Energization and escape of O+ into the Earth's polar cap and magnetotail


W.K. Peterson, J.B. Cladis, O.W. Lennartsson, H.L. Collin, T. Moore, C. Russell, C. Kletzing, N. Maynard, and G. Lu

 

At geocentric distances of 6 to 9 Re in the Earth's polar cap, state-of-the-art instruments on the POLAR spacecraft have monitored beams of escaping oxygen and other heavy ions for three years during solar minimum conditions. The densities of the observed O+ beams have varied from at or near the detection thresholds of ~0.01 cm^-3 to over 10 cm^3. The energies of the beams have varied from a few volts to over 10 keV. The physical (temporal) extent has varied from small patches to uniform outflow over the polar cap sampled by the POLAR satellite. In this report, we present observations from the TIMAS, TIDE, HYDRA, MAG, and EFI instruments on the POLAR spacecraft for representative quiet and disturved events and show how these state-of-the-art data combined with existing models can be used to deduce information about the various processes responsible for escape and energization of O+ and its transport into the magnetotail.

 

Notes

Karlheinz and Walter modified the moments from single spins are combined and I've put a filter on my code that reads the moments to consider moments only from intervals where the TIMAS partial density is greater than 0.015 cm^3. Please use this updated set for your calculations. Sorry about the decimal hours used in the labels, but since I'm doing the coding, you take what you get. (23.80 = 23:48)

The plots and files are at your favorite UTL: ftp://willow.colorado.edu/pub/timas/Cladis/ The postscript plot files

Mvel_h_19980924_2341_235.ps

Mvel_o_19980924_2341_235.ps

have 4 pages each. The last page has the components of the bulk velocities perpendicular to the magnetic field direction in both Fixed Platform (FP) and GSM coordinates. Its nice that the values and directions of the H+ and O+ perpendicular moments are more or less equal! The differences there can be intrepreted as a measure of the uncertainty of the moment determination caused by gaps in the TIMAS energy or angle coverage and temporal aliasing.

19980924_2341_2359_mrdf_e.ps

19980924_2341_2359_mrdf_p.ps

are the standard TIMAS spectrograms _e energy time and _p angle time

Labeled ASCII files of the numbers used to make the Mvel plots are in the four files.

fa_vel_one_spin_0_19980924_2341_2359.dat

fa_vel_one_spin_H_19980924_2341_2359.dat

gsm_vel_one_spin_0_19980924_2341_2359.dat

gsm_vel_one_spin_H_19980924_2341_2359.dat