Plasma clouds in the magnetosphere

Deforest, S. E.; McIlwain, C. E.

doi:10.1029/ja076i016p03587

Cited by 550 publications

(176 citation statements)

References 18 publications

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“…They show a relatively smooth region of precipitation (when looking at a logarithmic record) which is centered at 680 invariant latitude at midnight and at higher latitudes in the morning hours. There is also a clear shift in latitude for different energies: It has been shown by DeForest and McIlwain (1971) at 6.6 Re in the equatorial plane that the particles in these energies drift from the midnight region eastward. As this is very close to the precipitation maximum around midnight and there is no particular change in the character of the precipitation in these latitudes it is likely that the particles discussed here belong to the same category and drift from midnight towards dawn.…”

Section: Discussionmentioning

confidence: 92%

“…Distribution of particles in the equatorial plane deduced from the precipitation-maxima in the ionosphere It has been shown by DeForest and McIlwain (1971) that electrons in the energy range considered here are generally injected close to midnight and then drift eastward in longitude. Their measurements were carried out at ATS at 6.6 Re and should be applicable here at least for the higher energies.…”

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confidence: 99%

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Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Gustafsson¹

1973

J. Geophys. Res.

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Data from particle detectors on board the satellite Ogo 4 were used to study the precipitation of electrons in the energy range 0.7–24 kev. The latitude dependence of these particles in the local time region from midnight to dawn has been investigated in detail. The analysis shows that the precipitation of particles of energies 2.3–24 kev is centered at an invariant latitude of about 68° at midnight with a clear shift in latitude with increasing local time, and that this shift is more pronounced for lower energies. The highest fluxes of particles in this energy interval are measured at midnight, and they decrease rapidly with local time. In the dawn region, the location of the maximum precipitation for different energies varies about 1 ° of latitude for each unit of Kp, but the relative distribution remains almost unchanged. The fact that different energies have their maximums at different latitudes implies that the flux spectrum of precipitated particles, when measured at a certain latitude, has a peak at an energy corresponding to the energy of maximum precipitation at the latitude. The data in the energy range 2.3–24 kev support a theory in which particles are injected in the midnight region from the tail, gain energy owing to a betatron process, and then drift eastward in a combined electric and magnetic field. The main part of the electrons at 0.7 kev show a different behavior than do those at higher energies. They seem to undergo an acceleration process that is rather local, sometimes giving field‐aligned fluxes that may be superimposed on the background precipitation. The structural precipitation of 0.7‐kev electrons has been found to coincide on a statistical basis with the region of structural aurora indicating a relationship between the two phenomena.

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Section: Discussionmentioning

confidence: 92%

mentioning

confidence: 99%

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Gustafsson¹

1973

J. Geophys. Res.

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“…It was shown by Mauk et al [1996] This situation is very similar to the situation at Earth. Earth magnetospheric injections occur in regions where the plasma beta can be high and in the region of transition between dipolar and neutral sheet geometries [Hoffman, 1973;Williams, 1983;DeForest and Mcllwain, 1971;Kaufmann, 1987]. It is believed that the hot plasma injections are driven by energy that is stored in the form of magnetic fields and associated electric currents.…”

Section: Implications Of the Radial Distribution Of Injectionsmentioning

confidence: 99%

Storm‐like dynamics of Jupiter's inner and middle magnetosphere

Mauk¹,

Williams²,

McEntire³

et al. 1999

J. Geophys. Res.

114

168

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Abstract. The discovery of energy-time dispersed, charged particle signatures of dynamic, longitudinally confined charged particle injections within Jupiter's inner magnetosphere has been reported previously as measured in >20-keV particle intensities by the Galileo energetic particles detector (EPD). While these events have similarities to so-called substorm injections observed within the Earth's magnetosphere, it is unknown whether the driving mechanisms are similar. Over 100 Jovian injection events have now been documented between radial distances of -9 Rj (the inner boundary of most of the observations) and 27 Rj. Injections occur at all System III longitudes and local time positions. Similar to Earth magnetospheric injections, the Jovian injections occur throughout the broad radial region of transition between the quasidipolar and neutral sheet magnetic field configurations, and where the charged particle energy densities are competitive with the magnetic energy densities. The Jovian injections can be clustered in time, analogous to what often happens during well-known magnetic storms that occur in the Earth's magnetosphere. During one particular periapsis of Galileo's orbital trajectory, the magnetosphere was observed by EPD to become suddenly very disturbed with multiple injections following a prolonged period (>24 Earth hours) of relative quiescence. Because of the prestorm coincidence of a signature of an apparent Earth-like global magnetospheric disturbance, we hypothesize that this Jovian storm occurred when the inner and middle magnetosphere were triggered out of marginal stability by the passage of a magnetohydrodynamic fast mode wave launched at the magnetopause by a pressure variation in the interplanetary (solar wind) environment.

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“…28 Both magnetic and particle observations at the geosynchronous distance, together with the AE index. From the top, the Bz component of the magnetic field, electron and proton data and the AE index (Deforest and McIlwain 1971) (ii) Geosynchronous distance (6 Re) Thus, it is instructive to examine the accumulation of the magnetic energy at 6 Re and the resulting decrease (the inflation) of the magnetic field. Figure 28 shows an example of both the magnetic record and particle data taken by the ATS 6 satellite at the geosynchronous distance, together with the AE index.…”

Section: Growth Phase (A) Aurorasmentioning

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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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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Plasma clouds in the magnetosphere

Cited by 550 publications

References 18 publications

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Storm‐like dynamics of Jupiter's inner and middle magnetosphere

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

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