The Mid-Latitude Positive Bay and the MPB Index of Substorm Activity

2017 ◽  
pp. 93-124
Author(s):  
Robert L. McPherron ◽  
Xiangning Chu
Keyword(s):  
Substorm Activity

VLF emissions and substorm activity

1977 ◽  
Vol 25 (3) ◽  
pp. 261-264 ◽  
Author(s):  
A.C. Das ◽  
V.H. Kulkarni
Keyword(s):  
Substorm Activity ◽  
Vlf Emissions

scholarly journals Electron precipitation characteristics during isolated, compound and multi-night substorm events

2020 ◽  
Author(s):  
Noora Partamies ◽  
Fasil Tesema ◽  
Emma Bland ◽  
Erkka Heino ◽  
Hilde Nesse Tyssøy ◽  
...  
Keyword(s):  
Local Maximum ◽  
Recovery Phase ◽  
High Energy ◽  
Atmospheric Effects ◽  
Average Intensity ◽  
Cosmic Radio ◽  
Substorm Activity ◽  
Magnetic Deflection ◽  
Ground Magnetic ◽  
Isolated Compound

Abstract. A set of 24 isolated, 46 compound and 36 multi-night substorm events from the years 2008–2013 have been analysed in this study. Isolated substorm events are defined as single expansion-recovery phase pairs, compound substorms consist of multiple phase pairs, and multi-night substorm events refer to recurring substorm activity on consecutive nights. Approximately 200 nights of substorm activity observed over the Fennoscandian Lapland have been analysed for their magnetic disturbance magnitude and the level of cosmic radio noise absorption. Substorm events were automatically detected from the local electrojet index data and visually categorised. We show that isolated substorms have limited lifetimes and spatial extents, as compared to the other substorm types. The average intensity (both in absorption and ground-magnetic deflection) of compound and multi-night substorm events is similar. For multi-night substorm events, the first night is rarely associated with the strongest absorption. Instead, the high-energy electron population needed to cause the strongest absorption builds up over 1–2 additional nights of substorm activity. The non-linear relationship between the absorption and the magnetic deflection at high and low activity conditions is also discussed. We further collect in-situ particle spectra for expansion and recovery phases to construct median precipitation fluxes at energies from 30 eV up to about 800 keV. In the expansion phases the bulk of the spectra shows a local maximum flux in the range of a few keV to 10 keV, while in the recovery phases higher fluxes are seen in the range of tens of keV to hundreds of keV. These findings are discussed in the light of earlier observations of substorm precipitation and their atmospheric effects.

scholarly journals Modulation of nightside polar patches by substorm activity

2009 ◽  
Vol 27 (10) ◽  
pp. 3923-3932 ◽  
Author(s):  
A. G. Wood ◽  
S. E. Pryse ◽  
J. Moen
Keyword(s):  
Spatial Distribution ◽  
High Latitude ◽  
Ionospheric Plasma ◽  
Plasma Convection ◽  
Convection Pattern ◽  
Polar Cap ◽  
Incoherent Scatter ◽  
Repetition Time ◽  
Substorm Activity ◽  
European Sector

Abstract. Results are presented from a multi-instrument study showing the influence of geomagnetic substorm activity on the spatial distribution of the high-latitude ionospheric plasma. Incoherent scatter radar and radio tomography measurements on 12 December 2001 were used to directly observe the remnants of polar patches in the nightside ionosphere and to investigate their characteristics. The patches occurred under conditions of IMF Bz negative and IMF By negative. They were attributed to dayside photoionisation transported by the high-latitude convection pattern across the polar cap and into the nighttime European sector. The patches on the nightside were separated by some 5° latitude during substorm expansion, but this was reduced to some 2° when the activity had subsided. The different patch separations resulted from the expansion and contraction of the high-latitude plasma convection pattern on the nightside in response to the substorm activity. The patches of larger separation occurred in the antisunward cross-polar flow as it entered the nightside sector. Those of smaller separation were also in antisunward flow, but close to the equatorward edge of the convection pattern, in the slower, diverging flow at the Harang discontinuity. A patch repetition time of some 10 to 30 min was estimated depending on the phase of the substorm.

scholarly journals Prelude to THEMIS tail conjunction study

2007 ◽  
Vol 25 (4) ◽  
pp. 1001-1009 ◽  
Author(s):  
A. T. Y. Lui ◽  
Y. Zheng ◽  
Y. Zhang ◽  
V. Angelopoulos ◽  
G. K. Parks ◽  
...  
Keyword(s):  
Electric Field ◽  
Plasma Flow ◽  
Time History ◽  
Time Sequence ◽  
Dynamic Changes ◽  
Magnetometer Data ◽  
History Of ◽  
Substorm Activity ◽  
Auroral Imaging

Abstract. A close conjunction of several satellites (LANL, GOES, Polar, Geotail, and Cluster) distributed from the geostationary altitude to about 16 RE downstream in the tail occurred during substorm activity as indicated by global auroral imaging and ground-based magnetometer data. This constellation of satellites resembles what is planned for the THEMIS (Time History of Events and Macroscopic Interactions during Substorms) mission to resolve the substorm controversy on the location of the substorm expansion onset region. In this article, we show in detail the dipolarization and dynamic changes seen by these satellites associated with two onsets of substorm intensification activity. In particular, we find that dipolarization at ~16 RE downstream in the tail can occur with dawnward electric field and without plasma flow, just like some near-Earth dipolarization events reported previously. The spreading of substorm disturbances in the tail coupled with complementary ground observations indicates that the observed time sequence on the onsets of substorm disturbances favors initiation in the near-Earth region for this THEMIS-like conjunction.

The local time variation of ELF emissions during periods of substorm activity

1977 ◽  
Vol 82 (10) ◽  
pp. 1585-1590 ◽  
Author(s):  
R. M. Thorne ◽  
S. R. Church ◽  
W. J. Malloy ◽  
B. T. Tsurutani
Keyword(s):  
Local Time ◽  
Time Variation ◽  
Substorm Activity

Field-aligned current ordering in ground and space measurements

2020 ◽  
Author(s):  
Malcolm Dunlop ◽  
Junying Yang ◽  
Xiangcheng Dong ◽  
Mervyn Freeman ◽  
Neil Rogers ◽  
...  
Keyword(s):  
Large Scale ◽  
Correlation Coefficients ◽  
Lower Latitude ◽  
Time Shift ◽  
Small Scale ◽  
Maximum Correlation ◽  
Substorm Activity ◽  
The Mean ◽  
Field Aligned Current ◽  
Statistical Trends

<p>The orientation of field-aligned current sheets (FACs) can be inferred from dual-spacecraft correlations of the FAC signatures between two Swarm spacecraft (A and C), using the maximum correlations obtained from sliding data segments. Statistical analysis of both the correlations and the inferred orientations shows clear trends in magnetic local time (MLT) which reveal behaviour of both large and small scale currents. The maximum correlation coefficients show distinct behaviour in terms of either the time shift, or the shift in longitude between Swarm A and C for various filtering levels. The lower-latitude FACs show the strongest correlations for a broad range of MLT centred on dawn and dusk, with a higher correlation coefficient on the dusk-side and lower correlations near noon and midnight, and broadly follow the mean shape of the auroral boundary for the lower latitudes corresponding to Region 2 FACs (and are most well-ordered on the dusk side). Individual events sampled by higher altitude spacecraft (e.g. the 4 Cluster spacecraft), in conjunction with Swarm (mapping both to region 1 and 2), also show two different domains of FACs: time variable, small-scale (10s km), and more stationary large-scale (>100 km) FACs. We investigate further how these FAC regimes are dependent on geomagnetic activity, focusing on high activity events. Both the statistical trends, and individual conjugate events, show comparable effects seen in the ground magnetometer signals (dH/dt) during storm/substorm activity and show distributions that are similar.</p>

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