Identification of the ground signatures of magnetospheric current systems as a function of latitude during intense magnetic storms

We show that changes in the magnetospheric ring current and auroral currents during the magnetic storms of March 2015 and June 2015, are recorded in several specific ways by ground magnetometers. The ring current changes are detected in geomagnetic field measurements of ground stations at magnetic mid-latitudes from -50 to +50 degrees. The auroral currents changes are detected at high magnetic latitudes from 50 to about 73 degrees. Finally, for stations between 73 and about 85 degrees the measurements of the ground magnetometers seem to be directly correlated with the convection electric field VBSouth of the solar wind. Using the correlations among magnetic fields measured at stations ordered by latitude, a correlation diagram is obtained where the maximum correlation values for fields determined by the ring current form a distinct block. High-latitude magnetic fields from stations at higher latitudes, which are mainly determined by auroral currents, form a different block in the same diagram. This is in agreement with our earlier work using wavelet transforms on ground magnetic-field time series, where mid-latitude fields stations that are influenced mainly by the ring current, give a critical exponent greater than 2 while higher-latitude fields show a more complex dependence with two exponents. The maximum correlation values for mid-latitude fields correlated with the SYM-H index vary from 0.8 to 0.9, and, thus, we infer that those geomagnetic disturbances are mainly due to the ring current. The maximum correlations between the same fields and the solar wind VBSouth vary from 0.5 to 0.7. Fields at magnetic latitudes between 50 and 73 degrees exhibit greater correlation values for the AL index rather than the SYM-H index. This is expected since in the auroral zone, the convection- and substorm-associated auroral electrojets contribute significantly to the deviation of the geomagnetic field from its quiet-time value. In this case, maximum correlations vary between 0.6 and 0.7 for auroral latitude stations when compared with AL, as opposed to 0.4&#8211;0.5 when compared with SYM-H. Our results show how different measures of ground geomagnetic variations reflect the time evolution of several magnetospheric current systems and of the solar wind &#8211; magnetosphere coupling.

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Prediction of SYM-H index during large storms by NARX neural network from IMF and solar wind data

Annales Geophysicae ◽

10.5194/angeo-28-381-2010 ◽

2010 ◽

Vol 28 (2) ◽

pp. 381-393 ◽

Cited By ~ 10

Author(s):

L. Cai ◽

S. Y. Ma ◽

Y. L. Zhou

Keyword(s):

Neural Network ◽

Solar Wind ◽

Correlation Coefficient ◽

Characteristic Time ◽

Ring Current ◽

Wind Data ◽

Distinct Advantage ◽

Elman Network ◽

H Index ◽

Narx Neural Network

Abstract. Similar to the Dst index, the SYM-H index may also serve as an indicator of magnetic storm intensity, but having distinct advantage of higher time-resolution. In this study the NARX neural network has been used for the first time to predict SYM-H index from solar wind (SW) and IMF parameters. In total 73 time intervals of great storm events with IMF/SW data available from ACE satellite during 1998 to 2006 are used to establish the ANN model. Out of them, 67 are used to train the network and the other 6 samples for test. Additionally, the NARX prediction model is also validated using IMF/SW data from WIND satellite for 7 great storms during 1995–1997 and 2005, as well as for the July 2000 Bastille day storm and November 2001 superstorm using Geotail and OMNI data at 1 AU, respectively. Five interplanetary parameters of IMF Bz, By and total B components along with proton density and velocity of solar wind are used as the original external inputs of the neural network to predict the SYM-H index about one hour ahead. For the 6 test storms registered by ACE including two super-storms of min. SYM-H<−200 nT, the correlation coefficient between observed and NARX network predicted SYM-H is 0.95 as a whole, even as high as 0.95 and 0.98 with average relative variance of 13.2% and 7.4%, respectively, for the two super-storms. The prediction for the 7 storms with WIND data is also satisfactory, showing averaged correlation coefficient about 0.91 and RMSE of 14.2 nT. The newly developed NARX model shows much better capability than Elman network for SYM-H prediction, which can partly be attributed to a key feedback to the input layer from the output neuron with a suitable length (about 120 min). This feedback means that nearly real information of the ring current status is effectively directed to take part in the prediction of SYM-H index by ANN. The proper history length of the output-feedback may mainly reflect on average the characteristic time of ring current decay which involves various decay mechanisms with ion lifetimes from tens of minutes to tens of hours. The Elman network makes feedback from hidden layer to input only one step, which is of 5 min for SYM-H index in this work and thus insufficient to catch the characteristic time length.

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Extremely intense (SML ≤–2500 nT) substorms: isolated events that are externally triggered?

Annales Geophysicae ◽

10.5194/angeo-33-519-2015 ◽

2015 ◽

Vol 33 (5) ◽

pp. 519-524 ◽

Cited By ~ 30

Author(s):

B. T. Tsurutani ◽

R. Hajra ◽

E. Echer ◽

J. W. Gjerloev

Keyword(s):

Solar Wind ◽

Magnetic Fields ◽

Magnetic Storm ◽

Solar Wind Plasma ◽

Magnetic Storms ◽

Input Energy ◽

Stored Energy ◽

Ionospheric Currents ◽

Interplanetary Magnetic Fields ◽

Very High

Abstract. We examine particularly intense substorms (SML &leq;–2500 nT), hereafter called "supersubstorms" or SSS events, to identify their nature and their magnetic storm dependences. It is found that these intense substorms are typically isolated events and are only loosely related to magnetic storms. SSS events can occur during super (Dst &leq;–250 nT) and intense (−100 nT &geq; Dst >–250) magnetic storms. SSS events can also occur during nonstorm (Dst &geq;–50 nT) intervals. SSSs are important because the strongest ionospheric currents will flow during these events, potentially causing power outages on Earth. Several SSS examples are shown. SSS events appear to be externally triggered by small regions of very high density (~30 to 50 cm−3) solar wind plasma parcels (PPs) impinging upon the magnetosphere. Precursor southward interplanetary magnetic fields are detected prior to the PPs hitting the magnetosphere. Our hypothesis is that these southward fields input energy into the magnetosphere/magnetotail and the PPs trigger the release of the stored energy.

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Modeling of solar wind control of the ring current buildup: A case study of the magnetic storms in April 1997

Geophysical Research Letters ◽

10.1029/1998gl900006 ◽

1998 ◽

Vol 25 (20) ◽

pp. 3751-3754 ◽

Cited By ~ 50

Author(s):

Y. Ebihara ◽

M. Ejiri

Keyword(s):

Solar Wind ◽

Ring Current ◽

Magnetic Storms

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Influences on the radius of the auroral oval

Annales Geophysicae ◽

10.5194/angeo-27-2913-2009 ◽

2009 ◽

Vol 27 (7) ◽

pp. 2913-2924 ◽

Cited By ~ 54

Author(s):

S. E. Milan ◽

J. Hutchinson ◽

P. D. Boakes ◽

B. Hubert

Keyword(s):

Solar Wind ◽

Ring Current ◽

Geomagnetic Storms ◽

Auroral Oval ◽

Substorm Onset ◽

Polar Cap ◽

H Index ◽

Magnetic Perturbation

Abstract. We examine the variation in the radius of the auroral oval, as measured from auroral images gathered by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, in response to solar wind inputs measured by the Advanced Composition Explorer (ACE) spacecraft for the two year interval June 2000 to May 2002. Our main finding is that the oval radius increases when the ring current, as measured by the Sym-H index, is intensified during geomagnetic storms. We discuss our findings within the context of the expanding/contracting polar cap paradigm, in terms of a modification of substorm onset conditions by the magnetic perturbation associated with the ring current.

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Geomagnetic field variations caused by changes in the quiet-time solar wind pressure

Planetary and Space Science ◽

10.1016/0032-0633(72)90123-7 ◽

1972 ◽

Vol 20 (11) ◽

pp. 1909-1914 ◽

Cited By ~ 24

Author(s):

P. Verzariu ◽

M. Sugiura ◽

I.B. Strong

Keyword(s):

Solar Wind ◽

Geomagnetic Field ◽

Wind Pressure ◽

Quiet Time ◽

Solar Wind Pressure

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Scientific Basis and Geophysical Consequences of Geomagnetic Reversals and Excursions: A Fundamental Statement

Journal of Geography Environment and Earth Science International ◽

10.9734/jgeesi/2021/v25i330277 ◽

2021 ◽

pp. 59-69

Author(s):

J. Marvin Herndon

Keyword(s):

Solar Wind ◽

Geomagnetic Field ◽

Electromagnetic Induction ◽

Ring Current ◽

Volcanic Eruptions ◽

Electrical Energy ◽

Nuclear Fission ◽

Scientific Basis ◽

Meteorite Impact ◽

Fundamental Statement

Convection in Earth’s georeactor sub-shell is responsible for generating the geomagnetic field and for maintaining the critical balances necessary for stable sub-core nuclear fission. External factors capable of disrupting sub-shell convection are trauma at Earth’s surface, for example by meteorite impact, and electrical energy transfer via Faraday’s electromagnetic induction into the georeactor by changes in the solar wind or in the magnetospheric ring current. Reduced sub-shell convection not only leads to decreased geomagnetic field intensity, but to increased uranium settling out into the sub-core where it undergoes uncontrolled nuclear fission until sub-shell convection is reestablished. Periods of uncontrolled georeactor nuclear fission are responsible for causing geophysical phenomena at Earth’s surface that are associated with geomagnetic reversals and excursions. Anticipated consequences of sub-shell convection collapse include increases in volcanic activity, increases in the number and intensity of earthquakes, warming of the oceans, and diminishment of atmospheric convection resulting in global warming at the surface. The most worrisome potentiality is triggering the eruption of the Yellowstone super-volcano. Changes in solar wind flux, too small to cause geomagnetic field collapse, however, may cause increases in earthquakes and volcanic eruptions. The understanding described here potentially provides a basis for the development of earthquake and volcanic eruption prediction methodologies.

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Principal components' features of mid-latitude geomagnetic daily variation

Annales Geophysicae ◽

10.5194/angeo-28-2213-2010 ◽

2010 ◽

Vol 28 (12) ◽

pp. 2213-2226 ◽

Cited By ~ 7

Author(s):

P. De Michelis ◽

R. Tozzi ◽

G. Consolini

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Geomagnetic Field ◽

Daily Variation ◽

Time Dependent ◽

Statistical Features ◽

3 Dimensional ◽

Magnetic Elements ◽

Orthogonal Components ◽

Current Systems

Abstract. The ionospheric and magnetospheric current systems are responsible of the daily magnetic field changes. Recently, the Natural Orthogonal Components (NOC) technique has been applied to model the physical system responsible of the daily variation of the geomagnetic field, efficiently and accurately (Xu and Kamide, 2004). Indeed, this approach guarantees that the number of parameters used to represent the physical process is small as much as possible, and consequently process control for such system becomes apparent. We focus our present study on the analysis of the hourly means of the magnetic elements H, D and Z recorded at L'Aquila observatory in Italy from 1993 to 2004. We apply to this dataset the NOC technique to reconstruct the 3-dimensional structures of the different ionospheric and magnetospheric current systems which contribute to the geomagnetic daily variations. To support our interpretation in terms of the different ionospheric and magnetospheric current systems, the spectral and statistical features of the time-dependent amplitudes associated to the set of natural orthogonal components are analyzed and compared to those of a set of descriptors of the magnetospheric dynamics and solar wind changes.

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The size of the auroral belt during magnetic storms

Annales Geophysicae ◽

10.1007/s00585-998-0566-z ◽

1998 ◽

Vol 16 (5) ◽

pp. 566-573 ◽

Cited By ~ 29

Author(s):

N. Yokoyama ◽

Y. Kamide ◽

H. Miyaoka

Keyword(s):

Ring Current ◽

Time Lag ◽

Magnetic Storms ◽

Field Energy ◽

Quiet Time ◽

Magnetic Field Energy ◽

Equatorward Boundary ◽

Precipitation Boundary ◽

Auroral Phenomena ◽

Current Energy

Abstract. Using the auroral boundary index derived from DMSP electron precipitation data and the Dst index, changes in the size of the auroral belt during magnetic storms are studied. It is found that the equatorward boundary of the belt at midnight expands equatorward, reaching its lowest latitude about one hour before Dst peaks. This time lag depends very little on storm intensity. It is also shown that during magnetic storms, the energy of the ring current quantified with Dst increases in proportion to Le–3, where Le is the L-value corresponding to the equatorward boundary of the auroral belt designated by the auroral boundary index. This means that the ring current energy is proportional to the ion energy obtained from the earthward shift of the plasma sheet under the conservation of the first adiabatic invariant. The ring current energy is also proportional to Emag, the total magnetic field energy contained in the spherical shell bounded by Le and Leq, where Leq corresponds to the quiet-time location of the auroral precipitation boundary. The ratio of the ring current energy ER to the dipole energy Emag is typically 10%. The ring current leads to magnetosphere inflation as a result of an increase in the equivalent dipole moment.Key words. Ionosphere (Auroral ionosphere) · Magnetospheric physics (Auroral phenomena; storms and substorms)

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