Formation of Artificial Formation of Artificial Ionospheric DuctsIonospheric DuctsGennady Milikh, Dennis PapadopoulosGennady Milikh, Dennis Papadopoulos

University of Maryland, University of Maryland, Joe Huba, Glenn JoyceJoe Huba, Glenn Joyce Naval Research LaboratoryNaval Research Laboratory

Umran Inan, Dennys Piddyachiy,Umran Inan, Dennys Piddyachiy, Stanford UniversityStanford University

Chia-Lee ChangChia-Lee Chang, BAE systems, BAE systemsMichel ParrotMichel Parrot, LPCE/CNRS, France, LPCE/CNRS, FranceEvgenii MishinEvgenii Mishin, Boston College , Boston College

IntroductionIntroduction

• Naturally induced field aligned irregularities of the plasma density exhibit enhanced refractive indices and act as ducts that guide waves in the whistler range between the two hemispheres.

• HF heating of the ionosphere creates density perturbations that may propagate into the plasmasphere, thus produce artificial ducts.

ObjectivesObjectives

•To present the results of a theoretical study that addresses generation of artificial ducts by strong HF heating of the F-region of the ionosphere.

•To check the model against observations of the density perturbations caused by the HAARP while detected by the Demeter satellite.

The SAMI2 model of the ionosphereThe SAMI2 model of the ionosphere[Huba,Joyce,Fedder, [Huba,Joyce,Fedder, JGRJGR, , 105A,2000105A,2000]]

•SAMI2 models the plasma along the Earth’s dipole field from one hemisphere to another.

•The model solves ion continuity equations for seven ion species along with momentum and temperature equations for ions and electrons.

•It includes models of neutral atmosphere, horizontal winds, and photo-deposition into the atmosphere, along with model for the ion chemistry.

The SAMI2 model has been modifiedThe SAMI2 model has been modified[Perrine,Milikh,Papadopoulos,Huba,Joyce, [Perrine,Milikh,Papadopoulos,Huba,Joyce, RadRad

Sci,41Sci,41,2006] ,2006]

•A flexible source of electron heating was added.

•The source is characterized by the heating rate per electron (Q, in K/s), its altitude z0, vertical extent of the heated region, and its geographic coordinates.

- is the absorption coefficient, W – radiated HF - power,

V – the HF - heated volume.

For the current HAARP q could reach 5,000 K/s.

eVnWq

azzqsKQ

/

},/)(exp{)/( 220

Output of the ModelOutput of the Model• A thermal wave is generated near the F2 peak as

a result of strong electron HF-heating.

• Such a wave propagates through the ionosphere/magnetosphere, and can reach the conjugate point.

• Amplitude of the perturbations (in ion and electron temperature and density) have a non-linear saturation relationship to the strength of the heating source.

Ion TemperatureIon Temperature

Ion temperature with ambient conditions shown by dashed lines. Heating parameters for these data: Q = 5000 K/s, z0 = 380 km.

At 400 km from the source along the field line 8.0/ 0 ii TT

Ion fractionIon fraction

2.0/ 0 ii nnAt 400 km from the source along the field line

Analysis of the Demeter Analysis of the Demeter Observations Observations

• We focus on the ion temperature and density of O+, H+, He+ measured by Demeter flying at 670 km height.

•Altogether 6 observations were available

• In 2 cases the ionosphere was transparent for the HAARP radio beam )( 20Fff no perturbations were detected • In the rest 4 cases the increase of the ion temperature was detected along with the ion outflows.

f=3.2 MHzO-mode0.1 HzMagn. Zen.

No electrojet

6.0/ 0 ii TT

7.0/ 0 ii nn

The outflows of oxygen ions pushes upward the hydrogen ions, thus reducing their density at the Demeter’s altitude. Demeter measures Ey=250-300 mV/m thus VD=4-5 km/s• Since HF-heating starts 5-10 min before Demeter over-flies HAARP, the outflows spread by 1,500-2,000 km.• The ExB drift is directed Southward leading to the observed asymmetry in the ion outflows.

• The shift between the ion temperature and density peaks is due to two different generation mechanisms:

1. Local electron heating generates thermal wave.

2. Plasma density perturbed at the heated spot creates pressure imbalance driving plasma along B.

1414

f=3.3 MHzO-mode0.2 HZMagn. Zen

The shortest distance to

HAARP 137 km

3.0/ 0 ii TT

1/ 0 ii nn

F=2.85MHzO-mode0.7 HzMag. Zen.

Shortest distance to HAARP 94 km

2/ 0 ii TT

5.2/ 0 ii nn

f=4.4 MHzX-mode0.2 HzMagn. Zen.

Shortest distance to HAARP 110 km

2.0/ 0 ii TT

4.0/ 0 ii nn

ConclusionsConclusions• Ion outflows due to the ionospheric

heating by HAARP were detected by Demeter.

• The best conditions for the outflows generation occurred when matching F2 peak in the absence of the electrojet.

• Modified SAMI2 model provides qualitative predictions of the outflows amplitude.

• In order to improve our predictions a version of SAMI2 developed for studies of the high latitude ionosphere will be used.

Additional slidesAdditional slides

Comments: increase in O+ density was masked by the ionospheric disturbances occurred at 6:30. It is 1 min shift between Ti and ni peaks.

Comments: the electrojet is heated by the HF beam of X-mode, and relatively low intensity, however a weaker outflows occur. The hydrogen and helium ions are pushed upward by the outflows of the oxygen ions. It is no shift between Ti and ni peaks.