scholarly journals Roles of Flow Braking, Plasmaspheric Virtual Resonances, and Ionospheric Currents in Producing Ground Pi2 Pulsations

2018 ◽  
Vol 123 (11) ◽  
pp. 9187-9203 ◽  
Author(s):  
Kazue Takahashi ◽  
Michael D. Hartinger ◽  
Massimo Vellante ◽  
Balázs Heilig ◽  
Robert L. Lysak ◽  
...  
Keyword(s):  
Ionospheric Currents ◽  
Pi2 Pulsations

scholarly journals SABRE observations of Pi2 pulsations: case studies

1997 ◽  
Vol 15 (1) ◽  
pp. 40-53 ◽  
Author(s):  
E. G. Bradshaw ◽  
M. Lester
Keyword(s):  
Case Studies ◽  
Magnetic Activity ◽  
Auroral Zone ◽  
Field Of View ◽  
Ionospheric Currents ◽  
Pi2 Pulsation ◽  
First Case ◽  
Pi2 Pulsations ◽  
Generation Region

Abstract. The characteristics of substorm-associated Pi2 pulsations observed by the SABRE coherent radar system during three separate case studies are presented. The SABRE field of view is well positioned to observe the differences between the auroral zone pulsation signature and that observed at mid-latitudes. During the first case study the SABRE field of view is initially in the eastward electrojet, equatorward and to the west of the substorm-enhanced electrojet current. As the interval progresses, the western, upward field-aligned current of the substorm current wedge moves westward across the longitudes of the radar field of view. The westward motion of the wedge is apparent in the spatial and temporal signatures of the associated Pi2 pulsation spectra and polarisation sense. During the second case study, the complex field-aligned and ionospheric currents associated with the pulsation generation region move equatorward into the SABRE field of view and then poleward out of it again after the third pulsation in the series. The spectral content of the four pulsations during the interval indicate different auroral zone and mid-latitude signatures. The final case study is from a period of low magnetic activity when SABRE observes a Pi2 pulsation signature from regions equatorward of the enhanced substorm currents. There is an apparent mode change between the signature observed by SABRE in the ionosphere and that on the ground by magnetometers at latitudes slightly equatorward of the radar field of view. The observations are discussed in terms of published theories of the generation mechanisms for this type of pulsation. Different signatures are observed by SABRE depending on the level of magnetic activity and the position of the SABRE field of view relative to the pulsation generation region. A twin source model for Pi2 pulsation generation provides the clearest explanation of the signatures observed.

scholarly journals Network community structure of substorms using SuperMAG magnetometers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
L. Orr ◽  
S. C. Chapman ◽  
J. W. Gjerloev ◽  
W. Guo
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Easy Access ◽  
Directed Network ◽  
Coherent System ◽  
Dimensional System ◽  
Ionospheric Currents ◽  
Substorm Current Wedge ◽  
Spatially Extended ◽  
Current Wedge

AbstractGeomagnetic substorms are a global magnetospheric reconfiguration, during which energy is abruptly transported to the ionosphere. Central to this are the auroral electrojets, large-scale ionospheric currents that are part of a larger three-dimensional system, the substorm current wedge. Many, often conflicting, magnetospheric reconfiguration scenarios have been proposed to describe the substorm current wedge evolution and structure. SuperMAG is a worldwide collaboration providing easy access to ground based magnetometer data. Here we show application of techniques from network science to analyze data from 137 SuperMAG ground-based magnetometers. We calculate a time-varying directed network and perform community detection on the network, identifying locally dense groups of connections. Analysis of 41 substorms exhibit robust structural change from many small, uncorrelated current systems before substorm onset, to a large spatially-extended coherent system, approximately 10 minutes after onset. We interpret this as strong indication that the auroral electrojet system during substorm expansions is inherently a large-scale phenomenon and is not solely due to many meso-scale wedgelets.

scholarly journals Field-aligned and ionospheric currents by AMPERE and SuperMAG during HSS/SIR-driven storms

2021 ◽  
Author(s):  
Marcus N. Pedersen ◽  
Heikki Vanhamäki ◽  
Anita T. Aikio ◽  
Sebastian Käki ◽  
Abiyot B. Workayehu ◽  
...  
Keyword(s):  
Ionospheric Currents

scholarly journals Pi2 pulsations observed around the dawn terminator

2015 ◽  
Vol 120 (3) ◽  
pp. 2088-2098 ◽  
Author(s):  
S. Imajo ◽  
A. Yoshikawa ◽  
T. Uozumi ◽  
S. Ohtani ◽  
A. Nakamizo ◽  
...  
Keyword(s):  
Pi2 Pulsations

scholarly journals Interpolation of externally-caused magnetic fields over large sparse arrays using Spherical Elementary Current Systems

2010 ◽  
Vol 28 (9) ◽  
pp. 1795-1805 ◽  
Author(s):  
S. A. McLay ◽  
C. D. Beggan
Keyword(s):  
Magnetic Field ◽  
External Field ◽  
Current System ◽  
Electrical Current ◽  
Ionospheric Currents ◽  
Large Area ◽  
Physically Based ◽  
Subsurface Current ◽  
Current Systems ◽  
The Magnetic Field

Abstract. A physically-based technique for interpolating external magnetic field disturbances across large spatial areas can be achieved with the Spherical Elementary Current System (SECS) method using data from ground-based magnetic observatories. The SECS method represents complex electrical current systems as a simple set of equivalent currents placed at a specific height in the ionosphere. The magnetic field recorded at observatories can be used to invert for the electrical currents, which can subsequently be employed to interpolate or extrapolate the magnetic field across a large area. We show that, in addition to the ionospheric currents, inverting for induced subsurface current systems can result in strong improvements to the estimate of the interpolated magnetic field. We investigate the application of the SECS method at mid- to high geomagnetic latitudes using a series of observatory networks to test the performance of the external field interpolation over large distances. We demonstrate that relatively few observatories are required to produce an estimate that is better than either assuming no external field change or interpolation using latitudinal weighting of data from two other observatories.

scholarly journals The effects of neutral inertia on ionospheric currents in the high-latitude thermosphere following a geomagnetic storm

1993 ◽  
Vol 98 (A5) ◽  
pp. 7775-7790 ◽  
Author(s):  
W. Deng ◽  
T. L. Killeen ◽  
A. G. Burns ◽  
R. G. Roble ◽  
J. A. Slavin ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
High Latitude ◽  
Ionospheric Currents

scholarly journals Extremely intense (SML ≤–2500 nT) substorms: isolated events that are externally triggered?

2015 ◽  
Vol 33 (5) ◽  
pp. 519-524 ◽  
Author(s):  
B. T. Tsurutani ◽  
R. Hajra ◽  
E. Echer ◽  
J. W. Gjerloev
Keyword(s):  
Solar Wind ◽  
Magnetic Fields ◽  
Magnetic Storm ◽  
Solar Wind Plasma ◽  
Magnetic Storms ◽  
Input Energy ◽  
Stored Energy ◽  
Ionospheric Currents ◽  
Interplanetary Magnetic Fields ◽  
Very High

Abstract. We examine particularly intense substorms (SML ≤–2500 nT), hereafter called "supersubstorms" or SSS events, to identify their nature and their magnetic storm dependences. It is found that these intense substorms are typically isolated events and are only loosely related to magnetic storms. SSS events can occur during super (Dst ≤–250 nT) and intense (−100 nT ≥ Dst >–250) magnetic storms. SSS events can also occur during nonstorm (Dst ≥–50 nT) intervals. SSSs are important because the strongest ionospheric currents will flow during these events, potentially causing power outages on Earth. Several SSS examples are shown. SSS events appear to be externally triggered by small regions of very high density (~30 to 50 cm−3) solar wind plasma parcels (PPs) impinging upon the magnetosphere. Precursor southward interplanetary magnetic fields are detected prior to the PPs hitting the magnetosphere. Our hypothesis is that these southward fields input energy into the magnetosphere/magnetotail and the PPs trigger the release of the stored energy.

scholarly journals Effect of geomagnetic activity, solar wind and parameters of interplanetary magnetic field on regularities in intermittency of Pi2 geomagnetic pulsations

2015 ◽  
Vol 1 (3) ◽  
pp. 11-20 ◽  
Author(s):  
Надежда Куражковская ◽  
Nadezhda Kurazhkovskaya ◽  
Борис Клайн ◽  
Boris Klain
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Activity ◽  
Dynamic Pressure ◽  
Cumulative Distribution ◽  
Qualitative Assessment ◽  
Geomagnetic Pulsations ◽  
Magnetospheric Substorms ◽  
Pi2 Pulsations

We present the results of investigation of the influence of geomagnetic activity, solar wind and parameters of the interplanetary magnetic field (IMF) on properties of the intermittency of midlatitude burst series of Pi2 geomagnetic pulsations observed during magnetospheric substorms on the nightside (substorm Pi2) and in the absence of these phenomena (nonsub-storm Pi2). We considered the index α as a main characteristic of intermittency of substorm and nonsubstorm Pi2 pulsations. The index α characterizes the slope of the cumulative distribution function of Pi2 burst amplitudes. The study indicated that the value and dynamics of the index α varies depending on the planetary geomagnetic activity, auroral activity and the intensity of magnetospheric ring currents. In addition, the forms of dependences of the index α on the density n, velocity V, dynamic pressure Pd of the solar wind and IMF Bx-component are different. The behavior of the index α depending on the module of B, By- and Bz-components is similar. We found some critical values of V, Pd, B, By- and Bz-components, after reaching of which the turbulence of the magnetotail plasma during substorm development is decreased. The revealed patterns of the intermittency of Pi2 pulsations can be used for qualitative assessment of turbulence level in the magnetotail plasma depending on changing interplanetary conditions.

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