Sun activity: Wavelengths and temperatures

A grid of four animated colored globes from right to left, top to bottom. Red, gold, pink, and teal
Sun activity for September 9-10, 2023. A grid of 4 different images, at different wavelengths. From top to bottom, left to right, 304, 171, 211 and 131 angstroms. Images via SDO and JHelioviewer.

Sun Conditions on September 10, 2023: Spectral Bands and Temperatures

We’re approaching another peak in the 11-year solar cycle! Today’s top news: Happy Solar Year Day. The past day has been relatively calm, yet the animated set of four images shows different layers and temperatures of the sun at wavelengths. On the right side (southeast) and north, there are long dark structures, which are filaments of the sun. The red color represents temperatures of approximately 80,000 degrees Celsius (304 angstroms). The bright areas with sunspots and loops coming out are shown in gold, representing temperatures of around 100,000 degrees Celsius (171 angstroms). The dark areas in the south and north are coronal holes, with temperatures of 2 million degrees Celsius (211 angstroms) shown in pink. The bright flashes are solar flares, with temperatures of 10 million degrees Celsius (131 angstroms) shown in teal in the last image. Now, compare the large visible yellow sunspot image to the gold image. As we look higher at the layers of the sun (from the photosphere, visible light at 304 angstroms, to the chromosphere at 211, 171, and 131 angstroms), we see higher temperatures and shorter wavelengths. This highlights the famous coronal heating problem: why does the sun get hotter as you move away from its surface? Yesterday, from 11 UTC to 11 UTC, there was a C8.3 flare from the active region AR3423, including five C flares. We saw 14 C flares in the past day, with the largest being the C8.3 flare. Currently, the sun has five numbered active regions. Today’s forecast indicates a 5% chance of X flares, a 45% chance of M flares, and a 99% chance of C flares. No coronal mass ejections (CMEs) directed towards Earth have been observed in the available imagery. The magnetic field of Earth is quiet at the time of writing this (11 UTC on September 10). The geomagnetic field is expected to be quiet to unsettled on September 11 and tomorrow. However, due to the onset of high-speed solar wind from a coronal hole, active conditions are likely to increase on September 12.

The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 6 UTC on September 10, 2023. Original image, without labels, via NASA SDO. Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky. Today’s sun is posted by Armando Caussade. Why are east and west on the sun reversed?

Solar Events on September 9, 2023: A serpentine prominence and a nearly M-class flare

Currently, the sun has five active numbered regions. AR3425 released four flares, including the C8.5 flare. AR3421, on the other hand, produced seven flares, making it the first-place winner. However, both AR3425 and AR3421 were active producers of flares in the past day. The largest flare, a C8.5, occurred in the active region AR3421 at 01:20 UTC on September 9. We observed 14 C-class flares from 11:00 UTC to 11:00 UTC yesterday. Sun activity has decreased lately. It seems that the explosion must have occurred on the far side of the sun, as there was no associated event visible on the Earth-facing side. A full-halo event was observed by LASCO and SOHO at 11:54 UTC (C3) and 11:36 UTC (C2). Some faint ejecta from the blast could be seen blasting into space, as registered by the 304 angstrom SUVI on GOES-16. At 18:19 UTC on September, a C2.6 flare was associated with this event. Take a look at our top animation, which depicts the active prominence/filament that looked like an undulating snake in space. There was very little associated ejecta with the flares in the past day. The AR3425 sunspot continued flaring throughout the day.

Sun activity for September 8-9, 2023. Sunspot active region AR3425 continued blasting flares and hurling ejecta into space. The prominence product of one explosion was an unusual snake-like prominence, with in its path going into space. GOES-16 SUVI image via NOAA.
September 9, 2023. Sun activity is back to low, but sunspot AR3421 is trying to bring it out into moderate levels. Earlier today, it blasted a flare so very close to the boundaries of the Ms. A C8.5 flare exploded at 01:20 UTC on September 9 by AR3421. GOES-16 SUVI 304 angstrom. Image via NOAA.
September 8, 2023. LASCO C3 registered a full-halo event, starting at around 11:54 UTC. Specialists confirm there is no activity in the Earth-viewed side of our star related to this event. So this strong activity must have occurred on the far side. Image via NOAA.

Sun’s Activity on September 8, 2023: The Arrival of a New Sunspot Makes a Dramatic Entrance

Currently, the sun has seven active regions, including the newcomer AR3425, which fired four flares, including the lead producer flare, Flare M. This flare caused a minor R1 radio blackout over the Pacific Ocean off the west coast of Mexico. Between yesterday UTC 11 and today UTC 11, the sun blasted 18 flares, including the aforementioned Flare M and 17 C-class flares. This flare was the largest of the past day. Sun activity is back to moderate thanks to AR3245’s flare on September 7 at UTC 19:09. We are waiting for further analysis to know if it will collide with Earth if it is part of any CME with a speed of approximately 2381 km/s. Additionally, the blast created a type II radio burst, which is very useful as it can provide an estimate of the CME’s speed. You can see the coronal mass ejection’s ejection mass in the imagery from the C3 and C2 LASCO spacecrafts on SOHO. Both the GOES-16 satellite and the Solar Dynamics Observatory (SDO) observed the ejecta being fired out into space. Shortly after, it fired off an impressive M2.1 flare with an eruption of an impressive filament. The newcomer sunspot group, AR3425, has introduced itself with a bang, raising sun activity to moderate.

animated sequence of four images in a grid, from top to bottom, left to right, red, gold, pink, teal
Sun activity for September 7-8, 2023. AR3425 released an M2.1 flare with a filament eruption, producing a CME with a speed of around 1200 km/s. The event was observed by SDO in 304, 171, 211, and 131 angstroms. Image via SDO and JHelioviewer.
September 7, 2023. Sun activity is moderate after an M2.1 flare by sunspot AR3425. This newcomer said hello and hurled this superb filament into space. GOES-16 SUVI 304 angstrom. Image via NOAA.
September 7, 2023. Newcomer AR3425 opened its account with an M2.1 flare at 19:09 UTC on September 7. The explosion provoked on Earth an R1 (minor) radio blackout. AIA 131 angstrom. Image via SDO.
September 7, 2023. LASCO C2 registered this dramatic imagery of AR3425’s M2.1 flare. Image via NOAA.

Sun’s Activity on September 7, 2023: Sunspots Accelerate, Additional Ones Expected

AR3425 has now been labeled and has rotated into view, the illuminated area that we observed approaching from the northeast yesterday. Today, the sun has a total of eight active regions, each numbered accordingly. During this period, it discharged a total of eight out of the 16 flares. Despite this, it continued to maintain its position as the primary producer of flares, while the aforementioned region experienced a decrease in both size and magnetic complexity over the previous day. The most significant flare recorded was a C5.3, which occurred at 17:56 UTC on September 6, originating from AR3421. Over the course of the past day, the sun generated a total of 16 C flares (11 UTC yesterday and 11 UTC today). However, it is worth noting that the overall solar activity remains low, with only C flares observed within the past 24 hours. These eruptions are believed to have transpired on the far side of the sun, as experts failed to identify any flares on the side facing Earth that could account for these outbursts. To gain further insight, make sure to refer to the visuals below, which display several coronal mass ejections (CMEs) emanating from the sun in the form of magnificent halos, as observed by the SOHO spacecraft’s LASCO C3 instrument at approximately 14 UTC on September 5. It is crucial to acknowledge that helioseismology is not the sole method employed to monitor activity on the concealed side of the sun. As we approach the period when this portion of our star becomes visible from Earth, helioseismology has already identified a substantial region on the far side. It is plausible that these phenomena were generated by sunspot regions that will soon come into view, as evidenced by the presence of multiple sets of coronal loops (bright arcs of plasma propelled by the sun’s magnetic fields) protruding from the sun in the eastern direction. Furthermore, it appears that additional sunspots are anticipated, particularly evident in AR3423 located in the northeast, which has exhibited significant growth compared to the previous day. These newly formed sunspot regions have demonstrated an increase in flare productivity and are expanding in size. After focusing on filaments yesterday, sunspots are now reclaiming the spotlight.

An animated globe showing the left side and middle quarter in gold overlying blue/while.
Sun activity for September 6-7, 2023. Sun activity is considered low today, as we’ve only observed C flares. However, the newest sunspot regions have been growing in size and also picking up in terms of flare quantity. There are several sets of coronal loops on the east limb (edge), presumably coming from new regions over the limb. This view is shown clearly through the SDO 171 angstrom wavelength. This has been overlaid with SDO 1600 angstrom images that show both the sunspots and the magnetic network over the solar disk. Images via SDO and JHelioviewer.
September 6, 2023. Sun activity included exploding filaments all over the face of the Earth-viewed solar disk. If we could see these explosions from the side, some would appear as gorgeous prominences lifting off the limb (edge). AIA 304 angstrom. Image via SDO.
September 7, 2023. The west limb (edge) granted us dancing prominences. These are from active regions that have recently rotated out of view, and so you might think of them as reminiscences of past glories… GOES-18 SUVI 304 angstrom. Image via NOAA
September 5, 2023. LASCO C3 registered a couple of explosions, and we saw coronal mass ejections that produced full halo events. This attracted the attention of specialists. No correlated activity was found on the Earth-viewed side of our star after modeling and analysis, thus proving that the activity came from the far side of the sun. LASCO C3. Image via NOAA

Solar Events on September 6, 2023: Spiraling, rhythmic prominence

Stay tuned! In the coming days, these strands might have been generated by sunspots that will become visible as the east side of the sun rotates towards us. We observed eruptions on the southeast edge and bright loops of filaments on the northeast edge. The most remarkable prominence witnessed in the past day was the twisting and erupting dance on the south pole, resembling a tornado, which propelled plasma into space. Prominences, also known as filaments, can be observed protruding beyond the edge of our star. While most of these filaments are visible around the star’s edge, some are erupting within the solar disk. Filaments, which are ropes of solar material arcing from the sun’s surface, are vibrant and active.

Located close to the limb in the northeast, there is a new kid on the block, AR3424. Today, the sun has eight active regions numbered. Ten out of the twelve flares fired, obtaining the prize once again for the lead flare producer. However, AR3421 only produced flares of the M-class and did not produce any flares of the M-class. The second blackout occurred over the Pacific Ocean, south of Hawaii, and the first one affected an area off the west coast of California and Baja in the Pacific Ocean. This was caused by minor R1 radio blackouts produced by both M-class flares. Following this, at UTC 23:39, there was an M1.0 flare, which was then followed by the largest flare at UTC 19:45 in September, which was an M1.2 flare. Yesterday, there were ten C-class flares and two M-class flares, while today there were eleven flares, with one C-class flare and one M-class flare. Sun activity remains moderate in the last 24 hours.

The bottom part of a red sun over a black background shows prominences moving.
Sun activity for September 5, 2023. On the solar south pole we saw plasma whirling as a tornado-like, long-lasting prominence. GOES-18 SUVI 304 angstrom. Image via NOAA.
An upper left part of a red sun showing explosions.
September 6, 2023. In the northeast we can see a bright area coming into view. This could mean more action coming. GOES-18 SUVI 304 angstrom. Image via NOAA.
A teal round sun animation over a black background showing some bright spots.
September 5, 2023. Sun activity remains moderate with the production of two M flares. AR3421 is again the leading flare producer. This animation shows the M1.0 flare it fired at 23:39 UTC on September 5. GOES-18 SUVI 131 angstrom. Image via NOAA.

The sun’s activity on September 5, 2023 is moderate, with a total of 25 flares.

AR3423 and AR3422 are two new arrivals in the northeast. Currently, the sun has seven identified active regions. AR3421 was the main producer of flares for the day, generating nine flares, including the M flare. The aforementioned M flare from AR3421 caused a minor radio blackout (R1) over the Arabian Sea. This flare might actually be larger than C6.6 because it was partially blocked by the sun. Additionally, the former Earth-facing sunspot AR3413 maintained its activity from the northwest edge, releasing a C6.6 flare at 11:06 UTC on September 4. A fiery newcomer on the southeast edge discharged a C2.4 flare at 12:54 UTC on September 4, accompanied by a stunning filament eruption. The southeast region is exhibiting significant solar activity. In the past 24 hours (from 11 UTC yesterday to 11 UTC today), the sun produced a total of 25 flares: one M flare, 22 Cs flares, and 2 B flares. In the last 24 hours, solar activity has returned to moderate levels. Stay tuned for updates. This region could potentially be the next source of geoeffective events, such as mesmerizing auroral displays visible on Earth. Take a look at our imagery above to observe the development of AR3421. However, the delta region for AR3421 is not fully formed yet. As expected, solar activity has now increased. We have also observed the formation of a delta region, where a large cluster of magnetic field lines has pierced through the sun’s surface, creating the primary sunspot. Additionally, a smaller spot has emerged nearby, resulting in a magnetically complex region where particles become energized and can be forcefully expelled. This is currently the largest region on the sun as visible from Earth. Apart from producing the largest flare in the past day, it has grown rapidly since emerging near the center of the solar disk on September 3. This sunspot is quite intriguing. It has returned to moderate activity, producing a total of 25 flares in the past day, including an M2.0 flare from sunspot region AR3421. Last week, from our perspective on Earth, was relatively calm on the sun. It has completed just over a quarter-turn in its 27-day rotation. What does a week mean to the sun?

Sun activity for September 5, 2023. Since emerging 2 days ago, sunspot AR3421 has become the largest active region on the Earth-viewed solar disk! And it produced the biggest flare the past day, an M2.0 flare. Read more about it below. HMI Orange colorized image via SDO.
September 5, 2023. Sun activity is moderate with the production of an M2.0 flare at 8:12 UTC on September 5. It was released by sunspot AR3421. AIA 131 angstrom. Image via SDO.
September 4, 2023. A newcomer blasted a C2.4 flare at 12:54 UTC on September 4. The explosion developed into a fiery gorgeous prominence. Ejecta can be seen being sent into space, and we wait for specialists to report on whether any coronal mass ejection (CME) is coming our way. GOES-18 SUVI 304. Image via NOAA.
September 4, 2023. A C6.6 flare exploded at 11:06 UTC on September 4. It was blasted from beyond the limb (edge) on the northwest, and so there’s a good chance it was produced by the recently-departed AR3413. AIA 304 angstrom. Image via SDO.

The sun’s activity for September 4, 2023, is minimal. The season for auroras is approaching.

The sun has labeled six active regions. The largest flare, a C5.8, occurred at 12:03 UTC on September from sunspot AR3413. There were no Earth-directed CMEs, but the sun produced one B flare and 16 C flares today and yesterday, over the past day. Sun activity is low in the last 24 hours. If this combines with higher activity from CMEs directed towards our way, we can expect some spectacular auroras during the autumn season in 2023. This is why physicists call this time of the year the aurora season, as there are likely to be more auroral displays around the equinoxes in March and September. The September equinox is approaching. This is why physicists call this time of the year the aurora season, as there are likely to be more auroral displays around the equinoxes in March and September. The September equinox is approaching. While auroras are nice to see, their impact is weak. Some nice auroral displays were brought to us by the coronal mass ejections (CMEs) that hit on Saturday.

An animated golden globe rotating from left to right.
Sun activity for September 4, 2023 is back to low. Here are the last 24 hours on the sun as seen by the SWAP telescope on ESA’s PROBA2 mission. It views our star in the 174-angstrom wavelength of extreme ultraviolet light. Image via ESA.
The sun, seen as a large white sphere with small dark spots.
View at EarthSky Community Photos. | Patricio León in Santiago, Chile, captured this filtered image of the sun on September 3, 2023. Patricio wrote: “As for 2023 this is a ‘blank’ sun. No major sunspots at the Earth’s face, plus poor seeing in same weather.” Thank you, Patricio!
The sun, seen as a large yellow sphere with a mottled surface.
View at EarthSky Community Photos. | Mario Rana in Hampton, Virginia, captured this filtered image on September 3, 2023. Mario wrote: “Hydrogen-alpha image of the sun featuring active regions AR3417 and AR3418, along with some nice filaments and prominences.” Thank you, Mario!

The sunshine in the past few days

The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 3 UTC on September 9, 2023. Courtesy of NASA/ SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky.
The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 4 UTC on September 8, 2023. Courtesy of NASA/ SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky.
The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 3 UTC on September 7, 2023. Courtesy of NASA/ SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky.
The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 7 UTC on September 6, 2023. Courtesy of NASA/ SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky.
The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 0 UTC on September 5, 2023. Courtesy of NASA/ SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky.
The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 3 UTC on September 4, 2023. Courtesy of NASA/ SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky.
The sun, seen as a large yellow sphere with dark spots, each labeled.
This image shows sun activity – with the most active regions labeled – as of 5 UTC on September 3, 2023. Courtesy of NASA/ SDO and the AIA, EVE, and HMI science teams, with labeling by EarthSky.

Sun pictures from our community

We express our gratitude to those of you who have already shared a picture on our community page. Additionally, we greatly appreciate receiving your photographs! We warmly encourage all of you to submit your stunning and recent images of sunspots and auroras to us.

Please upload your photos here.

See community pictures here.

The sun, seen as a large yellow sphere with a mottled surface.
View at EarthSky Community Photos. | Mario Rana in Hampton, Virginia, captured this filtered image on September 8, 2023. Mario wrote: “Hydrogen-alpha image of the sun featuring active regions AR3425, AR3423 and AR3421.” Thank you, Mario!
The sun, seen as a large white sphere with small dark spots.
View at EarthSky Community Photos. | Patricio León in Santiago, Chile, captured this filtered image of the sun on September 7, 2023. Patricio wrote: “The sun has recovered presence thanks to complex sunspots AR3423 (left) and 3421; local cloudiness explains uneven disc illumination.” Thank you, Patricio!
The sun, seen as a sectional yellow sphere with a mottled surface.
View at EarthSky Community Photos. | Jim Militello in Tucson, Arizona, captured this hydrogen-alpha filtered image of the sun on September 2, 2023. Jim wrote: “Image shows active region 3417 and some nice prominences.” Thank you, Jim!

The Sun’s activity is relatively low on September 10, 2023. Today presents a favorable opportunity to observe the Sun across various wavelengths and temperatures.