Statistical characteristics of electromagnetic energy transfer between the magnetosphere, the ionosphere, and the thermosphere

Fujii, Ryoichi; Nozawa, Satonori; Buchert, S. C.; Brekke, A.

doi:10.1029/98ja02750

Cited by 46 publications

(79 citation statements)

References 20 publications

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“…(2), J ·E is the electromagnetic energy transfer rate, which is further converted into both Joule heating rate and mechanical energy transfer rate as stated above. Typical energy deposition rates derived from this method are 50 GW during moderate activity to several hundred GW during high geomagnetic activity (Lu et al, 1995;Thayer, 1998b;Fujii et al, 1999). The ability to establish the partitioning between the two components is a particular strength of the radar technique (Fujii et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Precipitating energetic particles induce ionization and heating via collisions, and the energy deposited in this process can be quantified by remote-sensing far-ultraviolet emissions (Rees et al, 1988;Lummerzheim et al, 1997). On the other hand, electromagnetic energy transferred from the magnetosphere to the ionosphere is dissipated as Joule heating (e.g., Cole, 1962) or converted into mechanical energy of the neutral gas (e.g., Thayer et al, 1995;Fujii et al, 1999). Evaluating the relative contributions of particle and electromagnetic energy transport to the ionosphere is central to understanding the effects of the energy on the dynamics of the ionosphere and thermosphere.…”

Section: Introductionmentioning

confidence: 99%

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High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

et al. 2005

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Abstract. We present a case study of a prolonged interval of strongly northward orientation of the interplanetary magnetic field on 16 July 2000, 16:00-19:00 UT to characterize the energy exchange between the magnetosphere and ionosphere for conditions associated with minimum solar windmagnetosphere coupling. With reconnection occurring tailward of the cusp under northward IMF conditions, the reconnection dynamo should be separated from the viscous dynamo, presumably driven by the Kelvin-Helmholtz (KH) instability. Thus, these conditions are also ideal for evaluating the contribution of a viscous interaction to the coupling process. We derive the two-dimensional distribution of the Poynting vector radial component in the northern sunlit polar ionosphere from magnetic field observations by the constellation of Iridium satellites together with drift meter and magnetometer observations from the Defense Meteorological Satellite Program (DMSP) F13 and F15 satellites. The electromagnetic energy flux is then compared with the particle energy flux obtained from auroral images taken by the far-ultraviolet (FUV) instrument on the Imager for Magnetopause to Aurora Global Exploration (IMAGE) spacecraft. The electromagnetic energy input to the ionosphere of 51 GW calculated from the Iridium/DMSP observations is eight times larger than the 6 GW due to particle precipitation all poleward of 78 • MLAT. This result indicates that the energy transport is significant, particularly as it is concentrated in a small region near the magnetic pole, even under conditions traditionally considered to be quiet and is dominated by the electromagnetic flux. We estimate the contributions of the high and mid-latitude dynamos to both the Birkeland currents and electric potentials finding that highlatitude reconnection accounts for 0.8 MA and 45 kV while we attribute <0.2 MA and ∼5 kV to an interaction at lower latitudes having the sense of a viscous interaction. Given that these conditions are ideal for the occurrence of the KH instability at the magnetopause and hence the viscous interaction, Correspondence to: H. Korth (haje.korth@jhuapl.edu) this result suggests that the viscous interaction is a small contributor to coupling solar wind energy to the magnetosphereionosphere system.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

et al. 2005

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“…[2] In studies of energy input to the ionosphere [e.g., Lu et al, 1995;Thayer et al, 1995;Fujii et al, 1999;Thayer, 2000;Richmond and Thayer, 2000], the rate of energy conversion from electromagnetic to mechanical form, J Á E, is commonly expressed as the sum of two terms, Joule heating and work done. Defining Joule heating in this context, however, is not as simple as might seem at first.…”

Section: Introductionmentioning

confidence: 99%

Meaning of ionospheric Joule heating

2005

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[1] The possibility of relating the electric current in the ionosphere to the electric field in the frame of reference either of the neutral atmosphere (as commonly done) or of the plasma raises the question: which should be used in calculating Joule heating? The energy equations for the plasma and for the neutral medium, including collision effects, can be combined with momentum equations to separate energy transfer into work done and heating (this is not the same as separation of energy content into bulk-flow kinetic energy and thermal energy). Heating/dissipation processes can be unambiguously identified, showing that true electromagnetic (Joule) heating rate is given by J Á E in the frame of reference of the plasma. The major part of energy dissipation associated with J and E in the ionosphere is heating by collisions between plasma and neutrals, proportional to the square of the difference in their bulk flow velocities and distributed approximately equally between the two. The conventionally calculated ionospheric Joule heating as J Á E in the frame of reference of the neutral atmosphere equals the sum of total heating rate of plasma (only a small part of which is true Joule heating) plus total heating rate of neutrals, plus a term equal to work done on plasma in the neutral-atmosphere frame of reference; the latter is assumed negligible, with J Â B/c balanced entirely by plasmaneutral collisions and with no net work done on the plasma. This assumption implies that all the magnetic stresses exerted on the plasma at ionospheric heights are taken up by the local neutral medium; hence the dynamics of the neutral atmosphere play an important role in magnetosphere/ionosphere interactions.

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“…First, this vertical velocity may rarely exceed 200 m/s, since the perpendicular plasma velocity seldom becomes larger than the corresponding velocity 1000 m/s (see e.g., Fig. 3a of Fujii et al, 1999). Hence the threshold criterion 2 for the maximum velocity 200 m/s is reasonable.…”

Section: Discussionmentioning

confidence: 99%

“…Although we do not fully understand what causes this MLT dependence, one possible explanation is as follows. Statistically, the electric ®eld strength, the electromagnetic energy input from the magnetosphere to the ionosphere and the Joule heating rate become largest in the dawn and dusk regions (Fujii et al, 1999), rather than in the midnight region. This MLT dependence may suggest that ions in the dawn and dusk regions more frequently obtain greater energy than those in the midnight region.…”

Section: Discussionmentioning

confidence: 99%

Ion upflow and downflow at the topside ionosphere observed by the EISCAT VHF radar

Endo¹,

Fujii²,

Ogawa³

et al. 2000

Annales Geophysicae

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Abstract. We have determined the MLT distribution and K P dependence of the ion up¯ow and down¯ow of the thermal bulk oxygen ion population based on a data analysis using the EISCAT VHF radar CP-7 data obtained at Tromsù during the period between 1990 and 1996: (1) both ion up¯ow and down¯ow events can be observed at any local time (MLT), irrespective of dayside and nightside, and under any magnetic disturbance level, irrespective of quiet and disturbed levels; (2) these up¯ow and down¯ow events are more frequently observed in the nightside than in the dayside; (3) the up¯ow events are more frequently observed than the down¯ow events at any local time except midnight and at any K P level and the di erence of the occurrence frequencies between the up¯ow and down¯ow events is smaller around midnight; and (4) the occurrence frequencies of both the ion up¯ow and down¯ow events appear to increase with increasing K P level, while the occurrence frequency of the down¯ow appears to stop increasing at some K P level.

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Statistical characteristics of electromagnetic energy transfer between the magnetosphere, the ionosphere, and the thermosphere

Cited by 46 publications

References 20 publications

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

Meaning of ionospheric Joule heating

Ion upflow and downflow at the topside ionosphere observed by the EISCAT VHF radar

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