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Subject The solar wind is currently almost non existent

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[quote:Anonymous Coward 832516:MV85MzY0OTZfMTQ1MjQ5MTVfMjlGODAyMUM=]
[quote:Ossie bloke]

It probably accounts for the rise in Cosmic Rays we've been seeing. I think it's going to get cold...

Sun is extremely quiet.

There hasn't been a rise in Cosmic Rays in recent days, nor should one be expected as a result of this dramatic stoppage of the solar wind. It takes several months for variations in the solar wind to reach the heliopause where the deflection of cosmic rays is believed to occur.
[/quote]

Actually, both deflect the Cosmic Rays (It was reported on GLP yesterday that we had seen a rise, and what better source is there :)

The flux (flow rate) of cosmic rays incident on the Earth’s upper atmosphere is modulated (varied) by two processes; the sun’s solar wind and the Earth's magnetic field. Solar wind is expanding magnetized plasma generated by the sun, which has the effect of decelerating the incoming particles, as well as excluding some of the particles with energies below about 1 GeV. The amount of solar wind is not constant due to changes in solar activity, for instance over its regular eleven-year cycle. Hence the level of modulation varies in anticorrelation with solar activity. Also the Earth's magnetic field deflects some of the cosmic rays, giving rise to the observation that the intensity of cosmic radiation is dependent on latitude, longitude and azimuth. The cosmic flux varies from eastern and western directions due to the polarity of the Earth’s geomagnetic field and the positive charge dominance in primary cosmic rays; this is termed the east-west effect. The cosmic ray intensity at the equator is lower than at the poles as the geomagnetic cutoff value is greatest at the equator. This is because charged particles tend to move in the direction of field lines and not across them, so that they are concentrated in the polar regions (where field lines are closest together). This is the reason the aurorae occur at the poles, since the field lines curve down towards the Earth’s surface there. Finally, the longitude dependence arises from the fact that the geomagnetic dipole axis is not parallel to the Earth’s rotation axis.

This modulation which describes the change in the interstellar intensities of cosmic rays as they propagate in the heliosphere is highly energy and spatial dependent, and it is described by the Parker's Transport Equation in the heliosphere. At large radial distances, far from the Sun (~94 AU), there exists the region where the solar wind undergoes a transition from supersonic to subsonic speeds called the solar wind termination shock. The region between the termination shock and the heliopause (the boundary marking the end of the heliosphere) is called the heliosheath. This region acts as a barrier to cosmic rays, decreasing their intensity at lower energies by about 90%; thus it is not only the Earth's magnetic field that protects us from cosmic ray bombardment.
[/quote]

Original Message PRESTO FROM SIDC - RWC BELGIUM Thu Dec 3 2009, 1247 UT

Except for a small magnetic dipole just passing the East limb in Extreme-UV images (probably a plage without sunspots), the Sun is featureless and is expected to remain inactive. Since early today, the solar wind has virtually vanished, reaching exceptionally low speeds (now at 250 km/s), low densities (< 0.1 electron/cm3) and low plasma temperatures (< 10⁴ K), based on ACE and SOHO/MTOF data. This leads also to exceptionally quiet geomagnetic conditions (Kp=0 at many ground stations). Those extremely quiet conditions certainly deserve special study. Only a weak solar wind stream expected tomorrow or on Dec.5 could restore more normal conditions, but just inducing temporarily unsettled geomagnetic conditions.

[link to sidc.oma.be]

[link to www.swpc.noaa.gov]

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