On May 29, 2020, a family of sunspots — dark spots that freckle the face of
the Sun, representing areas of complex magnetic fields — sported the biggest
solar flare since October 2017. Although the sunspots are not yet visible (they
will soon rotate into view over the left limb of the Sun), NASA spacecraft
spotted the flares high above them.
The flares were too weak to pass the threshold at which NOAA's Space
Weather Prediction Center (which is the U.S. government's official source for
space weather forecasts, watches, warnings and alerts) provides alerts. But
after several months of very few sunspots and little solar activity, scientists
and space weather forecasters are keeping their eye on this new cluster to see
whether they grow or quickly disappear. The sunspots may well be harbingers of
the Sun's solar cycle ramping up and becoming more active.
Or, they may not. It will be a few more months before we know for sure.
On the upper left side of this image from May 29,
2020, from NASA's Solar Dynamics Observatory — shown here in the 171-angstrom wavelength,
which is typically colorized in gold — one can see a spot of light hovering
above the left horizon. This light emanates from solar material tracing out
magnetic field lines that are hovering over a set of sunspots about to rotate
over the left limb of the Sun.
Credits: NASA/Solar Dynamics
Observatory/Joy Ng
As the Sun moves through its natural 11-year cycle, in which its activity
rises and falls, sunspots rise and fall in number, too. NASA and NOAA track
sunspots in order to determine, and predict, the progress of the solar cycle —
and ultimately, solar activity. Currently, scientists are paying close
attention to the sunspot number as it's key to determining the dates of solar
minimum, which is the official start of Solar Cycle 25. This new sunspot
activity could be a sign that the Sun is possibly revving up to the new cycle
and has passed through minimum.
However, it takes at least six months of solar observations and
sunspot-counting after a minimum to know when it's occurred. Because that minimum
is defined by the lowest number of sunspots in a cycle, scientists need to see
the numbers consistently rising before they can determine when exactly they
were at the bottom. That means solar minimum is an instance only recognizable
in hindsight: It could take six to 12 months after the fact to confirm when
minimum has actually passed.
This is partly because our star is extremely variable. Just because the
sunspot numbers go up or down in a given month doesn't mean it won't reverse
course the next month, only to go back again the month after that. So,
scientists need long-term data to build a picture of the Sun’s overall trends
through the solar cycle. Commonly, that means the number we use to compare any
given month is the average sunspot number from six months both backward and
forward in time — meaning that right now, we can confidently characterize what
October 2019 looks like compared to the months before it (there were definitely
fewer sunspots!), but not yet what November looks like compared to that.
On May 29, at 3:24 a.m. EST, a relatively small M-class solar flare blazed
from these sunspots. Solar flares are powerful bursts of radiation. Harmful
radiation from a flare cannot pass through Earth's atmosphere to physically
affect humans on the ground, however — when intense enough — they can disturb
the atmosphere in the layer where GPS and communications signals travel. The
intensity of this flare was below the threshold that could affect geomagnetic
space and below the threshold for NOAA to create an alert.
Nonetheless, it was the first M-class flare since October 2017 — and
scientists will be watching to see if the Sun is indeed beginning to wake up.
Source: https://www.nasa.gov/feature/goddard/2020/new-sunspots-herald-increased-solar-activity-cycle-sdo
By Karen Fox, Lina Tran
NASA's Goddard Space Flight Center, Greenbelt, Md.
NASA's Goddard Space Flight Center, Greenbelt, Md.
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