scholarly journals Saturation of polar cap potential by intense solar wind electric fields

2002 ◽  
Vol 29 (10) ◽  
pp. 62-1-62-4 ◽  
Author(s):  
Tsutomu Nagatsuma
Keyword(s):  
Solar Wind ◽  
Electric Fields ◽  
Polar Cap

Radar studies of high-latitude ionospheric flows

1989 ◽  
Vol 328 (1598) ◽  
pp. 107-118 ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Flow Pattern ◽  
Electric Fields ◽  
Strong Interactions ◽  
Plasma Convection ◽  
Polar Cap ◽  
Incoherent Scatter ◽  
Incoherent Scatter Radars ◽  
Coupling Processes

Strong interactions occur between the solar wind and the Earth’s magnetic field which result in the convection of ionospheric plasma over the polar cap regions. This generally forms a two-cell pattern with westward and eastward flows in the pre- and post-midnight sectors respectively. The flow pattern is sensitive to the flux of the solar wind and the direction of the interplanetary magnetic field. Observations of the flow pattern are thus of considerable value in the interpretation of the magnetosphere-ionosphere coupling processes and in identifying the influence of the solar wind on the Earth’s environment. The plasma convection can be observed by ground-based coherent and incoherent scatter radars and the flow vectors determined. Measurements for a range of flow conditions are presented. These are interpreted in terms of the interactions of the solar wind with the magnetosphere and the resulting electric fields which drive the plasma flows in the ionosphere.

scholarly journals IMF <i>B</i><sub><i>y</i></sub> effects in the plasma flow at the polar cap boundary

2011 ◽  
Vol 29 (7) ◽  
pp. 1305-1315 ◽  
Author(s):  
R. Lukianova ◽  
A. Kozlovsky
Keyword(s):  
Solar Wind ◽  
Electric Fields ◽  
Plasma Flow ◽  
Relative Reduction ◽  
Polar Cap ◽  
Azimuthal Component ◽  
Ionospheric Convection ◽  
Quantitative Characteristics ◽  
Night Side ◽  
The Imf

Abstract. We used the dataset obtained from the EISCAT Svalbard Radar during 2000–2008 to study statistically the ionospheric convection in a vicinity of the polar cap boundary as related to IMF By conditions separately for northward and southward IMF. The effect of IMF By is manifested in the intensity and direction of the azimuthal component of ionospheric flow. The most significant effect is observed on the day and night sides whereas on dawn and dusk the effect is essentially less prominent. However, there is an asymmetry with respect to the noon-midnight meridian. On the day side the intensity of By-related azimuthal flow is maximal exactly at noon, whereas on the night side the maximum is shifted toward the post-midnight hours (~03:00 MLT). On the dusk side the relative reduction of the azimuthal flow is much larger than that on the dawn side. Overall, the magnetospheric response to IMF By seems to be stronger in the 00:00–12:00 MLT sector compared to the 12:00–24:00 MLTs. Quantitative characteristics of the IMF By effect are presented and partly explained by the magnetospheric electric fields generated due to the solar wind and also by the position of open-closed boundary for different IMF orientation.

scholarly journals Magnetopause mapping to the ionosphere for northward IMF

2007 ◽  
Vol 25 (12) ◽  
pp. 2615-2625 ◽  
Author(s):  
I. I. Alexeev ◽  
E. S. Belenkaya ◽  
S. Yu. Bobrovnikov ◽  
V. V. Kalegaev ◽  
J. A. Cumnock ◽  
...  
Keyword(s):  
Solar Wind ◽  
Field Line ◽  
Open Field ◽  
Electric Fields ◽  
Interplanetary Space ◽  
Potential Drop ◽  
Wind Pressure ◽  
Polar Ionosphere ◽  
Polar Cap ◽  
Open Field Line

Abstract. We study the topological structure of the magnetosphere for northward IMF. Using a magnetospheric magnetic field model we study the high-latitude response to prolonged periods of northward IMF. For forced solar wind conditions we investigate the location of the polar cap region, the polar cap potential drop, and the field-aligned acceleration potentials, depending on the solar wind pressure and IMF By and Bx changes. The open field line bundles, which connect the Earth's polar ionosphere with interplanetary space, are calculated. The locations of the magnetospheric plasma domains relative to the polar ionosphere are studied. The specific features of the open field line regions arising when IMF is northward are demonstrated. The coefficients of attenuation of the solar wind magnetic and electric fields which penetrate into the magnetosphere are determined.

scholarly journals Space Weather, SuperDARN and the Tasmanian Tiger

1997 ◽  
Vol 50 (4) ◽  
pp. 773 ◽  
Author(s):  
Raymond A. Greenwald
Keyword(s):  
Solar Wind ◽  
Electric Fields ◽  
Space Weather ◽  
Interplanetary Space ◽  
Rapid Evolution ◽  
Upper Atmosphere ◽  
Global Network ◽  
Pressure Gradients ◽  
Earth’S Magnetosphere ◽  
Earth's Magnetosphere

The plasma environment extending from the solar surface through interplanetary space to the outermost reaches of the Earth’s atmosphere and magnetic field is dynamic, often disturbed, and capable of harming humans and damaging manmade systems. Disturbances in this environment have been identified as space weather disturbances. At the present time there is growing interest in monitoring and predicting space weather disturbances. In this paper we present some of the difficulties involved in achieving this goal by comparing the processes that drive tropospheric-weather systems with those that drive space-weather systems in the upper atmosphere and ionosphere. The former are driven by pressure gradients which result from processes that heat and cool the atmosphere. The latter are driven by electric fields that result from interactions between the streams of ionised gases emerging from the Sun (solar wind) and the Earth’s magnetosphere. Although the dimensions of the Earth’s magnetosphere are vastly greater than those of tropospheric weather systems, the global space-weather response to changes in the solar wind is much more rapid than the response of tropospheric-weather systems to changing conditions. We shall demonstrate the rapid evolution of space-weather systems in the upper atmosphere through measurements with a global network of radars known as SuperDARN. We shall also describe how the SuperDARN network is evolving, including a newly funded Australian component known as the Tasman International Geospace Environmental Radar (TIGER).

scholarly journals Validation of the stream function method used for reconstruction of experimental ionospheric convection patterns

2000 ◽  
Vol 18 (4) ◽  
pp. 454-460
Author(s):  
P.L. Israelevich ◽  
V. O. Papitashvili ◽  
A. I. Ershkovich
Keyword(s):  
Boundary Value Problem ◽  
Boundary Conditions ◽  
Stream Function ◽  
Electric Fields ◽  
Electric Potential ◽  
Potential Distribution ◽  
Function Method ◽  
Polar Cap ◽  
Ionospheric Convection ◽  
Convection Patterns

Abstract. In this study we test a stream function method suggested by Israelevich and Ershkovich for instantaneous reconstruction of global, high-latitude ionospheric convection patterns from a limited set of experimental observations, namely, from the electric field or ion drift velocity vector measurements taken along two polar satellite orbits only. These two satellite passes subdivide the polar cap into several adjacent areas. Measured electric fields or ion drifts can be considered as boundary conditions (together with the zero electric potential condition at the low-latitude boundary) for those areas, and the entire ionospheric convection pattern can be reconstructed as a solution of the boundary value problem for the stream function without any preliminary information on ionospheric conductivities. In order to validate the stream function method, we utilized the IZMIRAN electrodynamic model (IZMEM) recently calibrated by the DMSP ionospheric electrostatic potential observations. For the sake of simplicity, we took the modeled electric fields along the noon-midnight and dawn-dusk meridians as the boundary conditions. Then, the solution(s) of the boundary value problem (i.e., a reconstructed potential distribution over the entire polar region) is compared with the original IZMEM/DMSP electric potential distribution(s), as well as with the various cross cuts of the polar cap. It is found that reconstructed convection patterns are in good agreement with the original modelled patterns in both the northern and southern polar caps. The analysis is carried out for the winter and summer conditions, as well as for a number of configurations of the interplanetary magnetic field.Key words: Ionosphere (electric fields and currents; plasma convection; modelling and forecasting)

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

2017 ◽  
Vol 35 (6) ◽  
pp. 1309-1326 ◽  
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.

scholarly journals A new formulation for the ionospheric cross polar cap potential including saturation effects

2005 ◽  
Vol 23 (11) ◽  
pp. 3533-3547 ◽  
Author(s):  
A. J. Ridley
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Mach Number ◽  
Interplanetary Magnetic Field ◽  
Polar Cap ◽  
Pressure Balance ◽  
Simple Modification ◽  
Post Shock ◽  
Cross Polar Cap Potential ◽  
New Formulation

Abstract. It is known that the ionospheric cross polar cap potential (CPCP) saturates when the interplanetary magnetic field (IMF) Bz becomes very large. Few studies have offered physical explanations as to why the polar cap potential saturates. We present 13 events in which the reconnection electric field (REF) goes above 12mV/m at some time. When these events are examined as typically done in previous studies, all of them show some signs of saturation (i.e., over-prediction of the CPCP based on a linear relationship between the IMF and the CPCP). We show that by taking into account the size of the magnetosphere and the fact that the post-shock magnetic field strength is strongly dependent upon the solar wind Mach number, we can better specify the ionospheric CPCP. The CPCP (Φ) can be expressed as Φ=(10-4v2+11.7B(1-e-Ma/3)sin3(θ/2)) {rms/9 (where v is the solar wind velocity, B is the combined Y and Z components of the interplanetary magnetic field, Ma is the solar wind Mach number, θ=acos(Bz/B), and rms is the stand-off distance to the magnetopause, assuming pressure-balance between the solar wind and the magnetosphere). This is a simple modification of the original Boyle et al. (1997) formulation.

Sign in / Sign up

Export Citation Format

Share Document