A Comparative Study of Magnetic Storm Effects on the Ionosphere in Polar Cap and Auroal Oval -F-Region Negative Storm

2002 ◽  
Vol 45 (2) ◽  
pp. 154-163
Author(s):  
Shu-Ying MA ◽  
Hui-Xin LIU ◽  
K. Schlegel
Keyword(s):  
Comparative Study ◽  
Magnetic Storm ◽  
Polar Cap ◽  
Storm Effects ◽  
F Region

scholarly journals Positive storm effects in the dayside polar ionospheric F-region observed by EISCAT and ESR during the magnetic storm of 15 May 1997

2002 ◽  
Vol 20 (9) ◽  
pp. 1377-1384 ◽  
Author(s):  
S. Y. Ma ◽  
H. T. Cai ◽  
H. X. Liu ◽  
K. Schlegel ◽  
G. Lu
Keyword(s):  
Electron Temperature ◽  
Magnetic Storm ◽  
Radar Data ◽  
Auroral Oval ◽  
Soft Particle ◽  
Plasma Convection ◽  
Particle Precipitation ◽  
Storm Effects ◽  
Cusp Region ◽  
F Region

Abstract. EISCAT/ESR radar data and in situ FAST and POLAR satellite observations are coordinately analyzed to investigate positive ionospheric storm effects in the dayside upper F-region in both the polar cap and the auroral oval during the magnetic storm of 15 May 1997. An ionization enhancement, lasting for about 2.5 h, appeared first over the EISCAT site around magnetic noon; about one hour later, a similar ionization enhancement was also seen over ESR. During the concerned time period ion energy spectra measured on board FAST show clearly continuous energy-latitude dispersion when the satellite passed by over the EISCAT latitude. This implies that EISCAT was located under the polar cusp region which was highly active, and expanded greatly equatorwards due to magnetopause reconnections during long-lasting southward IMF. Simultaneously, soft particles of the magnetosheath precipitated into the F-region ionosphere and caused the positive storm effects over EISCAT. The coincident increase in electron temperature at EISCAT gives additional evidence for soft particle precipitation. Consistently, POLAR UV images show strong dayside aurora extending to as low as 62° N magnetic latitude. The ionization enhancement over ESR, however, seems not to be caused by local particle precipitation, evidenced by a lack of enhanced electron temperature. The observed plasma convection velocity and data-fitted convection patterns by AMIE suggested that it is likely to be a polar patch originating from the cusp region and traveling to the ESR site.Key words. Ionosphere (auroral ionosphere; particle percipitation) Magnetospheric physics (storms and substorms)

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

2011 ◽  
Vol 29 (8) ◽  
pp. 1355-1363 ◽  
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.

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

2016 ◽  
Vol 34 (12) ◽  
pp. 1243-1253 ◽  
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.

A Data-model comparative study of ionospheric positive storm phase in the midlatitude F region

2008 ◽  
pp. 63-75 ◽  
Author(s):  
G. Lu ◽  
L. P. Goncharenko ◽  
A. J. Coster ◽  
A. D. Richmond ◽  
R. G. Roble ◽  
...  
Keyword(s):  
Comparative Study ◽  
Data Model ◽  
F Region

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

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1589-1612 ◽  
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)

Magnetic storm effects on the variation of TEC over Ilorin an equatorial station

Radio Science ◽  
2014 ◽  
Vol 49 (12) ◽  
pp. 1245-1253 ◽  
Author(s):  
J. O. Adeniyi ◽  
P. H. Doherty ◽  
O. A. Oladipo ◽  
O. Bolaji
Keyword(s):  
Magnetic Storm ◽  
Equatorial Station ◽  
Storm Effects

scholarly journals EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary

2008 ◽  
Vol 26 (1) ◽  
pp. 87-105 ◽  
Author(s):  
A. T. Aikio ◽  
T. Pitkänen ◽  
D. Fontaine ◽  
I. Dandouras ◽  
O. Amm ◽  
...  
Keyword(s):  
Neutral Line ◽  
Broad Band ◽  
Low Frequency ◽  
Recovery Phase ◽  
Auroral Oval ◽  
Polar Cap ◽  
Early Recovery ◽  
F Region ◽  
Cluster Data ◽  
Cluster Satellite

Abstract. The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6° cgmLat) and Longyearbyen (75.2° cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5° cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm. During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4 RE mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H+ and O+ ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations. The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2° during ~5 min. The beginning of the poleward motion of the PCB was associated with an intensification of the downward FAC at the boundary. We suggest that the downward FAC sheet at the PCB is the high-altitude counterpart of the Earthward flowing FAC produced in the vicinity of the magnetotail neutral line by the Hall effect (Sonnerup, 1979) during a short-lived reconnection pulse.

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