A Unifying Theory of High-Latitude Geophysical Phenomena and Geomagnetic Storms

Axford, W. I.; Hines, C. O.

doi:10.1139/p61-172

Cited by 1,266 publications

(325 citation statements)

References 30 publications

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“…The potential drop across the magnetotail drives the (E × B) drift of plasmas in the magnetosphere and the ionosphere. In the ionosphere, the plasma drift produces the DD current (Axford and Hines 1961). The terminals of the Regions 1 and 2 currents are located just inside the magnetopause (Fig.…”

Section: Directly Driven Current System (Dd) (A) Circuitmentioning

confidence: 99%

“…18(a)). Axford and Hines (1961) projected the ionospheric current pattern (called the SD current) on the equatorial plane. This process allowed them to infer the location of the terminal in the magnetotail, which is located a little inside of the magnetopause; note that the morning (positive) and evening (negative) sides of the oval is surrounded the convection flow lines (Fig.…”

Section: Directly Driven Current System (Dd) (A) Circuitmentioning

confidence: 99%

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Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

Akasofu

2017

Space Sci Rev

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Auroral substorms are mostly manifestations of dissipative processes of electromagnetic energy. Thus, we consider a sequence of processes consisting of the power supply (dynamo), transmission (currents/circuits) and dissipations (auroral substorms-the end product), namely the electric current line approach. This work confirms quantitatively that after accumulating magnetic energy during the growth phase, the magnetosphere unloads the stored magnetic energy impulsively in order to stabilize itself. This work is based on our result that substorms are caused by two current systems, the directly driven (DD) current system and the unloading system (UL). The most crucial finding in this work is the identification of the UL (unloading) current system which is responsible for the expansion phase. A very tentative sequence of the processes leading to the expansion phase (the generation of the UL current system) is suggested for future discussions.(1) The solar wind-magnetosphere dynamo enhances significantly the plasma sheet current when its power is increased above 10 18 erg/s (10 11 w). (2) The magnetosphere accumulates magnetic energy during the growth phase, because the ionosphere cannot dissipate the increasing power because of a low conductivity. As a result, the magnetosphere is inflated, accumulating magnetic energy. (3) When the power reaches 3-5 × 10 18 erg/s (3-5 × 10 11 w) for about one hour and the stored magnetic energy reaches 3-5 × 10 22 ergs (10 15 J), the magnetosphere begins to develop perturbations caused by current instabilities (the current density ≈3 × 10 −12 A/cm 2 and the total current ≈10 6 A at 6 Re). As a result, the plasma sheet current is reduced. (4) The magnetosphere is thus deflated. The current reduction causes ∂B/∂t > 0 in the main body of the magnetosphere, producing an earthward electric field. As it is transmitted to the ionosphere, it becomes equatorward-directed electric field which drives both Pedersen and Hall currents and thus generates the UL current system. (6) The substorm intensity depends on the location of the energy accumulation (between 4 Re and 10 Re), the closer the location to the earth, the more intense substorms becomes, because the capacity of holding the energy is higher at closer distances. The convective flow toward the earth brings both the ring current and the plasma sheet current closer when the dynamo power becomes higher.This proposed sequence is not necessarily new. Individual processes involved have been considered by many, but the electric current approach can bring them together systematically and provide some new quantitative insights.

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Section: Directly Driven Current System (Dd) (A) Circuitmentioning

confidence: 99%

Section: Directly Driven Current System (Dd) (A) Circuitmentioning

confidence: 99%

Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

Akasofu

2017

Space Sci Rev

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“…across the polar magnetopause for southward IMF) is expected to lose its anti-sunward momentum by the J × B force, where J is the electric current density (in the present case, the magnetopause Chapman-Ferraro current) flowing against E (Roederer, 1977). The source of the motional electric field is not limited to the open magnetic field -viscous-like interaction at the magnetospheric boundary (Axford and Hines, 1961), e.g. through Kelvin-Helmholtz instability (Hasegawa et al, 2004), can also provide such an electric field in the magnetosphere.…”

Section: Introductionmentioning

confidence: 81%

Energy conversion through mass loading of escaping ionospheric ions for different Kp values

Yamauchi¹,

Slapak²

2018

Ann. Geophys.

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Abstract. By conserving momentum during the mixing of fast solar wind flow and slow planetary ion flow in an inelastic way, mass loading converts kinetic energy to other forms -e.g. first to electrical energy through charge separation and then to thermal energy (randomness) through gyromotion of the newly born cold ions for the comet and Mars cases. Here, we consider the Earth's exterior cusp and plasma mantle, where the ionospheric origin escaping ions with finite temperatures are loaded into the decelerated solar wind flow. Due to direct connectivity to the ionosphere through the geomagnetic field, a large part of this electrical energy is consumed to maintain field-aligned currents (FACs) toward the ionosphere, in a similar manner as the solar wind-driven ionospheric convection in the open geomagnetic field region. We show that the energy extraction rate by the mass loading of escaping ions ( K) is sufficient to explain the cusp FACs, and that K depends only on the solar wind velocity accessing the mass-loading region (u sw ) and the total mass flux of the escaping ions into this region (m load F load ), as K ∼ −m load F load u 2 sw /4. The expected distribution of the separated charges by this process also predicts the observed flowing directions of the cusp FACs for different interplanetary magnetic field (IMF) orientations if we include the deflection of the solar wind flow directions in the exterior cusp. Using empirical relations of u 0 ∝ Kp+1.2 and F load ∝ exp(0.45Kp) for Kp = 1-7, where u 0 is the solar wind velocity upstream of the bow shock, K becomes a simple function of Kp as log 10 ( K) = 0.2 · Kp + 2 · log 10 (Kp + 1.2) + constant. The major contribution of this nearly linear increase is the F load term, i.e. positive feedback between the increase of ion escaping rate F load through the increased energy consumption in the ionosphere for high Kp, and subsequent extraction of more kinetic energy K from the solar wind to the current system by the increased F load . Since F load significantly increases for increased flux of extreme ultraviolet (EUV) radiation, high EUV flux may significantly enhance this positive feedback. Therefore, the ion escape rate and the energy extraction by mass loading during ancient Earth, when the Sun is believed to have emitted much higher EUV flux than at present, could have been even higher than the currently available highest values based on Kp = 9. This raises a possibility that the ion escape has substantially contributed to the evolution of the Earth's atmosphere.

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“…opposite to the direction of the geomagnetic field, then the two fields can connect or effectively interact with each other like the opposite poles of two bar magnets. This linking of IMF with the terrestrial or earth's magnetic field is known as magnetic reconnection [10,11]. During the reconnection process efficient transfer of energy takes place from solar wind into magnetosphere as well as huge fluxes of charged particles enter the magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

Variability of Geomagnetic Field with Interplanetary Magnetic Field at Low, Mid and High Latitudes

et al. 2018

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The fluctuations in the Interplanetary Magnetic Field significantly affect the state of geomagnetic field particularly during the Coronal Mass Ejection (CME) events. In the present investigation we have studied the influence of Interplanetary Magnetic Field changes on the geomagnetic field components at high, low and mid latitudes. To carry out this investigation we have selected three stations viz. Alibag (18.6°N, 72.7°E), Beijing MT (40.3°N, 116.2°E) and Casey (66.2°S, 110.5°E) one each in the low, mid and high latitude regions. Then we selected geomagnetic storm events of three types namely weak (-50≤Dst≤-20), moderate (100≤Dst≤-50) and intense (Dst≤-100nT). In each storm category 10 events were considered. From our study we conclude that geomagnetic field components are significantly affected by the changes in the IMF at all the three latitudinal regions during all the storm events. At the same time we also found that the magnitude of change in geomagnetic field components is highest at the high latitudes during all types of storm events while at low and mid latitude stations the magnitude of effect is approximately the same.

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A Unifying Theory of High-Latitude Geophysical Phenomena and Geomagnetic Storms

Cited by 1,266 publications

References 30 publications

Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

Energy conversion through mass loading of escaping ionospheric ions for different Kp values

Variability of Geomagnetic Field with Interplanetary Magnetic Field at Low, Mid and High Latitudes

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