Rocket and satellite observations of electric fields and ion convection in the dayside auroral ionosphere

Electric-field observations from two high-altitude rocket flights in the polar cusp have been combined with satellite observations of ion drifts and energetic particles to infer details of the electric field and convection pattern of the dayside auroral ionosphere. A region of shear flow reversal could be inferred from the electric-field observations on one flight near 1530 magnetic local time 20 min after the Dynamics Explorer 2 (DE-2) satellite crossed through the same region. The drift patterns observed by the two spacecrafts were very similar, although shifted by 0.5°, a shift that is expected from the observed change in the interplanetary magnetic-field (IMF) BZ component during this time. A region of rotational flow reversal was covered by the other flight shortly after magnetic noon, at the same time the DE-2 satellite travelled along roughly the dawn–dusk meridian. By joining points of equal potential, integrated from the two data sets, and assuming the reversal boundary to be an equipotential, we could draw the instantaneous convection pattern showing crescent-shaped convection contours in the dusk cell and more circular-shaped contours in the dawn cell. This pattern has been shown to be in qualitative agreement with the predictions of a geometrical model proposed by Crooker in 1979, when the IMF is oriented towards dawn. The same characteristic patterns but with the dusk and dawn cells reversed, as presented in a recent radar-satellite study for the IMF oriented towards dusk, may serve as additional evidence in favour of this model.

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Response of ionospheric electric fields to variations in the interplanetary magnetic field

Annales Geophysicae ◽

10.1007/s00585-996-0794-z ◽

1996 ◽

Vol 14 (8) ◽

pp. 794-802 ◽

Cited By ~ 2

Author(s):

S. P. Mishra ◽

E. Nielsen

Keyword(s):

Magnetic Field ◽

Electric Field ◽

Interplanetary Magnetic Field ◽

Electric Fields ◽

Solar Wind Speed ◽

Auroral Oval ◽

Local Times ◽

Residual Effects ◽

Magnetospheric Substorms ◽

The Imf

Abstract. The STARE system (Scandinavian Twin Auroral Radar Experiment) provides estimates of electron drift velocities, and hence also of the electric field in the high-latitude E-region ionosphere between 65 and 70 degrees latitude. The occurrence of drift velocities larger than about 400 m/s (equivalent to an electric field of 20 mV/m) have been correlated with the magnitude of the Interplanetary Magnetic Field (IMF) components Bz and By at all local times. Observation days have been considered during which both southward (Bz<0) and northward (Bz>0) IMF occurred. The occurrence of electric fields larger than 20 mV/m increases with increases in Bz magnitudes when Bz<0. It is found that the effects of southward IMF continue for some time following the northward turnings of the IMF. In order to eliminate such residual effects for Bz<0, we have, in the second part of the study, considered those days which were characterized by a pure northward IMF. The occurrence is considerably lower during times when Bz>0, than during those when Bz is negative. These results are related to the expansion and contraction of the auroral oval. The different percentage occurrences of large electric field for By>0 and By<0 components of the IMF during times when Bz>0, clearly display a dawn-dusk asymmetry of plasma flow in the ionosphere. The effects of the time-varying solar-wind speed, density, IMF fluctuations, and magnetospheric substorms on the occurrence of auroral-backscatter observations are also discussed.

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Spatial distribution of conductances and currents associated with a north-south auroral form during a multiple-substorm period

Annales Geophysicae ◽

10.1007/s00585-999-1385-6 ◽

1999 ◽

Vol 17 (11) ◽

pp. 1385-1396 ◽

Cited By ~ 24

Author(s):

O. Amm ◽

A. Pajunpää ◽

U. Brandström

Keyword(s):

Electric Field ◽

Electric Fields ◽

Method Of Characteristics ◽

Auroral Ionosphere ◽

Hall Conductance ◽

Similarities And Differences ◽

Ground Magnetic ◽

Ionospheric Electric Field ◽

Electric Fields And Currents ◽

Field Disturbance

Abstract. Using the method of characteristics to invert ground-based data of the ground magnetic field disturbance and of the ionospheric electric field, we obtain spatial distributions of ionospheric conductances, currents, and field-aligned currents (FACs) associated with a north-south auroral form that drifts westwards over northern Scandinavia around 2200 UT on December 2, 1977. This auroral form is one in a sequence of such north-south structures observed by all-sky cameras, and appears 14 min after the last of several breakups during that extremely disturbed night. Our analysis shows that the ionospheric Hall conductance reaches values above 200 S in the center of the form, and upward flowing FACs of up to 25 µA/m2 are concentrated near its westward and equatorward edge. The strong upward flowing FACs are fed by an area of more distributed, but still very strong downward-flowing FACs northeastward of the auroral form. In contrast to the conductances, the electric field is only slightly affected by the passage of the form. We point out similarities and differences of our observations and results to previously reported observations and models of 'auroral fingers', 'north-south aurora', and 'auroral streamers' which are suggested to be ionospheric manifestations of bursty bulk flows in the plasma sheet.Key words. Ionosphere (auroral ionosphere; electric fields and currents) · Magnetospheric physics (magnetosphere · ionosphere interactions)

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Parallel electric field in the auroral ionosphere: excitation of acoustic waves by Alfvén waves

Annales Geophysicae ◽

10.5194/angeo-22-2797-2004 ◽

2004 ◽

Vol 22 (8) ◽

pp. 2797-2804 ◽

Cited By ~ 1

Author(s):

P. L. Israelevich ◽

L. Ofman

Keyword(s):

Electric Field ◽

Electric Fields ◽

Acoustic Waves ◽

Finite Amplitude ◽

Alfven Waves ◽

Plasma Pressure ◽

Alfvén Waves ◽

Small Scale ◽

Auroral Ionosphere ◽

Parallel Electric Field

Abstract. We investigate a new mechanism for the formation of a parallel electric field observed in the auroral ionosphere. For this purpose, the excitation of acoustic waves by propagating Alfvén waves was studied numerically. We find that the magnetic pressure perturbation due to finite amplitude Alfvén waves causes the perturbation of the plasma pressure that propagates in the form of acoustic waves, and gives rise to a parallel electric field. This mechanism explains the observations of the strong parallel electric field in the small-scale electromagnetic perturbations of the auroral ionosphere. For the cases when the parallel electric current in the small-scale auroral perturbations is so strong that the velocity of current carriers exceeds the threshold of the ion sound instability, the excited ion acoustic waves may account for the parallel electric fields as strong as tens of mV/m.

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IMF effect on sporadic-E layers at two northern polar cap sites: Part I – Statistical study

Annales Geophysicae ◽

10.5194/angeo-24-887-2006 ◽

2006 ◽

Vol 24 (3) ◽

pp. 887-900 ◽

Cited By ~ 1

Author(s):

M. Voiculescu ◽

A. T. Aikio ◽

T. Nygrén ◽

J. M. Ruohoniemi

Keyword(s):

Electric Field ◽

Electric Fields ◽

Statistical Study ◽

Polar Cap ◽

Sporadic E Layers ◽

Convection Model ◽

Sporadic E ◽

The Relationship ◽

Electric Field Mechanism ◽

The Imf

Abstract. In this paper we investigate the relationship between polar cap sporadic-E layers and the direction of the interplanetary magnetic field (IMF) using a 2-year database from Longyearbyen (75.2 CGM Lat, Svalbard) and Thule (85.4 CGM Lat, Greenland). It is found that the MLT distributions of sporadic-E occurrence are different at the two stations, but both are related to the IMF orientation. This relationship, however, changes from the centre of the polar cap to its border. Layers are more frequent during positive By at both stations. This effect is particularly strong in the central polar cap at Thule, where a weak effect associated with Bz is also observed, with positive Bz correlating with a higher occurrence of Es. Close to the polar cap boundary, at Longyearbyen, the By effect is weaker than at Thule. On the other hand, Bz plays there an equally important role as By, with negative Bz correlating with the Es occurrence. Since Es layers can be created by electric fields at high latitudes, a possible explanation for the observations is that the layers are produced by the polar cap electric field controlled by the IMF. Using electric field estimates calculated by means of the statistical APL convection model from IMF observations, we find that the diurnal distributions of sporadic-E occurrence can generally be explained in terms of the electric field mechanism. However, other factors must be considered to explain why more layers occur during positive than during negative By and why the Bz dependence of layer occurrence in the central polar cap is different from that at the polar cap boundary.

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IMF effect on sporadic-E layers at two northern polar cap sites: Part II – Electric field

Annales Geophysicae ◽

10.5194/angeo-24-901-2006 ◽

2006 ◽

Vol 24 (3) ◽

pp. 901-913 ◽

Cited By ~ 1

Author(s):

T. Nygrén ◽

A. T. Aikio ◽

M. Voiculescu ◽

J. M. Ruohoniemi

Keyword(s):

Electric Field ◽

Diurnal Variations ◽

Field Direction ◽

Convection Pattern ◽

Polar Cap ◽

Model Calculations ◽

Sporadic E Layers ◽

Electric Field Direction ◽

Sporadic E ◽

The Imf

Abstract. This paper is the second in a series on a study of the link between IMF and sporadic-E layers within the polar cap. In Paper I (Voiculescu et al., 2006), an analysis of the sporadic-E data from Thule and Longyearbyen was presented. Here we concentrate on the electric field mechanism of sporadic-E generation. By means of model calculations we show that the mechanism is effective even at Thule, where the direction of the geomagnetic field departs from vertical only by 4. The model calculations also lead to a revision of the electric field theory. Previously, a thin layer was assumed to grow at a convergent null in the vertical ion velocity, which is formed when the electric field points in the NW sector. Our calculations indicate that in the dynamic process of vertical plasma compression, a layer is generated at altitudes of high vertical convergence rather than at a null. Consequently, the layer generation is less sensitive than previously assumed to fluctuations of the electric field direction within the NW sector. The observed diurnal variations of sporadic-E occurrence at Longyearbyen and Thule are compared with the diurnal variations of the electric field, calculated using a representative range of IMF values by means of the statistical APL model. The results indicate that the main features of Es occurrence can be explained by the convection pattern controlled by the IMF. Electric fields calculated from the IMF observations are also used for producing distributions of sporadic-E occurrence as a function of electric field direction at the two sites. A marked difference between the distributions at Thule and Longyearbyen is found. A model estimate of the occurrence probability as a function of electric field direction is developed and a reasonable agreement between the model and the experimental occurrence is found. The calculation explains the differences between the distributions at the two sites in terms of the polar cap convection pattern. The conclusion is that the electric field is the major cause for sporadic-E generation and, consequently, IMF has a clear control on the occurrence of sporadic E within the polar cap.

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A Method of Estimating Electric Fields above Electrified Clouds from Passive Microwave Observations

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-14-00119.1 ◽

2015 ◽

Vol 32 (8) ◽

pp. 1429-1446 ◽

Cited By ~ 9

Author(s):

Michael Peterson ◽

Chuntao Liu ◽

Douglas Mach ◽

Wiebke Deierling ◽

Christina Kalb

Keyword(s):

Electric Field ◽

Electric Fields ◽

Electric Circuit ◽

Passive Microwave ◽

Field Observations ◽

Global Electric Circuit ◽

Convective Clouds ◽

Unique Approach ◽

Future Utility ◽

Unique Dataset

AbstractA unique dataset of coincident high-altitude passive microwave and electric field observations taken by the NASA ER-2 aircraft is used to assess the feasibility of estimating electric fields above electrified clouds using ubiquitous global and multidecadal satellite products. Once applied to a global dataset, such a product would provide a unique approach for diagnosing and monitoring the current sources of the global electric circuit (GEC).In this study an algorithm has been developed that employs ice scattering signals from 37- and 85-GHz passive microwave observations to characterize the electric fields above clouds overflown by the ER-2 aircraft at nearly 20-km altitude. Electric field estimates produced by this passive microwave algorithm are then compared to electric field observations also taken by the aircraft to assess its potential future utility with satellite datasets. The algorithm is shown to estimate observed electric field strengths over intense convective clouds at least 71% (58%) of the time over land and 43% (40%) of the time over the ocean to within a factor of 2 from 85-GHz (37 GHz) passive microwave observations. Electric fields over weaker clouds can be estimated 58% (41%) of the time over land and 22% (8%) of the time over the ocean from 85-GHz (37 GHz) passive microwave observations. The accuracy of these estimates is limited by systematic errors in the observations along with other factors. Despite these sources of error, the algorithm can produce reasonable estimates of electric fields over carefully selected individual electrified clouds that differ from observations by less than 20 V m−1 for clouds that produce 200–400 V m−1 electric fields at 20 km.

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Tuning the Electric Field Response of MOFs by Rotatable Dipolar Linkers

10.26434/chemrxiv.8153198.v1 ◽

2019 ◽

Author(s):

Johannes P. Dürholt ◽

Babak Farhadi Jahromi ◽

Rochus Schmid

Keyword(s):

Electric Field ◽

Electric Fields ◽

Structural Changes ◽

Dielectric Behavior ◽

Two Dimensions ◽

Dielectric Constants ◽

Electric Response ◽

Dipole Strength ◽

Metal Organic ◽

Dynamics Simulations

Recently the possibility of using electric fields as a further stimulus to trigger structural changes in metal-organic frameworks (MOFs) has been investigated. In general, rotatable groups or other types of mechanical motion can be driven by electric fields. In this study we demonstrate how the electric response of MOFs can be tuned by adding rotatable dipolar linkers, generating a material that exhibits paralectric behavior in two dimensions and dielectric behavior in one dimension. The suitability of four different methods to compute the relative permittivity κ by means of molecular dynamics simulations was validated. The dependency of the permittivity on temperature T and dipole strength μ was determined. It was found that the herein investigated systems exhibit a high degree of tunability and substantially larger dielectric constants as expected for MOFs in general. The temperature dependency of κ obeys the Curie-Weiss law. In addition, the influence of dipolar linkers on the electric field induced breathing behavior was investigated. With increasing dipole moment, lower field strength are required to trigger the contraction. These investigations set the stage for an application of such systems as dielectric sensors, order-disorder ferroelectrics or any scenario where movable dipolar fragments respond to external electric fields.

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The research study in the convergence of the results of processing radar images Sentinel-1A with field observations of agricultural sites

Geodesy and Cartography ◽

10.22389/0016-7126-2019-950-8-52-58 ◽

2019 ◽

Vol 950 (8) ◽

pp. 52-58

Author(s):

D.V. Mozer ◽

Е.L. Levin ◽

A.K. Satbergenova

Keyword(s):

Satellite Remote Sensing ◽

Satellite Images ◽

Research Study ◽

High Accuracy ◽

Agricultural Fields ◽

Field Observations ◽

Radar Images ◽

The Earth ◽

Radar Satellite ◽

Modern Technologies

The manuscript discusses how to monitor the condition of seedlings on agricultural fields planted with winter wheat, fodder maize and areas of fir forest located in the Freudenstadt district of Baden-Wuerttemberg in Germany. To solve the range of agricultural problems , they often use modern technologies such as satellite remote sensing of the Earth. The paper displays the monitoring results of the Sentinel-1A radar satellites scenes, as well as visual spectrum imagery of field observations are presented when leaving directly to terrain segments. The processing deployed data chain, consisting of 11 Sentinel-1A scenes acquired in the timefrane from March to November 2018. Specifically, the SNAP Sentinel Toolboxes software was used to process the radar satellite images Sentinel-1А, the. Based on the the research outcomes the Committee of Agriculture of the Freudenstadt district is able to predict the yield amount with high accuracy due to good data convergence. According to the study, the following three important problems can be resolved by means of Sentinel-1A imagery

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Meta-Deflectors Made of Dielectric Nanohole Arrays with Anti-Damage Potential

Photonics ◽

10.3390/photonics8040107 ◽

2021 ◽

Vol 8 (4) ◽

pp. 107

Author(s):

Haichao Yu ◽

Feng Tang ◽

Jingjun Wu ◽

Zao Yi ◽

Xin Ye ◽

...

Keyword(s):

Electric Field ◽

Electric Fields ◽

Laser Cutting ◽

High Complexity ◽

Damage Potential ◽

Optical Components ◽

Nanohole Arrays ◽

Intense Light ◽

Polarization Of Light ◽

Air Hole

In intense-light systems, the traditional discrete optical components lead to high complexity and high cost. Metasurfaces, which have received increasing attention due to the ability to locally manipulate the amplitude, phase, and polarization of light, are promising for addressing this issue. In the study, a metasurface-based reflective deflector is investigated which is composed of silicon nanohole arrays that confine the strongest electric field in the air zone. Subsequently, the in-air electric field does not interact with the silicon material directly, attenuating the optothermal effect that causes laser damage. The highest reflectance of nanoholes can be above 99% while the strongest electric fields are tuned into the air zone. One presentative deflector is designed based on these nanoholes with in-air-hole field confinement and anti-damage potential. The 1st order of the meta-deflector has the highest reflectance of 55.74%, and the reflectance sum of all the orders of the meta-deflector is 92.38%. The optothermal simulations show that the meta-deflector can theoretically handle a maximum laser density of 0.24 W/µm2. The study provides an approach to improving the anti-damage property of the reflective phase-control metasurfaces for intense-light systems, which can be exploited in many applications, such as laser scalpels, laser cutting devices, etc.

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Integrating flexible electronics for pulsed electric field delivery in a vascularized 3D glioblastoma model

npj Flexible Electronics ◽

10.1038/s41528-021-00115-x ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Marie C. Lefevre ◽

Gerwin Dijk ◽

Attila Kaszas ◽

Martin Baca ◽

David Moreau ◽

...

Keyword(s):

Electric Field ◽

Electric Fields ◽

Flexible Electronics ◽

Soft Tissues ◽

Multiphoton Microscopy ◽

Membrane Integrity ◽

Tumor Model ◽

Pulsed Electric Fields ◽

In Ovo ◽

Cell Membrane Integrity

AbstractGlioblastoma is a highly aggressive brain tumor, very invasive and thus difficult to eradicate with standard oncology therapies. Bioelectric treatments based on pulsed electric fields have proven to be a successful method to treat cancerous tissues. However, they rely on stiff electrodes, which cause acute and chronic injuries, especially in soft tissues like the brain. Here we demonstrate the feasibility of delivering pulsed electric fields with flexible electronics using an in ovo vascularized tumor model. We show with fluorescence widefield and multiphoton microscopy that pulsed electric fields induce vasoconstriction of blood vessels and evoke calcium signals in vascularized glioblastoma spheroids stably expressing a genetically encoded fluorescence reporter. Simulations of the electric field delivery are compared with the measured influence of electric field effects on cell membrane integrity in exposed tumor cells. Our results confirm the feasibility of flexible electronics as a means of delivering intense pulsed electric fields to tumors in an intravital 3D vascularized model of human glioblastoma.

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