Daytime geomagnetic disturbances at high latitudes during a strong magnetic storm of June 21–23, 2015: The storm initial phase
The high-latitude geomagnetic effects of an unusually long initial phase of the largest magnetic storm ( SymH ~–220 nT) in cycle 24 of the solar activity are considered. Three interplanetary shocks characterized by considerable solar wind density jumps (up to 50–60 cm –3 ) at a low solar wind veloci...
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Published in | Geomagnetism and Aeronomy Vol. 56; no. 3; pp. 281 - 292 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Moscow
Pleiades Publishing
01.05.2016
Springer Nature B.V |
Subjects | |
Online Access | Get full text |
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Summary: | The high-latitude geomagnetic effects of an unusually long initial phase of the largest magnetic storm (
SymH
~–220 nT) in cycle 24 of the solar activity are considered. Three interplanetary shocks characterized by considerable solar wind density jumps (up to 50–60 cm
–3
) at a low solar wind velocity (350–400 km/s) approached the Earth’s magnetosphere during the storm initial phase. The first two dynamic impacts did not result in the development of a magnetic storm, since the IMF
Bz
remained positive for a long time after these shocks, but they caused daytime polar substorms (magnetic bays) near the boundary between the closed and open magnetosphere. The magnetic field vector diagrams at high latitudes and the behaviour of high-latitude long-period geomagnetic pulsations (
ipcl
and
vlp
) made it possible to specify the dynamics of this boundary position. The spatiotemporal features of daytime polar substorms (the dayside polar electrojet,
PE
) caused by sudden changes in the solar wind dynamic pressure are discussed in detail, and the singularities of ionospheric convection in the polar cap are considered. It has been shown that the main phase of this two-stage storm started rapidly developing only when the third most intense shock approached the Earth against a background of large negative IMF
Bz
values (to–39 nT). It was concluded that the dynamics of convective vortices and the related restructing of the field-aligned currents can result in spatiotemporal fluctuations in the closing ionospheric currents that are registered on the Earth’s surface as bay-like magnetic disturbances. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0016-7932 1555-645X 0016-7940 |
DOI: | 10.1134/S0016793216030051 |