Behold the Behemoth: The Super-Active Sunspot AR3664 was visible with the Naked Eye!

15th May 2024
Behold the Behemoth: The Super-Active Sunspot AR3664 was visible with the Naked Eye!

The giant sunspot AR3664 has earned the title of being one of the largest in this century. Currently, it can already engulf up to 15 Earths. The impact from such solar flares seriously threatens to knock out communication systems and affect critical services on Earth, from the banking system to emergency services.

AR3664 became so large that we could observe it from Earth using solar eclipse glasses (preferably those that correspond to the international safety standard ISO 12312-2). Can we still witness it? Let’s find out.

Solar Superstorms: Now & Before

X3.9-class Solar Flare erupted on 10 May. Credits: ESA

The primary threat posed by massive solar flares lies in the emission of significant amounts of X-ray and ultraviolet radiation, originating within the magnetic field of the sunspot. Upon reaching Earth, these rays initiate ionization in the upper layers of our atmosphere. Such a phenomenon can become either a beautiful evening show in the form of aurora, appearing in unusual places around the world, or a serious problem for satellite communication systems, GPS navigation, and radio communications.

The solar superstorm of 1859, also known as the Carrington Event, is considered the most powerful solar flare in the history of astronomical observations. Back then, the electromagnetic storm that swept over Earth triggered the emergence of the northern lights in the Caribbean. Additionally, in specific regions, observers witnessed high-energy radiation, causing sparks to fly from telegraph poles.

Drawings of a sunspot by British scientist Richard Carrington, September 1, 1859. Credits:

While today’s AR3664 has yet to reach the same magnitude as its 19th-century counterpart, we cannot dismiss the possibility that future solar flares may attain comparable levels of intensity.

Classification of Solar Flares

Sunspots are a common occurrence on the Sun, but most remain relatively small and pose no significant threat to Earth with intense electromagnetic (EM) radiation emissions. Their formation is attributed to the Sun’s robust magnetic activity, which triggers a powerful compression of solar plasma, culminating in subsequent explosions that unleash colossal energy outbursts into space.

The first solar photons reach Earth’s upper atmosphere in about 8.5 minutes, followed by the arrival of potent streams of charged particles within tens of minutes. Clouds of solar plasma generated by the flare typically reach Earth within 2-3 days of the initial release. Despite the brief duration of the pulse phase of a solar flare, lasting only a few minutes, the energy released during this time amounts to billions of megatons (in TNT equivalent) impacting Earth.

Map showing the degree of distribution of solar protons. Credits:

Solar flares are categorized into 5 main classes, according to the classification proposed by D. Baker in 1970. It was based on data provided by solar satellites:

  • X-class — the most powerful solar flares, the intensity at the peak is up to 10−4 (V/m2)
  • M-class — the next most energetic flare, intensity at the peak from 1,0×10−5 to 10−4 (V/m2)
  • C-class — Intensities ranging from 1,0×10−6 to 10−5 (V/m2)
  • B-class — Intensities ranging from 1,0×10−7 to 10−6 (V/m2)
  • A-class — Intensities below less than 10−7 (V/m2

Despite extensive media coverage, the recent flare AR3664 was classified as an M-class event, while the preceding flare AR3663 was designated as an X-class event. According to the National Oceanic and Atmospheric Administration (NOAA), AR3663 triggered a solar storm classified as G4, whereas AR3664 resulted in a weaker storm falling within the G1-G2 range.

Can We See It?

The sunspot known as AR3664 has been quite active lately, firing off solar flares left and right. On May 10, it unleashed an X5.8-class flare, and in the past 12 hours alone, three more X-class flares have burst forth: one at X1.7, another at X1.3, and the grandest of them all, an X8.7 flare, which happens to be the largest solar flare seen in the current 11-year solar cycle.

In today’s update (14 May), NOAA’s Space Weather Prediction Center exclaimed that region 3664 just had ANOTHER X-ray flare as it moves away from the Western side of the sun. However, the major storm has passed, and just a couple of days ago, sunspot AR3664 was so huge that you could see it without fancy solar telescopes, just through your solar eclipse glasses. Now, the storm is not that visible. According to NOAA forecasters, we might experience minor (G1) to moderate (G2) geomagnetic storms today due to a glancing blow coronal mass ejection (CME) from the departing sunspot AR3664.

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