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Studies of the Lower Ionosphere at NRL

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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Studies of the Lower Ionosphere at NRL

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  1. 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. 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

  2. New interest in HF absorption 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?

  3. HF Absorption: Empirical Model(Pederick and Cervera, Radio Sci 2014) Error in labeling, unclear which is FIRI or stnd IRI. But, evidence for 2ndary peak in HF absorption below 70 km.

  4. OASIS: Originally Austrian Study of the IonoSphere. 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) D region studies SABER: Sounding of the Atmosphere with Broadband Emission Radiometry on NASA/TIMED satellite Measures IR emission from ozone, CO2(temperature), OH airglow etc.

  5. Ion-chemistry, 86 km

  6. Below 80 km: Negative Ions Starts with: e- + O2 + O2  O2- + O2

  7. Role of Atomic Oxygen Controls the partitioning between negative ions and electrons O2- + O  e- + O + O2 or O2- + X  X- + O2 X can be CO2 or NO2

  8. Summary of D region Overview of D region, different regimes, different ionization sources vs. alt. Negative ions: extending OASIS below 80 km. How it handles negative ions. Basic processes 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)

  9. Historically, O not well studied below 80 km 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)

  10. A SABER O climatology vs SZA Variability is generally small except w.r.t. SZA. 70 km behavior is interesting Equator 45oN

  11. SABER vs. Local Time Equator 45N 70 km 70 km

  12. Some results/validation I_total I_NO [e-] PH+ O2- I_GCR X- Ann Geo., 2012

  13. New data from Kwajalein, Sep 20, 2004 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)

  14. Overview of Rocket Data: HF/MF radio absorption Kwajalein Atoll Or Indian Ocean Wallops Is., VA, USA About 30-40 useful low/mid-latitude measurements since WWII

  15. Faraday IRI, nudges data to empirical model

  16. Nitric Oxide

  17. Equatorial Electron Densities Hints of big disagreement between theory and empirical model

  18. Data Taken by Friedrich et al., 2 MHz absorption, Sep 19, 2004

  19. Variations with latitude: model vs FIRI Model shows increasing [e-] latitude  tracks cosmic ray flux FIRI shows equatorial peak; harder to understand

  20. Conclusions 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

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