8.2.3                 Auroral charging environment

a.              For auroral charging assessment, the following worst­case electron distribution function shall be used.

¾              For E ≤17,44 keV:

f(v) = 3,9 × 10-18   s3m-6

(8‑1)

¾              For E > 17,44:

(8‑2)

where

f(v)    is the distribution function in sec3 m-6

N0      is the density in m-3

me       is the electron mass in kg

kT0     is the thermal energy in J

E0       is in J

E        is energy in J

and parameters of the worst case environment are:

N0      = 1,13E6 m-3

kT0     = 3,96 keV

E0       = 17,44 keV

NOTE              This comes from [RD.7] and is based on work described in [RD.8]. Unfortunately, it is printed in [RD.7] with a typographical error.

b.              For worst case auroral charging assessments, a thermal ion density of 125 cm-3 and temperature 0,2 eV shall be used.

NOTE              This low ion density comes from a severe charging case seen on the DMSP spacecraft by [RD.9]. Measuring ionospheric thermal ion density during a strong charging event is potentially prone to errors because of the way the charged satellite alters ion trajectories, so there is a degree of uncertainty in this measurement.