This file define the constants in the equation Ne(EFW) = A * exp(-(Vs-Vp)/B) Ne is the density of electrons in cm^-3 Vs is the spacecraft potential in V Vp is the probe potential in V -(Vs-Vp) is "Cluster X efw E py 10Hz any" in ISDAT, (X,y = 1,2,3,4) first ref. : Electron density estimations derived from spacecraft potential measurements on Cluster in tenuous plasma regions. A. Pedersen, B. Lybekk, M. Andre, A. Eriksson, A. Masson, F. S. Mozer, P.-A. Lindqvist, P. M. E. Decreau, I. Dandouras, J.-A. Sauvaud, A. Fazakerley, M. Taylor, G. Paschmann, K. R. Svenes, K. Torkar, and E. Whipple JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, A07S33, doi:10.1029/2007JA012636, (2008) http://www.agu.org/journals/ja/ja0805/2007JA012636/ second ref. : Solar cycle variations of the Cluster spacecraft potential and its use for electron density estimations Lybekk, B., A. Pedersen, S. Haaland, K. Svenes, A. N. Fazakerley, A. Masson, M. G. Taylor, and J.-G. Trotignon (2011), J. Geophys. Res., doi:10.1029/2011JA016969A and B are constants determined by EUV and X-ray solar radiation that varies over the solar cycle. (p is probe and s is satellite).
Usage in Calculator: p0y = ne_efw(q0,q1,q2,q3,q4,'max_level') q0 is Cluster X efw E pY 10Hz any X = 1,2,3 or 4 Y = 3 on SC1, SC3 and SC4, 1 on SC2 q1 is Cluster X efw E pY 10Hz any X same as on q0 Y = 4 on SC1, SC3 and SC4, 2 on SC2 q2 is Cluster X efw st whisper_transmit X same as on q0 q3 is Cluster X efw st sweep_on X same as on q0 q4 is CSDS_PP CX ASPOC I_ion__CX_PP_ASP or CAA CX ASPOC IONC Ion Emission Current X same as on q0The optional 'max_level' is the maximum probe potential in volt for the function.
The ne_efw operator returns EFW_FILLVALUE (-1.0) when one of:
The constants A and B are found in the file ne_efw_def.h .
The values when the EFW probes are saturated are found in the file
The saturation value is about -68 Volt, and have slightly different values on all the 16 EFW probes, (4 SC * 4 probes /SC) .
The CSDS ASPOC data is not available after summer 2008.
After the ASP_SCX_IGNORE_AFTER dates given in the file ne_efw_def.h the fifth quantity (q4) can be repaced with another quantity, eg. Cluster X efw E pY 10Hz any.
X = 1,2,3 or 4
After this date the ASPOC ion current is ignored in this operator.
The EFW Ne calibration is valid only for C4. For the other spacecraft a correlation
factor found in the file ne_efw_corr.h is used by this operator.