UPDATED - Please scroll down
NOAA 3842 rotated over the southeast solar limb on 27 September, gradually growing in size and complexity. It developed an important magnetic delta structure in its leading spot as shown in the white light image and magnetogram underneath resp. left and right (SDO).
Following an M7 flare late on 30 September, this region produced an X7.1 flare on 1 October peaking at 22:20UTC (GOES). This is the second strongest flare so far this solar cycle (SC25). The extreme ultraviolet (EUV) imagery underneath to the right is from SDO/AIA 094 and shows the X7.1 flare near the time of its maximum. The blooming and diffraction patterns that can be seen in this image are instrumental (more information is in Note 1 of this STCE newsitem).
The greater than 10 MeV proton flux is still at background levels. The flaring event was also the source of a radio disturbance especially at all observed frequencies (NOAA/USAF network). Coronagraphic imagery by SOHO and STEREO-A show a CME directed to the southeast. In view of the location of the source region and the CME's width, it's virtually certain that this CME has an earth-directed component (see the SIDC website for further updates). Further strong flaring from NOAA 3842 over the next few days is very likely, with a chance on an earth-directed CME as well as an increasing chance on a proton event as the active region moves into the western solar hemisphere.
The X-class flare affected HF communications (3-30 MHz) mainly over the Pacific Ocean. This can be seen on the D-RAP map underneath (NOAA/SWPC). An advisory to civil aviation has been issued (PECASUS ).
UPDATES
UPDATE 3 October 2024 at 17:00UTC - NOAA 3842 has just produced the strongest flare of solar cycle 25 (SC25). The X9.0 flare peaked at 12:18UTC today 3 October (GOES ; JSON). This was already the second strong X-class flare in as many days by this sunspot group which still has a strong magnetic delta structure in its leading portion. The SDO/AIA 094 imagery underneath shows the eruption in extreme ultraviolet (EUV). The blooming and diffraction patterns that can be seen in the GOES/SUVI 131 images are instrumental (more information is in Note 1 of this STCE newsitem).
The greater than 10 MeV proton flux is still at background levels. The flaring event was also the source of a radio disturbance especially at all observed frequencies (NOAA/USAF network). It was especially strong at 410 MHz (160.000 sfu!) and also at 245 MHz (43.000 sfu), and also affected the 10.7cm radio flux. The radio astronomy station at Humain (HuRAS) recorded a Type II and Type IV radio burst, as shown in the radio spectrogram underneath.
Coronagraphic imagery by SOHO and STEREO-A show a halo CME, and is directed to Earth, with an expected arrival on 5 or 6 October. Standing-by further analysis by the SIDC forecaster (see SIDC website for further updates). The imagery underneath combines EUV imagery from SDO with coronagraphic images from SOHO/LASCO C2. Further strong flaring from NOAA 3842 over the next few days is very likely, with a chance on an earth-directed CME as well as an increasing chance on a proton event as the active region advances further into the western solar hemisphere.
The X-class flare affected HF communications (3-30 MHz) over most of Africa, the mid- and south-Atlantic Ocean, and east Brazil. This can be seen on the D-RAP map underneath (NOAA/SWPC). An advisory to civil aviation has been issued (PECASUS). Associated with this flare, some magnetometer stations on the daylight side of the Earth such as on Tenerife (Spain), in Tamanrasset (Algeria) and on Tatuoca (Brazil) registered a strong solar flare effect (SFE) of 50-75 nT pending their location to the subsolar point (Intermagnet (BGS)). For comparison, the Carrington flare showed an SFE of 110 nT (Cliver & Svalgaard, 2004). An SFE happens when one or more components of the magnetic field strength shows a spike around the time of the flare's peak due to ionospheric enhancement by the flare's x-ray and (E)UV radiation (also known as a "magnetic crochet").
