GONG data processing update

 Processing of the network-merged daily velocity and magnetogram images,  p-mode-coefficient time series, and ring-diagram analysis products for GONG month 313,  and  the  p-mode frequency data products for central GONG month 312 is completed and the data products are now available.

Solar Activity Report: May 18 - 24, 2026

 Solar activity at the beginning of the week was at low levels, with the X‑ray flux holding in the B range except for a few low‑intensity C‑class flares. Activity dipped even further on 20 May, when the flux remained entirely below the B–C threshold. By mid‑day on 21 May, conditions shifted. Activity rose following three short‑duration, high‑intensity impulsive C‑class flares from Active Region 14436 as it approached the northwest limb: C5.6, C8.3, and C9.5. A more substantial increase occurred on 22 May, when an M2.3 flare erupted from just beyond the northwest limb, near the same active region, pushing activity into the moderate range. On 23 May, a series of low and medium intensity C‑class flares were recorded and the week concluded with low flaring activity. Most of the flaring during the last two days originated from newly emerged Active Region 14446 near the southeast limb. Multiple CMEs were observed in coronagraph imagery, but none were Earth‑directed.

Helioseismic map of the far hemisphere (see the attached pictures) reveals two strong active regions, marked by while circles, forecast to return to Earth view on 27 and 31 May.  A third region, marked by a red circle, shows a detectable helioseismic signature, but its probability of appearance remains below our confidence threshold. If it continues to strengthen, it should reach the east limb on 29 May. The far‑side active region mentioned in last week’s report has now rotated onto the front side and has been assigned NOAA 14446.

Small flare near solar central meridian

 Not all solar flares are large. This example shows a relatively weak flare (X-ray C1.3 class), which erupted from active region 14439 on 22 May 2026. The flare started at about 4:38 UT and peaked at 4:50 UT.  C-class flares are typically not associated with the Coronal Mass Ejections (CMEs). GONG at Learmonth, Australia captured the flare with its H-alpha instrument, as shown in this short video (4:20 UT - 7:12 UT)

 

GONG Network Window Function

Last week, NISP Data Center has been working on re-instating the GONG network window function monthly plots that were generated and discontinued a few years ago. Once completed, the window function plots would be available at https://gong.nso.edu/data/merged/gong+_merged_plots.html. Example of old-format window function for the month of April, 2026 is shown below. For each day of the month, red-colored bars represent periods with network observations. Gaps shown in the white color are periods without observations. The impact of missing observations from GONG at Mauna Loa observatory is clearly visible as larger data gaps in late (20-24 UT)  and early (0-4 UT) periods of the day. Numbers of the right side of the plot show average daily duty cycle (% of 24 hour period with observations). Even with one station down, the network still meets the required duty cycle. 

Solar Activity Report: May 11 - 17, 2026

 Solar activity during the reporting period remained mostly at low levels, rising to moderate levels at the end of the week when several low‑intensity M‑class flares were produced. The X‑ray flux generally stayed in the B range, with only a few low‑level C‑class flares until May 13. Activity then increased gradually, with medium‑ to high‑intensity C‑class flares, followed by four M‑class flares on May 16 and 17. The strongest events were two M1.9 flares on May 16. The remaining M‑class flares were an M1.3 on May 16 and an M1.7 on May 17. These events originated from active regions 14435 and 14436, with AR 14436 also producing a C9.7 flare on May 17. No Earth‑directed CMEs were detected during this period.

The latest helioseismic map of the Sun’s far side (see attached image) shows a large active region in the southern hemisphere that has continued to strengthen since it first appeared. It is visible in the image as a prominent bright spot. It is expected to rotate onto the East limb late on May 23. This substantial region has also been observed by ESA’s Solar Orbiter and NASA’s Perseverance rover, both of which currently have partial views of the Sun’s far hemisphere. Solar Orbiter has already detected a couple of X‑class flares and nearly a dozen M‑class flares over the past three days. If the region maintains its magnetic structure and continues to intensify, solar activity levels are likely to increase toward the end of the week.

Solar M5.8 class flare as observed by GONG

 Video: Niles Oien, NSO

 A major solar flare of X-ray class M5.8 erupted on May 10, 2026 from active region 14436 near the solar East limb (N19E65). M- and X-class flares are some of the most energetic solar events, typically associated with the coronal mass ejections (CMEs). However, CMEs originating near solar East limb are less likely to impact the Earth.  Attached video shows the development of this flare as observed by GONG H-alpha at Cerro Tololo, Chile.

  

A Recent Visitor to the Boulder GONG Farm

When a cloud is not a cloud! Roosting birds like this visiting hawk can cause a false cloud indication in the site's pyranometer data (see large dip in intensity plot on the right). Pyranometer is a device to measure the amount of sunlight at each site from the sunrise (left side of the plot), noon (peak), and sunset (right side of the plot). Clouds appear as dips in this otherwise a smooth plot. Colloquially, GONG engineering site (in Boulder, Colorado) is often referred to as "GONG farm". This originates in early period of GONG development, when the test site was set up on the grounds on the Agricultural Experiment Station of the University of Arizona in Tucson.

  

Photo: Detrick Branston / NSO