Updated

Updated · spaceweather.gov · Aug 27

NOAA Issues G2 Geomagnetic Storm Watch for Aug. 28-29 as CME Effects Extend 2 Days

Updated

Updated · spaceweather.gov · Aug 27

NOAA Issues G2 Geomagnetic Storm Watch for Aug. 28-29 as CME Effects Extend 2 Days

Q: Will the incoming CME's magnetic field align perfectly to trigger unexpected satellite disruptions and rare auroras this Friday?

No one can say yet. Forecasts suggest this CME will likely deliver only a glancing blow to Earth around Friday morning, with an arrival window near 6–7 a.m. EDT and roughly seven hours of uncertainty, but the key variable is the CME’s magnetic field orientation when it reaches Earth. Scientists are watching for a southward-pointing magnetic field, because that is what couples most efficiently with Earth’s magnetosphere and can strengthen geomagnetic activity. That alignment cannot be confirmed far in advance; NOAA and NASA stress that the storm’s real strength is often only known once the CME is measured near Earth. Based on current modeling, severe impacts are not expected. Forecasters are calling mainly for unsettled to active conditions, with a chance of a minor geomagnetic storm. That means any satellite effects would more likely be limited and manageable, such as temporary disruptions, increased atmospheric drag for some low-Earth-orbit spacecraft, or minor navigation and radio issues, rather than widespread unexpected failures. Auroras are possible, but probably not rare or far-reaching unless conditions line up unusually well. The best-case scenario for skywatchers would be a southward magnetic field arriving at the same time as a fast solar wind stream from a coronal hole, which could amplify the disturbance. Even then, visibility in North America is expected to be limited to a relatively small number of favorable northern locations.

3 articles · Updated · spaceweather.gov · Aug 27

A G2 moderate geomagnetic storm watch is now active for Aug. 28-29, with forecasters extending expected solar-storm impacts through Aug. 29.
CMEs that left the Sun on Aug. 25 are driving the stronger watch, while a G1 minor storm watch remains in place for Aug. 27 because of expected coronal-hole high-speed stream effects.
The upgraded outlook follows earlier forecasts that auroras could be visible across parts of the northern U.S., with recent reports pointing to Kp values around 5 to 6 during the Aug. 27-29 window.
The multi-day watch underscores how overlapping solar eruptions and fast solar wind can prolong geomagnetic activity beyond an initial one-day forecast.