CME wind speed

[hb9tmc]

Hi,

When a CME hits the earth, why doesn't the fastest stream arrive first? I.E: during the event from sep 26th, the wind was at first 500km/s and 10h later 700km/s. By simple math, the 500km/s particles should have had a delay of one day compared to the 700km/s ones (and one day later it was 500km/s again)

The only theory i have is that the first particles are decelerated by earths magnetosphere. The further the magnetosphere gets penetrated, the faster the particles can travel to the measuring satellite.


73, Stefan

EDIT: I made an ugly graph with the expected wind speed (assuming the CME was from sep 24th M7 LDE). The wind speed should have peaked 886km/s.

[Bob k6tr]

Stefan CME are capable of accelleration after the depart the sun. Both in a linear manner causing an increase in speed but also in a tangential manner resulting in a change of direction.

[lsvalgaard]

Sept 29, 2011 10:40:42 GMT hb9tmc said:

Hi,

When a CME hits the earth, why doesn't the fastest stream arrive first? I.E: during the event from sep 26th, the wind was at first 500km/s and 10h later 700km/s. By simple math, the 500km/s particles should have had a delay of one day compared to the 700km/s ones (and one day later it was 500km/s again)

The only theory i have is that the first particles are decelerated by earths magnetosphere. The further the magnetosphere gets penetrated, the faster the particles can travel to the measuring satellite.

The speed is measured a million miles away upstream from the magnetosphere, so penetration has nothing to do with it.

[hb9tmc]

Sept 29, 2011 14:12:46 GMT Bob k6tr said:

Stefan CME are capable of accelleration after the depart the sun. Both in a linear manner causing an increase in speed but also in a tangential manner resulting in a change of direction.

It's a fact that the fastest particles from this CME traveled at an average of ~880km/s (47h for 150*10⁶km) but that speed has not been measured.

If the mass would have changed speed on the way, the fastest particles would still have arrived first, so they had to decelerate near earth.


Sorry if i haven't got it right, my english (and maybe also my physics ) is not too good.


73, Stefan