Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

Abstract. The equatorial ionosphere parameters, Kp, Dst, AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere - ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

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The solar wind-magnetosphere coupling and daytime disturbance electric fields in equatorial ionosphere during consecutive recurrent geomagnetic storms

Journal of Atmospheric and Solar-Terrestrial Physics ◽

10.1016/j.jastp.2019.03.004 ◽

2019 ◽

Vol 187 ◽

pp. 40-52 ◽

Cited By ~ 2

Author(s):

Thana Yeeram

Keyword(s):

Solar Wind ◽

Electric Fields ◽

Geomagnetic Storms ◽

Equatorial Ionosphere

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Midday reversal of equatorial ionospheric electric field

Annales Geophysicae ◽

10.1007/s00585-997-1309-2 ◽

1997 ◽

Vol 15 (10) ◽

pp. 1309-1315 ◽

Cited By ~ 16

Author(s):

R. G. Rastogi

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Electric Field ◽

Electric Fields ◽

Ring Current ◽

Geomagnetic Storms ◽

Low Latitude ◽

E Region ◽

Sporadic E ◽

Ionospheric Electric Field

Abstract. A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

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Total electron content responses to HILDCAAs and geomagnetic storms over South America

Annales Geophysicae ◽

10.5194/angeo-35-1309-2017 ◽

2017 ◽

Vol 35 (6) ◽

pp. 1309-1326 ◽

Cited By ~ 5

Author(s):

Patricia Mara de Siqueira Negreti ◽

Eurico Rodrigues de Paula ◽

Claudia Maria Nicoli Candido

Keyword(s):

Solar Wind ◽

South America ◽

Total Electron Content ◽

Geomagnetic Storm ◽

Electric Fields ◽

Geomagnetic Storms ◽

Time Variability ◽

Electron Content ◽

Quiet Time ◽

Total Electron

Abstract. Total electron content (TEC) is extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. This subject is of greatest importance for space weather applications. Under disturbed conditions the two main sources of electric fields, which are responsible for changes in the plasma drifts and for current perturbations, are the short-lived prompt penetration electric fields (PPEFs) and the longer-lasting ionospheric disturbance dynamo (DD) electric fields. Both mechanisms modulate the TEC around the globe and the equatorial ionization anomaly (EIA) at low latitudes. In this work we computed vertical absolute TEC over the low latitude of South America. The analysis was performed considering HILDCAA (high-intensity, long-duration, continuous auroral electrojet (AE) activity) events and geomagnetic storms. The characteristics of storm-time TEC and HILDCAA-associated TEC will be presented and discussed. For both case studies presented in this work (March and August 2013) the HILDCAA event follows a geomagnetic storm, and then a global scenario of geomagnetic disturbances will be discussed. Solar wind parameters, geomagnetic indices, O ∕ N2 ratios retrieved by GUVI instrument onboard the TIMED satellite and TEC observations will be analyzed and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS networks were used to calculate TEC over South America. We show that a HILDCAA event may generate larger TEC differences compared to the TEC observed during the main phase of the precedent geomagnetic storm; thus, a HILDCAA event may be more effective for ionospheric response in comparison to moderate geomagnetic storms, considering the seasonal conditions. During the August HILDCAA event, TEC enhancements from ∼  25 to 80 % (compared to quiet time) were observed. These enhancements are much higher than the quiet-time variability observed in the ionosphere. We show that ionosphere is quite sensitive to solar wind forcing and considering the events studied here, this was the most important source of ionospheric responses. Furthermore, the most important source of TEC changes were the long-lasting PPEFs observed on August 2013, during the HILDCAA event. The importance of this study relies on the peculiarity of the region analyzed characterized by high declination angle and ionospheric gradients which are responsible for creating a complex response during disturbed periods.

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Recurrent high-speed solar wind co-rotating interaction region imprint on the ionosphere and atmosphere: GPS TEC variations and atmospheric gravity waves

10.5194/egusphere-egu2020-6464 ◽

2020 ◽

Author(s):

James M. Weygand ◽

Paul Prikryl ◽

Reza Ghoddousi-Fard ◽

Lidia Nikitina ◽

Bharat S. R. Kunduri

Keyword(s):

Solar Wind ◽

Gravity Waves ◽

High Latitude ◽

High Speed ◽

Geomagnetic Storms ◽

Coronal Holes ◽

Lower Thermosphere ◽

Ionospheric Currents ◽

Atmospheric Gravity Waves ◽

Atmospheric Gravity

High-speed streams (HSS) from coronal holes dominate solar wind structure in the absence of coronal mass ejections during solar minimum and the descending branch of solar cycle. Prominent and long-lasting coronal holes produce intense co-rotating interaction regions (CIR) on the leading edge of high-speed plasma streams that cause recurrent ionospheric disturbances and geomagnetic storms. Through solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system they affect the ionosphere and neutral atmosphere at high latitudes, and, at mid to low latitudes, by the transmission of the electric fields [1] and propagation of atmospheric gravity waves from the high-latitude lower thermosphere [2].The high-latitude ionospheric structure, caused by precipitation of energetic particles, strong ionospheric currents and convection, results in changes of the GPS total electron content (TEC) and rapid variations of GPS signal amplitude and phase, called scintillation [3]. The GPS phase scintillation is observed in the ionospheric cusp, polar cap and auroral zone, and is particularly intense during geomagnetic storms, substorms and auroral breakups. Phase scintillation index is computed for a sampling rate of 50 Hz by specialized GPS scintillation receivers from the Canadian High Arctic Ionospheric Network (CHAIN). A proxy index of phase variation is obtained from dual frequency measurements of geodetic-quality GPS receivers sampling at 1 Hz, which include globally distributed receivers of the RT-IGS network that are monitored by the Canadian Geodetic Survey in near-real-time [4]. Temporal and spatial changes of TEC and phase variations following the arrivals of HSS/CIRs [5] are investigated in the context of ionospheric convection and equivalent ionospheric currents derived from&#160; a ground magnetometer network using the spherical elementary current system method [6,7].The Joule heating and Lorentz forcing in the high-latitude lower thermosphere have long been recognized as sources of internal atmospheric gravity waves (AGWs) [2] that propagate both upward and downward, thus providing vertical coupling between atmospheric layers. In the ionosphere, they are observed as traveling ionospheric disturbances (TIDs) using various techniques, e.g., de-trended GPS TEC maps [8].In this paper we examine the influence on the Earth&#8217;s ionosphere and atmosphere of a long-lasting HSS/CIRs from recurrent coronal holes at the end of solar cycles 23 and 24. The solar wind MIA coupling, as represented by the coupling function [9], was strongly increased during the arrivals of these HSS/CIRs.&#160;[1] Kikuchi, T. and K. K. Hashimoto, Geosci. Lett. , 3:4, 2016.[2] Hocke, K. and K. Schlegel, Ann. Geophys., 14, 917&#8211;940, 1996.[3] Prikryl, P., et al., J. Geophys. Res. Space Physics, 121, 10448&#8211;10465, 2016.[4] Ghoddousi-Fard et al., Advances in Space Research, 52(8), 1397-1405, 2013.[5] Prikryl et al. Earth, Planets and Space, 66:62, 2014.[6] Amm O., and A. Viljanen, Earth Planets Space, 51, 431&#8211;440, 1999.[7] Weygand J.M., et al., J. Geophys. Res., 116, A03305, 2011.[8] Tsugawa T., et al., Geophys. Res. Lett., 34, L22101, 2007.[9] Newell P. T., et al., J. Geophys. Res., 112, A01206, 2007.

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Ring current influence on auroral electrojet predictions

Annales Geophysicae ◽

10.1007/s00585-999-1268-x ◽

1999 ◽

Vol 17 (10) ◽

pp. 1268-1275 ◽

Cited By ~ 5

Author(s):

H. Gleisner ◽

H. Lundstedt

Keyword(s):

Solar Wind ◽

Ring Current ◽

Geomagnetic Storms ◽

Wind Data ◽

Common Source ◽

Neural Net ◽

Operational Forecasting ◽

Storms And Substorms ◽

Highly Correlated ◽

Strong Control

Abstract. Geomagnetic storms and substorms develop under strong control of the solar wind. This is demonstrated by the fact that the geomagnetic activity indices Dst and AE can be predicted from the solar wind alone. A consequence of the strong control by a common source is that substorm and storm indices tend to be highly correlated. However, a part of this correlation is likely to be an effect of internal magnetospheric processes, such as a ring-current modulation of the solar wind-AE relation. The present work extends previous studies of nonlinear AE predictions from the solar wind. It is examined whether the AE predictions are modulated by the Dst index.This is accomplished by comparing neural network predictions from Dst and the solar wind, with predictions from the solar wind alone. Two conclusions are reached: (1) with an optimal set of solar-wind data available, the AE predictions are not markedly improved by the Dst input, but (2) the AE predictions are improved by Dst if less than, or other than, the optimum solar-wind data are available to the net. It appears that the solar wind-AE relation described by an optimized neural net is not significantly modified by the magnetosphere's Dst state. When the solar wind alone is used to predict AE, the correlation between predicted and observed AE is 0.86, while the prediction residual is nearly uncorrelated to Dst. Further, the finding that Dst can partly compensate for missing information on the solar wind, is of potential importance in operational forecasting where gaps in the stream of real time solar-wind data are a common occurrence.Key words. Magnetospheric physics (solar wind · magnetosphere interactions; storms and substorms)

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The HIA instrument on board the Tan Ce 1 Double Star near-equatorial spacecraft and its first results

Annales Geophysicae ◽

10.5194/angeo-23-2757-2005 ◽

2005 ◽

Vol 23 (8) ◽

pp. 2757-2774 ◽

Cited By ~ 60

Author(s):

H. Rème ◽

I. Dandouras ◽

C. Aoustin ◽

J. M. Bosqued ◽

J. A. Sauvaud ◽

...

Keyword(s):

Solar Wind ◽

Ring Current ◽

Geomagnetic Storms ◽

Distribution Functions ◽

Double Star ◽

Magnetospheric Substorms ◽

Scientific Cooperation ◽

Low Latitude ◽

First Results ◽

Academy Of Sciences

Abstract. On 29 December 2003, the Chinese spacecraft Tan Ce 1 (TC-1), the first component of the Double Star mission, was successfully launched within a low-latitude eccentric orbit. In the framework of the scientific cooperation between the Academy of Sciences of China and ESA, several European instruments, identical to those developed for the Cluster spacecraft, were installed on board this spacecraft. The HIA (Hot Ion Analyzer) instrument on board the TC-1 spacecraft is an ion spectrometer nearly identical to the HIA sensor of the CIS instrument on board the 4 Cluster spacecraft. This instrument has been specially adapted for TC-1. It measures the 3-D distribution functions of the ions between 5 eV/q and 32 keV/q without mass discrimination. TC-1 is like a fifth Cluster spacecraft to study the interaction of the solar wind with the magnetosphere and to study geomagnetic storms and magnetospheric substorms in the near equatorial plane. HIA was commissioned in February 2004. Due to the 2 RE higher apogee than expected, some in-flight improvements were needed in order to use HIA in the solar wind in the initial phase of the mission. Since this period HIA has obtained very good measurements in the solar wind, the magnetosheath, the dayside and nightside plasma sheet, the ring current and the radiation belts. We present here the first results in the different regions of the magnetosphere and in the solar wind. Some of them are very new and include, for example, ion dispersion structures in the bow shock and ion beams close to the magnetopause. The huge interest in the orbit of TC-1 is strongly demonstrated.

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Induced telluric currents play a major role in the interpretation of geomagnetic variations

10.5194/angeo-2020-21 ◽

2020 ◽

Cited By ~ 1

Author(s):

Liisa Juusola ◽

Heikki Vanhamäki ◽

Ari Viljanen ◽

Maxim Smirnov

Keyword(s):

Magnetic Field ◽

Electric Fields ◽

Time Derivative ◽

Three Dimensional ◽

Image Data ◽

Geomagnetically Induced Currents ◽

Ionospheric Currents ◽

Geomagnetic Variations ◽

Near Surface ◽

Telluric Currents

Abstract. Geomagnetically induced currents (GIC) are directly described by ground electric fields, but estimating them is time-consuming and requires knowledge of the ionospheric currents as well as the three-dimensional distribution of the electrical conductivity of the Earth. The time derivative of the horizontal component of the ground magnetic field (dH/dt) is closely related to the electric field via Faraday's law, and provides a convenient proxy for the GIC risk. However, forecasting dH/dt still remains a challenge. We use 25 years of 10 s data from the North European International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network to show that part of this problem stems from the fact that instead of the primary ionospheric currents, the measured dH/dt is dominated by the signature from the secondary induced telluric currents nearly at all IMAGE stations. The largest effects due to telluric currents occur at coastal sites close to highly-conducting ocean water and close to near-surface conductivity anomalies. The secondary magnetic field contribution to the total field is a few tens of percent, in accordance with earlier studies. Our results have been derived using IMAGE data and are thus only valid for the involved stations. However, it is likely that the main principle also applies to other areas. Consequently, it is recommended that the field separation into internal (telluric) and external (ionospheric and magnetospheric) parts is performed whenever feasible, i.e., a dense observation network is available.

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Induced currents due to 3D ground conductivity play a major role in the interpretation of geomagnetic variations

Annales Geophysicae ◽

10.5194/angeo-38-983-2020 ◽

2020 ◽

Vol 38 (5) ◽

pp. 983-998

Author(s):

Liisa Juusola ◽

Heikki Vanhamäki ◽

Ari Viljanen ◽

Maxim Smirnov

Keyword(s):

Magnetic Field ◽

Electric Fields ◽

Time Derivative ◽

Three Dimensional ◽

Geomagnetically Induced Currents ◽

Ionospheric Currents ◽

Geomagnetic Variations ◽

Near Surface ◽

Induced Currents ◽

Telluric Currents

Abstract. Geomagnetically induced currents (GICs) are directly described by ground electric fields, but estimating them is time-consuming and requires knowledge of the ionospheric currents and the three-dimensional (3D) distribution of the electrical conductivity of the Earth. The time derivative of the horizontal component of the ground magnetic field (dH∕dt) is closely related to the electric field via Faraday's law and provides a convenient proxy for the GIC risk. However, forecasting dH∕dt still remains a challenge. We use 25 years of 10 s data from the northern European International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network to show that part of this problem stems from the fact that, instead of the primary ionospheric currents, the measured dH∕dt is dominated by the signature from the secondary induced telluric currents at nearly all IMAGE stations. The largest effects due to telluric currents occur at coastal sites close to high-conducting ocean water and close to near-surface conductivity anomalies. The secondary magnetic field contribution to the total field is a few tens of percent, in accordance with earlier studies. Our results have been derived using IMAGE data and are thus only valid for the stations involved. However, it is likely that the main principle also applies to other areas. Consequently, it is recommended that the field separation into internal (telluric) and external (ionospheric and magnetospheric) parts is performed whenever feasible (i.e., a dense observation network is available).

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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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Ionospheric dynamic and coupling processes during geomagnetic storms

10.5194/egusphere-egu2020-10498 ◽

2020 ◽

Author(s):

Chaosong Huang

Keyword(s):

Electric Fields ◽

Geomagnetic Storms ◽

Equatorial Ionosphere ◽

Ion Composition ◽

Hemispheric Differences ◽

Ion Density ◽

Ion Drift ◽

Low Latitudes ◽

Coupling Processes ◽

Ionospheric Dynamics

Geomagnetic storms cause the largest disturbances in the ionosphere-thermosphere system. We use measurements with satellites and ground based radars to study storm-induced variations in ionospheric plasma drift, ion density, and ion composition at low latitudes. It is found that the storm-time change of ion drift velocity in the equatorial ionosphere can reach 200-300 m/s, the change of ion density can be one or two orders of magnitude, and the change of ion composition can be 50-80%. These extremely large changes in the ionosphere can last for several hours or even a few days during the main and recovery phases of magnetic storms. The longitudinal, latitudinal and hemispheric differences of storm-time ionospheric disturbances are analyzed from measurements of multiple satellites or radar chain. Very long, continuous penetration of interplanetary electric fields to the equatorial ionosphere for 6 or even 14 hours are observed, and the time when disturbance dynamo electric fields become dominant is identified. The interplay of penetration, shielding, and disturbance dynamo electric fields in the storm-time ionosphere will be addressed. Mechanisms responsible for storm-time ionospheric dynamics will be discussed.

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