Topic
Earth's magnetic field
About: Earth's magnetic field is a research topic. Over the lifetime, 20360 publications have been published within this topic receiving 446747 citations. The topic is also known as: magnetic field of Earth & geomagnetic field.
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TL;DR: In this paper, the interdiurnal variability (IDV) index has been used to measure the interplanetary magnetic field strength and its correlation with the strength of the solar magnetic field (B; R2 = 0.75).
Abstract: [1] On the basis of a consideration of Bartels' historical u index of geomagnetic activity, we devise an equivalent index that we refer to as the interdiurnal variability (IDV). The IDV index has the interesting and useful property of being highly correlated with the strength of the interplanetary magnetic field (B; R2 = 0.75) and essentially unaffected by the solar wind speed (V; R2 = 0.01) as measured by spacecraft. This enables us to obtain the variation of B from 1872 to the present, providing an independent check on previously reported results for the evolution of this parameter. We find that solar cycle average B increased by ∼25% from the 1900s to the 1950s and has been lower since. If predictions for a small solar cycle 24 bear out, solar cycle average B will return to levels of ∼100 years ago during the coming cycle(s).
127 citations
TL;DR: Palaeomagnetic records of the path of the pole during reversals of the Earth's magnetic field provide a test of the hypothesis that dipolar or low-order axisymmetric components of the field dominate during the reversals as discussed by the authors.
Abstract: Palaeomagnetic records of the path of the pole during reversals of the Earth's magnetic field provide a test of the hypothesis that dipolar or low-order axisymmetric components of the field dominate during reversals. Multiple records of reversals during the past 12 Myr show no simple or consistent geographical pattern. Although a more robust analysis of the transitional field awaits a greater number of well-distributed sampling sites, the present data are not inconsistent with the simplest models, in which a field reminiscent of the non-dipole component of the present-day field becomes dominant.
127 citations
TL;DR: Vine and Matthews as mentioned in this paper showed that the pattern of local magnetic anomalies on the flanks of a mid-oceanic ridge is strongly lineated parallel to the ridge, and that these magnetic "stripes" represent strips of material in the upper mantle the directions of permanent magnetization of which are alternately parallel and anti-parallel to the present local geomagnetic field.
Abstract: Vine and Matthews1 suggest that the pattern of local magnetic anomalies on the flanks of a mid-oceanic ridge is strongly lineated parallel to the ridge, and that these magnetic ‘stripes’ represent strips of material in the upper mantle the directions of permanent magnetization of which are alternately parallel and anti-parallel to the present local geomagnetic field. Vine and Matthews suggest that mantle material cools as it rises convectively under a ridge and then spreads2 horizontally outward. As the material cools through its Curie point it is magnetized parallel to the contemporary local geomagnetic field. Because this field reverses quasi-periodically3,4 with a period 2T, T being of the order of 0.5–1.0 million years, stripes of alternate permanent magnetization are produced the width of which is vT, v being the local horizontal velocity with which material at the surface of the mantle spreads away from the centre of the ridge. The stripes are observed1 to have widths of the order of 20 km. If T is 0.5 million years, v is 4 cm/yr. Convective velocities of this order are also indicated by palaeomagnetic data5.
127 citations
TL;DR: The largest geomagnetic storm of solar cycle 23 occurred on 2003 November 20 with a Dst index of −472 nT, due to a coronal mass ejection (CME) from active region 0501 as discussed by the authors.
Abstract: [1] The largest geomagnetic storm of solar cycle 23 occurred on 2003 November 20 with a Dst index of −472 nT, due to a coronal mass ejection (CME) from active region 0501. The CME near the Sun had a sky-plane speed of ∼1660 km/s, but the associated magnetic cloud (MC) arrived with a speed of only 730 km/s. The MC at 1 AU (ACE Observations) had a high magnetic field (∼56 nT) and high inclination to the ecliptic plane. The southward component of the MC's magnetic field was made up almost entirely of its axial field because of its east-south-west (ESW) chirality. We suggest that the southward pointing strong axial field of the MC reconnected with Earth's front-side magnetic field, resulting in the largest storm of the solar cycle 23.
127 citations
TL;DR: Interplanetary magnetic field and plasma effect on geomagnetic activity during quiet sun conditions was studied in this paper, showing that the effect of solar magnetic fields and plasma effects can be significant.
Abstract: Interplanetary magnetic field and plasma effect on geomagnetic activity during quiet sun conditions
127 citations