Overview of Solar Wind–Magnetosphere–Ionosphere–Atmosphere Coupling and the Generation of Magnetospheric Currents

Milan, S. E.; Clausen, L. B. N.; Coxon, J. C.; Carter, J. A.; Walach, Maria-Theresia; Laundal, K. M.; Østgaard, Nikolai; Tenfjord, P.; Reistad, Jone Peter; Snekvik, K.; Korth, H.; Anderson, B. J.

doi:10.1007/978-94-024-1225-3_19

Cited by 15 publications

(27 citation statements)

References 87 publications

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“…10.1029/2019GL082824 (SCW), and (C) westward electrojet. Whereas B is associated with the SCW, or DP1 perturbations, A and C can be related to the general magnetospheric convective system, DP2 (Nishida, 1968), which is enhanced during substorm growth and expansion phases (Milan et al, 2017). To summarize the above results, we identify key time ranges, before and after onset: 0 ≤ t1 ′ < 10, 10 ≤ t2 ′ < 20, 20 ≤ t3 ′ < 30 and t4 ′ ≥ 30 in terms of normalized time, t ′ .…”

Section: Geophysical Research Lettersmentioning

confidence: 99%

Directed Network of Substorms Using SuperMAG Ground‐Based Magnetometer Data

Orr

Chapman

Gjerloev

2019

Geophysical Research Letters

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We quantify the spatiotemporal evolution of the substorm ionospheric current system utilizing the SuperMAG 100+ magnetometers. We construct dynamical directed networks from this data for the first time. If the canonical cross‐correlation between vector magnetic field perturbations observed at two magnetometer stations exceeds a threshold, they form a network connection. The time lag at which canonical cross‐correlation is maximal determines the direction of propagation or expansion of the structure captured by the network connection. If spatial correlation reflects ionospheric current patterns, network properties can test different models for the evolving substorm current system. We select 86 isolated substorms based on nightside ground station coverage. We find, and obtain the timings for, a consistent picture in which the classic substorm current wedge forms. A current system is seen premidnight following the substorm current wedge westward expansion. Later, there is a weaker signal of eastward expansion. Finally, there is evidence of substorm‐enhanced convection.

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Section: Geophysical Research Lettersmentioning

confidence: 99%

Directed Network of Substorms Using SuperMAG Ground‐Based Magnetometer Data

Orr

Chapman

Gjerloev

2019

Geophysical Research Letters

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“…Flow shears in this convection pattern are associated with the divergence of electric field and Pedersen current in the ionosphere and the corresponding FACs sensed by AMPERE. Auroras produced by precipitating electrons carrying upward FACs move to lower and higher latitudes as the polar cap expands and contracts, as described by the expanding and contracting polar cap (ECPC) model (Clausen et al, 2012;Cowley & Lockwood, 1992;Milan et al, 2003Milan et al, , 2007Milan et al, , 2017.…”

Section: Introductionmentioning

confidence: 99%

Bifurcated Region 2 Field‐Aligned Currents Associated With Substorms

et al. 2020

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We analyze the magnetosphere-ionosphere field-aligned currents associated with substorms using the Active Magnetosphere and Planetary Electrodynamics Response Experiment. We report a new phenomenon related to substorm onset: the development of a second pair of R2 field-aligned currents located equatorward of the preexisting R1/R2 currents, especially in the dusk sector. The appearance of such events favors the summer hemisphere, suggesting that ionospheric conductance modulates this phenomenon. During ongoing geomagnetic activity, the events have a quasiperiodicity of approximately 1 hr. We suggest that this phenomenon is related to subauroral polarization streams, which are strong westward flows in the dusk sector midlatitude ionosphere. This paper proposes a new mechanism that describes the formation of these current bifurcations: Consecutive particle injections into the inner magnetosphere during disturbed geomagnetic conditions cause separate partial ring currents to form, leading to the presence of distinct R2 current systems, all flowing into the R1 current.

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“…The main goal of the current study was to determine some properties of the electrical conductivity parallel to the geomagnetic field in the ionosphere at Swarm altitude. When considering climatological conductivity maps based on 4 years of observations we found that: Two conductivity maxima occur: one at very high QD latitudes (at

\sim 80 °

) around noon and one at low latitudes (within

\pm 20 °

) at dawn; which may be associated to the R1 and the cusp region (Milan et al., 2017) and the morning overshoot (Stolle et al., 2011), respectively There is an evident and expected conductivity asymmetry from day to night. In the dayside the effect of solar EUV is dominant and conductivity has a peak at 15:00 MLT and at

\pm 50 °

QD latitude.…”

Section: Discussionmentioning

confidence: 88%

“…Here, the electrical conductivity for both Northern (left) and Southern (right) Hemispheres saturated between 2.5 and

5.0 \times {normal10}^{11} {normals}^{- 1}

is reported in the first row. The conductivity ranges between

\sim

2.1 and

\sim 6 \times {normal10}^{11} {normals}^{- 1}

, has a maximum error (computed as explained above) of

\sim 0.6 %

, and is characterized by the existence of two maxima: at very high latitudes (around

\pm normal80 °

) between 09:00 and 12:00 MLT, in correspondence with the Region R0 and the polar magnetic cusp (Milan et al., 2017), and at low latitudes (within

\pm normal20 °

) around 06:00 MLT. The latter peak, which represents the absolute maximum value of

σ_{false‖}

, corresponds to the morning overshoot (Stolle et al., 2011).…”

Section: Resultsmentioning

confidence: 99%

Parallel Electrical Conductivity in the Topside Ionosphere Derived From Swarm Measurements

et al. 2021

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Our knowledge of the physical properties of the topside ionosphere is still incomplete. A key point still not fully understood is how field‐aligned currents are generated, evolve and dissipate in the ionosphere. Answering to this question is fundamental for a better understanding of the mechanisms regulating the coupling between magnetosphere and ionosphere and to shed light on the physical processes inherent to space weather events occurring in the Earth's ionosphere. In this framework a relevant role is played by the ionospheric conductivity. The purpose of this study is to analyze the main properties of the electrical conductivity parallel to the geomagnetic field from a climatological point of view. The statistical study of the electrical conductivity is proposed using four years of in‐situ electron density and temperature measurements at 1 Hz acquired by the European Space Agency's Swarm A satellite. Variations due to seasonal effects are also investigated. Finally, starting from observations and comparing our results with those obtained using International Reference Ionosphere model, we give a first estimation of the conductivity mainly due to particle precipitation.

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Overview of Solar Wind–Magnetosphere–Ionosphere–Atmosphere Coupling and the Generation of Magnetospheric Currents

Cited by 15 publications

References 87 publications

Directed Network of Substorms Using SuperMAG Ground‐Based Magnetometer Data

Directed Network of Substorms Using SuperMAG Ground‐Based Magnetometer Data

Bifurcated Region 2 Field‐Aligned Currents Associated With Substorms

Parallel Electrical Conductivity in the Topside Ionosphere Derived From Swarm Measurements

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