing handheld exposures of 3 seconds — long enough to easily capture a moderate- to bright aurora. Hold the phone to the sky, tap the shutter release button, and keep the two crosses that appear on your screen aligned. If you have a DSLR or mirrorless camera, attach it to a tripod and focus on a bright star using the camera’s live view feature. A wide-angle lens is best, from 15 to 35mm. Open the lens to its lowest f-stop (f/2 or 2.8 is best if you have it) to let in the maximum amount of light. Expose at ISO 1600 or 3200 for 5-20 seconds. Check the replay to see if you’re on target. If not, adjust the exposure or ISO accordingly.

How do I find out where the sky is clear if it’s cloudy at my house?
Check the GOES satellite images at GOES East or GOES West (for skywatchers in the far western U.S.). Click on your location on the map for an enlarged view. To see clouds at night, click on the Choose bar and select Channel 7, the third option down. You can also go to Windy.com and click the Satellite heading for an excellent cloud map. Or just Google and download the Windy app.

What’s a good aurora alert app?
SpaceweatherLive, free for Android and iPhones.

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