Emission from the Polar Cap and Slot Gap

2010 ◽  
pp. 79-98
Author(s):  
Alice K. Harding ◽  
Isabelle A. Grenier
Keyword(s):  
Polar Cap

A large rotating structure around AB Doradus A at VLBI scale

2019 ◽  
Vol 15 (S354) ◽  
pp. 189-194
Author(s):  
J. B. Climent ◽  
J. C. Guirado ◽  
R. Azulay ◽  
J. M. Marcaide
Keyword(s):  
Magnetic Reconnection ◽  
Main Sequence ◽  
Complex Structure ◽  
Main Sequence Star ◽  
Polar Cap ◽  
Vlbi Observations ◽  
Rotating Structure ◽  
Source Structure ◽  
Expected Position

AbstractWe report the results of three VLBI observations of the pre-main-sequence star AB Doradus A at 8.4 GHz. With almost three years between consecutive observations, we found a complex structure at the expected position of this star for all epochs. Maps at epochs 2007 and 2010 show a double core-halo morphology while the 2013 map reveals three emission peaks with separations between 5 and 18 stellar radii. Furthermore, all maps show a clear variation of the source structure within the observing time. We consider a number of hypothesis in order to explain such observations, mainly: magnetic reconnection in loops on the polar cap, a more general loop scenario and a close companion to AB Dor A.

scholarly journals Deep Learning Models for Estimation of the SuperDARN Cross Polar Cap Potential

2020 ◽  
Vol 7 (8) ◽  
Author(s):  
Erxiao Liu ◽  
Hongqiao Hu ◽  
Jianjun Liu ◽  
Lei Qiao
Keyword(s):  
Deep Learning ◽  
Learning Models ◽  
Polar Cap ◽  
Cross Polar Cap Potential

scholarly journals Space weather challenges of the polar cap ionosphere

2013 ◽  
Vol 3 ◽  
pp. A02 ◽  
Author(s):  
Jøran Moen ◽  
Kjellmar Oksavik ◽  
Lucilla Alfonsi ◽  
Yvonne Daabakk ◽  
Vineenzo Romano ◽  
...  
Keyword(s):  
Space Weather ◽  
Polar Cap

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 PC index: review of methods

2010 ◽  
Vol 28 (10) ◽  
pp. 1887-1903 ◽  
Author(s):  
H. McCreadie ◽  
M. Menvielle
Keyword(s):  
Scientific Community ◽  
Polar Cap ◽  
Scientific Merit ◽  
Controversial Topic

Abstract. The Polar Cap (PC) index is a controversial topic within the IAGA scientific community. Since 1997 discussions of the validity of the index to be endorsed as an official IAGA index have ensued. There is no doubt as to the scientific merit of the index which is not discussed here. What is in doubt is the methodology of the derivation of the index by different groups. The Polar Cap index (PC: PCN, northern; PCS, southern) described in Troshichev et al. (2006) and Stauning et al. (2006), both termed the "unified PC index", and the PCN index routinely derived at DMI are inspected using only available published literature. They are found to contain different derivation procedures, thus are not unified. The descriptions of the derivation procedures are found to not be adequate to independently derive the PC indices.

scholarly journals Central polar cap convection response to short duration southward Interplanetary Magnetic Field

2000 ◽  
Vol 18 (8) ◽  
pp. 887-896 ◽  
Author(s):  
P. T. Jayachandran ◽  
J. W. MacDougall
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Short Duration ◽  
Initial Response ◽  
Plasma Convection ◽  
Polar Cap ◽  
Ionosphere Plasma ◽  
Rapid Transition ◽  
Convection Speed ◽  
A Chain

Abstract. Central polar cap convection changes associated with southward turnings of the Interplanetary Magnetic Field (IMF) are studied using a chain of Canadian Advanced Digital Ionosondes (CADI) in the northern polar cap. A study of 32 short duration (~1 h) southward IMF transition events found a three stage response: (1) initial response to a southward transition is near simultaneous for the entire polar cap; (2) the peak of the convection speed (attributed to the maximum merging electric field) propagates poleward from the ionospheric footprint of the merging region; and (3) if the change in IMF is rapid enough, then a step in convection appears to start at the cusp and then propagates antisunward over the polar cap with the velocity of the maximum convection. On the nightside, a substorm onset is observed at about the time when the step increase in convection (associated with the rapid transition of IMF) arrives at the polar cap boundary.Key words: Ionosphere (plasma convection; polar ionosphere) - Magnetospheric physics (solar wind - magnetosphere interaction)

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