The effect of nonlinear ionospheric conductivity enhancement on magnetospheric substorms

Abstract. We introduce the effect of enhanced ionospheric conductivity into a low-order, physics-based nonlinear model of the nightside magnetosphere called WINDMI. The model uses solar wind and interplanetary magnetic field (IMF) parameters from the ACE satellite located at the L1 point to predict substorm growth, onset, expansion and recovery measured by the AL index roughly 50–60 min in advance. The dynamics introduced by the conductivity enhancement into the model behavior is described, and illustrated through using synthetically constructed solar wind parameters as input. We use the new model to analyze two well-documented isolated substorms: one that occurred on 31 July 1997 from Aksnes et al. (2002), and another on 13 April 2000 from Huang et al. (2004). These two substorms have a common feature in that the solar wind driver sharply decreases in the early part of the recovery phase, and that neither of them are triggered by northward turning of the IMF Bz. By controlling the model parameters such that the onset time of the substorm is closely adhered to, the westward auroral electrojet peaks during substorm expansion are qualitatively reproduced. Furthermore, the electrojet recovers more slowly with enhanced conductivity playing a role, which explains the data more accurately.

Download Full-text

Causality and Information Transfer Between the Solar Wind and the Magnetosphere–Ionosphere System

Entropy ◽

10.3390/e23040390 ◽

2021 ◽

Vol 23 (4) ◽

pp. 390

Author(s):

Pouya Manshour ◽

Georgios Balasis ◽

Giuseppe Consolini ◽

Constantinos Papadimitriou ◽

Milan Paluš

Keyword(s):

Solar Wind ◽

Information Transfer ◽

Linear Time ◽

Vertical Component ◽

Causal Link ◽

Theoretic Approach ◽

Geomagnetic Disturbances ◽

Magnetospheric Substorms ◽

Solar Wind Parameters ◽

Information Theoretic Approach

An information-theoretic approach for detecting causality and information transfer is used to identify interactions of solar activity and interplanetary medium conditions with the Earth’s magnetosphere–ionosphere systems. A causal information transfer from the solar wind parameters to geomagnetic indices is detected. The vertical component of the interplanetary magnetic field (Bz) influences the auroral electrojet (AE) index with an information transfer delay of 10 min and the geomagnetic disturbances at mid-latitudes measured by the symmetric field in the H component (SYM-H) index with a delay of about 30 min. Using a properly conditioned causality measure, no causal link between AE and SYM-H, or between magnetospheric substorms and magnetic storms can be detected. The observed causal relations can be described as linear time-delayed information transfer.

Download Full-text

Seasonal and diurnal variations of geomagnetic activity and their role in Space Weather forecast

Canadian Journal of Physics ◽

10.1139/p01-049 ◽

2001 ◽

Vol 79 (6) ◽

pp. 907-920 ◽

Cited By ~ 6

Author(s):

W Lyatsky ◽

A M Hamza

Keyword(s):

Solar Wind ◽

Seasonal Variation ◽

Diurnal Variation ◽

Geomagnetic Activity ◽

Space Weather ◽

Weather Forecast ◽

Diurnal Variations ◽

Ionospheric Conductivity ◽

Solar Wind Parameters ◽

Possible Cause

A possible test for different models explaining the seasonal variation in geomagnetic activity is the diurnal variation. We computed diurnal variations both in the occurrence of large AE (auroral electrojet) indices and in the AO index. (AO is the auroral electrojet index that provides a measure of the equivalent zonal current.) Both methods show a similar diurnal variation in geomagnetic activity with a deep minimum around (37) UT (universal time) in winter and a shallower minimum near 59 UT in equinoctial months. The observed UT variation is consistent with the results of other scientists, but it is different from that expected from the RussellMcPherron mechanism proposed to explain the seasonal variation. It is suggested that the possible cause for the diurnal and seasonal variations may be variations in nightside ionospheric conductivity. Recent experimental results show an important role for ionospheric conductivity in particle acceleration and geomagnetic disturbance generation. They also show that low ionospheric conductivity is favorable to the generation of auroral and geomagnetic activity. The conductivity in conjugate nightside auroral zones (where substorm generation takes place) is minimum at equinoxes, when both auroral zones are in darkness. The low ionospheric conductivity at equinoxes may be a possible cause for the seasonal variation in the geomagnetic activity with maxima in equinoctial months. The diurnal variation in geomagnetic activity can be produced by the UT variation in the nightside ionospheric conductivity, which in winter and at equinoxes has a maximum around 45 UT that may lead to a minimum in geomagnetic activity at this time. We calculated the correlation patterns for the AE index versus solar-wind parameters inside and outside the (27) UT sector related to the minimum in geomagnetic activity. The correlation patterns appear different in these two sectors indeed, which is well consistent with the UT variation in geomagnetic activity. It also shows that it is possible to improve significantly the reliability of the Space Weather forecast by taking into account the dependence of geomagnetic activity not only on solar-wind parameters but also on UT and season. Our test shows that a simple account for the dependence of geomagnetic activity on UT can improve the reliability of the Space Weather forecast by at least 50% in the 27 UT sector in winter and equinoctial months. PACS No.: 91.25Le

Download Full-text

Effects of solar wind parameters on the development of magnetospheric substorms

Planetary and Space Science ◽

10.1016/0032-0633(75)90069-0 ◽

1975 ◽

Vol 23 (1) ◽

pp. 75-91 ◽

Cited By ~ 71

Author(s):

Takashi Murayama ◽

Kazuyuki Hakamada

Keyword(s):

Solar Wind ◽

Magnetospheric Substorms ◽

Solar Wind Parameters

Download Full-text

A model of region 1 field-aligned currents dependent on ionospheric conductivity and solar wind parameters

Journal of Geophysical Research Atmospheres ◽

10.1029/2000ja900052 ◽

2000 ◽

Vol 105 (A9) ◽

pp. 21119-21127 ◽

Cited By ~ 19

Author(s):

Igor I. Alexeev ◽

Elena S. Belenkaya ◽

C. Robert Clauer

Keyword(s):

Solar Wind ◽

Ionospheric Conductivity ◽

Solar Wind Parameters

Download Full-text

Electron precipitation events in the lower ionosphere and the geospace conditions

Annals of Geophysics ◽

10.4401/ag-6242 ◽

2013 ◽

Vol 56 (2) ◽

Author(s):

José Henrique Fernandez ◽

Emília Correia

Keyword(s):

Solar Wind ◽

Geomagnetic Storms ◽

Close Association ◽

Low Frequency ◽

Lower Ionosphere ◽

Recovery Phase ◽

Activity Level ◽

23Rd Solar Cycle ◽

Solar Wind Parameters ◽

Precipitation Events

<p>We present an analysis of localized ionospheric perturbations detected at Comandante Ferraz Brazilian Antarctic Station (McIlwain parameter L~2.25) as fast-amplitude variations of very low frequency (VLF) signals transmitted from Hawaii (NPM, at 21.4 kHz), also known as Trimpi events. The study covers the first six months of 2007, during the period of minimum activity in the 23rd solar cycle. The occurrence of Trimpi events in the Antarctica peninsula region was studied in association with solar-wind parameters in the neighborhood of the Earth (geospace), along with the geomagnetic activity level (Ap, Dst indices). The analysis shows that the Trimpi events occurred predominantly during geomagnetically disturbed periods, but they have a more intricate association with the geospace regimes. The events achieve higher occurrence during the recovery phase of some geomagnetic storms, and also show a close association with electron flux enhancements in the belt region, especially those with higher energy. The higher event incidence occurred a few hours after what we call the 'angle bracket' phenomenon: when the solar wind velocity rises simultaneous with a decrease in its density.</p>

Download Full-text

Unusual strong quasi-monochromatic ground Pc5 geomagnetic pulsations in the recovery phase of November 2003 superstorm

Annales Geophysicae ◽

10.5194/angeo-23-2621-2005 ◽

2005 ◽

Vol 23 (7) ◽

pp. 2621-2634 ◽

Cited By ~ 14

Author(s):

N. G. Kleimenova ◽

O. V. Kozyreva ◽

J. Manninen ◽

A. Ranta

Keyword(s):

Solar Wind ◽

Large Amplitude ◽

Energetic Electron ◽

Recovery Phase ◽

Mhd Waves ◽

Geomagnetic Pulsations ◽

Solar Wind Density ◽

Wide Range ◽

Magnetic Pulsations ◽

Solar Wind Parameters

Abstract. Unusually large-amplitude morning Pc5 magnetic pulsations during the recovery phase of the huge magnetic storm in November 2003 have been studied by using ground-based multi-point observations. Two main spectral Pc5 enhancements were observed: at f≈2 mHz, which featured slowly increasing frequency with decreasing latitude, and at f≈3 mHz, which was latitude independent. The Pc5 pulsations were observed at wide range of latitudes (more than 10°) with the same very strong amplitude (up to 500nT) and with the same polarization. Only the 3-mHz peak was clearly seen in the spectra of pulsating auroral radio absorption, as observed by the Finnish riometer chain. Short and localized bursts of PiB (f~50–100 mHz) magnetic pulsations and simultaneous short bursts of energetic electron precipitation were observed in the morning sector, as well. The beginning of the large-amplitude morning Pc5 activity occurred simultaneously with a substorm onset in the evening and midnight sectors. However, the spectra of pulsations in the morning and evening sectors were different. They were compared with spectra of IMF and solar wind parameters, measured by ACE spacecraft. The similarity between the spectra of morning Pc5 and IMF By was found, but the spectra of evening Pi3 pulsations were similar to the spectra of solar wind density variations. The Pc5 and PiB pulsations, as well as bursts of the auroral radio absorption, suddenly disappeared, when the solar wind density abruptly dropped. We suppose that the ~2-mHz Pc5 geomagnetic pulsations could be attributed to field line resonance (FLR), however, the 3-mHz oscillations were apparently non-resonance origin. Keywords. Magnetospheric physics (MHD waves and instabilities; Solar wind-magnetosphere interaction; Storms and substorms)

Download Full-text

Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm

Annales Geophysicae ◽

10.1007/s00585-994-0602-6 ◽

1994 ◽

Vol 12 (7) ◽

pp. 602-611 ◽

Cited By ~ 19

Author(s):

Y. I. Feldstein ◽

A. E. Levitin ◽

S. A. Golyshev ◽

L. A. Dremukhina ◽

U. B. Vestchezerova ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Ring Current ◽

Recovery Phase ◽

Main Phase ◽

Storm Main Phase ◽

Low Latitudes ◽

Solar Wind Parameters ◽

Magnetic Field Variations ◽

Current Magnetic Field

Abstract. The relationship between the auroral electrojet indices (AE) and the ring current magnetic field (DR) was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'). To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE') which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence) of saturation for minimum (maximum) AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY) was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF Bz variations than the symmetric ring current. ASY increases (decreases) faster during the main phase (the recovery phase) than DR. The magnetic field decay at low latitudes in the recovery phase occurs faster in the afternoon sector than at dusk.

Download Full-text