Ionospheric modification experiments with the Tromsø heating facility

Stubbe, P.; Kopka, H.; Rietveld, M. T.; Frey, A.; Høeg, Per; Kohl, H.; Nielsen, E.; Rose, G.; Hoz, C. La; Barr, R.; Derblan, H.; Hedberg, Å.; Thidé, Bo; Jones, T. B.; Robinson, T. R.; Brekke, A.; Hansen, Truls Lynne; Holt, H. E.

doi:10.1016/0021-9169(85)90085-6

Cited by 91 publications

(44 citation statements)

References 49 publications

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“…These changes lead to the modification of ionospheric conductivity that in turn affects the ionospheric current closure. In a series of EISCAT experiments (Stubbe et al, 1982;1985) the HF heating signal has been modulated in the ULF frequency range leading to the generation of ULF magnetic pulsations. However, the amplitude of the stimulated ULF pulsations, registered by ground-based magnetometers, turned out to be almost two orders of magnitude higher than predicted by the theory.…”

Section: Introductionmentioning

confidence: 99%

Simulations of resonant Alfvén waves generated by artificial HF heating of the auroral ionosphere

Pokhotelov

Lotko²,

Streltsov³

2004

Ann. Geophys.

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Abstract. Numerical two-dimensional two-fluid MHD simulations of dynamic magnetosphere-ionosphere (MI) coupling have been performed to model the effects imposed on the auroral ionosphere by a powerful HF radio wave transmitter. The simulations demonstrate that modifications of the ionospheric plasma temperature and recombination due to artificial heating may trigger the ionospheric feedback instability when the coupled MI system is close to the state of marginal stability. The linear dispersion analysis of MI coupling has been performed to find the favorable conditions for marginal stability of the system. The development of the ionospheric feedback instability leads to the generation of shear Alfvén waves which resonate in the magnetosphere between the heated ionospheric E-region and the strong gradient in the Alfvén speed at altitudes of 1-2 R E . The application of the numerical results for the explanation of observations performed by low-orbiting satellites above the highlatitude ionosphere heated with a high power ground-based HF transmitter is discussed.

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Section: Introductionmentioning

confidence: 99%

Simulations of resonant Alfvén waves generated by artificial HF heating of the auroral ionosphere

Pokhotelov

Lotko²,

Streltsov³

2004

Ann. Geophys.

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“…The ElSCAT high power facility (heater) at Tromso, Norway, has been used extensively to generate both VLF and ULF electromagnetic radiations by means of modulated heating of the ionospheric conducting layers [Stubbe et al, 1982[Stubbe et al, , 1985Stubbe, 1996]. The EISCAT heater operates in the HF band between 3.9 and 8 MHz.…”

Section: Introductionmentioning

confidence: 99%

FAST observations of ULF waves injected into the magnetosphere by means of modulated RF heating of the auroral electrojet

Robinson¹,

Strangeway²,

Wright³

et al. 2000

Geophysical Research Letters

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Abstract. Results are reported from an experiment in which the HF high power facility at Tromso was utilised to inject artificial ULF waves into the magnetosphere by means of modulated heating of the auroral electrojet. Local electric field oscillations associated with the artificially stimulated ULF waves were detected on board the FAST spacecraft, at an altitude of 2550 km. In addition, a modulated downward flux of electrons was also detected. The artificially excited waves, together with these energised downward electrons, were observed in a narrow region only a few tens of km across the geomagnetic field, which mapped down the geomagnetic field line to the heated volume in the ionosphere.Furthermore, the downward flux exhibited energy dispersion in a manner that was consistent with the artificially excited waves having followed the geomagnetic field line out beyond the spacecraft, where they appear to have stimulated electron precipitation back down the field line.

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“…(2) and the radiation field is proportional to @ t J e (t À r/v A ) given by @ t J e ¼ ð5n 0 e 2 E 0 =6mÞf½xðX e 2 À en 2 Þ Àŷ 2X e en =ð en 2 þ X e 2 Þ 2 gð en =T e Þ@ t T e : (8) With the aid of Eqs. (2) and (8) …”

Section: A Formulation Of Electrojet Modulationmentioning

confidence: 97%

“…The induced alternating current (AC) in the electrojet is then the antenna current for VLF radiation at the modulation frequency and its harmonics. Generation of VLF waves in the high latitude ionosphere via electrojet modulation has been studied experimentally [1][2][3][4][5][6][7][8][9][10][11][12][13] and theoretically. [12][13][14][15][16][17][18][19][20][21][22] The heating and cooling rates as well as the available heating and cooling times in one modulation period affect the efficacy of conductivity modulation by an intensity modulated HF heater.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric very low frequency transmitter

Kuo

2015

Physics of Plasmas

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The theme of this paper is to establish a reliable ionospheric very low frequency (VLF) transmitter, which is also broad band. Two approaches are studied that generate VLF waves in the ionosphere. The first, classic approach employs a ground-based HF heater to directly modulate the high latitude ionospheric, or auroral electrojet. In the classic approach, the intensity-modulated HF heater induces an alternating current in the electrojet, which serves as a virtual antenna to transmit VLF waves. The spatial and temporal variations of the electrojet impact the reliability of the classic approach. The second, beat-wave approach also employs a ground-based HF heater; however, in this approach, the heater operates in a continuous wave mode at two HF frequencies separated by the desired VLF frequency. Theories for both approaches are formulated, calculations performed with numerical model simulations, and the calculations are compared to experimental results. Theory for the classic approach shows that an HF heater wave, intensity-modulated at VLF, modulates the electron temperature dependent electrical conductivity of the ionospheric electrojet, which, in turn, induces an ac electrojet current. Thus, the electrojet becomes a virtual VLF antenna. The numerical results show that the radiation intensity of the modulated electrojet decreases with an increase in VLF radiation frequency. Theory for the beat wave approach shows that the VLF radiation intensity depends upon the HF heater intensity rather than the electrojet strength, and yet this approach can also modulate the electrojet when present. HF heater experiments were conducted for both the intensity modulated and beat wave approaches. VLF radiations were generated and the experimental results confirm the numerical simulations. Theory and experimental results both show that in the absence of the electrojet, VLF radiation from the F-region is generated via the beat wave approach. Additionally, the beat wave approach generates VLF radiations over a larger frequency band than by the modulated electrojet. V C 2015 AIP Publishing LLC.

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Ionospheric modification experiments with the Tromsø heating facility

Cited by 91 publications

References 49 publications

Simulations of resonant Alfvén waves generated by artificial HF heating of the auroral ionosphere

Simulations of resonant Alfvén waves generated by artificial HF heating of the auroral ionosphere

FAST observations of ULF waves injected into the magnetosphere by means of modulated RF heating of the auroral electrojet

Ionospheric very low frequency transmitter

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