Studies of the Lower Ionosphere at NRL. David Siskind Space Science Division Naval Research Laboratory Washington DC, USA with M. Friedrich, Graz University of Technology, Austria Jorg Gumbel, Stockholm University. OASIS: Originally Austrian Study of the IonoSphere .
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Space Science Division
Naval Research Laboratory
Washington DC, USA
M. Friedrich, Graz University of Technology, Austria
Jorg Gumbel, Stockholm University
OASIS: Originally Austrian Study of the IonoSphere.
1. New interest in the D region:
HF communications (e.g. Eccles et al., Radio Sci, 2005)
2. History at NRL, OASIS (Gumbel et al., 2003)
3. New data to constrain D region models emphasis on lowermost altitudes (below 70 km)
Work at NRL sponsored by the Office of Naval Research
Eccles et al, Space Weather, 2005
Absorption coefficient scales as product of [e-] and e-n collision frequency (which
in turn, scales as the neutral density)
Implication: although [e-] decreases with decreasing altitude, ne can increase.
Which wins out?
Error in labeling, unclear
which is FIRI or stnd IRI.
But, evidence for 2ndary
peak in HF absorption
below 70 km.
Frederich and Torkar (1983), brought to NRL by Jorge Gumbel in 2002
Inputs: neutral atmosphere (including NO),
Ly A, EUV, Xray, GCR, energetic particle fluxes
Outputs: positive ions, negative ions, hydrated ions, electrons
Options for aerosol-ion interaction
(so-called [e-] biteouts seen in polar summer mesosphere)
SABER: Sounding of the Atmosphere with Broadband Emission Radiometry
on NASA/TIMED satellite
Measures IR emission from ozone, CO2(temperature), OH airglow etc.
Starts with: e- + O2 + O2 O2- + O2
Controls the partitioning between negative ions and electrons
O2- + O e- + O + O2
O2- + X X- + O2
X can be CO2 or NO2
Overview of D region, different regimes, different ionization sources vs. alt.
Negative ions: extending OASIS below 80 km. How it handles negative ions.
O2+ attach to H2O,
NO+ attaches to N2 and CO2 and eventually (H2O)n
Proton hydrates dominate below 80 or 85 km (dep upon T and H2O)
My initial interest is when free electrons attach to neutrals (below 70 -75 km)
e- + O2 + M O2- + M
Three things happen to O2-
Photodetachment (fast): O2- + hn e- + O2
reaction with O to neutralize: O2- + O e- + O + O2
charge exchange to produce heavier ions: O2- + X X- + O2
(X- have much slower photodetachments)
X can be several species; OASIS bundles it all into X (seems to work)
From Barabash’s paper
SABER O: Inferred from ozone measurements.
O/O3 = JO3/(k [O2][M])
Above 80 km, validated w/ Meinel Band (OH(v’)) technique
(Smith et al., 2010; Mlynczak et al 2014)
Variability is generally small except w.r.t. SZA. 70 km behavior is interesting
Ann Geo., 2012
This new data suggests that [e-] densities between 60-65 km greater than 100-400 cm-3
are a robust feature. This is 4-10 times greater than the model (which is probably
already biased high due to the high O)
Or Indian Ocean
Wallops Is., VA, USA
About 30-40 useful low/mid-latitude measurements since WWII
Hints of big disagreement
between theory and
Model shows increasing [e-] latitude tracks cosmic ray flux
FIRI shows equatorial peak; harder to understand
OASIS works and is validated down to 60km. Some cleaning up of higher altitudes
needed (photoelectrons from X rays)
Tested with a variety of atomic oxygen profiles (not shown)
SABER O can be a valuable constraint on model inputs that is underappreciated.
Evidence for large [e-] below 70 km which suggests:
a) a problem with the models and
b) confirms significant HF absorption between 60-70 km