Polar cap X‐rays and electrons under low density solar wind conditions: Coordinated PIXIE and DMSP observations on 11 May 1999

Anderson, P. C.; McKenzie, D. L.; Datlowe, D. W.; Hawley, J. D.; Petrinec, S. M.; Schulz, Michael; Larson, D. E.

doi:10.1029/2000gl011983

Cited by 6 publications

(5 citation statements)

References 12 publications

(11 reference statements)

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“…In an investigation of X‐ray images and coincident DMSP satellite particle measurements during a period of low solar wind density Andersen et al [1999] found an intense emission and multi‐component precipitation at high latitude. They interpreted the lower‐energy component (few hundred eV) as suprathermal electrons from the solar wind, and the higher‐energy component (centered around 7 keV) as electrons which were accelerated in solar flares.…”

Section: Discussionmentioning

confidence: 99%

“…During several of our coincident FAST passes, we observe similar two electron components with energies below 100 eV and around 400–1000 eV in the polar cap (not shown here). Here, we concentrate on the very localized emission which they describe as “inverted‐V'” electron fluxes at the dusk side above 80° latitude [see Andersen et al , 1999, Figure 1], and which they claim would have produced little in the way of X‐ray fluxes to be observed by PIXIE because their energies were too low. These electrons should have produced intense FUV emission.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Properties of localized, high latitude, dayside aurora

Frey

Immel

et al. 2003

J. Geophys. Res.

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[1] The FUV instrument on the IMAGE spacecraft frequently observes intense ultraviolet (UV) emission from a localized dayside region poleward of the general auroral oval location. One type of these emissions has been described as the signature of direct proton precipitation into the cusp after lobe reconnection during northward interplanetary magnetic field (IMF) and high solar wind dynamic pressure periods . Here we describe a completely different type of high latitude aurora, which does not show any signature of precipitating protons. It also occurs during northward IMF conditions however, only during periods of very low solar wind dynamic pressure. It occurs at a much higher geomagnetic latitude than the normal cusp location and only during periods of positive IMF B y . The intensity of the UV emission is somewhat anti-correlated with the solar wind dynamic pressure, much in contrast to the cusp emission. The brightness of the localized emission changes rapidly on time scales between 30 and 70 minutes without corresponding changes in solar wind properties. Coincident measurements by the FAST spacecraft verify that this is not the cusp, that ion precipitation is absent in these regions, and that strong precipitation of field-aligned accelerated electrons causes the aurora. We interpret this aurora as the optical signature of electron precipitation in the upward leg of a current system which closes the downward leg of the current system into the cusp in the ionosphere.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Properties of localized, high latitude, dayside aurora

Frey

Immel

et al. 2003

J. Geophys. Res.

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“…X-ray observations therefore provide a remote mapping of the entire auroral region at high temporal and spatial resolution, including the energy of the detected X-rays. In addition to observing discrete aurora, X-ray emissions from diffuse aurora (due to diffuse energetic electron precipitation) are observable [Anderson et al, 2000;Chen et al, 2005]. Electron energy deposition and spectral characteristics as a function of latitude and local time can readily be derived from the global X-ray observations.…”

Section: Mission Conceptmentioning

confidence: 99%

Auroral Imaging Suite (AIS)

Petrinec,

Mobilia

2023

Bulletin of the AAS

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The Auroral Instrument Suite mission is to provide simultaneous measurements over the entire Earth's auroral region in multiple wavelengths using two satellites with identical payloads.Auroral emissions provide quantitative measures of energy and particle deposition into the Earth's ionosphere, which can result in sudden and significant changes in conductivity and largescale currents which relate to physical phenomena at lower atmospheric layers and ground level geomagnetic activity. Knowledge of such changes to the ionosphere as observed by auroral activity can provide actionable information for various agencies, institutes, and other interested parties.Satellite auroral imagers are widely recognized as essential tools for providing diagnostics of global (macro) magnetospheric activity. Most measurements today still consist of ground-based and in situ observations. These are heavily interpolated between widely spaced samples, and do not provide the necessary temporal and spatial resolution.Continuous coverage of high-latitudes and over all local times is not possible with a single spacecraft. Two properly placed spacecraft in high inclination orbits will measure all local times while providing conjugate data from the other hemisphere.

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“…Energetic electrons from solar electron events have long been known to enter the magnetotail and in fact were early evidence that tail field lines were connected to the IMF [ Lin and Anderson , 1966]. More recently, Anderson et al [2000] used Polar observations to detect X‐ray emissions over the polar cap that were associated with >10 keV precipitating solar electrons measured with DMSP. To our knowledge, however, the precipitation of solar electron bursts over the polar cap at energies <10 keV has not been previously reported.…”

Section: Solar Electron Eventmentioning

confidence: 99%

Polar rain gradients and field‐aligned polar cap potentials

et al. 2008

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[1] ACE SWEPAM measurements of solar wind field-aligned electrons have been compared with simultaneous measurements of polar rain electrons precipitating over the polar cap and detected by DMSP spacecraft. Such comparisons allow investigation of cross-polar-cap gradients in the intensity of otherwise-steady polar rain. The generally good agreement of the distribution functions, f, from the two data sources confirms that direct entry of solar electrons along open field lines is indeed the cause of polar rain. The agreement between the data sets is typically best on the side of the polar cap with most intense polar rain but the DMSP f's in less intense regions can be brought into agreement with ACE measurements by shifting all energies by a fixed amounts that range from tens to several hundred eV. In most cases these shifts are positive which implies that field-aligned potentials of these amounts exist on polar cap field lines which tend to retard the entry of electrons and produce the observed gradients. These retarding potentials undoubtedly appear in order to prevent the entry of low-energy electrons and maintain charge quasi-neutrality that would otherwise be violated since most tailward flowing magnetosheath ions are unable to follow polar rain electrons down to the polar cap. In more limited regions near the boundary of the polar cap there is sometimes evidence for field-aligned potentials of the opposite sign that accelerate polar rain electrons. A solar electron burst is also studied and it is concluded that electrons from such bursts can enter the magnetotail and precipitate in the same manner as polar rain.

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Polar cap X‐rays and electrons under low density solar wind conditions: Coordinated PIXIE and DMSP observations on 11 May 1999

Cited by 6 publications

References 12 publications

Properties of localized, high latitude, dayside aurora

Properties of localized, high latitude, dayside aurora

Auroral Imaging Suite (AIS)

Polar rain gradients and field‐aligned polar cap potentials

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