People from many countries stepped out of the comfort of their homes to witness a natural spectacle of light happening in the middle of two nights in May 2024. The Northern Lights, as Auroras are known to many of us in the northern hemisphere, reached unbelievably low latitudes, as far as Mexico and Puerto Rico. In the southern hemisphere, the Aurora Australis reached as far as Australia, South Africa, and Paraguay.
Incredible photos started pouring with dark silhouettes of forests, cities, buildings, and people against skies that look more like the canvas on an art piece, where green, pink, blue, violet, and white light strokes decorate the background. There is no way to show them all here, but I want to post a few.
[Carrusel or Collage with Aurora photos only]
Among these photos, one from the National Astronomical Observatory in San Pedro Martir, Baja California, Mexico, sets the domes of the telescopes I visited while studying for my Master's in Astrophysics, against the pink sky.
[auroras-San-PedroMartir,jpg]
Auroras are usually visible at high north or south latitudes and within a band about 500 km wide that stretches about 10 deg to 20 deg from the geomagnetic poles. Currently, the [north geomagnetic pole: https://www.ncei.noaa.gov/news/tracking-changes-earth-magnetic-poles] is close to the north tip of Ellesmere Island, NU, Canada, at about 80 degrees north. The south geomagnetic pole is in Antarctica, also about 80 deg, but in the southern hemisphere. NOAA has an [aurora forecast:https://www.swpc.noaa.gov/communities/aurora-dashboard-experimental] portal where it is possible to find where they will be and where these are visible. Although the magnetic poles on Earth slightly shift position over the years, controlled by the variations of its magnetic field strength, the auroras are common in countries like Norway, Alaska, Canada, and Sweden. You can even find companies offering trips to these locations to see this magnificent event.
Credit: NOAA
The Sun changed our statistics when the solar region AR3664 had a spree of solar or coronal mass ejections (CMEs) on May 9, 2024[1]. The CMEs sent loads of highly charged particles to Earth, developing a severe geomagnetic storm that gave rise to the incredible auroras people saw for several days in uncommon places. The first CMEs reached Earth on May 10, 2024, at 12:37 pm EDT. One hour later, NOAA Space Weather Prediction Center (SWPC) observed [G4 conditions:https://www.swpc.noaa.gov/noaa-scales-explanation] -- the classification given to geomagnetic storms that have the potential to affect power, spacecraft operations, and other systems. The intensity and rate of these CMEs were not a surprise to scientists, as 2024 is a year when the activity of the Sun peaks. It is Solar Cycle 25, as indicated by the number of Sunspots appearing at its surface, which are also associated with the number of solar flares and CMEs observed[2].
The CMEs should not be confused with solar flares; both can be simultaneous but are different events. Solar flares emit energetic radiation, mostly in the form of ultraviolet light and X-rays. This radiation travels at the speed of light and reaches the sunlit side of Earth within 8 minutes. CMEs, on the other hand, are highly charged bubbles of solar plasma emerging from the outer atmosphere, known as the corona. As the bubble radiates outward, it drags within it the Sun's magnetic field, or Interplanetary Magnetic Field (IMF). A CME can travel at speeds slower than 250 kilometers per second (km/s) to as fast as about 3000 km/s -- the fastest Earth-directed CMEs can reach our planet in as little as 15-18 hours, but slower CMEs can take several days to arrive. When they arrive on Earth, they collide with the magnetosphere and can produce a severe geomagnetic storm. The magnetosphere, generated by the convective motion of charged, molten iron far below the surface in Earth's outer core, is the barrier that deflects high energy particles in the solar wind and protects the Earth’s atmosphere[3]. However, during a geomagnetic storm, the IMF turns southward, interacting with the Earth's magnetic field, which points northward. The interaction disrupts the magnetosphere, allowing energetic particles to fall through the magnetic lines at the poles and giving rise to the auroras.
The first signs of the solar storm started with two strong flares sometime late May 7. The activity continued until May 11, with at least seven CMEs and eight solar flares of the most powerful type, X-type, peaking at X5.8. A day after the big CMEs, sunspots were visible in region AR3664. Large X-ray flares appeared a day after, and on May 14, NASA observed the largest flare seen in this solar cycle, a flare type X8.7, indicating this region was still active[4]. The solar flares observed after May 9 had no impact on Earth; however, as the Sun rotates, AR 3664 will reappear on the east side during the first days of June, showing us how active it is[9]. The [NOAA Space Weather Prediction Center: https://www.swpc.noaa.gov/] provides detailed information about severe geomagnetic storms.
Throughout 2024, the Sun will be at a solar maximum, which happens every 11 years. Although we might not see another aurora like the one on Mother’s Day weekend, we can follow the increased activity of the Sun through the eyes of the Solar & Heliospheric Observatory [SOHO: https://soho.nascom.nasa.gov/] or the Solar Dynamics Observatory [SDO: https://sdo.gsfc.nasa.gov/mission/] missions [5][6]. Also, a Belgian group keeps information about auroras in several languages at their website [SpaceWeatherLive.com: https://www.spaceweatherlive.com/en/auroral-activity.html].
We should also remember that although auroras are beautiful, a severe geomagnetic storm can be dangerous. Depending on its [scale: https://www.swpc.noaa.gov/noaa-scales-explanation], geomagnetic storms can disrupt radio communications, degrade the accuracy and reliability of GPS systems, result in navigation information for planes and ships that is inaccurate by several miles, affect electric power systems, and even increases corrosion of pipelines for natural gas, oil, water, etc. [7].
References
[3]
[4]
Aurora photos:
- Colm Doyle-Tnzmania——Amateur photographer Colm Doyle captured this picture of the aurora along WA's south coast.(Supplied: Colm Doyle
—SouthernLightsJimWorrall. —-https://jimworrall.blog/2024/05/14/southern-lights-aurora-australis-11th-may-2024/
—Aurora_borealis_pillars —-https://www.esa.int/Science_Exploration/Space_Science/Space_weather
—Space_weather_article-—https://www.esa.int/Science_Exploration/Space_Science/Space_weather
—-Debrad, Slovakia —- https://www.space.com/sun-storms-aurora-show-mothers-day-2024 Credit: Robert Nemeti/Anadolu via Getty Images)
JamenPercy —- https://bgr.com/science/northern-lights-may-be-visible-in-these-us-states-this-weekend/