Magnetospheric Substorm Onset by Current Disruption Processes

2015 ◽  
pp. 163-176 ◽  
Author(s):  
Anthony T. Y. Lui
Keyword(s):  
Substorm Onset ◽  
Magnetospheric Substorm ◽  
Current Disruption

scholarly journals Substorm onset location and dipole tilt angle

2006 ◽  
Vol 24 (2) ◽  
pp. 577-588 ◽  
Author(s):  
J. Wanliss
Keyword(s):  
Magnetic Field ◽  
Tilt Angle ◽  
Source Region ◽  
Radial Distance ◽  
Substorm Onset ◽  
Magnetospheric Substorms ◽  
Data Set ◽  
Current Disruption ◽  
Onset Location ◽  
Dipole Tilt

Abstract. From an initial data set of over 200 substorms we have studied a subset of 30 magnetospheric substorms close to magnetic midnight to investigate, in a statistical fashion, the source region of the auroral arc that brightens at the onset of expansive phase. This arc is usually identified as the ionospheric signature of the expansive phase onset that occurs in the magnetotail. All the substorm onsets were identified via ground-based magnetometer and photometer data from the CANOPUS array. Various Tsyganenko global magnetic field models were used to map magnetic field lines from the location of the onset arc out to its greatest radial distance in the magnetotail. The results appear to favour the current disruption model of substorms since the average onset location has an average of 14.1 Earth radii (RE) and is therefore more consistent with theories that place the onset location in the inner magnetotail. For the narrow range of tilts available our modeling indicates the parameter that appears to strongly influence the location of the substorm onset is the dipole tilt angle; as tilt becomes less negative onsets occur further downtail.

scholarly journals Timing of magnetic reconnection initiation during a global magnetospheric substorm onset

2002 ◽  
Vol 29 (24) ◽  
pp. 43-1-43-4 ◽  
Author(s):  
D. N. Baker ◽  
W. K. Peterson ◽  
S. Eriksson ◽  
X. Li ◽  
J. B. Blake ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Substorm Onset ◽  
Magnetospheric Substorm

scholarly journals Polar substorm on 7 December 2015: preonset phenomena and features of auroral breakup

2020 ◽  
Vol 38 (4) ◽  
pp. 901-918
Author(s):  
Vladimir V. Safargaleev ◽  
Alexander E. Kozlovsky ◽  
Valery M. Mitrofanov
Keyword(s):  
Large Scale ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Substorm Onset ◽  
Optical Observations ◽  
Time Interval ◽  
Polar Cap ◽  
Local Maxima ◽  
Current Disruption ◽  
Auroral Breakup

Abstract. Comprehensive analysis of a moderate 600 nT substorm was performed using simultaneous optical observations inside the auroral oval and in the polar cap, combined with data from satellites, radars, and ground magnetometers. The onset took place near the poleward boundary of the auroral oval that is not typical for classical substorms. The substorm onset was preceded by two negative excursions of the interplanetary magnetic field (IMF) Bz component, with a 1 min interval between them, two enhancements of the antisunward convection in the polar cap with the same time interval, and 15 min oscillations in the geomagnetic H component in the auroral zone. The distribution of the pulsation intensity along meridian has two local maxima, namely at the equatorial and poleward boundaries of the auroral oval, where pulsations occurred in the out-of-phase mode resembling the field line resonance. At the initial stage, the auroral breakup developed as the auroral torch stretched and expanded poleward along the meridian. Later it took the form of the large-scale coiling structure that also distinguishes the considered substorm from the classical one. Magnetic, radar, and the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellite data show that, before the collapse, the coiling structure was located between two field-aligned currents, namely downward at the poleward boundary of structure and upward at the equatorial boundary. The set of GEOTAIL satellites and ground data fit to the near-tail current disruption scenario of the substorm onset. We suggest that the 15 min oscillations might play a role in the substorm initiation.

scholarly journals Polar substorm on 7 December 2015: pre-onset phenomena and features of auroral breakup

2019 ◽  
Author(s):  
Vladimir V. Safargaleev ◽  
Alexander E. Kozlovsky ◽  
Valery M. Mitrofanov
Keyword(s):  
Large Scale ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Substorm Onset ◽  
Optical Observations ◽  
Polar Cap ◽  
Local Maxima ◽  
Current Disruption ◽  
Initial Stage ◽  
Auroral Breakup

Abstract. Comprehensive analysis of a moderate 600-nT substorm was performed with using simultaneous optical observations inside the auroral oval and in the polar cap, combined with data from satellites, radars, and ground magnetometers. The onset took place near the poleward boundary of the auroral oval that is not typical for classical substorms. The substorm onset was preceded by two negative excursions of the IMF Bz component with 15-min interval between them, two enhancements of the antisunward convection in the polar cap with the same repetition period, and 15-minute oscillations in geomagnetic H-component in the auroral zone. The distribution of the pulsation intensity along meridian has two local maxima – at equatorial and poleward boundaries of the auroral oval where pulsations occurred in the out-of-phase mode resembling the field-line resonance. At initial stage, the auroral breakup developed as auroral torch stretching and expanding poleward along the meridian. Some later it took a form of the large-scale coiling structure that also distinguishes the considered substorm from classical one. Magnetic, radar and AMPERE satellite data show that before the collapse the coiling structure was located between two field-aligned currents: downward at poleward boundary of structure and upward at equatorial boundary. The set of GEOTAIL satellite and ground data fits to the near-tail current disruption scenario of the substorm onset. We suggest that the 15-min oscillations might play a role in the substorm initiation.

scholarly journals The high latitude convection response to an interval of substorm activity

1996 ◽  
Vol 14 (5) ◽  
pp. 518-532 ◽  
Author(s):  
T. K. Yeoman ◽  
M. Pinnock
Keyword(s):  
High Latitude ◽  
Neutral Line ◽  
Substorm Onset ◽  
Hf Radar ◽  
The West ◽  
Expansion Phase ◽  
Incoherent Scatter ◽  
Current Disruption ◽  
Substorm Activity ◽  
Substorm Onsets

Abstract. On 17 March 1991, five clear substorm onsets/intensifications took place within a three hour interval. During this interval ground-based data from the EISCAT incoherent scatter radar, a digital CCD all sky camera, and an extensive array of magnetometers were available, in addition to data from the CRRES and DMSP spacecraft, whose footprints passed over Scandinavia very close to most of the ground-based instrumentation. This interval of substorm activity has been interpreted as being in support of a near-Earth current disruption model of substorm onset. In the present study the ionospheric convection response, observed some four hours to the west in MLT by the Halley HF radar in Antarctica, is related to the growth, expansion and recovery phases of two of the substorm onsets/expansions observed in the Northern Hemisphere. Bursts of ionospheric flow and motion of the convection reversal boundary (CRB) are observed at Halley in response to the substorm activity and changes in the IMF. The delay between the substorm expansion phase onset and the response in the CRB location is dependent on the local time separation from, and latitude of, the initial substorm onset region. These results are interpreted in terms of a synthesis of the very near-Earth current disruption model and the near-Earth neutral line model of substorm onset.

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