CH HSS sparks isolated periods of G1 geomagnetic storming

Our planet is under the influence of a coronal hole high speed stream (CH HSS) which is causing isolated periods of G1 – Minor geomagnetic storming over the past 2 days, August 17 and 18, 2017. Meanwhile, solar activity is very low. There is only one numbered active region on the Earth-side of the Sun and it's only showing B-class activity.

Over the past 24 hours, the greater than 2 MeV electron flux was at normal to moderate levels due to electron redistribution associated with CIR arrival and CH HSS onset. It is expected to be at normal to moderate levels on August 18 and increase to moderate to high levels due to continued CH HSS influence. The greater than 10 MeV proton flux was at background levels and is expected to remain like that over the next three days.

Solar wind parameters were indicative of CH HSS influences. Solar wind speeds increased to maximum speeds averaging near 600 km/s. Total field strength underwent a steady decreasing trend, from values near 10 nT to 6 nT. The Bz component settled to +/- 4 nT. The phi angle was positive.

Solar wind environment is expected to remain enhanced during the next three days (August 18 – 20).

The geomagnetic field was mostly quiet to active over the past 24 hours, with isolated periods of G1 – Minor storm levels. It is expected to be unsettled to active with isolated periods of G1 storming likely on August 18 as CH HSS influences continue.

Unsettled to active levels are expected on August 19 and 20 as CH HSS effects diminish.

Featured image: Geoeffective coronal hole on August 15, 2017. Credit: NASA SDO/AIA,  LMSAL