Solar activity - what can be expected
posted: Jan 23, 2012
The Sun has again an activity revival since Jan 16, not an extra ordinary revival, but high. No records were broken. There was a series of plasma ejections, not straight to Earth, but glancing blows from above. The most dangerous aspect up to now is the ongoing proton event.
For aurora-watchers: the chance for aurora in Belgium is very small.

The event of Jan 23 was the strongest of the last days. The Sun showed off with a combination of three sorts of energy releases. Speaking in terms of x-ray radiation, the Jan 23 flare reached the M8.3 level. The speed of the mass ejection of Jan 23 was relatively speaking high compared to the ones of the previous days: 1400 km/s compared with 700 km/s at most. What differs from the previous mass ejections, is that the component that intersects with the ecliptic - and pass along the Earth - is stronger. The event triggered a proton storm: particles with relativistic speeds fly through space into the direction of Earth. They harm satellites, eventually disrupting their pointing, attacking their solar cells, ... Those particles can intrude the Earth's magnetosphere through the north/south polar door. This is the strongest proton storm since May 2005. At this very moment (Jan 23, 20:00UT), the proton event continues.

The ejected mass did not yet arrive at Earth. At arrival, the magnetosphere might be disturbed. We speak about a geomagnetic storm causing unwanted effects on satellites and their performances. A geomagnetic storm can alter also the features of the ionosphere, a layer which is crucial for signals transmitted to satellites or from an earth transmitter to an earth receiver. This list of failures is not exhaustive. However, we don't forecast an extra ordinary geomagnetic show. For Belgium, this means that the chance for aurora is almost nihil.

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With the figures below, you can reconstruct what kept us busy since Jan 16. Orange stands for events on the solar disk, blue stands for the situation a few solar radii away from the Sun, while green describes the situation near Earth.
Click on the three pictures to enlarge.



Some facts

Solar flare
  • a brightening of a part of the solar disk - a light flash.
  • Travels at the speed of light - it takes 8 minutes to bridge the distance between the Sun and the Earth. All radiation has the same speed.
  • Intensity is an attribute of a flare. Compare it to light bulbs that shine more intense then others.
  • A flare has no weight.
  • A flare has no direction. Of course, when a flare occures behind the Sun, we don't see it.
  • The earth's atmosphere protects us against harmfull solar radiation.
  • The earth's atmosphere is transparant for visible light - otherwise it would be dark on Earth.
Plasma ejection - coronal mass ejection, CME
  • This is plasma, solar mass that is ejected from a source in the corona of the Sun. The corona is the solar atmosphere.
  • It's a tsunami/gas blob running over the solar wind.
  • We attribute weight and velocity to a plasma ejection, i.e. kinetic energy.
  • Plasma is ejected in a direction. A halo CME is a CME thrown in the direction of the Earth.
  • It takes a plasma cloud around 3 days to bridge a distance Sun - Earth. Their exact travel time depends on their speed. The speed varies for CME to CME.
  • The earth's magnetosphere is our magnetic shielding against plasma ejections and the solar wind.
  • While bumping on the earth's magnetosphere, a geomagnetic storm can occur. Aurora is a side-effect of a geomagnetic storm.
Proton storm
  • These are fast particles blown away from the Sun.
  • It takes them 30 minutes to 1 hour to bridge a distance Sun - Earth. Their speed differs from event to event.
  • They are tide to magnetic field lines which are present allover our solar system. The Sun is the source of these radial magnetic field lines.
  • As a consequence of their stickiness to magnetic field lines, they travel in a direction.