Daytime ionospheric absorption features in the polar cap associated with poleward drifting F-region plasma patches

<p>Following substorm auroral onset, the active aurora region usually expands poleward toward the poleward auroral boundary. Such poleward expansion is often associated with a bulge region that expands westward and forms the westward travelling surge (WTS). In this paper we show all-sky imager and Poker Flat Advanced Modular Incoherent Scatter Radar (PFISR) radar observations of two surge events to investigate the relationship between the surge and flow from the polar cap. For both events, we observe auroral streamers, with an adjacent flow channel consisting of decreased density and cool electron temperature plasma flowing equatorward. This flow channel appears to impinge and lead/feed surge formation, and to stay connected to the surge as it moves westward. Also, for both events, streamer observations indicate that, following initial surge development, similar flows led to explosive surge enhancements. The observation that the streamers connected to the auroral polar boundary and that the flow channels consisted of low density, low electron temperature plasma indicates that the impinging plasma came from the polar cap. For both events, the altitude variations of F region plasma within the surges are related with aurora emission and the poleward/equatorward flow, and the surges develop strong auroral streamers that initiate along the poleward auroral boundary when contacted with flow from the polar cap. These results suggest that the polar cap flow channels play a crucial role in auroral surges by feeding low entropy plasma into surge initiation and development, and also playing an important role in the dynamics within a surge.</p>

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Signatures of moving polar cap arcs in the F-region PolarDARN echoes

Annales Geophysicae ◽

10.5194/angeo-30-441-2012 ◽

2012 ◽

Vol 30 (3) ◽

pp. 441-455 ◽

Cited By ~ 9

Author(s):

A. V. Koustov ◽

K. Hosokawa ◽

N. Nishitani ◽

K. Shiokawa ◽

H. Liu

Keyword(s):

Spectral Width ◽

Global Scale ◽

Auroral Oval ◽

Polar Cap ◽

Common Features ◽

F Region ◽

Radar Network ◽

Radar Measurements ◽

Resolute Bay ◽

Region Plasma

Abstract. Joint observations of the all-sky camera at Resolute Bay (Nunavut, Canada) and the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Rankin Inlet and Inuvik (Canada) are considered to establish radar signatures of poleward moving polar cap arcs "detaching" from the auroral oval. Common features of the events considered are enhanced power or echo occurrence in the wake of the arcs and enhanced spectral width of these echoes. When the arcs were oriented along some of the radar beams, velocity reversals at the arc location were observed with the directions of the arc-associated flows corresponding to a converging electric field. For the event of 9 December 2007, two arcs were poleward progressing almost along the central beams of the Inuvik radar at the speed close to the E × B drift of the bulk of the F-region plasma as inferred from HF Doppler velocities and from independent measurements by the Resolute Bay ionosonde. In global-scale convection maps inferred from all Super Dual Auroral Radar Network (SuperDARN) radar measurements, the polar cap arcs were often seen close to the reversal line of additional mesoscale convection cells located poleward of the normal cells related to the auroral oval.

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Observations of AGW/TID propagation across the polar cap: a case study

Annales Geophysicae ◽

10.5194/angeo-29-1355-2011 ◽

2011 ◽

Vol 29 (8) ◽

pp. 1355-1363 ◽

Cited By ~ 11

Author(s):

H. T. Cai ◽

F. Yin ◽

S. Y. Ma ◽

I. W. McCrea

Keyword(s):

Large Scale ◽

Source Region ◽

Polar Cap ◽

Night Time ◽

F Region ◽

Atmospheric Disturbances ◽

Geomagnetic Pole ◽

Ionization Waves ◽

North Polar ◽

Propagation Properties

Abstract. In this paper, we present observational evidence for the trans-polar propagation of large-scale Traveling Ionospheric Disturbances (TIDs) from their nightside source region to the dayside. On 13 February 2001, the 32 m dish of EISCAT Svalbard Radar (ESR) was directing toward the geomagnetic pole at low elevation (30°) during the interval 06:00–12:00 UT (MLT ≈ UT + 3 h), providing an excellent opportunity to monitor the ionosphere F-region over the polar cap. The TIDs were first detected by the ESR over the dayside north polar cap, propagating equatorward, and were subsequently seen by the mainland UHF radar at auroral latitudes around geomagnetic local noon. The propagation properties of the observed ionization waves suggest the presence of a moderately large-scale TIDs, propagating across the northern polar cap from the night-time auroral source during substorm conditions. Our results agree with the theoretical simulations by Balthazor and Moffett (1999) in which poleward-propagating large-scale traveling atmospheric disturbances were found to be self-consistently driven by enhancements in auroral heating.

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Characteristics of Medium-Scale F-region Plasma Irregularities at Equatorial and Mid Latitudes, as Observed by COSMIC Radio Occultation Receivers

2018 2nd URSI Atlantic Radio Science Meeting (AT-RASC) ◽

10.23919/ursi-at-rasc.2018.8471462 ◽

2018 ◽

Author(s):

C. Watson ◽

N. Pedatella

Keyword(s):

Radio Occultation ◽

Cosmic Radio ◽

Plasma Irregularities ◽

Medium Scale ◽

F Region ◽

Region Plasma

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The story of plumes: the development of a new conceptual framework for understanding magnetosphere and ionosphere coupling

Annales Geophysicae ◽

10.5194/angeo-34-1243-2016 ◽

2016 ◽

Vol 34 (12) ◽

pp. 1243-1253 ◽

Cited By ~ 10

Author(s):

Mark B. Moldwin ◽

Shasha Zou ◽

Tom Heine

Keyword(s):

Conceptual Framework ◽

Ionospheric Plasma ◽

Short Review ◽

Auroral Zone ◽

Causal Chain ◽

Elevated Plasma ◽

Polar Cap ◽

Paper Briefly ◽

Low Latitude ◽

F Region

Abstract. The name “plume” has been given to a variety of plasma structures in the Earth's magnetosphere and ionosphere. Some plumes (such as the plasmasphere plume) represent elevated plasma density, while other plumes (such as the equatorial F region plume) represent low-density regions. Despite these differences these structures are either directly related or connected in the causal chain of plasma redistribution throughout the system. This short review defines how plumes appear in different measurements in different regions and describes how plumes can be used to understand magnetosphere–ionosphere coupling. The story of the plume family helps describe the emerging conceptual framework of the flow of high-density–low-latitude ionospheric plasma into the magnetosphere and clearly shows that strong two-way coupling between ionospheric and magnetospheric dynamics occurs not only in the high-latitude auroral zone and polar cap but also through the plasmasphere. The paper briefly reviews, highlights and synthesizes previous studies that have contributed to this new understanding.

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Low Latitude Mesospheric Gravity Wave And F-Region Plasma Depletion Studies From Cachoeira-Paulista, Brasil

10.3997/2214-4609-pdb.217.422 ◽

2001 ◽

Author(s):

M.J. Taylor ◽

A. Fragoso de Medeiros ◽

H. Takahashi

Keyword(s):

Gravity Wave ◽

Low Latitude ◽

F Region ◽

Plasma Depletion ◽

Region Plasma

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Equatorial F-Region Plasma Bubbles Studies

10.3997/2214-4609-pdb.299.348 ◽

1997 ◽

Author(s):

P.R. Fagundes

Keyword(s):

Plasma Bubbles ◽

F Region ◽

Region Plasma

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Electron heating by HF pumping of high-latitude ionospheric F-region plasma near magnetic zenith

Annales Geophysicae ◽

10.5194/angeo-38-297-2020 ◽

2020 ◽

Vol 38 (2) ◽

pp. 297-307 ◽

Cited By ~ 1

Author(s):

Thomas B. Leyser ◽

Björn Gustavsson ◽

Theresa Rexer ◽

Michael T. Rietveld

Keyword(s):

Electron Temperature ◽

Pump Beam ◽

Electron Heating ◽

Incoherent Scatter ◽

F Region ◽

Left Handed ◽

Parameter Values ◽

Uhf Radar ◽

Region Plasma ◽

Magnetic Zenith

Abstract. High-frequency electromagnetic pumping of ionospheric F-region plasma at high and mid latitudes gives the strongest plasma response in magnetic zenith, antiparallel to the geomagnetic field in the Northern Hemisphere. This has been observed in optical emissions from the pumped plasma turbulence, electron temperature enhancements, filamentary magnetic field-aligned plasma density irregularities, and in self-focusing of the pump beam in magnetic zenith. We present results of EISCAT (European Incoherent SCATter association) Heating-induced magnetic-zenith effects observed with the EISCAT UHF incoherent scatter radar. With heating transmitting a left-handed circularly polarized pump beam towards magnetic zenith, the UHF radar was scanned in elevation in steps of 1.0 and 1.5∘ around magnetic zenith. The electron energy equation was integrated to model the electron temperature and associated electron heating rate and optimized to fit the plasma parameter values measured with the radar. The experimental and modelling results are consistent with pump wave propagation in the L mode in magnetic zenith, rather than in the O mode.

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Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobe

Annales Geophysicae ◽

10.5194/angeo-19-1589-2001 ◽

2001 ◽

Vol 19 (10/12) ◽

pp. 1589-1612 ◽

Cited By ~ 16

Author(s):

M. Lockwood ◽

H. Opgenoorth ◽

A. P. van Eyken ◽

A. Fazakerley ◽

J.-M. Bosqued ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Propagation Delay ◽

Polar Cap ◽

F Region ◽

Electrons And Ions ◽

Transient Events ◽

Low Energy Electron ◽

Convection Patterns ◽

Magnetopause Reconnection

Abstract. During the interval between 8:00–9:30 on 14 January 2001, the four Cluster spacecraft were moving from the central magnetospheric lobe, through the dusk sector mantle, on their way towards intersecting the magnetopause near 15:00 MLT and 15:00 UT. Throughout this interval, the EISCAT Svalbard Radar (ESR) at Longyearbyen observed a series of poleward-moving transient events of enhanced F-region plasma concentration ("polar cap patches"), with a repetition period of the order of 10 min. Allowing for the estimated solar wind propagation delay of 75 ( ± 5) min, the interplanetary magnetic field (IMF) had a southward component during most of the interval. The magnetic footprint of the Cluster spacecraft, mapped to the ionosphere using the Tsyganenko T96 model (with input conditions prevailing during this event), was to the east of the ESR beams. Around 09:05 UT, the DMSP-F12 satellite flew over the ESR and showed a sawtooth cusp ion dispersion signature that also extended into the electrons on the equatorward edge of the cusp, revealing a pulsed magnetopause reconnection. The consequent enhanced ionospheric flow events were imaged by the SuperDARN HF backscatter radars. The average convection patterns (derived using the AMIE technique on data from the magnetometers, the EISCAT and SuperDARN radars, and the DMSP satellites) show that the associated poleward-moving events also convected over the predicted footprint of the Cluster spacecraft. Cluster observed enhancements in the fluxes of both electrons and ions. These events were found to be essentially identical at all four spacecraft, indicating that they had a much larger spatial scale than the satellite separation of the order of 600 km. Some of the events show a correspondence between the lowest energy magnetosheath electrons detected by the PEACE instrument on Cluster (10–20 eV) and the topside ionospheric enhancements seen by the ESR (at 400–700 km). We suggest that a potential barrier at the magnetopause, which prevents the lowest energy electrons from entering the magnetosphere, is reduced when and where the boundary-normal magnetic field is enhanced and that the observed polar cap patches are produced by the consequent enhanced precipitation of the lowest energy electrons, making them and the low energy electron precipitation fossil remnants of the magnetopause reconnection rate pulses.Key words. Magnetospheric physics (polar cap phenomena; solar wind – magnetosphere interactions; magnetosphere – ionosphere interactions)

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