1 Duct Formation by HF heating Gennady Milikh, Aram Vartanyan, Dennis Papadopoulos, University of Maryland Evgenii Mishin, Air Force Research Lab, Hanscom AFB, MA Joe Huba, Glenn Joyce, Naval Research Laboratory Michel Parrot, LPCE/CNRS, France

2 Motivation Naturally occurring density inhomogeneities in the ionosphere act as ducts that allow low loss propagation of whistler waves in the VLF range along trans-ionospheric paths. HF-heating of the F-region can create controlled artificial ducts which allows guided propagation of VLF signals in the ionosphere.

3 Objectives Undertake a systematic study of the processes controlling formation of artificial ionospheric ducts by using HAARP as a heater and DEMETER and DMSP satellites as major diagnostic tools. The observations were analyzed and checked against the numerical model of artificial ionospheric ducts, based on SAMI2 code.

4 The physical model applied SAMI2 model developed at NRL [Huba et al., 2000]. It is 2D inter- hemispheric, and can simulate the plasma along a bunch of magnetic dipole field lines. Model modified to describe HF-heating. Flexible local source of HF-heating introduced as heating rate per electron The key parameter in the model is the wave absorption efficiency The model verification made by comparison with the Tromso observations [ Rietveld et al., JGR, 2003 ].

5 Comparison with the EISCAT experiment The absorption efficiencies=0.16, 0.32 and 0.64.

6 Validation of numerical model of ducts Modified model reproduces observations with high accuracy, which establishes it as a key tool for the study of the artificial ionospheric modifications.

7 DEMETER It flied in circular (670 km altitude) sun-synchronous polar orbit. We use the plasma analyzer that measures the ion density, temperature and composition, and Langmuir probe that measures the electron temperature and density. DMSP satellites They fly in circular (840 km altitude) sun-synchronous polar orbits. We use the SSIES suite of sensors measuring the densities and drift motions of ionospheric ions. Ground based Diagnostics The HAARP ionosonde provides ionograms and skymaps, and Kodiak radar. Instrumentation

8 Duct detection by DEMETER DEMETER overflies HAARP twice a day 6-7 UT (local night) and UT (local day). Ducts were detected during both, day- and nighttime. Usually nighttime ducts are broader than that at day (more than 100 km versus 70 km) and having higher amplitude (ion density perturbations of 8-20% versus 5-10%)

9 Example DEMETER daytime observations 11/07/10 f=6.5 MHz, O-mode CW, Magn. Zen.

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14 04/24/07 f=3.2 MHz O-mode 0.1 Hz Magn. Zen. No electrojet Example of DEMETER nighttime observations 10/21/09 f=2.8 MHz, O-mode CW, Magn. Zen.

16 Comparison of SAMI2 results with DEMETER measurements (6:27-6:30 10/21/09 flying over at 27 km of the MZ)

17 Comparison of SAMI2 results with DEMETER measurements (20:18 – 20:20 11/07/10 flying over at 56 km of the MZ)

Model of day- and nighttime Ne artificial perturbations at 670 km 18

19 Ducts detection by DMSP satellites Although DMSP’s are less sensitive than DEMETER they have detected ducts on a regular basis The best ducts detection occurs at dusk (17:30-18:00 LT) almost 100% successful detections In the morning (10-11 LT) ~50% successful detections During nighttime (20-22 LT) a few occasional detections.

20 Example of DMSP observations (dusk) 10/31/10 f=5.6 MHz, O- mode CW, Magn. Zen.

21 Ducts detection by DMSP satellites 10/31/10 f=5.6 MHz, O-mode CW, Magn. Zen.

22 Kodiak radar diagnostics HF-heating

23 DMSP experiments (morning) 11/01/10 f=4.1 MHz, O- mode CW, Magn. Zen.

24 Ducts detection by DMSP satellites

25 Kodiak radar diagnostics HF-heating

26 Duct detection by DMSP satellites (dusk)

27 DMSP Experiment 02/04/10 2:10-2:30 UT

28 Conclusions Conclusions Artificial ducts were detected on a regular basis by DEMETER and DMSPs during HAARP campaigns. DEMETER always detects ducts for the quiet ionosphere when flies close to MZ. DMSPs detection efficiency of ducts depends on the time of the day (highest at dusk, lowest at night). Modified SAMI2 model provides quantitative predictions of the ducts amplitude and extension which established it as a key tool for the study of ducts.