Investigating COSMIC GPS Radio Occultation Observables as Diagnostics for Ionospheric HF Heating Experiments ChengYung Huang Institute for Scientific Research, Boston College Chin S. Lin, E. Mishin, and T. Pedersen Space Vehicles Directorate Air Force Research Laboratory
Outlines Ionospheric HF Heating Experiments Simulating Ionospheric HF Heating COSMIC/FORMOSAT-3 Radio Occultation Observations Conclusions
HF Observables and Experiments (HAARP) High-power HF (2.85MHz) waves have numerous effects on the ionosphere Electron heating Density perturbations Irregularity generation Excitation of optical emissions Experiments HF experiments from a focused transmitter beam at HAARP were made between 3 and 5 UT on February 23, 2008. The HF transmitter was operated at 2.85 MHz, the beam position switched between vertical and magnetic zenith. Ionograms were acquired every 5 min
Ionosonde Observations -The lower trace was most distinct during 04:20 and 04:25 UT when transmitter was pointing in vertical direction. Density Profiles Ionogram showing vertical O-mode echoes (red and pink) at 0425 UT on Feb. 23, 2008 (left). Corresponding X-mode traces are in green and light green.
TEC observations by GPS network Oblique TEC observations made on Feb. 24, 2008 using a receiver of GPS network monitoring GPS PRN 23. Gray shading indicates the time periods the HAARP transmitter tte was turned on.
Field Line Interhemispheric Plasma Model (FLIP) One-dimensional model that calculates the plasma densities and temperatures along entire magnetic flux tubes from below 100 km. FLIP solves the continuity and momentum equations for O +,H +, He +, and N +. Chemical equilibrium i densities are obtained for NO +, O + + 2+, N 2+, O + ( 2 P), and O + ( 2 D) Minor neutral species include NO, O( 1 D), N( 2 D), N( 4 S)
FLIP Magnetic Field Model IGRF magnetic field model FLIP follows HAARP s magnetic field line The position for the northern hemisphere end of magnetic field line is fixed at the HAARP location. Dayside field line Nightside field line
FLIP Flow chart Input parameters Specify 1. Solar declination & ephemeris time 2. Geophysical parameters 3. Ap and F10.7 4. ExB drift Initialization and neutral atmosphere 1. MSIS model 2. Initial temperature and density profiles Production rates O+, H+, DENSITIES + electron and ion TEMPERATURES 1. Evaluate primary production rates 2. Calculate ionization rates He+, N, N(2D), N(4S), NO, and N2* DENSITIES
FLIP Modeling Parameters HAARP Latitude Magnetic Field Lines Heating Area HF Frequency : 2.85MHz Plasma Density : 10 5 #/cm^3 10% ( ~230 km ) Heating Rate : 4 x 10 4 Joule s -1 cm3 Heating Time: 22:00:00 22:02:00 LT FLIP Time Step: 5 sec
Electron Temperatures Temperature increases to 4000 K, after the heating rate is added from 22:00 LT. A temperature peak appear around the heating area (~230km). After 10:02, temperature start to recovery to background condition by exponential function of time, almost recovery to background condition at 10:08.
Electron Density at Different Field Lines The peak density of F-region is around 280 km. The peak density decreases and moves downward during heating. The density inside the heating area around 230 km increases.
Difference of Electron Density Movie Density Difference = Density during heating ambient density 22:00 When the heating is on, the density around the heating altitude (~230km) starts to increase, and the peak density of the F layer decreases and moves downward. 22:04 The density at the heating altitude returns to the original value. 22:12 The peak density in F-region starts to recover and moves upward to background condition.
Electron Temperature above HAARP FLIP model indicates electron temperature enhancement about the heating altitude (230 km).
Electron Density above HAARP FLIP modeling indicates electron density increase near FLIP modeling indicates electron density increase near the heating altitude (~230 km) and density decreases above the heating altitude.
630.0nm Emission (O1D) Higher electron temperature t produces 630 nm emissions. i
557.7nm Emission (O1S) FLIP modeling suggests weak 557.5 5 nm emission. i
Simulation of Electron Density Profiles An electron density enhancement is assumed around 220 km The Electron density profile is retrieved from the enhancement TEC by Abel inversion.
COSMIC/FORMOSAT-3 Observations (1/2) Electron Density Profile HTEC EDP Scintillation S4 Index COSMIC Path HAARP in 4 min on 4 min off mode at 3.4 MHz. Density perturbations seen 30 min earlier and 30 min later.
COSMIC/FORMOSAT-3 RO observation HAARP was in the heater on mode at 3.4 MHz. Density perturbations were seen in the ionogram. Large scintillation were seen in the COSMIC RO data.
Conclusions Simulation of Radio Occultation (RO) during HAARP heating suggests that TEC would increase about 8 % around 230 km. The retrieved density profiles are found to be insensitive to HAARP heating. The TEC and density profiles deduced from COSMIC RO data do not show clear evidence of HAARP heating. The S4 index showed higher scintillation during the HAARP experiments. Denser RO measurements in conjunction with ground GPS network observations remain to be investigated i dfor diagnosing i ionospheric effects of HAARP experiments.