The Sun was pretty active so far in November considering we are still far away from solar maximum. The month started with an interplanetary shock (IPS) due to high speed stream (HSS). On the first day of the month, there were several M class solar flares and C type CMEs. The second day, while the HSS was still present, an O type "Cannibal CME" with the speed of 1150 km/s has been observed. The reason it is called "Cannibal CME" is that this O type Halo CME, catch the earlier two C type slower CMEs and it added them to itself and created a powerful CME with a complex magnetic field and plasma. Since this process is like eating the slower CMEs, this type of CMEs are called Cannibal CMEs. This CME caused IPS, solar energetic particles (SEP), magnetopause crossing and a geomagnetic storm with a maximum Kp 7.
(SOHO LASCO c2, 2021)
The next day on November 4, the Sun was quiet until another O type CME with a speed of 1310 km/s on November 9. Fortunately that CME was not Earth-directed. Later on November 16, solar wind speed increased up to 600 km/s and since then, the solar wind speed has been around 500-600 km/s.
Within the last 24 hours, the solar activity was at very low levels. There is 22 active regions, yet there was no significant solar flares. One C type CME with a speed of 551 km/s has been observed via SOHO LASCO C2 coronograph at 13:48 UTC on 18 November, yet it was not Earth-directed. The HSS caused by the two coronal holes at the South pole and South hemisphere has been started to decay. The maximum strength of the southward IMF was -2.6 nT. The minimum magnetopause standoff distance was 8 Re. The maximum Kp index var 1. Geomagnetic indices Dst and AE indicated quiet conditions aswell. The F10.7 radio flux was 82 sfu which is normal during the ascending phase of the solar cycle.
Solar activity is expected to remain at low levels in the following days. No CME arrivals are expected since the latest CME on 18 November was not Earth-directed. ASSA flare model predicts the occurencepossibility of C, M and X class flares as 19%, 2% and 0% respectively. Solar wind speed is expected decrease to nominal levels.
Forecaster: Ezgi Gülay
MSc. Student
Faculty of Aeronautics and Astronautics, ITU
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