= The Plasmasphere =

|| {{ attachment:plasmasphere.png }} || Most of the mass of particles in server sky orbits is [[ http://www.johnstonsarchive.net/physics/RBtutorial.pdf | cold (<1eV) plasma ]], in the upper fringes of the atmosphere.  The total mass of these particles is small.  This plot shows density versus distance.  <<BR>><<BR>> This plot is modified from http://plasmasphere.nasa.gov/media/meridianswing.html ||

|| orbit || Radius   || L,,min,, || L,,max,, || Dens,,min,, || Dens,,max,, || Volume       ||   Mass   ||
|| m288  || 12789 km || 1.93     || 2.14     || 4500/cm^3^  || 7000/cm^3^  || 1.8e12 km^3^ || 17000 kg ||
|| m360  || 14441 km || 2.19     || 2.42     || 2500/cm^3^  || 4000/cm^3^  || 2.6e12 km^3^ || 14000 kg ||
|| m480  || 16756 km || 2.55     || 2.79     || 1200/cm^3^  || 2500/cm^3^  || 3.5e12 km^3^ || 11000 kg ||
||<-6> Earth                                                               || 1.1e12 km^3^ || 6e24 kg  ||
||<-6> Troposphere                                                         ||   8e9 km^3^  || 5e18 kg  ||

A few thousand tons of thinsats will vastly increase the number of coulomb scattering centers.

MoreLater

== The magnetosphere ==

The dipole field at the equator is 31000nT.  A geomagnetic storm changes this by depositing a westward ring of electric current, which induces a negative change in the field:

||  -30nT to  -50nT ||     weak storm ||
||  -50nT to -100nT || moderate storm ||
|| > -100nT         || intense        ||
|| > -300nT         || "a few times per solar cycle ||
 . Shrivjer and Siscoe "Heliophysics" pp265 Cambridge 2010
 . Also see www.nerc.com/files/GMD_Workshop_Report_April_2011.pdf (chair Don Watkins BPA)