Three Solar Eruptions Combine to Trigger Bright Auroral Show

From a flash on the Sun to a glimmer in the sky, last week’s solar storms illustrated the connection between the Sun and Earth. Three solar eruptions made their journey to Earth, culminating in aurora borealis, or northern lights, visible as far south as Utah.

It began with two active regions on the Sun – places where the Sun’s magnetic field is especially intense. All the active regions present on the Sun on Nov. 1 are shown below on a magnetic map of the Sun created by the Helioseismic and Magnetic Imager (HMI) instrument aboard NASA’s Solar Dynamics Observatory. Pay special attention to Active Region (AR) 12887, toward the bottom right, and AR 12891, near the middle of the Sun.

magnetic map of the Sun with labels
Active regions on the Sun Nov. 1. Credit: NASA/SDO

On Nov. 1, AR 12887 erupted with a C1.3-class flare, reaching peak brightness at about 2 p.m. EDT. (Solar flares are divided into A, B, C, M and X-classes, each class ten times stronger than its predecessor. The number provides more information about its strength: A C2 is twice as intense as an C1, a C3 is three times as intense, etc.

Classes A through C typically have little to no effect on Earth.) Three hours later, an even brighter C4-class flare followed; two hours after that, an M1.6-class flare erupted from AR 12891 towards the center of the Sun. The Solar Dynamics Observatory’s Atmospheric Imaging Assembly instrument captured images of each flare at 193 Angstroms, a wavelength that highlights hot solar material more than a million degrees Fahrenheit.

animated image of the Sun showing three small flares
Three flares erupt from the Sun in this timelapse image from SDO’s AIA 193 channel. The first two flares, in the bottom right region, peak at 2021-11-01T18:01 UT and 2021-11-01T21:33 UT. The third flare, near the center of the image, peaks at 2021-11-02T03:01 UT. Credit: NASA/SDO

These flares were not strong enough to have noticeable impacts on Earth. But even weaker solar flares sometimes coincide with coronal mass ejections, or CMEs – bursts of solar material that escape the Sun and spill out to space – which can still have impacts, as these did.

The European Space Agency/NASA’s Solar and Heliospheric Observatory, or SOHO mission, stationed at the first Lagrange point where forces from the satellite motion and the Sun and Earth’s gravity balance, carries an ideal instrument for detecting CMEs. This instrument, called a coronagraph, blocks the Sun’s bright surface to reveal its faint corona, or outer atmosphere, where solar eruptions are more easily spotted. In SOHO’s imagery from the event, the CMEs following each flare appear like clouds of smoke issuing from the Sun.

animated image of solar eruptions
ESA/NASA’s SOHO spacecraft captured three CMEs erupting from the Sun. The first two appear from the bottom right of the central disk at 2021/11/1 19:00 and 22:00; the third from around the disk at about 2021/11/2 03:00. Credit: ESA/NASA/SOHO

Scientists at NASA’s Moon to Mars Space Weather Office retrieved the spacecraft data and entered it into a model to simulate the likely path of the CMEs. The simulation, shown below, depicts the Sun at the center, marking the current locations of several planets and spacecraft. Earth appears as a yellow dot at 3 o’clock.

simulation of solar eruption
The ENLIL model simulation the three CMEs as they merge and travel toward Earth. Credit: NASA/M2M

The simulations suggested that the three CMEs would blend together, creating a shockwave headed towards Earth and expected to arrive sometime late on Nov. 3 or early on Nov. 4.

Earth’s magnetic field and thick atmosphere protects its surface (and us) from most effects of solar eruptions. But the highest layers of our atmosphere can undergo many changes. As a CME collides with Earth’s magnetic field, it can generate geomagnetic storms: disturbances to Earth’s magnetic environment that have a variety of impacts, including the northern and southern lights.

By 5 p.m. EDT on Nov. 3, the shockwave had arrived. Magnetometers across the planet registered a Kp index – a measure of disturbance to Earth’s magnetic field – of 7, corresponding to a strong geomagnetic storm. Kp index levels range from 0 (quiet) to 9 (intense).

In the early morning hours of Nov. 4, aurora watchers across the Northern Hemisphere documented the results. The animated gif below shows the aurora over Utah, captured by NASA JPL producer Bill Dunford on Nov. 4 between 1:30-1:42 a.m. MDT.

aurora borealis on the horizon
Aurora Borealis, or northern lights, as viewed from Utah on Nov. 4. Credit: NASA/Bill Dunford.

This geomagnetic storm is now over, but as Solar Cycle 25 picks up and the Sun becomes more active, there is sure to be more.

To see how such space weather may affect Earth, please visit NOAA’s Space Weather Prediction Center https://spaceweather.gov/, the U.S. government’s official source for space weather forecasts, watches, warnings, and alerts. NASA works as a research arm of the nation’s space weather effort. NASA observes the Sun and our space environment constantly with a fleet of spacecraft that study everything from the Sun’s activity to the solar atmosphere, and to the particles and magnetic fields in the space surrounding Earth.

By Miles Hatfield
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Active October Sun Releases X-Class Flare

Brighter than a shimmering ghost, faster than the flick of a black cat’s tail, the Sun cast a spell in our direction, just in time for Halloween. This imagery captured by NASA’s Solar Dynamics Observatory covers a busy few days of activity between Oct. 25-28 that ended with a significant solar flare.

From late afternoon Oct. 25 through mid-morning Oct. 26, an active region on the left limb of the Sun flickered with a series of small flares and petal-like eruptions of solar material.

Meanwhile, the Sun was sporting more active regions at its lower center, directly facing Earth. On Oct. 28, the biggest of these released a significant flare, which peaked at 11:35 a.m. EDT.

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.

This flare was classified as an X1-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, and so on. Flares that are classified X10 or stronger are considered unusually intense.

This was the second X-class flare of Solar Cycle 25, which began in Dec. 2019. A new solar cycle comes roughly every 11 years. Over the course of each cycle, the Sun transitions from relatively calm to active and stormy, and then quiet again; at its peak, known as solar maximum, the Sun’s magnetic poles flip.

Two other eruptions blew off the Sun from this active region: an eruption of solar material called a coronal mass ejection and an invisible swarm of solar energetic particles. These are high-energy charged particles accelerated by solar eruptions.

NASA’s fleet of Heliophysics missions keeps constant watch on the Sun and space to help us understand what causes such eruptions on the Sun, as well as how this activity affects space, including near Earth, where it can impact astronauts and satellites.

To download this video, visit NASA’s Scientific Visualization Studio.

By Lina Tran
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Sun Releases Significant Solar Flare

The Sun emitted a significant solar flare peaking at 11:35 a.m. EDT on Oct. 28, 2021. NASA’s Solar Dynamics Observatory, which watches the Sun constantly, captured an image of the event.

A satellite image of the Sun, colored in teal, shows a bright flare at the Sun's lower center.
NASA’s Solar Dynamics Observatory captured this image of a solar flare — as seen in the bright flash at the Sun’s lower center — on Oct. 28, 2021. The image shows a subset of extreme ultraviolet light that highlights the extremely hot material in flares and which is colorized here in teal. Credit: 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.

This flare is classified as an X1-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. Flares that are classified X10 or stronger are considered unusually intense.

To see how such space weather may affect Earth, please visit NOAA’s Space Weather Prediction Center https://spaceweather.gov/, the U.S. government’s official source for space weather forecasts, watches, warnings, and alerts. NASA works as the research arm of the nation’s space weather effort. NASA observes the Sun and our space environment constantly with a fleet of spacecraft that study everything from the Sun’s activity to the solar atmosphere, and to the particles and magnetic fields in the space surrounding Earth.

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 http://spaceweather.gov 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 http://spaceweather.gov, 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.

Coronal Holes and Fast Solar Wind

The dark spot across the north pole of the Sun – as captured in this image on July 31, 2020, from NASA’s Solar Dynamics Observatory, or SDO – is an area of relatively cooler material in the solar atmosphere, known as a coronal hole. Coronal holes are regions on the Sun where the magnetic field is open to interplanetary space, sending solar material speeding out in a high-speed stream of solar wind.  (The extreme ultraviolet light in this SDO image is normally invisible to the eye, but is colorized here in bronze.)

In this case, instruments such as those on NOAA’s DSCOVR spacecraft observed a high-speed stream arrival on Aug. 2. and climb in speed over the next couple days, as can be seen in the graph of the solar wind speed shown here.

Coronal holes appear throughout the Sun’s approximately-11-year solar cycle, but can last for much longer periods of time during solar minimum – a period of time when activity on the Sun is substantially diminished, and which the Sun is just beginning to wake up from now.

 

 

New Sunspots Potentially Herald Increased Solar Activity

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.

A satellite image of the Sun, colorized in gold. A bright spot of light hovers over the left horizon.
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.

Read this story on the NASA homepage.