Southern Hemisphere poleward moving auroral forms

Drury, Easan; Mende, S. B.; Frey, H. U.; Doolittle, J. H.

doi:10.1029/2001ja007536

Cited by 27 publications

(36 citation statements)

References 32 publications

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“…While the IMF By dependence is qualitatively consistent with the tilt of the two-cell convection pattern (e.g., Weimer 2005), the patches are often seen to exit before 9 MLT under large negative IMF By (~−5.0 nT). The patch departures can be found as early as ~6 MLT, which is much farther away from noon than previously studied by Drury et al (2003), while the qualitative trend is consistent with their study. Since the throat of two-cell convection is not generally expected at such MLT, the patch motion likely involves substantial azimuthal propagation from initial PMAF locations closer to noon to the patch departure location.…”

Section: Imf By and Bz Dependencesupporting

confidence: 80%

“…PMAFs initiate near the poleward boundary of the dayside auroral oval and then propagate poleward before fading away (Lorentzen et al 2010). The mean lifetime of PMAFs is ~10 min, anti-sunward velocity is ~1 km/s, and latitudinal motion is ~5° (Drury et al 2003 and references therein).…”

Section: Introductionmentioning

confidence: 99%

“…While most cases have steady IMF conditions during the 20-min IMF averaging period, three cases have IMF Bz sign changes of more than ±1 nT and thus these cases may involve large changes in background convection. Here, the threshold is based on the earlier study by Drury et al (2003). These cases are marked in red when they appear in the panels of Fig.…”

Section: Imf By and Bz Dependencementioning

confidence: 99%

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Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

et al. 2016

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Recent imager and radar observations in the nightside polar cap have shown evidence that polar cap patches are associated with localized flow channels. To understand how flow channels propagate from the dayside auroral oval into the polar cap, we use an all-sky imager in Antarctica and DMSP (F13, F15, F16, F17 and F18) to determine properties of density and flows associated with dayside polar cap patches. We identified 50 conjunction events during the southern winter seasons of 2007-2011. In a majority (45) of events, longitudinally narrow flow enhancements directed anti-sunward are found to be collocated with the patches, have velocities (up to a few km/s) substantially larger than the large-scale background flows (~500 m/s) and have widths comparable to patch widths (~400 km). While the patches start with poleward moving auroral forms (PMAFs) as expected, many PMAFs propagate azimuthally away from the noon over a few hours of MLT, resulting in formation of polar cap patches quite far away from the noon, as early as ~6 MLT. The MLT separation from the noon is found to be proportional to the IMF |By|. Fast polar cap flows of >~1500 m/s are predominantly seen during large IMF |By| and small |Bz|. The presence of fast, anti-sunward flow channels associated with the polar cap patches suggests that the flow channels form in the dayside auroral oval through transient reconnection and can be the source of flow channels propagating into the polar cap.

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Section: Imf By and Bz Dependencesupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Imf By and Bz Dependencementioning

confidence: 99%

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Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

et al. 2016

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“…Thus, we find that the PMAF activity is limited to a more narrow clock angle regime (∼90-140 • ) than usually thought (on this point, see also Drury et al, 2003). By the term PMAF activity we mean an equatorward boundary intensification (EBI), manifest in the BPS aurora, followed by the activation of a cusp form (LLBL/cusp/mantle precipitation) which is moving northwest or northeast, depending on the IMF B y polarity, as described above.…”

Section: Summary Of Observationsmentioning

confidence: 84%

Dayside aurora and the role of IMF ∣By∣/∣Bz∣: detailed morphology and response to magnetopause reconnection

2004

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Abstract. We document the detailed spatio-temporal structure of the dayside aurora during intervals of ongoing dayside magnetopause reconnection, primarily during interplanetary magnetic field (IMF) B z ≤0 conditions. The present study is based on ground auroral observations in combination with particle precipitation data from a DMSP spacecraft. We describe auroral forms corresponding to the following particle precipitation regimes identified by Newell and Meng (1994): (i) central plasma sheet (CPS), (ii) precipitation void, (iii) dayside boundary plasma sheet (BPS), and (iv) cusp (LLBL/cusp/mantle). Two distinctly different auroral configurations are observed, corresponding to different regimes of the IMF clock angle (θ ) and the |B y |/|B z | ratio. Two regimes are defined. In regime (I) θ lies within ∼ 90-135 • and |B y |/|B z |>1 (B y -dominated), while in regime (II) θ is in the range 135 • -180 • and |B y |/|B z |<1 (B z -dominated). Within regime (I) the auroral response to reconnection events typically progresses from lower to higher latitudes in stages as indicated below: (A) equatorward boundary intensifications (EBIs): sequential brightenings of closely spaced, fragmented, rayed bands (BPS aurora) within the ∼08:00-15:00 MLT sector, each of which are moving noonward/sunward, (B) poleward moving auroral forms (PMAFs): forms expanding westward from the postnoon side (B y >0) and later appearing as a poleward expanding form in the convection throat in the ∼09:00-12:00 MLT sector, with a fading phase in the regime of mantle precipitation. During strongly southward IMF conditions (regime II), the intense PMAF activity is replaced by a more latitudinally restricted, but longitudinally wide aurora of moderate intensity. The latter auroral state is accompanied by a 2-cell convection pattern which is rather symmetrical about noon. This state is very different from the convection/FAC configuration present during IMF regime (I), with its strong zonal flows (convection current), more intense FAC sheets and PMAF activity in the midday sector. The strong Correspondence to: P. E. Sandholt (p.e.sandholt@fys.uio.no) IMF regulation of the dayside BPS aurora, consisting of keV electrons, and its location with respect to the green line auroral gap (precipitation void), indicate that it is an important signature of the reconnection process, located on open boundary layer field lines. The observed longitudinal bifurcation of the auroral brightenings (EBIs) preceding PMAFs is consistent with antiparallel magnetopause reconnection.

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“…A special purpose dual wavelength low light level auroral all-sky imager 22 was developed for the AGO application by Stephen Mende and Jack H. Doolittle at the Lockheed Palo Alto Research Laboratories. The lifetime of the parent state of 630 nm is long ͑110 s͒ and the emission takes place only if the excited atom avoids collisions during this time.…”

Section: A Dual Channel Monochromatic All-sky Imagermentioning

confidence: 99%

Observations of Earth space by self-powered stations in Antarctica

Mende

Rachelson

Sterling

et al. 2009

Review of Scientific Instruments

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Coupling of the solar wind to the Earth magnetosphere/ionosphere is primarily through the high latitude regions, and there are distinct advantages in making remote sensing observations of these regions with a network of ground-based observatories over other techniques. The Antarctic continent is ideally situated for such a network, especially for optical studies, because the larger offset between geographic and geomagnetic poles in the south enables optical observations at a larger range of magnetic latitudes during the winter darkness. The greatest challenge for such ground-based observations is the generation of power and heat for a sizable ground station that can accommodate an optical imaging instrument. Under the sponsorship of the National Science Foundation, we have developed suitable automatic observing platforms, the Automatic Geophysical Observatories (AGOs) for a network of six autonomous stations on the Antarctic plateau. Each station housed a suite of science instruments including a dual wavelength intensified all-sky camera that records the auroral activity, an imaging riometer, fluxgate and search-coil magnetometers, and ELF/VLF and LM/MF/HF receivers. Originally these stations were powered by propane fuelled thermoelectric generators with the fuel delivered to the site each Antarctic summer. A by-product of this power generation was a large amount of useful heat, which was applied to maintain the operating temperature of the electronics in the stations. Although a reasonable degree of reliability was achieved with these stations, the high cost of the fuel air lift and some remaining technical issues necessitated the development of a different type of power unit. In the second phase of the project we have developed a power generation system using renewable energy that can operate automatically in the Antarctic winter. The most reliable power system consists of a type of wind turbine using a simple permanent magnet rotor and a new type of power control system with variable resistor shunts to regulate the power and dissipate the excess energy and at the same time provide heat for a temperature controlled environment for the instrument electronics and data system. We deployed such systems and demonstrated a high degree of reliability in several years of operation in spite of the relative unpredictability of the Antarctic environment. Sample data are shown to demonstrate that the AGOs provide key measurements, which would be impossible without the special technology developed for this type of observing platform.

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Southern Hemisphere poleward moving auroral forms

Cited by 27 publications

References 32 publications

Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

Dayside aurora and the role of IMF ∣<i>B<sub>y</sub></i>∣/∣<i>B<sub>z</sub></i>∣: detailed morphology and response to magnetopause reconnection

Observations of Earth space by self-powered stations in Antarctica

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Southern Hemisphere poleward moving auroral forms

Cited by 27 publications

References 32 publications

Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

Dayside aurora and the role of IMF ∣&lt;i&gt;B&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt;∣/∣&lt;i&gt;B&lt;sub&gt;z&lt;/sub&gt;&lt;/i&gt;∣: detailed morphology and response to magnetopause reconnection

Observations of Earth space by self-powered stations in Antarctica

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Dayside aurora and the role of IMF ∣<i>B<sub>y</sub></i>∣/∣<i>B<sub>z</sub></i>∣: detailed morphology and response to magnetopause reconnection