Filament eruption produces partial-halo CME, glancing blow expected


A solar filament eruption took place shortly before 12:00 UTC on February 20, 2021producing a partial-halo CME. Analysis suggests a glancing blow from the periphery of the CME is likely on February 23 or 24.

The CME signature was first observed in SOHO/LASCO C2 imagery beginning at 12:00 UTC on February 20.

Analysis and modeling of the event suggest the bulk of the plasma is headed downstream of Earth. However, a glancing blow from the periphery of the CME is likely on February 23 or 24, SWPC forecasters said.

Unsettled to active geomagnetic field levels are likely as a result, with a chance for isolated G1 – Minor storm conditions.

Solar wind parameters in 24 hours to 00:30 UTC on February 22, were reflective of negative polarity coronal hole high speed stream (CH HSS) influence with speeds between 525 – 600 km/s. 

Total field generally ranged from 4 – 7 nT while the Bz component remained mostly southward to -5 to -6 nT. Phi was in a predominately negative solar sector.

Solar wind speeds are expected to remain enhanced through February 24, with the  CH HSS influences expected to begin to wane on February 22.

The geomagnetic field was at unsettled to active levels due to CH HSS influences over the past 36 hours and is expected to be at quiet to unsettled levels, with isolated periods of active possible, on February 22 as CH HSS influences begin to wane. 

Unsettled to active levels are likely on February 23 and 24, with a chance for isolated G1 – Minor storm conditions, due to the anticipated arrival of the February 20 CME.

Featured image credit: NASA/SDO AIA 304


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