The Plasmasphere During Major Geomagnetic Storms: Analysis Of Trapped Particles In The Outer Radiation Belt

2020 ◽  
Author(s):  
Jessy Matar ◽  
Benoit Hubert ◽  
Stan Cowley ◽  
Steve Milan ◽  
Zhonghua Yao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Geomagnetic Field ◽  
Radiation Belt ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Outer Radiation Belt ◽  
Trapped Particles ◽  
The Earth ◽  
Field Lines

<p> The coupling between the Earth’s magnetic field and the interplanetary magnetic field (IMF) transported by the solar wind results in a cycle of magnetic field lines opening and closing generally known as the Dungey substorm cycle, mostly governed by the process of magnetic reconnection. The geomagnetic field lines can therefore have either a closed or an open topology, i.e. lower latitude field lines are closed (map from southern ionosphere to the northern), while higher latitude field lines are open (map from one polar ionosphere into interplanetary space). Closed field lines can trap electrically charged particles that bounce between mirror points located in the North and South hemispheres while drifting in longitude around the Earth, forming the plasmasphere, the radiation belts and the ring current. The outer boundary of the plasmasphere is the plasmapause. Its location is mostly driven by the interplay of the corotation electric field of ionospheric origin, and the convection electric field that results from the interaction between the IMF and the geomagnetic field. At times of prolonged intense coupling between these fields, the response of the magnetosphere becomes global and a geomagnetic storm develops. The ring current created by the motion of the trapped energetic particles intensifies and then decays as the storm abates. This study aims to find a possible relationship between the evolution of the trapped population and the process of magnetic reconnection during storm times. The EUV instrument on board the NASA-IMAGE spacecraft observed the distribution of the trapped helium ions (He+) in the plasmasphere. We consider several cases of intense geomagnetic storms observed by the IMAGE satellite. We identify the plasmapause location (Lpp) during those cases. We find a strong correlation between the Dst index and Lpp. The ring current and the trapped particles are expected to vary during storms. We use the Tsyganenko magnetic field model to map the electric potential between the Heppner-Maynard boundary (HMB) in the ionosphere and the magnetosphere and estimate the voltage and electric field in the vicinity of the plasmapause. The ionospheric electric field is deduced from the ionospheric convection velocity measured by the SuperDARN (SD) radar network at high latitudes. The tangential electric field component of the moving plasmapause boundary is estimated from IMAGE-EUV observations of the plasmasphere and is compared with expectations based on the SD data. We combine measurements of the trapped population from IMAGE-EUV and IMAGE-FUV observations of the aurora to better understand and quantify the variability of the Earth's outer radiation belt during strong storms. The auroral precipitation at ionospheric latitude is studied using FUV imaging and compared to the He+ response during the storms.</p>

A neutral line discharge theory of the aurora polaris

1961 ◽  
Vol 253 (1031) ◽  
pp. 359-406 ◽  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Equatorial Plane ◽  
Geomagnetic Field ◽  
Ring Current ◽  
Neutral Line ◽  
Dark Side ◽  
The Earth ◽  
The Magnetic Field ◽  
Lines Of Force

A theory of the aurora polaris is proposed which attempts to explain many features of the complicated morphology of auroral displays. One basis of the theory is the presence, during magnetic disturbance, of additional or enhanced magnetic fields due to electric currents within a distance of several earth radii from the earth’s centre. One such field (denoted by DCF) is due to electric currents flowing near the inner surface of the solar stream that then envelopes the earth. A hollow is carved in the stream by the geomagnetic field. The other field (denoted by DR) is that of an electric ring current, additional or enhanced, that flows westward round the earth. This is carried by the particles of the Van Allen belts. A third field (denoted by DP) is that of the disturbance currents that flow in the ionosphere, under the impulsion of electromotive forces generated mainly in polar regions. We consider it likely that during magnetic storms and auroral displays, neutral lines appear in the magnetic field near the earth. These will lie mainly on the dark side of the earth, in or near the equatorial plane, on the nearer side of the ring current. At times these lines may extend over more than 180° of longitude, so that a part of them may lie on the sunward side of the earth. These neutral lines are of two types, which we call O and X they appear together, in pairs. During disturbed conditions there may be more than one pair. Lines of force cross at points on X neutral lines, but they do not pass through O neutral lines. As Dungey has shown, charged particles will tend to be concentrated near X points (of which the X neutral lines are the locus). Charges drawn toward the neutral line will be discharged into the earth’s atmosphere along the lines of magnetic force. We suggest that the location, nature and motions of the auroral forms are determined by the position, form and motion of the X neutral lines, lying in or near the plane of the geomagnetic equator. It seems necessary to suppose, in addition, that an electric field arises sporadically along the X lines. When this is absent, the aurora appears as a quiet arc. The onset of the suggested electric field concentrates the charges more narrowly near the X line and near the lines of force that extend from it to the auroral zone. This produces extremely thin-rayed auroral arcs. The above concentration of electrons near an X neutral line produces a large flux of electrons, while the proton flux is diminished. A dynamical instability due to this flux difference (the space charge density is supposed to be very small) produces a slight separation of protons and electrons along and near the lines of force through the X line. Hence in the auroral ionosphere there is an associated electric field. This is usually directed towards the equator. It drives electric current, usually westward, along the auroral zones, and produces the strong magnetic disturbances (DP) there observed. Birkeland called these polar elementary storms. The rapid auroral changes are ascribed to instabilities of the magnetic field in the region near the X line or lines, to the rear of the earth, where the resultant magnetic field is weak. The ray structure in the auroral arc is ascribed to an instability of the thin sheet of electron flow. Cosmic rockets have shown that the magnetic field, up to and beyond ten earth radii, departs from the values corresponding to the internally produced main geomagnetic field. As yet these explorations do not seem to have disclosed the existence of reversals of the field in or near the magnetic equatorial plane. But on the basis of our auroral hypothesis, we predict with considerable confidence that such reversals will be found to occur, on the dark side of the earth, during great auroral displays. The theory here proposed is discussed in connexion with recent I. G. Y. and I. G. C. auroral, magnetic and other data.

scholarly journals On a Correlation between the Ionospheric Electric Field and the Time Derivative of the Magnetic Field

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
R. R. Ilma ◽  
M. C. Kelley ◽  
C. A. Gonzales
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Ring Current ◽  
Time Derivative ◽  
Incoherent Scatter ◽  
The Earth ◽  
Current Location ◽  
Field Lines ◽  
Ionospheric Electric Field ◽  
The Magnetic Field

A correlation of the ionospheric electric field and the time derivative of the magnetic field was noticed over thirty years ago and has yet to be explained. Here we report on another set of examples during the superstorm of November 2004. The electric field in the equatorial ionosphere, measured with the Jicamarca incoherent scatter radar, exhibited a 3 mV/m electric field pulse that was not seen in the interplanetary medium. It was, however, accompanied by a correlation with the time derivative of the magnetic field measured at two points in Peru. Our inclination was to assume that the field was inductive. However, the time scale of the pulse was too short for the magnetic field to penetrate the crust of the Earth. This means that the area threaded by∂B/∂twas too small to create the observed electric field by induction. We suggest that the effect was caused by a modulation of the ring current location relative to the Earth due to the electric field. This electric field is required, as the magnetic field lines are considered frozen into the plasma in the magnetosphere. The closer location of the ring current to the Earth in turn increased the magnetic field at the surface.

scholarly journals Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

2016 ◽  
Vol 34 (1) ◽  
pp. 55-65 ◽  
Author(s):  
A. D. M. Walker ◽  
G. J. Sofko
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Magnetic Field Line ◽  
Geomagnetic Field ◽  
Geomagnetic Field Models ◽  
Spatial Derivatives ◽  
Field Lines ◽  
The Magnetic Field

Abstract. When studying magnetospheric convection, it is often necessary to map the steady-state electric field, measured at some point on a magnetic field line, to a magnetically conjugate point in the other hemisphere, or the equatorial plane, or at the position of a satellite. Such mapping is relatively easy in a dipole field although the appropriate formulae are not easily accessible. They are derived and reviewed here with some examples. It is not possible to derive such formulae in more realistic geomagnetic field models. A new method is described in this paper for accurate mapping of electric fields along field lines, which can be used for any field model in which the magnetic field and its spatial derivatives can be computed. From the spatial derivatives of the magnetic field three first order differential equations are derived for the components of the normalized element of separation of two closely spaced field lines. These can be integrated along with the magnetic field tracing equations and Faraday's law used to obtain the electric field as a function of distance measured along the magnetic field line. The method is tested in a simple model consisting of a dipole field plus a magnetotail model. The method is shown to be accurate, convenient, and suitable for use with more realistic geomagnetic field models.

scholarly journals Storm-time ring current: model-dependent results

2012 ◽  
Vol 30 (1) ◽  
pp. 177-202 ◽  
Author(s):  
N. Yu. Ganushkina ◽  
M. W. Liemohn ◽  
T. I. Pulkkinen
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Boundary Conditions ◽  
Electric Fields ◽  
Ring Current ◽  
Current Model ◽  
Current Data ◽  
Storm Events ◽  
Boundary Location ◽  
Field Lines

Abstract. The main point of the paper is to investigate how much the modeled ring current depends on the representations of magnetic and electric fields and boundary conditions used in simulations. Two storm events, one moderate (SymH minimum of −120 nT) on 6–7 November 1997 and one intense (SymH minimum of −230 nT) on 21–22 October 1999, are modeled. A rather simple ring current model is employed, namely, the Inner Magnetosphere Particle Transport and Acceleration model (IMPTAM), in order to make the results most evident. Four different magnetic field and two electric field representations and four boundary conditions are used. We find that different combinations of the magnetic and electric field configurations and boundary conditions result in very different modeled ring current, and, therefore, the physical conclusions based on simulation results can differ significantly. A time-dependent boundary outside of 6.6 RE gives a possibility to take into account the particles in the transition region (between dipole and stretched field lines) forming partial ring current and near-Earth tail current in that region. Calculating the model SymH* by Biot-Savart's law instead of the widely used Dessler-Parker-Sckopke (DPS) relation gives larger and more realistic values, since the currents are calculated in the regions with nondipolar magnetic field. Therefore, the boundary location and the method of SymH* calculation are of key importance for ring current data-model comparisons to be correctly interpreted.

scholarly journals Satellite observations of currents and waves in space plasmas

1988 ◽  
Vol 6 (3) ◽  
pp. 503-511 ◽  
Author(s):  
T. A. Potemra ◽  
M. J. Engebretson ◽  
L. J. Zanetti ◽  
R. E. Erlandson ◽  
P. F. Bythrow
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Geomagnetic Field ◽  
Large Scale ◽  
Field Experiments ◽  
Outer Space ◽  
Solar Wind Plasma ◽  
Field Configuration ◽  
The Earth ◽  
Field Lines

When viewed from outer space, the earth's magnetic field does not resemble a simple dipole, but is severely distorted into a comet-shaped configuration by the continuous flow of solar wind plasma. A complicated system of currents flows within this distorted magnetic field configuration called the ‘magnetosphere’ (See figure 1). For example, the compression of the geomagnetic field by the solar wind on the dayside of the earth is associated with a large-scale current flowing across the geomagnetic field lines, called the ‘Chapman-Ferraro’ or magnetopause current. The magnetospheric system includes large-scale currents that flow in the ‘tail’, the ring current that flows at high altitudes around the equator of the earth, field-aligned ‘Birkeland’ currents that flow along geomagnetic field lines into and away from the two auroral regions, and a complex system of currents that flows completely within the layers of the ionosphere, the earth's ionized atmosphere. The intensities of these various currents reach millions of amperes and are closely related to solar activity. The geomagnetic field lines can also oscillate, like giant vibrating strings, at specified resonant frequencies. The effects of these vibrations, sometimes described as ‘standing Alfvén waves’, have been observed on the ground in magnetic field recordings dating back to the beginning of the century. Observations of currents and waves with satellite-borne magnetic field experiments have provided a new perspective on the complicated plasma processes that occur in the magnetosphere. Some of the new observations are described here.

Magnetospheric response to solar wind driving

2021 ◽  
Author(s):  
Tatiana Výbošťoková ◽  
Zdeněk Němeček ◽  
Jana Šafránková
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Field ◽  
Geomagnetic Storms ◽  
Interplanetary Space ◽  
Time Lags ◽  
Interplanetary Shocks ◽  
Geomagnetic Indices ◽  
The Earth ◽  
The Magnetic Field

<p>Interaction of solar events propagating throughout the interplanetary space with the magnetic field of the Earth may result in disruption of the magnetosphere. Disruption of the magnetic field is followed by the formation of the time-varying electric field and thus electric current is induced in Earth-bound structures such as transmission networks, pipelines or railways. In that case, it is necessary to be able to predict a future state of the magnetosphere and magnetic field of the Earth. The most straightforward way would use geomagnetic indices. Several studies are investigating the relationship of the response of the magnetosphere to changes in the solar wind with motivation to give a more accurate prediction of geomagnetic indices during geomagnetic storms. To forecast these indices, different approaches have been attempted--from simple correlation studies to neural networks.</p><p>We study the effects of interplanetary shocks observed at L1 on the Earth's magnetosphere with a database of tens of shocks between 2009 and 2019. Driving the magnetosphere is described as integral of reconnection electric field for each shock. The response of the geomagnetic field is described with the SYM-H index. We created an algorithm in Python for prediction of the magnetosphere state based on the correlation of solar wind driving and magnetospheric response and found that typical time-lags range between tens of minutes to maximum 2 hours. The results are documented by a large statistical study.</p>

Magnetic World: The Historiography of an Inherently Complex Science, Geomagnetism, in The 20th Century

2007 ◽  
Vol 26 (2) ◽  
pp. 281-299 ◽  
Author(s):  
Gregory Good
Keyword(s):  
Magnetic Field ◽  
20Th Century ◽  
Geomagnetic Field ◽  
Plate Tectonics ◽  
Radiation Belts ◽  
Problem Area ◽  
Early 20Th Century ◽  
The Earth ◽  
History Of ◽  
Field Lines

The 20th century witnessed a succession of remarkable developments in the history of geomagnetic research. After 1900, geomagnetic researchers increased their activity as they adopted theories by C. F. Gauss and J. C. Maxwell and developed means to bridge the gulf between these theories and masses of data of global phenomena. This paper outlines three main streams in 20th-century geomagnetic research: investigations of processes deep inside the Earth that produce the main geomagnetic field, examinations of crustal magnetism, and research into processes on the edge of space, where Earth's magnetic field interacts with the interplanetary environment. This discussion places these research streams in the historiographic context of disciplinary specialization and transformation. In the early 20th century, geomagnetic researchers thought of their domain as all of Earth's magnetic and electric phenomena. In mid-century, however, many researchers began to narrow their gaze to one problem area or another. This specialization contributed to a period of dramatic developments in the latter half of the century: geodynamo theory, paleomagnetic evidence of plate tectonics, computer modeling of magnetic reversals, and discovery of the solar wind, radiation belts, and magnetic substorms. But there was more to this period than simple specialization. As researchers gradually shifted their research programs, their methods, instruments, and theories moved from one program to another, researchers sometimes going with them. Chameleons and opportunists frequently left one research program for another, more promising one. This paper closes with a discussion of the possibility of "re-connection" among these specializations, as researchers have begun once again to communicate across inter-field lines.

scholarly journals Statistical characteristics of geomagnetic storm activity during solar cycle 24, 2009–2020

2020 ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Cycle ◽  
Geomagnetic Field ◽  
Geomagnetic Storms ◽  
Radio Channel ◽  
Statistical Characteristics ◽  
The Earth ◽  
Solar Cycle 24 ◽  
Cycle 24

Urgency. The atmosphere and geospace are widely used as a radio channel in solving problems of radar, radio navigation, direction finding, radio communication, radio astronomy, and the remote sensing of the Earth from space or the near-earth environment from the surface of the planet. The parameters of the atmospheric-space radio channel are determined by the state of tropospheric and space weather, which is formed mainly by non-stationary processes on the Sun (solar storms) and partly by high-energy processes on the Earth and in the atmosphere. Geospace storms give rise to the strongest disturbances of the atmospheric-space radio channel, and it is important to note that these storms are diverse, so that no two storms are alike. At the same time, storms have both similar and individual features. Currently, there is insufficient knowledge about both of these features, and their study remains an urgent task of space geophysics and space radio physics. In particular, the identification of general patterns is advisable by performing a statistical analysis of a large number of storms. The aim of this work is to statistically analyze the parameters of the solar wind and geomagnetic field during the Solar Cycle 24 activity (2009–2020). Methods and Methodology. The parameters of the disturbed solar wind (number density nsw, velocity Vsw, and temperature Tsw), the disturbed values of the By- and Bz-components of the interplanetary magnetic field, which is the cause of magnetic storms on Earth, as well as the indices of geomagnetic activity (AE, Dst and Kp) are selected as source input to the study. In this paper, geomagnetic storms with Kр ≥ 5 or G1, G2, G3, and G4 geomagnetic storms are considered. In total, there were 153 storms with Kp ≥ 5. The time series of the nsw, Vsw, Tsw maximum values, of the By- and Bz-components, and of the AE, Dst and Kp indices, as well as of the Bz-component and the Dst index minimum values have been analyzed. Results. The main statistical characteristics of the parameters of the solar wind, interplanetary magnetic field, and of the geomagnetic field have been determined for 153 events that took place during Solar Cycle 24. Conclusions. The geomagnetic situation during Solar Cycle 24 was calmer than during Solar Cycle 23.

scholarly journals Influence of the Earth's ring current strength on Størmer's allowed and forbidden regions of charged particle motion

2019 ◽  
Vol 37 (4) ◽  
pp. 535-547
Author(s):  
Alexander S. Lavrukhin ◽  
Igor I. Alexeev ◽  
Ilya V. Tyutin
Keyword(s):  
Radiation Belt ◽  
Ring Current ◽  
Current Strength ◽  
Trapping Region ◽  
Trapped Particles ◽  
The Earth ◽  
Forbidden Regions ◽  
Trapping Regions ◽  
Critical Ring ◽  
Earth’S Radiation Belt

Abstract. Størmer's particles' trapping regions for a planet with an intrinsic dipolar magnetic field are considered, taking into account the ring current which arises due to the trapped particles' drift for the case of the Earth. The influence of the ring current on the particle trapping regions' topology is investigated. It is shown that a critical strength of the ring current exists under which further expansion of the trapping region is no longer possible. Before reaching this limit, the dipole field, although deformed, retains two separated Størmer regions. After transition of critical magnitude, the trapping region opens up, and charged particles, which form the ring current, get the opportunity to leave it, thus decreasing the ring current strength. Numerical calculations have been performed for protons with typical energies of the Earth's radiation belt and ring current. For the Earth's case, the Dst index for the critical ring current strength is calculated.

scholarly journals Midday reversal of equatorial ionospheric electric field

1997 ◽  
Vol 15 (10) ◽  
pp. 1309-1315 ◽  
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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