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X1.7 solar flare – the 7th largest in Solar Cycle 24


Earth-orbiting satellites detected a powerful X1.7 solar flare today, January 27, at 18:37 UTC. The source was departing sunspot 1402 which rotate onto the far side of the sun, so the blast site was not Earth directedGoddard Space Weather Lab’s analysists say the CME cloud raced away from the sun at 2500 km/s or 5.6 million mph. 


An R3 Level Radio Blackout resulted, which led to the fading of HF signals on the sunlit side of Earth. Signals have since recovered but proton levels are on the rise again and the Moderate S2 level Radiation Storm threshold has been reached. Most proton storms take two or more hours from the time of visual detection to reach Earth’s orbit. This event generated Type II and Type IV sweep frequency events. A 10cm Radio Burst (TenFlare) lasting 37 minutes was observed and measured 810 pfu.


Even though the flare peaked and quickly subsided, the proton flux at GOES as risen substantially.  A flare at the limb shouldn’t produce a large increase in the proton flux, but this one did according to Solar Dynamics Observatory (SDO)

Full Halo coronal mass ejection (CME) is seen in the latest Lasco and STEREO Ahead COR2 images. Due to the spots location, initial indications appear that it is directed to the west.

STEREO Ahead and STEREO Behind images (Source: STEREO) SOHO’s LASCO C2 and LASCO C3 images (Source: SOHO) Image sequence of SOHO’s LASCO C2 show recent X-class solar flare eruption

Let’s not forget, last year we had 8 X-class solar  flare events. SolarHam made the  top 10 list of Solar Flares during Solar Cycle 24. Today’s X1.7  ranks #7. Below is the updated Top 10 list of solar flares during Cycle 24 and is organized by Size, Date, Year and Sunspot number.

X6.9 – August 9 2011 (1263)
X2.2 – February 15 2011 (1158)
X2.1 – September 6 2011 (1283)
X1.9 – November 3 2011 (1339)
X1.9 – September 24 2011 (1302)
X1.8 – September 7 2011 (1283)
X1.7 – January 27 2012 (1402)
X1.5 – March 9 2011 (1166)
X1.4 – September 22 2011 (1302)
M9.3 – August 4 2011 (1261)

The soft X-ray flux of X class flares increases the ionization of the upper atmosphere, which can interfere with short-wave radio communication and can heat the outer atmosphere and thus increase the drag on low orbiting satellites, leading to orbital decay. Energetic particles in the magnetosphere contribute to the aurora borealis and aurora australis. Energy in the form of hard x-rays can be damaging to spacecraft electronics and are generally the result of large plasma ejection in the upper chromosphere.


A solar wind stream is heading for Earth, due to arrive on Jan. 28-29. NOAA forecasters estimate a 15% chance of geomagnetic storms at high latitudes. S2-Solar Radiation storms are in effect. R3 Radio Blackouts were observed at around 1830Z. Also, Protons, greater than 100 MeV, are above the 1 pfu threshold.  A CME was also observed, associated with this event, however initial analysis shows this CME as not being Earth directed.

Joint USAF/NOAA Report of Solar and Geophysical Activity (27 Jan 2012)
Solar activity was high. Region 1402 (N29W88) produced an X1/1f flare at 27/1837Z with associated Type II (est. speed 1523 km/s) and Type IV Radio Sweeps, along with an 810 pfu Tenflare. An associated CME was first visible in SOHO/LASCO C2 imagery at 27/1827Z. The majority of the ejecta is directed towards the STEREO A spacecraft, however, further analysis is necessary to determine potential geoeffectiveness.Solar activity is expected to be low on day one (28 January) with a chance for isolated M-class activity as Region 1402 rotates around the west limb. Activity is expected to be very low to low on days two and three (29-30 January).

The geomagnetic field was quiet to unsettled with isolated active periods observed at mid-latitudes and an isolated minor storm period observed at high latitudes. The increase in activity is due to the arrival of a recurrent coronal hole high speed stream (CH HSS). The greater than 10 MeV and greater than 100 MeV proton flux at geosynchronous orbit were above event threshold during the period due to the X1 flare mentioned above. The greater than 10 MeV proton event, which began at 27/1905Z and reached 96 pfu at the time of this writing, is still in progress. The greater than 100 MeV proton event, which began at 27/1900Z and reached 11 pfu at the time of this writing, is also still in progress. The Penticton 10.7 cm flux value was enhanced due to the X1 flare mentioned above. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels during the period. The geomagnetic field is expected to be quiet to unsettled on day one (28 January) due to continued effects from the CH HSS. Mostly quiet conditions are expected for days two and three (29-30 January). The greater than 10 MeV and 100 MeV proton events are expected to continue on day one. A more reliable end time will be possible once the peak levels are observed.

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