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GEOMAGNETIC STORM WATCH: NOAA forecasters estimate a 60% chance of polar geomagnetic storms on Feb. 3rd. They say a high-speed solar wind stream and a CME could hit Earth's magnetic field on Wednesday--a double whammy almost certain to spark some degree of geomagnetic activity.
Mid-latitudes 0-24 hr 24-48 hr
ACTIVE 60 % 35 %
MINOR 10 % 50 %
SEVERE 05 % 15 %
High latitudes 0-24 hr 24-48 hr
ACTIVE 60 % 20 %
MINOR 20 % 60 %
SEVERE 10 % 20 %
Geophysical Activity Forecast: The geomagnetic field is expected to be unsettled to active with a chance for a minor storm on day 1 (2 February) due to coronal hole effects along with intermittent periods of Bz south. On day 2 (3 February), unsettled to active conditions are forecast until the anticipated mid-day arrival of the CME from 30 January, when an isolated minor storm will become likely. Conditions on day 3 (4 February) are expected to be mostly unsettled to active as coronal hole effects begin to wane.
Originally posted by this_is_who_we_are
I'm still waiting for that geomagnetic storm. Anyone else?
Geomagnetic Storm Forecasts
The geomagnetic storm probabilities are the estimated chances of at least one 3-hour K index, at the indicated level, for each of the next 3 days.
Active: K = 4.
Minor storm: K = 5.
Major or Severe storm: K > 6.
The "K index" is a 3-hourly quasi-logarithmic local index of geomagnetic activity relative to an assumed quiet-day curve for the recording site. Range is from 0 to 9. The K index measures the deviation of the most disturbed horizontal component of the magnetic field.
The Sun is a big magnet
. During solar minimum the Sun's magnetic field, like Earth's, resembles that of an iron bar magnet, with great closed loops near the equator and open field lines near the poles. Scientists call such a field a "dipole." The Sun's dipolar field is about as strong as a refrigerator magnet, or 50 gauss. Earth's magnetic field is 100 times weaker.
During the years around solar maximum (2000 and 2001 are good examples) spots pepper the face of the Sun. Sunspots are places where intense magnetic loops -- hundreds of times stronger than the ambient dipole field -- poke through the photosphere. Sunspot magnetic fields overwhelm the underlying dipole; as a result, the Sun's magnetic field near the surface of the star becomes tangled and complicated.
The Sun's magnetic field isn't confined to the immediate vicinity of our star. The solar wind carries it throughout the solar system. Out among the planets we call the Sun's magnetic field the "Interplanetary Magnetic Field" or "IMF." Because the Sun rotates (once every 27 days) the IMF has a spiral shape -- named the "Parker spiral" after the scientist who first described it.
Above: Steve Suess (NASA/MSFC) prepared this figure, which shows the Sun's spiraling magnetic field from a vantage point ~100 AU from the Sun.
Earth has a magnetic field, too. It forms a bubble around our planet called the magnetosphere, which deflects solar wind gusts. (Mars, which does not have a protective magnetosphere, has lost much of its atmosphere as a result of solar wind erosion.) Earth's magnetic field and the IMF come into contact at the magnetopause: a place where the magnetosphere meets the solar wind. Earth's magnetic field points north at the magnetopause. If the IMF points south -- a condition scientists call "southward Bz" -- then the IMF can partially cancel Earth's magnetic field at the point of contact.
"When Bz is south, that is, opposite Earth's magnetic field, the two fields link up," explains Christopher Russell, a Professor of Geophysics and Space Physics at UCLA. "You can then follow a field line from Earth directly into the solar wind" -- or from the solar wind to Earth. South-pointing Bz's open a door through which energy from the solar wind can reach Earth's atmosphere!
Southward Bz's often herald widespread auroras, triggered by solar wind gusts or coronal mass ejections that are able to inject energy into our planet's magnetosphere.
NOAA forecasters estimate a 60% chance of polar geomagnetic storms on Feb. 3rd when a coronal mass ejection is due to hit Earth's magnetic field. A solar wind stream following close behind the CME could extend the action into Feb. 4th and 5th.