Energization of ions in the auroral plasma by broadband waves: Generation of ion conics

Singh, Nagendra; Schunk, R. W.

doi:10.1029/ja089ia07p05538

Cited by 36 publications

(8 citation statements)

References 31 publications

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“…This produces transverse acceleration of the ions, which manifests as a temperature anisotropy. The transversely accelerated ions are then accelerated upward by the mirror force [Singh and Schunk, 1984;André et al, 1988;Chang et al, 1986]. Ion acceleration may also be driven by Alfvén waves at altitudes above the aurora [Lysak, 1986;Li and Temerin, 1993;Stasiewicz et al, 2000;Chaston et al, 2004;Singh et al, 2007;Seyler and Liu, 2007].…”

Section: 1002/2015ja021536mentioning

confidence: 99%

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

et al. 2016

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We present an analysis of in situ measurements from the MICA (Magnetosphere‐Ionosphere Coupling in the Alfvén Resonator) nightside auroral sounding rocket with comparisons to a multifluid ionospheric model. MICA made observations at altitudes below 325 km of the thermal ion kinetic particle distributions that are the origins of ion outflow. Late flight, in the vicinity of an auroral arc, we observe frictional processes controlling the ion temperature. Upflow of these cold ions is attributed to either the ambipolar field resulting from the heated electrons or possibly to ion‐neutral collisions. We measure trueE→×trueB→ convection away from the arc (poleward) and downflows of hundreds of m s−1 poleward of this arc, indicating small‐scale low‐altitude plasma circulation. In the early flight we observe DC electromagnetic Poynting flux and associated ELF wave activity influencing the thermal ion temperature in regions of Alfvénic aurora. We observe enhanced, anisotropic ion temperatures which we conjecture are caused by transverse heating by wave‐particle interactions (WPI) even at these low altitudes. Throughout this region we observe several hundred m s−1 upflow of the bulk thermal ions colocated with WPI; however, the mirror force is negligible at these low energies; thus, the upflow is attributed to ambipolar fields (or possibly neutral upwelling drivers). The low‐altitude MICA observations serve to inform future ionospheric modeling and simulations of (a) the need to consider the effects of heating by WPI at altitudes lower than previously considered viable and (b) the occurrence of structured and localized upflows/downflows below where higher‐altitude heating rocesses are expected.

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Section: 1002/2015ja021536mentioning

confidence: 99%

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

et al. 2016

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“…Given that a lower hybrid wave amplitude of roughly 10 mV/m can be excited up to 5000 km above a 250 kW VLF transmitter, what heating rates can be expected for suprathermal ions? This question is difficult to answer precisely since there is presently no commonly accepted mechanism for the heating of ions by lower hybrid waves, and both resonant [Chang and Coppi, 1981] and nonresonant [Singh and Schunk, 1984] heating mechanisms have been proposed, as well as nonlinear resonant heating [Karney and Bers, 1977;Karney, 1978;Papadopoulos et al, 1980]. For the sake of argument, we assume that linear resonant heating is the dominant mechanism and that the effect of the Earth's magnetic field on the motion of the ions can be neglected [Chang and Coppi, 1981].…”

Section: Appendix' Heating Calculationsmentioning

confidence: 99%

Lower hybrid waves excited through linear mode coupling and the heating of ions in the auroral and subauroral magnetosphere

Bell¹,

Helliwell²,

Hudson³

1991

J. Geophys. Res.

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Experimental observations on the ISIS 1, ISIS 2, ISEE 1, and DE 1 spacecraft demonstrate that strong lower hybrid (LH) waves can be excited by VLF electromagnetic (em) whistler mode waves as the em waves propagate through regions of the ionosphere and magnetosphere where small‐scale magnetic‐field‐aligned irregularities exist in the mean plasma density. There is strong evidence that the LH waves are excited by linear mode coupling as the em waves scatter from the irregularities. The present paper considers two related aspects of the linear mode conversion mechanism: (1) the controlled heating of suprathermal ions in the ionosphere and magnetosphere over a powerful VLF/ELF transmitter using LH waves excited by the em transmitter signals through linear mode conversion; (2) the excitation of intense LH waves in the auroral regions through the linear conversion of VLF/ELF em auroral hiss, and the subsequent heating of ions by the excited LH waves. In addressing both aspects a critical feature is the behavior of the mode coupling mechanism at frequencies less than 10.2 kHz, the lowest value observed in earlier experiments. Using the results of controlled experiments carried out at Siple Station, Antarctica, it is demonstrated that strong LH waves can be excited by em waves down to frequencies as low as 2 kHz in the subauroral low‐altitude magnetosphere. Extrapolating from these observations and making use of ISEE 1 satellite wave amplitude data, we conclude that a ∼250 kW VLF/ELF transmitter operating in the subauroral region at 2 kHz could excite sufficiently intense LH waves to heat suprathermal 1 eV H+ ions and 16 eV O+ ions to roughly 50 eV in a region extending in altitude from 1000 to 5000 km above the transmitter with a horizontal scale of ∼500 km. Furthermore, if coherent wave stochastic heating occurs, the energy gain of O+ ions could be as large as 200 eV. This effect would be readily measurable with available satellite instrumentation. Using a recently developed model of the linear mode coupling mechanism, we furthermore conclude that a significant portion of the LH waves observed in the auroral zone in regions of ion conic development may be excited by em VLF/ELF auroral hiss as the hiss propagates through the irregular background plasma commonly observed in the auroral regions.

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“…Even if this approximation of long wavelength is not valid, as in the case of electrostatic ion cyclotron waves, it is possible to cast the heating rate in the form of (1) but with • replaced by an effective power spectral density properly weighted over the wave numbers and the Bessel functions which appear in the quasi-linear heating rate [e.g., Lysak et al, 1980]. Heating rates similar to (1) have been used for plasma heatings by Ichimaru [ 1975] and Singh and Schunk [1984] when the broadband feature of the plasma turbulence is included.…”

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Perpendicular ion heating effects on the refilling of the outer plasmasphere

Singh¹,

Hwang²

1987

J. Geophys. Res.

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The trapping and the thermalization of the outflowing ionospheric plasma in the outer plasmaspheric flux tubes during refilling after geomagnetic storms involves microscopic processes, which in the initial stage of the refilling are essentially collisionless. Although there are several observations on upflowing ions with anisotropic pitch angle distributions at superthermal energies in the region of the refilling, the role of such heated ions in the refilling has not been examined. It is shown here that an extended perpendicular ion heating by a low‐level background plasma noise near the ion cyclotron frequency with spectral power density ψ ∼ 10−11 V² m−2 Hz−1 can be effective in trapping the bulk of the ions in the flux tube. Such electric field noise levels can be generated by fluctuations associated with the equilibrium near marginal stability of a low‐density plasma mainly consisting of very hot ions originating from the ring current. The heated bulk ions have energies (∼ 1 eV) characteristic of the filled plasmasphere. When the turbulence level exceeds the above level, the heated ions show the features of the ion conies in the superthermal energy range observed along the field lines of refilling. In contrast to the weak extended heating, when the heating is intense and localized in the equatorial region, the trapped ions are shown to set up parallel electric fields pointing away from the equator. The potential drop associated with such fields are found to be large enough to stop interhemispheric flow by reflecting the ionospheric plasma streams.

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Energization of ions in the auroral plasma by broadband waves: Generation of ion conics

Cited by 36 publications

References 31 publications

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

Lower hybrid waves excited through linear mode coupling and the heating of ions in the auroral and subauroral magnetosphere

Perpendicular ion heating effects on the refilling of the outer plasmasphere

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