A relation between the energy deposition by electron precipitation and geomagnetic indices during substorms

Østgaard, Nikolai; Vondrak, R. R.; Gjerloev, J. W.

doi:10.1029/2001ja002003

Cited by 65 publications

(65 citation statements)

References 24 publications

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“…The spatial extent of vertical motion will naturally depend on the driving forces which are acting. Spatially localized impulsive heating events, for example, associated with auroral precipitation and/ or locally enhanced Joule heating (common during substorms [e.g., Chun et al, 2002;Østgaard et al, 2002]), may drive strong vertical winds in the upper thermosphere which are confined to relatively small horizontal areas. Large-scale driving forces, possibly associated with quasi-stationary (in a Sun-aligned coordinate system) sources of heating or divergent/convergent ion motion, might be expected to produce a similarly large-scale vertical wind response.…”

Section: Discussionmentioning

confidence: 99%

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

et al. 2011

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[1] Results are presented from two nights of bistatic Doppler measurements of neutral thermospheric winds using Fabry-Perot spectrometers at Mawson and Davis stations in Antarctica. A scanning Doppler imager (SDI) at Mawson and a narrow-field Fabry-Perot spectrometer (FPS) at Davis have been used to estimate the vertical wind at three locations along the great circle joining the two stations, in addition to the vertical wind routinely observed above each station. These data were obtained from observations of the 630.0 nm airglow line of atomic oxygen, at a nominal altitude of 240 km. Low-resolution all-sky images produced by the Mawson SDI have been used to relate disturbances in the measured vertical wind field to auroral activity and divergence in the horizontal wind field. Correlated vertical wind responses were observed on a range of horizontal scales from ∼150 to 480 km. In general, the behavior of the vertical wind was in agreement with earlier studies, with strong upward winds observed poleward of the optical aurora and sustained, though weak, downward winds observed early in the night. The relation between vertical wind and horizontal divergence was seen to follow the general trend predicted by Burnside et al. (1981), whereby upward vertical winds were associated with positive divergence and vice versa; however, a scale height approximately 3-4 times greater than that modeled by NRLMSISE-00 was required to best fit the data using this relation.

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Section: Discussionmentioning

confidence: 99%

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

et al. 2011

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“…As particle precipitation through ionization affects the Hall conductance and thereby increases the Hall currents resulting in disturbances of the geomagnetic field, U A is believed to be related to the AE (or AL ) indices [ Akasofu , 1981; Spiro et al , 1982; Ahn et al , 1983; Richmond , 1990; Lu et al , 1998; Østgaard et al , 2002]. Where instantaneous global measurements of electron precipitation are not available, the U A have to be derived indirectly from radars or magnetic data or from statistical particle measurements by low‐altitude satellites.…”

Section: Introductionmentioning

confidence: 99%

Energy analysis of substorms based on remote sensing techniques, solar wind measurements, and geomagnetic indices

Østgaard

Stadsnes

Vondrak

2002

Journal of Geophysical Research: Space Physics

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[1] Observations from the Polar Ionospheric X-ray Imaging Experiment (PIXIE) and the Ultraviolet Imager (UVI) on board the Polar satellite have been used to examine the energy deposition in the Northern Hemisphere by precipitating electrons for seven substorms during 1997. By combining the results from these two remote sensing techniques we derive the 5 min average electron energy distributions from 100 eV to 100 keV with a spatial resolution of $700 km. During growth phase we find that most of the energy is carried by electrons below 10 keV. The study shows that the maximum intensity of the substorm is mostly defined by the flux of electrons below 10 keV. In contrast, the electrons above 10 keV show a greater intensification at substorm onset and are more confined azimuthally during the expansion phase. By using the most appropriate parameterized methods to estimate the energy increase of the ring current (U R ) and the Joule heating rate in both hemispheres (U J ) and by adding the rate of energy deposition in both hemispheres by precipitating electrons (U A ), we estimate the total energy dissipation rate during substorms (U T ). Our estimate of U A is a factor 2-4 larger than that reported in earlier studies. We find that the contributions to the total time-integrated energy dissipation over the duration of the substorm, W(U T ), from W(U R ), W(U J ), and W(U A ) on average are 15%, 56%, and 29%. Comparing W(U T ) and the time-integrated parameter, W(), which approximates the solar wind input due to dayside reconnection, we find that the parameter does not always provide enough energy into the magnetosphere to balance W(U T ). An additional energy transfer mechanism is needed to balance the energy budget. We find that a viscous interaction that transfers 0.17% of the solar wind kinetic energy in addition to the energy transfer due to dayside reconnection, estimated by the parameter, is sufficient to balance the total energy dissipation U T .INDEX TERMS: 2784 Magnetospheric Physics: Solar wind/ magnetosphere interactions; 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions; 2455 Ionosphere: Particle precipitation; 2716 Magnetospheric Physics: Energetic particles, precipitating; KEYWORDS: energy budget of substorms, X-ray and UV imaging, particle precipitation, Joule heating, ring current, solar wind Citation: Østgaard, N., G. Germany, J. Stadsnes, and R. R. Vondrak, Energy analysis of substorms based on remote sensing techniques, solar wind measurements, and geomagnetic indices,

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“…The transport mechanism might change, so that the way by which the energy flux is carried is different at different altitudes. There is also the possibility that energy is transported as kinetic energy carried by particles, see, for example, Ostgaard et al (2002).…”

Section: Introductionmentioning

confidence: 99%

Intense high-altitude auroral electric fields - temporal and spatial characteristics

et al. 2004

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Abstract. Cluster electric field, magnetic field, and energetic electron data are analyzed for two events of intense auroral electric field variations, both encountered in the Plasma Sheet Boundary Layer (PSBL), in the evening local time sector, and at approximately 5 R E geocentric distance. The most intense electric fields (peaking at 450 and 1600 mV/m, respectively) were found to be quasi-static, unipolar, relatively stable on the time scale of at least half a minute, and associated with moving downward FAC sheets (peaking at ∼10 µA/m 2 ), downward Poynting flux (peaking at ∼35 mW/m 2 ), and upward electron beams with characteristic energies consistent with the perpendicular potentials (all values being mapped to 1 R E geocentric distance). For these two events in the return current region, quasi-static electric field structures and associated FACs were found to dominate the upward acceleration of electrons, as well as the energy transport between the ionosphere and the magnetosphere, although Alfvén waves clearly also contributed to these processes.

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A relation between the energy deposition by electron precipitation and geomagnetic indices during substorms

Cited by 65 publications

References 24 publications

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

Energy analysis of substorms based on remote sensing techniques, solar wind measurements, and geomagnetic indices

Intense high-altitude auroral electric fields - temporal and spatial characteristics

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