Common features and differences between “jerks” of 1947, 1958 and 1969

Golovkov, V. P.; Zvereva, T. I.; Simonyan, A. O.

doi:10.1080/03091928908243465

Cited by 23 publications

(15 citation statements)

References 4 publications

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“…The internal origin of these jerks seems to be accepted (Malin and Hodder, 1982). Geomagnetic jerks have been investigated and discussed by various authors (Courtillot and Le Mouël, 1984;McLeod, 1985McLeod, , 1989Golovkov et al, 1989;Stewart and Whaler, 1992;Le Huy et al, 1998, 2000. These analyses have revealed the predominantly worldwide character and internal origin of these events.…”

Section: Discussionmentioning

confidence: 99%

The time-varying geomagnetic field of Southern Africa

Kotzé

2014

Earth Planet Sp

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The geomagnetic field at any given epoch is a function of space coordinates, varying differently at each location with time. It has been known that secular change is a comparatively local phenomenon and that it does not proceed in a regular way all over the Earth, giving rise to regions where the field changes more rapidly than elsewhere, like for instance southern Africa. The Hermanus Magnetic Observatory routinely executes geomagnetic repeat surveys, which includes South Africa, Namibia, Zimbabwe and Botswana. Spherical cap modelling of field survey and observatory secular variation data at 5 year intervals between 1975 and 2000 shows that a geomagnetic jerk occurred between 1980 and 1985 over southern Africa. The secular variation models are based on 70 repeat station data central differences as well as the 3 magnetic observatories at Hermanus, Hartebeesthoek and Tsumeb (Namibia) and include terms up to spatial degree 3 and temporal degree 2. Although each model allows for 48 coefficients, only 42 were found to be statistically significant.

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Section: Discussionmentioning

confidence: 99%

The time-varying geomagnetic field of Southern Africa

Kotzé

2014

Earth Planet Sp

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“…An internal origin has been supported by a variety of analyses and authors (e.g. Malin and Hodder, 1982;Courtillot et al, 1984;Malin et al, 1983;Courtillot and Le Mouël, 1985;McLeod, 1985;Gavoret et al, 1986;Golovkov et al, 1989;Alexandrescu et al, 1995Alexandrescu et al, , 1996Bellanger et al, 2001;Bloxham et al, 2002). Although an internal origin is now widely accepted, the processes causing geomagnetic jerks as a whole are not yet wellunderstood.…”

Section: Introductionmentioning

confidence: 93%

Geomagnetic jerks from the Earth’s surface to the top of the core

2007

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Rapid changes in the magnetic field characterised by an abrupt change in the secular variation have been named “secular variation impulses” or “geomagnetic jerks”. Three of these events, around 1968, 1978 and 1990, occurred during the time-span covered by the comprehensive model CM4 (Sabaka et al., 2002, 2004). This model, providing the best temporal resolution between 1960 and 2002 as well as a fine separation of the different magnetic sources, can be used to study rapid phenomena of internal origin. In order to analyse these events all over the globe, synthetic time series were obtained from the CM4 model between 1960–2002. Geomagnetic jerks are detected here as a rapid movement of the zero isoline of the second field derivative. Analysis of the area swept out by this isoline as a function of time allows us to map the spatial extent of jerks though time, and to identify an event around 1985 that is localized in the Pacific area. At the core surface, we compute the fluid flows under the frozen-flux and tangentially geostrophic assumptions. The flows do not exhibit any special pattern at jerk times, but instead show a smooth temporal evolution over the whole time period. However, the mean amplitude of the dynamical pressure associated with these flows present maxima at each jerk occurrence and helps to confirm the identification of a jerk in 1985.

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“…The distributions of the jerk amplitudes for the X component δ 3 X in periods 1961-1963, 1965-1967, 1968-1970, 1977-1979, 1982-1984, 1987-1989, 1990-1992, and 1993-1995 obtained 1961-1963, 1965-1967, 1968-1970, 1977-1979, 1982-1984, 1987-1989, 1990-1992, and 1993-1995 obtained 0000-0100LT 0600-0700LT 1200-1300LT 1800-1900LT 19621966196919781983198819911994. The distributions of the jerk amplitudes for the Z component δ 3 Z in periods 1961-1963, 1965-1967, 1968-1970, 1977-1979, 1982-1984, 1987-1989, 1990-1992, and 1993-1995 obtained from the data at 0000-0100 LT, 0600-0700 LT, 1200-1300 LT, and 1800-1900 LT.…”

Section: -0100ltmentioning

confidence: 99%

“…0600-0700LT 1200-1300LT 1800-1900LT 19621966196919781983198819911994. The distributions of the jerk amplitudes for the X component δ 3 X in periods 1961-1963, 1965-1967, 1968-1970, 1977-1979, 1982-1984, 1987-1989, 1990-1992, and 1993-1995 obtained 1961-1963, 1965-1967, 1968-1970, 1977-1979, 1982-1984, 1987-1989, 1990-1992, and 1993-1995 obtained 0000-0100LT 0600-0700LT 1200-1300LT 1800-1900LT 19621966196919781983198819911994.…”

Section: -0100ltmentioning

confidence: 99%

“…Alldredge (1984) and Alldredge (1985), however, questioned the data selection and the method of analysis by Malin and Hodder (1982), and insisted that an external current system could generate the observed jerks. Despite of many researches on the jerks, whether their sources are internal or external is still controversial (e.g., Kerridge and Barraclough, 1985;McLeod, 1985;Gavoret et al, 1986;Gubbins and Tomlinson, 1986;Thompson and Cain, 1987;Whaler, 1987;Golovkov et al, 1989;McLeod, 1992). It is suggested that the jerks may have some correlations with abrupt changes in decadal length-of-day variation (e.g., Courtillot et al, 1978;Le Mouël and Courtillot, 1981;Davis and Whaler, 1997;Mandea et al, 2000) and with motion of fluid flow at the top 0000-0100LT 0600-0700LT 1200-1300LT 1800-1900LT Fig.…”

Section: Introductionmentioning

confidence: 99%

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Local time features of geomagnetic jerks

et al. 2014

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The geomagnetic jerk amplitudes, which are defined as abruptness of changes in the trends of geomagnetic time series, are investigated with geomagnetic monthly means computed from hourly mean values at each local time.A statistical time series model in which the trend component is expressed by a second order spline function with variable knots is constructed for each time series. The optimum parameter values of the model including positions of knots are estimated by the maximum likelihood method, and the optimum number of parameters including

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Common features and differences between “jerks” of 1947, 1958 and 1969

Cited by 23 publications

References 4 publications

The time-varying geomagnetic field of Southern Africa

The time-varying geomagnetic field of Southern Africa

Geomagnetic jerks from the Earth’s surface to the top of the core

Local time features of geomagnetic jerks

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