Solar Eruption Arrives at Earth

A mass of solar material that erupted from the Sun on Oct. 9, 2021, reached Earth on Oct. 12. The Earth-directed coronal mass ejection, or CME, elevated the Kp index, a measure of disturbance to Earth’s magnetic field, to 6 (moderate level). Kp index levels range from 0 (quiet) to 9 (intense).

The CME was associated with an M1.6 class solar flare from Active Region 2882 on that peaked on Oct. 9 at 6:38 UTC (2:38 a.m. EDT). M-class flares are a tenth the size of the most intense flares, the X-class flares. The number provides more information about its strength. An M2 is twice as intense as an M1, an M3 is three times as intense, etc. The flare also generated a solar energetic particle eruption that was detected by NASA’s Solar Terrestrial Relations Observatory-Ahead, or STEREO-A spacecraft, at 7:51 UTC (3:51 a.m. EDT).

teal colored sun showing solar flare
Active Region 2882, shown here near the middle of the Sun’s disk, erupted with a moderate level solar flare on Oct. 9, 2021. This animated gif shows images from the 131 Angstrom channel of NASA’s Solar Dynamics Observatory spacecraft/Atmospheric Imaging Assembly instrument. Credit: NASA/SDO

STEREO-A also detected the CME from its vantage point away from Earth. The CME’s initial speed was estimated by NASA’s Moon to Mars Space Weather Operations Office to be approximately 983 kilometers per second (610 miles per second). This and other information about the event is reported in the Space Weather Database Of Notifications, Knowledge, Information (DONKI) catalog.

red coronagraph image showing solar eruption
The COR2 coronagraph on NASA’s Solar Terrestrial Relations Observatory-A spacecraft, which views the Sun’s corona by occluding its bright surface, detected this Earth-directed CME on Oct. 9, 2021. Credit: NASA/STEREO

NOAA’s Space Weather Prediction Center is the official source for space weather forecasts, watches, warnings and alerts. Visit for information about potential impacts from this event.

Significant Solar Flare Erupts from Sun

The Sun emitted a significant solar flare peaking at 10:29 a.m. EDT on July 3, 2021. NASA’s Solar Dynamics Observatory, which watches the Sun constantly, captured an image of the event.

image of solar flare
This image comes from the Atmospheric Imaging Assembly telescope/94 Angstrom channel, which shows solar material at about 10 million degrees Fahrenheit. Credits: NASA/SDO

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.

To see how such space weather may affect Earth, please visit NOAA’s Space Weather Prediction Center at, the U.S. government’s official source for space weather forecasts, watches, warnings and alerts.

This flare is classified as an X1.5-class flare.

X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc.