Wednesday, May 25, 2016

Today the Earth Crosses a Solar Sector Boundary

What is a Solar Sector Boundary Crossing?
As the solar wind flows away from the Sun, the interplanetary magnetic field (IMF) is carried with it and has a spiral shape. Along the ecliptic plane (direct line between the sun and Earth), the IMF generally has 2 or 4 sectors per solar rotation (27 days) where it is pointed toward or away from the Sun. The surface separating the polarities is called the heliospheric current sheet. A sector boundary crossing occurs when the polarity of the IMF reverses. A well defined sector boundary crossing has a uniform field direction for about 4 days before and after the crossing.

SOLAR SECTOR BOUNDARY CROSSING: Late on May 25th, Earth will cross a fold in the heliospheric current sheet and enter a region of space filled with negative polarity magnetic fields. Such fields can open a crack in Earth's magnetosphere, allowing solar wind to pour in and fuel geomagnetic disturbances.  According to NOAA forecasters, the odds of a G1-class storm is 20% to 30%
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