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

1996 ◽  
Vol 14 (8) ◽  
pp. 794-802 ◽  
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.

scholarly journals The influence of the interplanetary medium on SuperDARN radar scattering occurrence

2000 ◽  
Vol 18 (12) ◽  
pp. 1576-1583 ◽  
Author(s):  
P. Ballatore ◽  
J. P. Villain ◽  
N. Vilmer ◽  
M. Pick
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Interplanetary Medium ◽  
Solar Wind Speed ◽  
Auroral Oval ◽  
Small Degree ◽  
Radio Science ◽  
Ionospheric Physics ◽  
Radar Scattering

Abstract. The effects of the characteristics of the interplanetary medium on the radar scattering occurrence, related to the whole array of SuperDARN radars installed in the Northern Hemisphere, have been studied over a two-year period. Statistically significant correlations of the variation of the scattering occurrence are found with the merging electric field and with the negative Bz component of the interplanetary magnetic field, independent of the seasonal period considered. This result demonstrates that the merging rate (and in particular the reconnection process) between the interplanetary magnetic field and the magnetosphere is a relevant factor affecting the occurrence of scattering. For comparison, we note that no statistically significant correlations are obtained when the interplanetary ion density or the solar wind speed are considered, although also these variables affect to a small degree the scattering occurrence variation. The study of the latitudinal and magnetic local time dependence of the observations shows an association between the considered correlation and the location of the auroral oval and the cusp/cleft region.Key words: Ionosphere (ionospheric irregularities) · Magnetospheric physics (solar wind-magnetosphere interactions) · Radio science (ionospheric physics)

scholarly journals An event study on broadband electric field noises and electron distributions in the lunar wake boundary

2022 ◽  
Vol 74 (1) ◽  
Author(s):  
Masaki N. Nishino ◽  
Yoshiya Kasahara ◽  
Yuki Harada ◽  
Yoshifumi Saito ◽  
Hideo Tsunakawa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Field ◽  
Interplanetary Magnetic Field ◽  
Electric Fields ◽  
Lunar Surface ◽  
Electron Beams ◽  
The Moon ◽  
Link Type ◽  
Electron Distributions

AbstractWave–particle interactions are fundamental processes in space plasma, and some plasma waves, including electrostatic solitary waves (ESWs), are recognised as broadband noises (BBNs) in the electric field spectral data. Spacecraft observations in recent decades have detected BBNs around the Moon, but the generation mechanism of the BBNs is not fully understood. Here, we study a wake boundary traversal with BBNs observed by Kaguya, which includes an ESW event previously reported by Hashimoto et al. Geophys Res Lett 37:L19204 10.1029/2010GL044529 (2010). Focusing on the relation between BBNs and electron pitch-angle distribution functions, we show that upward electron beams from the nightside lunar surface are effective for the generation of BBNs, in contrast to the original interpretation by Hashimoto et al. Geophys Res Lett 37:L19204 10.1029/2010GL044529 (2010) that high-energy electrons accelerated by strong ambipolar electric fields excite ESWs in the region far from the Moon. When the BBNs were observed by the Kaguya spacecraft in the wake boundary, the spacecraft’s location was magnetically connected to the nightside lunar surface, and bi-streaming electron distributions of downward-going solar wind strahl component and upward-going field-aligned beams (at $$\sim$$ ∼ 124 eV) were detected. The interplanetary magnetic field was dominated by a positive $$B_Z$$ B Z (i.e. the northward component), and strahl electrons travelled in the antiparallel direction to the interplanetary magnetic field (i.e. southward), which enabled the strahl electrons to precipitate onto the nightside lunar surface directly. The incident solar wind electrons cause negative charging of the nightside lunar surface, which generates downward electric fields that accelerate electrons from the nightside surface toward higher altitudes along the magnetic field. The bidirectional electron distribution is not a sufficient condition for the BBN generation, and the distribution of upward electron beams seems to be correlated with the BBNs. Ambipolar electric fields in the wake boundary should also contribute to the electron acceleration toward higher altitudes and further intrusion of the solar wind ions into the deeper wake. We suggest that solar wind ion intrusion into the wake boundary is also an important factor that controls the BBN generation by facilitating the influx of solar wind electrons there. Graphical Abstract

scholarly journals Magnetospheric response to the solar wind as indicated by the cross-polar potential drop and the low-latitude asymmetric disturbance field

2001 ◽  
Vol 19 (6) ◽  
pp. 649-653 ◽  
Author(s):  
S. Eriksson ◽  
L. G. Blomberg ◽  
N. Ivchenko ◽  
T. Karlsson ◽  
G. T. Marklund
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Field ◽  
Interplanetary Magnetic Field ◽  
Electric Fields ◽  
Potential Drop ◽  
Plasma Convection ◽  
Low Latitude ◽  
The Cross ◽  
Disturbance Field

Abstract. The cross-polar potential drop Φpc and the low-latitude asymmetric geomagnetic disturbance field, as indicated by the mid-latitude ASY-H magnetic index, are used to study the average magnetospheric response to the solar wind forcing for southward interplanetary magnetic field conditions. The state of the solar wind is monitored by the ACE spacecraft and the ionospheric convection is measured by the double probe electric field instrument on the Astrid-2 satellite. The solar wind-magnetosphere coupling is examined for 77 cases in February and from mid-May to mid-June 1999 by using the interplanetary magnetic field Bz component and the reconnection electric field. Our results show that the maximum correlation between Φpc  and the reconnection electric field is obtained approximately 25 min after the solar wind has reached a distance of 11 RE from the Earth, which is the assumed average position of the magnetopause. The corresponding correlation for ASY-H shows two separate responses to the reconnection electric field, delayed by about 35 and 65 min, respectively. We suggest that the combination of the occurrence of a large magnetic storm on 18 February 1999 and the enhanced level of geomagnetic activity which peaks at Kp = 7- may explain the fast direct response of ASY-H to the solar wind at 35 min, as well as the lack of any clear secondary responses of Φpc  to the driving solar wind at time delays longer than 25 min.Key words. Magnetospheric physics (solar wind-magnetosphere interactions; plasma convection) – Ionosphere (electric fields and currents)

scholarly journals Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field

2000 ◽  
Vol 18 (4) ◽  
pp. 436-444 ◽  
Author(s):  
S. E. Milan ◽  
M. Lester ◽  
S. W. H. Cowley ◽  
M. Brittnacher
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
High Latitude ◽  
Auroral Oval ◽  
Large Field ◽  
Convection Flow ◽  
Plasma Convection ◽  
Flow Measurements ◽  
Auroral Emission ◽  
The Imf

Abstract. We investigate the dayside auroral dynamics and ionospheric convection during an interval when the interplanetary magnetic field (IMF) had predominantly a positive Bz component (northward IMF) but varying By. Polar UVI observations of the Northern Hemisphere auroral emission indicate the existence of a region of luminosity near local noon at latitudes poleward of the dayside auroral oval, which we interpret as the ionospheric footprint of a high-latitude reconnection site. The large field-of-view afforded by the satellite-borne imager allows an unprecedented determination of the dynamics of this region, which has not previously been possible with ground-based observations. The location of the emission in latitude and magnetic local time varies in response to changes in the orientation of the IMF; the cusp MLT and the IMF By component are especially well correlated, the emission being located in the pre- or post-noon sectors for By < 0 nT or By > 0 nT, respectively. Simultaneous ground-based observations of the ionospheric plasma drift are provided by the CUTLASS Finland HF coherent radar. For an interval of IMF By \\approx 0 nT, these convection flow measurements suggest the presence of a clockwise-rotating lobe cell contained within the pre-noon dayside polar cap, with a flow reversal closely co-located with the high-latitude luminosity region. This pattern is largely consistent with recent theoretical predictions of the convection flow during northward IMF. We believe that this represents the first direct measurement of the convection flow at the imaged location of the footprint of the high-latitude reconnection site.Key words: Magnetospheric physics (auroral phenomena; magnetopause · cusp · and boundary layers; plasma convection)

scholarly journals Double layers in the downward current region of the aurora

2003 ◽  
Vol 10 (1/2) ◽  
pp. 45-52 ◽  
Author(s):  
R. E. Ergun ◽  
L. Andersson ◽  
C. W. Carlson ◽  
D. L. Newman ◽  
M. V. Goldman
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Phase Space ◽  
Electric Field ◽  
Electric Fields ◽  
Double Layers ◽  
Parallel Electric Field ◽  
Electrostatic Waves ◽  
Current Region ◽  
Decisive Evidence

Abstract. Direct observations of magnetic-field-aligned (parallel) electric fields in the downward current region of the aurora provide decisive evidence of naturally occurring double layers. We report measurements of parallel electric fields, electron fluxes and ion fluxes related to double layers that are responsible for particle acceleration. The observations suggest that parallel electric fields organize into a structure of three distinct, narrowly-confined regions along the magnetic field (B). In the "ramp" region, the measured parallel electric field forms a nearly-monotonic potential ramp that is localized to ~ 10 Debye lengths along B. The ramp is moving parallel to B at the ion acoustic speed (vs) and in the same direction as the accelerated electrons. On the high-potential side of the ramp, in the "beam" region, an unstable electron beam is seen for roughly another 10 Debye lengths along B. The electron beam is rapidly stabilized by intense electrostatic waves and nonlinear structures interpreted as electron phase-space holes. The "wave" region is physically separated from the ramp by the beam region. Numerical simulations reproduce a similar ramp structure, beam region, electrostatic turbulence region and plasma characteristics as seen in the observations. These results suggest that large double layers can account for the parallel electric field in the downward current region and that intense electrostatic turbulence rapidly stabilizes the accelerated electron distributions. These results also demonstrate that parallel electric fields are directly associated with the generation of large-amplitude electron phase-space holes and plasma waves.

scholarly journals Magnetopause energy transfer dependence on the interplanetary magnetic field and the Earth's magnetic dipole axis orientation

2012 ◽  
Vol 30 (3) ◽  
pp. 515-526 ◽  
Author(s):  
M. Palmroth ◽  
R. C. Fear ◽  
I. Honkonen
Keyword(s):  
Magnetic Field ◽  
Energy Transfer ◽  
Interplanetary Magnetic Field ◽  
Large Data ◽  
Seasonal Effect ◽  
Dipole Orientation ◽  
Data Set ◽  
Axis Orientation ◽  
Simulation Results ◽  
The Imf

Abstract. We examine the spatial variation of magnetospheric energy transfer using a global magnetohydrodynamic (MHD) simulation (GUMICS-4) and a large data set of flux transfer events (FTEs) observed by the Cluster spacecraft. Our main purpose is to investigate whether it is possible to validate previous results on the spatial energy transfer variation from the GUMICS-4 simulation using the statistical occurrence of FTEs, which are manifestations of magnetospheric energy transfer. Previous simulation results have suggested that the energy transfer pattern at the magnetopause rotates according to the interplanetary magnetic field (IMF) orientation, and here we investigate whether a similar rotation is seen in the locations at which FTE signatures are observed. We find that there is qualitative agreement between the simulation and observed statistics, as the peaks in both distributions rotate as a function of the IMF clock angle. However, it is necessary to take into account the modulation of the statistical distribution that is caused by a bias towards in situ FTE signatures being observed in the winter hemisphere (an effect that has previously been predicted and observed in this data set). Taking this seasonal effect into account, the FTE locations support the previous simulation results and confirm the earlier prediction that the energy transfers in the plane of the IMF. In addition, we investigate the effect of the dipole orientation (both the dipole tilt angle and its orientation in the plane perpendicular to the solar wind flow) on the energy transfer spatial distribution. We find that the energy transfer occurs mainly in the summer hemisphere, and that the dayside reconnection region is located asymmetrically about the subsolar position. Finally, we find that the energy transfer is 10% larger at equinox conditions than at solstice, contributing to the discussion concerning the semiannual variation of magnetospheric dynamics (known as "the Russell-McPherron effect").

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 Interplanetary magnetic field and its possible effects on the mid-latitude ionosphere III

1996 ◽  
Vol 39 (4) ◽  
Author(s):  
Y. Tulunay
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Interplanetary Magnetic Field ◽  
Seasonal Effects ◽  
Ionospheric Variability ◽  
Winter Anomaly ◽  
The Mean ◽  
The Imf

Using critical frequencies, f0F2 from the Lannion, Slough, Poitiers, Garchy, Dourbes, Rome, Juliusrud, Gibilmanna, Pruhonice, Uppsala, Kaliningrad, Miedzeszyn, Sofia, Athens and Kiev ionosonde stations, the possible effects of the orientation of the Interplanetary Magnetic Field (IMF) on mid-latitude ionosphere are further investigated. This time, only the southward polarity changes in IMF Bz with seasonal effects were considered. The same method of analysis was employed to facilitate a comparison between the recent results presented here with those which appeared in the preceding papers in the series. That is, the regular diurnal, seasonal and solar cycle variations in the f0F2 data were removed by subtracting the mean of the f0F2 for the same UT on all magnetically quite days (Ap < 6) within 15 days around the IMF Bz turnings (Tulunay, 1994). This last paper also includes the seasonal effects on the ionospheric data. The results confirm that much of the day-to-day variability of the mid-latitude ionosphere may be related to the orientation of the southward IMF Bz , characterized by the ionospheric winter anomaly. Day-to-day ionospheric variability becomes more significant towards higher latitudes.

scholarly journals A parallel finite‐difference approach for 3D transient electromagnetic modeling with galvanic sources

Geophysics ◽  
2004 ◽  
Vol 69 (5) ◽  
pp. 1192-1202 ◽  
Author(s):  
Michael Commer ◽  
Gregory Newman
Keyword(s):  
Magnetic Field ◽  
Finite Difference ◽  
Electric Field ◽  
Electric Fields ◽  
Time Derivative ◽  
Stable Solution ◽  
Parallel Computer ◽  
Staggered Grid ◽  
Electromagnetic Modeling ◽  
Transient Electromagnetic

A parallel finite‐difference algorithm for the solution of diffusive, three‐dimensional (3D) transient electromagnetic field simulations is presented. The purpose of the scheme is the simulation of both electric fields and the time derivative of magnetic fields generated by galvanic sources (grounded wires) over arbitrarily complicated distributions of conductivity and magnetic permeability. Using a staggered grid and a modified DuFort‐Frankel method, the scheme steps Maxwell's equations in time. Electric field initialization is done by a conjugate‐gradient solution of a 3D Poisson problem, as is common in 3D resistivity modeling. Instead of calculating the initial magnetic field directly, its time derivative and curl are employed in order to advance the electric field in time. A divergence‐free condition is enforced for both the magnetic‐field time derivative and the total conduction‐current density, providing accurate results at late times. In order to simulate large realistic earth models, the algorithm has been designed to run on parallel computer platforms. The upward continuation boundary condition for a stable solution in the infinitely resistive air layer involves a two‐dimensional parallel fast Fourier transform. Example simulations are compared with analytical, integral‐equation and spectral Lanczos decomposition solutions and demonstrate the accuracy of the scheme.

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