Magnetotail changes in relation to the solar wind magnetic field and magnetospheric substorms

Aubry, M. P.; McPherron, R. L.

doi:10.1029/ja076i019p04381

Cited by 120 publications

(58 citation statements)

References 17 publications

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“…lijima (1972) and McPherron (1973) have also employed the technique of keying on the temporally-isolated low-latitude onset time to confirm and quantify previous results of Fairfield and Ness (1970) and Aubry and McPherron (1971) concerning pre-and post-onset variations of the tail-lobe magnetic energy density. The results of McPherron (1973), which are similar to.those of lijima (1972) are shown in Figure 2.…”

Section: Tail-lobe Magnetic Variationsmentioning

confidence: 77%

“…Such adjustments of large-scale magnetospheric flow patterns often can be inferred from phenomena such as ground magnetic variations at polar-cap and equatorial latitudes (Nishida and Kokubun, 1971;, variations in tail-lobe magnetic energy density (Aubry and McPherron, 1971;Nishida and Nagayama, 1973;Meng and Colburn, 1973), and latitudinal shifts of dayside auroras and the associated F-layer irregularity.zones or FLIZ . Quantitative studies of such phenomena as they -14 -respond to changes in the strength and direction of .the INF are beginning to yield important new information on the nature of the interaction between the interplanetary and geomagnetic fields.…”

Section: The Interplanetary Magnetic Field and Magnetospheric Convectionmentioning

confidence: 99%

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Observations of interactions between interplanetary and geomagnetic fields

Burch¹

1974

Reviews of Geophysics

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Magnetospheric effects associated with variations of the north‐south component of the interplanetary magnetic field (IMF) are examined in light of recent experimental and theoretical results. Although the occurrence of magnetospheric substorms is statistically related to periods of southward IMF, the details of the interaction are not understood. In particular, attempts to separate effects resulting directly from the interaction between interplanetary and geomagnetic fields from those associated with substorms have produced conflicting results. One can, however, say with some assurance that the transfer of magnetic flux from the day side to the night side magnetosphere, as evidenced by equatorward motion of the polar cusp and increases of the magnetic energy density in the lobes of the geomagnetic tail, is a direct consequence of the southward IMF. On the other hand, the formation of a macroscopic X‐type neutral line at tail distances less than 35 RE appears to be a substorm phenomenon. Although other plasma and field phenomena in the outer magnetosphere and at low altitudes may be directly associated with the southward IMF, the evidence is less convincing. The quantitative results that have been obtained are compared with current theoretical models of the reconnection process.

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Section: Tail-lobe Magnetic Variationsmentioning

confidence: 77%

Section: The Interplanetary Magnetic Field and Magnetospheric Convectionmentioning

confidence: 99%

Observations of interactions between interplanetary and geomagnetic fields

Burch¹

1974

Reviews of Geophysics

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“…We note that for this event, we have no means of precisely determining the arrival time of the southward field at the magnetopause. As discussed originally by Aubry and McPherron [1971], it is reasonable to assume that the solar wind convection time is a good estimate of the delay.…”

Section: Substormsmentioning

confidence: 99%

Substorms in space: The correlation between ground and satellite observations of the magnetic field

McPherron¹,

Russell²,

Kivelson³

et al. 1973

Radio Science

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Satellite studies of magnetospheric substorms are necessarily statistical since there are few properly instrumented satellites in space at any one time. To carry out these studies, one selects an ensemble of similar substorms, determines an origin for substorm time, and performs an ensemble average to eliminate noise. Similarity between different substorms can be determined from contour maps of midlatitude magnetic perturbations as a function of longitude and universal time. The origin of substorm time can also be determined from midlatitude perturbations and is usually taken as the beginning of the positive bay near midnight. Use of these techniques has led to a phenomenological model of magnetospheric substorms that includes a growth phase. The controversy over the existence of the growth phase is at least partially a consequence of differing definitions of the origin of substorm time. Use of auroral zone magnetograms often gives an earlier onset than midlatitude magnetograms. However, midlatitude onsets do appear to order satellite data systematically. In this paper we illustrate the discrepancy between these two onset times and show how midlatitude onsets order satellite data in agreement with the growth phase model. Three events of increasing complexity are considered. Each has been previously reported in the literature and later criticized. We speculate that a polar magnetic substorm begins when a pair of X-and O-type neutral lines form on closed field lines within the plasma sheet. Subsequently, the midlatitude positive bay begins when magnetic merging first encounters open field lines in the lobe of the tail.

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“…Aubry and McPherron [1971] and Caan et al [1975Caan et al [ , 1978 observed that the magnetic field strength in the tail lobes decreases at expansion phase onset, implying the removal of magnetic flux from the lobes. This observation is not conclusive regarding the exact timing of the increase in magnetotail reconnection, however.…”

Section: Introductionmentioning

confidence: 99%

Magnetotail reconnection rate during magnetospheric substorms

Blanchard¹,

Lyons²,

Beaujardière³

1997

J. Geophys. Res.

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Abstract. The magnetotail reconnection rate during substorms is studied using data taken by the Sondreslrom incoherent scatter radar during an ensemble of 24 substorms. A superposed epoch analysis indicates that magnetotail reconnection increases marginally significantly above its average level near the time of substorm expansion phase onset. Our data set shows this increase with 87% confidence within +5 min of onset and with greater than 99% confidence at 10 + 5 min after onset. However, the median reconnection rate measurement does not begin to increase until 20 rain after onset. This effect is shown to be due to a spatial variation in the development of magnetotail reconnection during substorms; magnetotail reconnection increases very soon after onset in a small magnetic local time sector near midnight, while over most of the separatrix, the increase in the reconnection rate is delayed. The average delay in the local time sectors greater that 1.5 hours from midnight is approximately 20 min. We assign functional forms to the average dependence of the magnetotail reconnection rate on magnetic local time, on the interplanetary magnetic field, and on substorm activity, and analyze the generalized linear combination of these functions. The resulting expression consists of the sum of the average interplanetary magnetic field and substorm dependence of the reconnection rate gated by the average spatial variation and accounts for 36% of the variance in the reconnection rate (0.55 linear correlation), which is most of the low-frequency (f < 0.5 h 'l) variation. The residual variance in the reconnection rate is mostly noise at a level consistent with the reconnection rate measurement uncertainty.

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Magnetotail changes in relation to the solar wind magnetic field and magnetospheric substorms

Cited by 120 publications

References 17 publications

Observations of interactions between interplanetary and geomagnetic fields

Observations of interactions between interplanetary and geomagnetic fields

Substorms in space: The correlation between ground and satellite observations of the magnetic field

Magnetotail reconnection rate during magnetospheric substorms

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