Wednesday, March 18, 2015

Sun Fart

Our geomagnetic field is currently doing a song and dance with old Sol.

Via The Watchers:
A sequence of events led to an Earth-directed asymmetric halo CME on March 15, 2015. The events began with a 14 degree long filament eruption, centered near S24W38, lifting off between 00:45 to 02:00 UTC. This was followed by C2.4 flare at 00:41 UTC and a long duration C9.1 at 02:13 UTC, both from Region 2297. 
Associated with the C9.1 flare were low-frequency radio emissions including Type II (estimated velocity 745 km/s) and Type IV radio sweeps. WSA/ENLIL modelling showed an approximate arrival time around 20:00 on March 17. However, it appears this CME arrived some 16 hours earlier (see update #2).
An interplanetary shock wave arrived at the ACE spacecraft around 04:15 UTC and at Earth a half hour later.Geomagnetic K-index of 5 (G1 - Minor) threshold was reached at 05:59 UTC. Potential impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude. Weak power grid fluctuations can occur. Minor impact on satellite operations are possible. Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
A G2 - Moderate geomagnetic storm warning has been issued based on solar wind signatures at the ACE spacecraft. Under G2 conditions, area of impact is primarily poleward of 55 degrees Geomagnetic Latitude. Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms. Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible. HF (high frequency) radio propagation can fade at higher latitudes. Aurora may be seen as low as New York to Wisconsin to Washington state.
Update #1: 
Geomagnetic K-index of 6 (G2 Moderate geomagnetic storm) threshold was reached at 08:46 UTC.
Update #2:
Initial SWPC's diagnosis suggested the arrival of the anticipated CME from March 15, however, the subsequent temperature and density measurements pointed towards a recurrent negative polarity coronal hole high speed solar wind stream (CH HSS). 
The disturbed conditions may be the combined effects of the high speed stream and CME.
Geomagnetic K-index of 7 or greater (G3 or greater - Strong to Extreme) is expected as the impacts from today's shock continue. 
Update #3:
Geomagnetic K-index of 8 (G4 Severe) threshold was reached at 13:58 UTC. 
I wasn't on the radio at all this afternoon (17-Mar) so I can't say how the conditions on the higher bands were. Tonight (18-Mar @ 0300 UTC) 40m has a noise level at S3, with occasional crashes as high as S5. The A index was 100 earlier, currently 117 with a K of 6.

9Q0HQ (Dem. Rep. of Congo) is about S4 on 40m, maybe a little weaker than they've been this past week but still readable; 7QAA (Malawi) is a bit stronger at S5 on 40m and about S4 on 30m. Oddly, hardly any other stations heard on 30m at this time other than a few stateside ops, but there are a few EU signals on 40m.

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