After several weeks of relatively calm solar activity, the Sun surprized space weather forecasters with an X1.1 flare peaking at 15:21UTC (GOES; graph). The source of this X1.1 flare seems to be close to the east solar limb and is apparently related to the eruption of a small filament just behind NOAA 4046 which is all-in-all a simple sunspot region at this time. The eruption subsequently interacted with a nearby prominence located to the north thus producing an impressive coronal mass ejection (CME). The GOES/SUVI 304 imagery underneath shows the eruption in extreme ultraviolet at temperatures near 80,000 degrees. The next clip is at a much lower cadence and zooms in on the blast site with SUVI 195 imagery (temperatures around 1 million degrees) overlaid with GONG H-alpha imagery (annotated pre-flare image). A SUVI 195 clip without the H-alpha overlaid can be found here.
Based on the currently available imagery as well as the source of the eruption, this CME does not seem to have an earth-directed component. Underneath is an image of the SOHO/LASCO C2 coronagraph showing the complexity of the associated CME. Standing-by further coronagraphic imagery. UPDATED (31 March): Further analysis by the SIDC forecaster (see this clip) revealed that the bulk of the CME was directed away from the Earth, but that there remained a small possibility of a glancing blow from this partial halo CME. A small shock was observed around 10:16 UTC on 31 March, likely associated with a partial-halo coronal mass ejection observed on 28 March. Geomagnetic conditions are expected to become disturbed, with active to minor storm levels possible depending on the Bz component.
The greater than 10 MeV proton flux has remained at background levels so far, well below the alert threshold of 10 pfu (GOES). UPDATED (31 March): The greater than 10 MeV GOES proton flux exceeded the 10pfu threshold, reaching a maximum value of 10.5 pfu as measured by GOES-18 at 11:05 UTC on 31 March. This is probably related to the partial halo coronal mass ejection observed on 28 March. There are currently no reports of a Type II radio burst in the NOAA/USAF events report, but the Owens Valley Solar Array (OVSA) recorded a Type II burst as can be seen in the radio spectrogram underneath (Horizontal axis: time; vertical axis: frequency, with highest values on top). OVSA and the NOAA/USAF network recorded modest radio emission over a very broad range of frequencies including 2695 MHz (380 sfu). As a result, the 17UTC Penticton 10.7cm radio flux value (NRCan) seems to have been mildly affected by the radio emission of this flare, i.e. about 10 to 15 sfu higher than the expected value. Influence on the 20UTC value is thought to be even lower, barring radio emission from any new strong flares. The source location of the X-class flare merits further observation as it rotates onto the solar disk. Pending its complexity, further strong flaring is possible.
The X-class flare affected the lower frequency portion of the High Frequency communication band (HF Com ; 3-30 MHz) mainly over South-America, the Atlantic Ocean, the eastern portion of the USA, and the western portion of Europe and Africa. This can be seen on the D-RAP map underneath (NOAA/SWPC). An advisory to civil aviation has been issued (PECASUS/CRC).
