Stormtime ring current heating of the plasmasphere and ionosphere

Abstract. In order to investigate the causal relationship between magnetic storms and substorms, variations of the mid-latitude geomagnetic indices, ASY (asymmetric part) and SYM (symmetric part), at substorm onsets are examined. Substorm onsets are defined by three different phenomena; (1) a rapid increase in the mid-latitude asymmetric-disturbance indices, ASY-D and ASY-H, with a shape of so-called `mid-latitude positive bay\\'; (2) a sharp decrease in the AL index; (3) an onset of Pi2 geomagnetic pulsation. The positive bays are selected using eye inspection and a pattern-matching technique. The 1-min-resolution SYM-H index, which is essentially the same as the hourly Dst index except in terms of the time resolution, does not show any statistically significant development after the onset of substorms; it tends to decay after the onset rather than to develop. It is suggested by a simple model calculation that the decay of the magnetospheric tail current after substorm onset is responsible for the decay of the Dst field. The relation between the IMF southward turning and the development of the Dst field is re-examined. The results support the idea that the geomagnetic storms and substorms are independent processes; that is, the ring-current development is not the result of the frequent occurrence of substorms, but that of enhanced convection caused by the large southward IMF. A substorm is the process of energy dissipation in the magnetosphere, and its contribution to the storm-time ring-current formation seems to be negligible. The decay of the Dst field after a substorm onset is explained by a magnetospheric energy theorem.

Download Full-text

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.

Download Full-text

Non-uniform growth of the ring current belt

Planetary and Space Science ◽

10.1016/0032-0633(69)90190-1 ◽

1969 ◽

Vol 17 (4) ◽

pp. 707-714 ◽

Cited By ~ 7

Author(s):

S.-I. Akasofu ◽

C.-I. Meng

Keyword(s):

Ring Current ◽

Uniform Growth

Download Full-text

Designing Ring-Current Patterns: [10,5]-Coronene, a Circulene with Inverted Rim and Hub Currents

The Journal of Physical Chemistry A ◽

10.1021/jp0600559 ◽

2006 ◽

Vol 110 (23) ◽

pp. 7447-7452 ◽

Cited By ~ 37

Author(s):

Guglielmo Monaco ◽

Rosario G. Viglione ◽

Riccardo Zanasi ◽

Patrick W. Fowler

Keyword(s):

Ring Current

Download Full-text

Coherent Ring Currents in Chiral Aromatic Molecules Induced by Linearly Polarized UV Laser Pulses

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.543.381 ◽

2013 ◽

Vol 543 ◽

pp. 381-384 ◽

Cited By ~ 2

Author(s):

Manabu Kanno ◽

Hirohiko Koho ◽

Hirobumi Mineo ◽

Sheng Hsien Lin ◽

Yuichi Fujimura

Keyword(s):

Aromatic Ring ◽

Quantum Dynamics ◽

Ring Current ◽

Molecular System ◽

Laser Pulses ◽

Uv Laser ◽

Aromatic Molecules ◽

Ring Currents ◽

Linearly Polarized ◽

Coherent Ring

In recent years, laser control of electrons in molecular system and condensed matter has attracted considerable attention with rapid progress in laser science and technology [. In particular, control of π-electron rotation in photo-induced chiral aromatic molecules has potential utility to the next-generation ultrafast switching devices. In this paper, we present a fundamental principle of generation of ultrafast coherent ring currents and the control in photo-induced aromatic molecules. This is based on quantum dynamics simulations of π-electron rotations and preparation of unidirectional angular momentum by ultrashort UV laser pulses properly designed. For this purpose, we adopt 2,5-dichloro [(3,6) pyrazinophane (DCPH) fixed on a surface, which is a real chiral aromatic molecule with plane chirality. Here π electrons can be rotated along the aromatic ring clockwise or counterclockwise by irradiation of a linearly polarized laser pulse with the properly designed photon polarization direction and the coherent ring current with the definite direction along the aromatic ring is prepared. This is contrast to ordinary ring current in an achiral aromatic ring molecule with degenerate electronic excited state, which is prepared by a circularly polarized laser [2]. In this case, π electrons rotate along the Z-axis of the laboratory coordinates, while for the present case electrons rotate along the z-axis in molecular Cartesian coordinates. It should be noted that signals originated from the coherent ring currents prepared by linearly polarized ultrashort UV lasers are specific to the chiral molecule of interest.

Download Full-text