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

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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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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Magnetospheric reconfiguration during the substorm cycle as inferred from the data-based modeling.

10.5194/egusphere-egu21-809 ◽

2021 ◽

Author(s):

Nikolai Tsyganenko ◽

Varvara Andreeva ◽

Mikhail Sitnov ◽

Jesper Gjerloev ◽

Xiangning Chu ◽

...

Keyword(s):

Ring Current ◽

Full Range ◽

Temporal Trends ◽

Basis Functions ◽

Polar Cap ◽

Low Latitude ◽

Quarter Century ◽

Expansion Phase ◽

First Results ◽

The Magnetic Field

<p>First results are presented of reconstructing the evolution of magnetospheric configurations through the full cycle of isolated substorms. The modeling covers the low- and mid-latitude magnetosphere in the range of radial distances from 2 to 20 Re and is based on a synthesis of (1) a high-resolution representation of the magnetic field by cylindrical basis functions, (2) the ever largest pool of magnetospheric and interplanetary data spanning the last quarter century (1995-2019), (3) an archive of concurrent ground-based indices and their temporal trends, quantifying the geomagnetic activity over the full range of latitudes, including the low-latitude ring current SMR-index, the midlatitude positive bay MPB-index, the auroral SML-index, and the polar cap PC-index, (4) the data-mining nearest-neighbour (NN) technique of the data selection and weighting in the geometric and parametric spaces. The obtained successive diagrams of magnetic depression/compression, electric current, and field line maps demonstrate all the typical features of the substorm cycle: the initial relatively slow stretching of the nightside tail during the growth phase, followed by its sudden collapse associated with a dramatic disruption of the tail current at R~11-16 Re, and finally a gradual recovery of the configuration after the expansion phase is over.</p>

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A Global Survey of Geospace Electrons with eVlasiator: First Results

10.5194/egusphere-egu21-10638 ◽

2021 ◽

Author(s):

Markku Alho ◽

Markus Battarbee ◽

Yann Pfau-Kempf ◽

Urs Ganse ◽

Lucile Turc ◽

...

Keyword(s):

Solar Wind ◽

Spatial Resolution ◽

Kinetic Models ◽

Electron Distribution ◽

State Of The Art ◽

Distribution Functions ◽

Upper Atmosphere ◽

Electron Precipitation ◽

Gas Dynamic ◽

First Results

<div> <p>Models of the&#160;geospace&#160;plasma environment have been proceeding towards more realistic descriptions of the solar wind&#8212;magnetosphere interaction, from gas-dynamic to MHD and hybrid ion-kinetic models such as the state-of-the-art&#160;Vlasiator&#160;model.&#160;Advances in computational capabilities have enabled global&#160;simulations of detailed physics, but the electron scale has so far been out of reach in a truly global setting.&#160;</p> </div><div> <p>In this work we present results from eVlasiator, an offshoot of the Vlasiator model, showing first results from a global 2D+3V kinetic electron geospace simulation. Despite truncation of some electron physics and use of ion-scale spatial resolution, we show that realistic electron distribution functions are obtainable within the magnetosphere and describe these in relation to MMS observations. Electron precipitation to the upper atmosphere from these velocity distributions is estimated.</p> </div>

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

Annales Geophysicae ◽

10.5194/angeo-22-3195-2004 ◽

2004 ◽

Vol 22 (9) ◽

pp. 3195-3202 ◽

Cited By ~ 17

Author(s):

L. Z. Biktash

Keyword(s):

Solar Wind ◽

Electric Fields ◽

Ring Current ◽

Geomagnetic Storms ◽

Equatorial Ionosphere ◽

Experimental Investigations ◽

Polar Regions ◽

Ionospheric Currents ◽

Geomagnetic Variations ◽

Activity Effect

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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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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Observation of three distinct ion populations at the Kelvin-Helmholtz-unstable magnetopause

Annales Geophysicae ◽

10.5194/angeo-26-1559-2008 ◽

2008 ◽

Vol 26 (6) ◽

pp. 1559-1566 ◽

Cited By ~ 21

Author(s):

M. G. G. T. Taylor ◽

B. Lavraud

Keyword(s):

Boundary Layer ◽

Solar Wind ◽

Solar Wind Plasma ◽

Double Star ◽

Single Event ◽

Helmholtz Instability ◽

Temperature Anisotropy ◽

Low Latitude ◽

Solar Wind Origin ◽

Unambiguous Conclusion

Abstract. We report Double Star spacecraft observations of the dusk-flank magnetopause and its boundary layer under predominantly northward interplanetary magnetic field (IMF). Under such conditions the flank low-latitude boundary layers (LLBL) of the magnetosphere are known to broaden. The primary candidate processes associated with the transport of solar wind plasma into the LLBL are: (1) local diffusive plasma transport associated with the Kelvin-Helmholtz instability (KHI), (2) local plasma penetration owing to magnetic reconnection in the vicinity of the KHI-driven vortices, and (3) via a pre-existing boundary layer formed through double high-latitude reconnection on the dayside. Previous studies have shown that a cold population of solar wind origin is typically mixed with a hot population of magnetospheric origin in the LLBL. The present observations show the coexistence of three distinct ion populations in the dusk LLBL, during an interval when the magnetopause is unstable to the KHI: (1) a typical hot magnetospheric population, (2) a cold population that shows parallel temperature anisotropy, and (3) a distinct third cold population that shows perpendicular temperature anisotropy. Although no unambiguous conclusion may be drawn from this single event, we discuss the possible mechanisms at work and the origin of each population by envisaging three likely sources: hot magnetospheric plasma sheet, cold magnetosheath of solar wind origin, and cold plasma of ionospheric origin.

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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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Predicting geomagnetic storms from solar-wind data using time-delay neural networks

Annales Geophysicae ◽

10.1007/s00585-996-0679-1 ◽

1996 ◽

Vol 14 (7) ◽

pp. 679-686 ◽

Cited By ~ 56

Author(s):

H. Gleisner ◽

H. Lundstedt ◽

P. Wintoft

Keyword(s):

Neural Networks ◽

Solar Wind ◽

Time Delay ◽

Input Data ◽

Ring Current ◽

Geomagnetic Storms ◽

Time History ◽

Recovery Phase ◽

Wind Data ◽

Data Sequence

Abstract. We have used time-delay feed-forward neural networks to compute the geomagnetic-activity index Dst one hour ahead from a temporal sequence of solar-wind data. The input data include solar-wind density n, velocity V and the southward component Bz of the interplanetary magnetic field. Dst is not included in the input data. The networks implement an explicit functional relationship between the solar wind and the geomagnetic disturbance, including both direct and time-delayed non-linear relations. In this study we especially consider the influence of varying the temporal size of the input-data sequence. The networks are trained on data covering 6600 h, and tested on data covering 2100 h. It is found that the initial and main phases of geomagnetic storms are well predicted, almost independent of the length of the input-data sequence. However, to predict the recovery phase, we have to use up to 20 h of solar-wind input data. The recovery phase is mainly governed by the ring-current loss processes, and is very much dependent on the ring-current history, and thus also the solar-wind history. With due consideration of the time history when optimizing the networks, we can reproduce 84% of the Dst variance.

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A statistical analysis of the relationship between Pc4 and Pc5 ULF waves, solar winds and geomagnetic storms for predicting earthquake precursor signatures in low latitude regions

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/880/1/012010 ◽

2021 ◽

Vol 880 (1) ◽

pp. 012010

Author(s):

S N A Syed Zafar ◽

Roslan Umar ◽

N H Sabri ◽

M H Jusoh ◽

A Yoshikawa ◽

...

Keyword(s):

Solar Wind ◽

Geomagnetic Field ◽

Geomagnetic Storms ◽

Earthquake Precursor ◽

Ulf Waves ◽

Low Latitude ◽

Geomagnetic Indices ◽

Solar Winds ◽

Solar Wind Parameters ◽

The Relationship

Abstract Short-term earthquake forecasting is impossible due to the seismometer’s limited sensitivity in detecting the generation of micro-fractures prior to an earthquake. Therefore, there is a strong desire for a non-seismological approach, and one of the most established methods is geomagnetic disturbance observation. Previous research shows that disturbances in the ground geomagnetic field serves as a potential precursor for earthquake studies. It was discovered that electromagnetic waves (EM) in the Ultra-Low Frequency (ULF) range are a promising tool for studying the seismomagnetic effect of earthquake precursors. This study used a multiple regression approach to analyse the preliminary study on the relationship between Pc4 (6.7-22 mHz) and Pc5 (1.7-6.7 mHz) ULF magnetic pulsations, solar wind parameters and geomagnetic indices for predicting earthquake precursor signatures in low latitude regions. The ground geomagnetic field was collected from Davao station (7.00° N, 125.40° E), in the Philippines, which experiences nearby earthquake events (Magnitude <5.0, depth <100 km and epicentre distance from magnetometer station <100 km). The Pc5 ULF waves show the highest variance with four solar wind parameters, namely SWS, SWP, IMF-Bz, SIE and geomagnetic indices (SYM/H) prior to an earthquake event based on the regression model value of R2 = 0.1510. Furthermore, the IMF-Bz, SWS, SWP, SWE, and SYM/H were found to be significantly correlated with Pc5 ULF geomagnetic pulsation. This Pc5 ULF magnetic pulsation behaviour in solar winds and geomagnetic storms establishes the possibility of using Pc5 to predict earthquakes.

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