A strong solar flare measuring M5.6 erupted from Active Region (AR) 4046 at 06:46 UTC on April 1, 2025. The event started at 06:37 and ended at 06:53 UTC.
A 10cm radio burst (Tenflare) was associated with this event. This type of burst indicates that the flux density of radio emissions at the 10cm wavelength (2.8 GHz) reached at least twice the background level, indicating an intense enhancement of solar radio output coinciding with the flare. Such emissions are typically short-lived but can produce significant radio noise, potentially interfering with sensitive systems, including radar, GNSS (GPS), and satellite communications.
No accompanying radio signatures were observed that would indicate a coronal mass ejection (CME) was produced. However, given the position of AR 4046 (beta-gamma configuration) in the northeastern quadrant, the potential for Earth-directed CMEs remains and may increase as the region rotates further into view.
Another region of interest is AR 4048, currently exhibiting a beta-gamma-delta magnetic configuration. It is a large, magnetically complex region moving into a geoeffective position and continues to display signs of growth, particularly within its intermediate polarity zone. This region will require close monitoring in the coming days.
The greater than 2 MeV electron flux was at moderate to high levels in 24 hours to 00:30 UTC today, with a peak flux of 2 040 pfu at 16:05 UTC on March 31. The greater than 10 MeV proton flux reached S1 – Minor levels at 11:05 UTC yesterday, with a current peak of 147 pfu at 04:25 UTC today. The enhancement is attributable to the X1.1 flare on March 28, according to the SWPC.
The S2 – Moderate solar radiation storm threshold was reached at 02:05 UTC today. At this level, the increased flux of energetic protons can result in minor radiation exposure for passengers and crew on high-latitude, high-altitude flights. Spaceborne assets may experience infrequent single-event upsets, particularly in sensitive electronic components. Additionally, polar high-frequency (HF) radio propagation may be subject to degradation, including signal fades at lower frequencies.
S2 solar radiation storms are moderate events, occurring approximately 25 times per 11-year solar cycle.
Solar wind parameters became weakly enhanced after 10:17 UTC on March 31 when a weak shock was observed at the ACE spacecraft, likely due to glancing effects from the X1.1 flare. The total field increased from 8 nT to 11 nT while the Bz component was between +9/-7 nT. Solar wind speed increased from approximately 416 km/s to averaging around 480 km/s while the phi angle was positive.
During the same period, the geomagnetic field was at quiet to unsettled levels.
Solar activity is expected to be moderate, with a 75% chance of M-class and a 25% chance of X-class solar flares through April 3.
The greater than 2 MeV electron flux is expected to continue at moderate to high levels through April 3. The greater than 10 MeV proton flux is expected to persist above the S1 – Minor threshold on April 2, with a chance for the levels to continue above the S1 level through April 3.
Solar wind parameters are expected to remain slightly enhanced due to the aforementioned CME influences combined with weak positive coronal hole high speed stream (CH HSS) influences. An additional weak enhancement is possible due to a CME that left the Sun on March 27. A trend towards a more nominal environment is anticipated on April 2 and 3.
References:
1 Forecast Discussion – SWPC – Issued at 00:30 UTC on April 1, 2025