About the Dayside Automated Identifications

    The dayside automated region identification program, in conjuction with the new nightside identification algorithm, replaces the old neural network. The identifications are now based on quantitative rules and context. This approach proves to offer more flexibility in making improvements as a better understanding of precipitation and the magnetosphere is gained. For example, the new algorithm explicitly separates the open LLBL which lie immediately equatorward of the cusp from the closed LLBL signature (the "classic LLBL" which fits the spectra introduced by Haerendel et al. [1978] and Newell et al. [1991c]).

    Most of the fundamentals of quantitative identification have been published in the literature (references are given at the end).

Format

1. "void", meaning fluxes are generally near or below noise levels;

2. "p rn", or polar rain, the superthermal component of solar wind electrons often observed over the polar cap (only intense polar rain is listed -- a weak polar rain is nearly always resolvable with some effort in the polar cap;

3. "mantle", de-energized magnetosheath ions observable poleward of the dayside oval

4. "cusp", full intensity magnetosheath ions and electrons. Although the cusp can join the open LLBL reasonably smoothly, the cusp is taken to be where the ion and electron fluxes begin to approximate magnetosheath values, which generally occurs where the ion cutoff drops to at least 1-3 keV and below.

5. "opll" clearly open LLBL, with low-energy ion cutoffs and magnetosheath electrons at reduced fluxes, observed immediately equatorward of the cusp;

6. "llbl" closed LLBL with no low energy ion cutoffs, and spectra closely resembling published high altitude LLBL passes such as Haerendel et al. [1978] and Traver et al. [1990]. Such signatures are generally observed away from noon, not immediately equatorward of the southward IMF cusp.

7. "bps" precipitation which closely resembles the poleward portion of the nightside auroral oval. The electrons have a typical temperature of about 300 eV, somewhat higher than the LLBL (which in turn is somewhat higher than the cusp).

8. "cps" the hard zone of electron precipitation on the dayside. These consist of electrons which have been injected into the near-Earth region on the nightside and subsequently drift around the Earth. Typical energies are above 1 keV.

9. "uncl" or unclassified. When the flux levels are clearly significant but the precipitation did not fit any of the quantitative rules for other regions it is labeled unclassified. (Relatively short regions of unclassified precipitation are generally assigned according to context).

Consider the following example from December 1, 1985:

F07   85  335   31415   30504
void  031415  031411  -56.6 10.5(-41.1,110.5)///-56.7 10.5(-41.3,110.6)
cps   031410  031225  -56.9 10.5(-41.4,110.6)///-62.8 10.6(-47.4,112.9)
void  031224  031046  -62.9 10.6(-47.5,112.9)///-68.5 10.7(-53.1,115.5)
cps   031045  030819  -68.5 10.7(-53.1,115.5)///-76.8 11.1(-61.5,120.7)
bps   030818  030802  -76.8 11.1(-61.5,120.7)///-77.7 11.2(-62.4,121.4)
llbl  030801  030757  -77.9 11.2(-62.5,121.5)///-78.0 11.2(-62.7,121.6)
cusp  030756  030751  -78.0 11.2(-62.7,121.6)///-78.3 11.2(-63.0,121.9)
mant  030750  030528  -78.4 11.3(-63.1,122.0)///-85.6 13.3(-70.9,131.2)
void  030527  030504  -85.6 13.3(-70.9,131.2)///-86.4 14.3(-72.1,133.4)

void   .25   .02  7337.  5715.    .41   .03 11298.  6704. 031413 031414
cps    .21   .02  6164.  7606.    .41   .05 11625. 14086. 031409 031402
void   .10   .01  5104.  6718.    .26   .04  7010.  9874. 031114 031146
cps    .39   .01  3451.  5528.   1.13   .04  8455. 13611. 030919 030819
bps   1.77   .03   356.  8208.  19.45   .09  1187.  6017. 030802 030802
llbl  6.36   .30   654.  3474.  25.03   .47  1145.  3528. 030801 030759
cusp   .18   .46   168.  2287.    .34   .63   205.  2082. 030755 030755
mant   .20   .03   178.  1372.   7.98   .26   232.  2474. 030747 030750
void   .04   .01  1763.  4397.    .09   .02  5974.  9141. 030514 030524
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    The region identifications were given above. The second and third columns are respectively the equatorward and poleward UTs of crossing through each boundary. The fourth and fifth columns are the equatorward boundary in MLAT/MLT (PACE coordinates). The values in paranthesis are the same boundary in glat/glong (geocentric, from NORAD elements). Finally the poleward boundary is given after the "///" in the same manner.

    Each region is then repeated with particle flux information rather than boundary information. The second and third columns are respectively electron and ion average energy fluxes (ergs/cm**2 s). The third and fourth columns are the average electron and ion energy in the region. The next four columns are the same information, except the are the PEAK values rather than the average values. Finally the last two columns give the UT of the electron and ion peaks respectively, within the region.

References

Newell, P. T., and C.-I. Meng, The cusp and the cleft/boundary layer: low-altitude identifications and statistical local time variation, J. Geophys. Res., 93, 14549, 1988.

Newell, P. T., W. J. Burke, C.-I. Meng, E. R. Sanchez, and M. E. Greenspan, Identification and observations of the plasma mantle at low altitudes, J. Geophys. Res., 96, 35, 1991a.

Newell, P. T., S. Wing, C.-I. Meng, and V. Sigillito, The auroral position, structure, and intensity of precipitation from 1984 onwards: an automated online data base, J. Geophys. Res., 96, 5877, 1991b. {The old neural network based identification system}.

Newell, P. T., W. J. Burke, E. R. Sanchez, C-I. Meng, M. E. Greenspan, and C. R. Clauer, The low latitude b oundary layer and the boundary plasma sheet at low altitude: prenoon precipitation regions and convection reversal boundaries, J. Geophys. Res., 96, 21013, 1991c. {Especially refer to the "Thumbnail guide" to precipitation identification given in Section 4}.

Newell, P. T., and C.-I. Meng, Cusp low-energy ion cutoffs: A survey and implications for merging, J. Geophys. Res., 100, 21943, 1995. {The presence of low-energy ion cutoffs is a powerful indicator that field lines have recently been opened}.

Traver, D. P., D. G. Mitchell, D. J. Williams, L. A. Frank, and C.-Y. Huang, Particle observations during transversals of the low-latitude boundary layer, J. Geophys. Res., 96, 21025, 1991.

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