Comfort, R. Hugh

Craven, Paul D.

Gallagher, D. L.

Goldstein, Jerry

NASA Technical Reports Server

The Data and Fits for a New Global 
Core Plasma Model 
 and the Oddities Revealed 
D. L. Gallagher, NASA/MSFC, Jerry Goldstein, SwRI, Paul D. Craven, 
NASA/MSFC, R. Hugh Comfort, UAH/Emeritus 
“The Magnetosphere: New Tools, New Thinking, and New Results” 
November 12-17, 2017, Puerto Varas, Chile 
https://ntrs.nasa.gov/search.jsp?R=20170011128 2019-08-31T01:29:56+00:00Z
Outline 
• Notes about Dynamics Explorer 1 and the 
Retarding Ion Mass Spectrometer (RIMS) 
• The DE 1 RIMS moments database?  What is in it? 
What are the limitations? 
• Densities (spatial and long term variations) 
• Temperatures (spatial and long term variations) 
• Summary 
• Editorial 
Dynamics Explorer 1 
• Launched August 3, 1981 
• High inclination,  
• Altitude 568km x 23,290km (4.6RE) 
orbit 
• 6.8 hour orbital period 
Retarding Ion Mass Spectrometer 
(RIMS) 
• 3-sensor heads 
– two spin-axis w/55⁰ fov 
– radial w/20 ⁰ x 110 ⁰ fov 
• 0-45 eV energy/charge 
range 
• 1-32 μ mass/charge range 
• 16 msec time resolution 
• Included annular collar for 
potential control 
 
The RIMS Moments Dataset 
• https://plasmasphere.nasa.gov 
• 1 minute sums, uses all 3 sensors, Maxwellian distribution 
assumed, ion densities and temperatures; method 
discussed in Craven et al., JGR, 102/A2, pg.2279, 1997 
• Ion order in file is H+, He++, He+, O+, O++ 
• RIMS_starter_kit includes data, data description, and 
sample read routines in C and IDL code 
• Includes this synoptic study in PDF 
• All will be offered to the NASA/SPDF 
• Data file description is still incomplete 
Density and Temperature Data Set 
• H+, He+, He++, O+, & O++ 
• October 8, 1981 thru 1984 
36,291 samples 7,601 samples 
All H+ Densities 
~0.3 ~0.6 
𝜎𝜎 𝑜𝑜𝑜𝑜 𝑡𝑡𝑡𝑡𝑡 𝑙𝑙𝑜𝑜𝑙𝑙10 𝑑𝑑𝑡𝑡𝑑𝑑𝑑𝑑𝑑𝑑𝑡𝑡𝑑𝑑  
• The red line shows the 
Carpenter and Anderson 1992 
saturated plasmasphere 
density profile. 
• The black line borders the 
upper range of densities at 
middle L-values, for 
comparison to C&A. 
• The lower boundary appears 
to demonstrate plasmapause 
variability with activity, that 
rarely extends inside L=2.2. 
• The in situ derived densities 
often do not provide a 
smooth, continuous 
plasmapause boundary. 
• Increased densities at higher 
L-value may arise from storm 
enhancement or plumes. 
C&A 
 1.375 1.625 1.875 2.125 2.375 2.625 2.875 3.125 3.375 3.625 3.875 4.125 4.375 4.750 5.250 5.750 
 3.399 3.469 3.455 3.270 2.980 2.632 2.372 2.075 1.978 1.932 1.908 1.924 2.013 2.090 1.850 1.673 
 0.320 0.286 0.327 0.536 0.601 0.627 0.656 0.610 0.548 0.524 0.509 0.530 0.516 0.627 0.755 0.746 
 
Fits are for the log10(density) 
openw, 3, txt_name 
printf, 3, Lset, form='(16f6.3)' 
printf, 3, denset, form='(16f6.3)' 
printf, 3, stdset, form='(16f6.3)' 
close,3 
Rims_HpN_vs_L.txt 
The strong drop in oxygen density above the ionospheric peak is followed by an enhancement 
in the region dominated by geomagnetic activity; more dramatically than that of the light ions. 
Other Ion Densities 
He+ Versus H+ 
𝑁𝑁𝐻𝐻𝐻𝐻 ≈ 0.06 ∗ 𝑁𝑁𝐻𝐻 
• Only first order dependencies are expressed here and in the following content. 
• The density comparison has the same result as that of Craven et al., JGR, 1997. 
• Over all the He+ densities are an average of about 6% of H+ densities. 
• He+ and H+ temperatures are about the same under all conditions. 
• Fit parameters are shown with associated σ.  
• The separately stated σ is for differences between ratio values and fit. 
Black dotted line marks equal densities. 
Single vs Doubly Ionized Ions 
• The density of He+ is about 50x that of He++ on average, without significant 
statistical variation away from a constant factor. 
• O++ densities are found to be statically higher than O+ when below 1 cm-3 and 
lower when above that density. 
• Nearly all of the O++ below L=2.2 is less dense than O+, with increasing 
divergence at lower altitude (greater density). 
• It is at higher L-value and low density that O++ has higher density than O+. 
Black dotted lines mark equal densities. 
Ion Temperatures: H+ & He+ 
Relative to light ion densities, the temperatures have somewhat less scatter, 
though still more above L=2.2 where geomagnetic activity has its strongest 
influence. 
Temperatures rise as densities fall, though not as much. 
• The He++ temperatures are interestingly odd. 
Temperatures initially fall with increasing L-
value before rising after L=2.25. There is the 
suggestion that the low and high L-value 
populations overlap, hence are distinct.  
• There is the suggestion of another population 
at 2x higher temperature and at low L, 
consistent with D+. 
• O+ behavior is no less interesting. 
• O++ behaves more like the light ions. 
Ion Temperatures: He++, O +, & O + + 
Solar Cycle Variation 
• Both a seasonal and solar cycle variation in 
plasmaspheric density have long been 
observed. These plots clearly display a strong 
relationship between f10.7 and light ion 
density as solar minimum is approached. 
Mean Density vs f10.7: H+ & He+ 
• Only part of one solar cycle is available in these data. 
• Like previous studies, such as Carpenter & Anderson 1992, there is a significant 
increase in density with increasing solar activity. 
• Perhaps not previously seen is the stronger response in He+ relative to H+. 
Mean Density vs Season: H+ & He+ 
• Density versus the day of the year is plotted here after removing the density versus 
f10.7 trend shown in the last slide. 
• There is the suggestion of annual periodicity, especially in H+. 
• There is also the suggestion of periodicity on the order of 24 days or one solar 
rotation period.  Examination of surface features, such as flares, during these times 
will resolve this possibility, but that remains to be done. 
Density Range vs f10.7 
• Not previously noted is that the range of all observed densities 
also increases with increasing solar activity.   
• Again, the response of He+ appears to be stronger than that of H +. 
• There are not enough O + and O + + ion values to perform either 
analysis. 
Mean Temperature vs f10.7: H+ & He+ 
Temperature does not show the same sensitivity to solar cycle, but may show 
a weak seasonal response. 
Summary 
• These conservatively derived densities and temperatures provide unique 
H +, He +, He + +, O +, and O + + ion properties. 
• On average He+ is about 6% of H+density. 
• He++ is about 50x less than He+ in density. 
• H+ and He+ temperatures rise with increasing L-value at a ratio of 1. 
• Inside of L=2.25 He++ temperatures fall with increasing L-value, then rise 
beyond that.  In addition, D+ appears to be present. 
• Contrary to the light ions, O + temperature rises sharply with increasing L-
value up to L=2.2, then falls gradually beyond that.   
• Oddly, O + + follows the light ion behavior. 
• Overall average H+ and He+ densities fall with falling f10.7 in the declining 
solar cycle in the mid-1980s. 
• In addition the range of light ion densities also diminishes with falling f10.7.  
This is seen for all values without regard for location or conditions. 
• Light ion temperature does not show a significant f10.7 dependence. 
Upon Reflection 
• The RIMS moments data set will be provided to the NASA 
Space Physics Data Facility this year.  The data file and an IDL 
example to read it are available online at 
http://plasmasphere.nasa.gov. 
• DE 1 RIMS densities and temperatures remain a unique 
resource for the community, but the spatial and temporal 
sampling is limited. 
• These data are without reliable identification of their 
morphological origin: plasmasphere, plasmapause, trough, 
auroral zone, polar cap. 
• If we are to understand the processes of refilling, wave-
particle instabilities, and wave transport, it is critical to obtain 
full phase-space, Sub-eV to 100 eV energies, mass 
spectroscopy, and ions and electrons.   A more equatorial 
perspective across all inner magnetospheric L-values in 
concert with the global context is also needed. 


The Data and Fits for a New Global Core Plasma Model and the Oddities Revealed

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