Ionospheric Convection in the Polar Cap as Seen by Optical Imaging

1989 ◽  
pp. 127-136 ◽  
Author(s):  
J. H. Doolittle ◽  
S. B. Mende ◽  
G. R. Swenson ◽  
R. M. Robinson
Keyword(s):  
Optical Imaging ◽  
Polar Cap ◽  
Ionospheric Convection

scholarly journals Small-scale characteristics of extremely high latitude aurora

2009 ◽  
Vol 27 (9) ◽  
pp. 3335-3347 ◽  
Author(s):  
J. A. Cumnock ◽  
L. G. Blomberg ◽  
A. Kullen ◽  
T. Karlsson ◽  
Keyword(s):  
High Latitude ◽  
Large Scale ◽  
Small Scale ◽  
Strong Correlations ◽  
Polar Cap ◽  
Plasma Flows ◽  
Ionospheric Convection ◽  
Local Closure ◽  
Scale Characteristics

Abstract. We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF By. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.

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 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.

Electrodynamics surrounding polar cap auroral arcs

2021 ◽  
Author(s):  
Amalie Ø. Hovland ◽  
Kjellmar Oksavik ◽  
Jone P. Reistad ◽  
Marc R. Hairston
Keyword(s):  
High Latitude ◽  
Optical Data ◽  
Polar Cap ◽  
Ionospheric Convection ◽  
Ion Drift ◽  
Polar Latitude ◽  
Mesoscale Structure ◽  
Radar Network ◽  
Auroral Arcs

&lt;p&gt;This multi-instrument case study investigates the electrodynamics surrounding polar cap auroral arcs. A long-lasting auroral arc is observed in the high latitude dusk-sector at ~80&amp;#176; Apex latitude in the northern hemisphere. Ion drift measurements from the SSIES system on the DMSP spacecraft have been combined with multiple ground-based observations. Line of sight velocity data from three polar latitude high-frequency Super Dual Auroral Radar Network (SuperDARN) radars show mesoscale structure in the ionospheric convection in the region surrounding the arc. The convection electric field in this region is modelled using a Spherical Elementary Convection Systems (SECS) technique, using curl-free basis functions only. The result is a regional model of the ionospheric convection based on the fairly dense and distributed flow observations and the curl-free constraint. The model is compared to optical data of the auroral arc from two high latitude Redline Emission Geospace Observatory (REGO) all-sky imagers as well as UV images and particle measurements from the DMSP spacecraft to describe the local electrodynamics in the vicinity of the high latitude arc throughout the event.&lt;/p&gt;

Quantifying the lobe reconnection rate during dominant IMF By periods

2021 ◽  
Author(s):  
Jone Peter Reistad ◽  
Karl Magnus Laundal ◽  
Anders Ohma ◽  
Nikolai Østgaard ◽  
Spencer Hatch ◽  
...  
Keyword(s):  
Transverse Component ◽  
Conceptual Level ◽  
Polar Cap ◽  
Reconnection Rate ◽  
Ionospheric Convection ◽  
Relative Contribution ◽  
Close Proximity ◽  
Lobe Reconnection ◽  
Dipole Tilt ◽  
The Imf

&lt;p&gt;Lobe reconnection is usually considered to play an important role in geospace dynamics only when the Interplanetary Magnetic Field (IMF) is mainly northward. This is because the most common signature of lobe reconnection is the strong sunward convection in the polar cap ionosphere observed during these conditions. During more typical conditions, when the IMF is mainly in a dawn-dusk direction, plasma flows initiated by dayside as well as lobe reconnection map to high latitude ionospheric locations in close proximity to each other. This has been emphasized in the literature earlier, mainly on a conceptual level, but quantifying the relative importance of lobe reconnection to the observed ionospheric convection is highly challenging during these IMF By dominated conditions, since one has to identify and distinguish these regions. By normalizing the ionospheric convection (observed by SuperDARN) to the polar cap boundary (inferred from simultaneous AMPERE observations), we are able to do this separation, allowing us to quantify the relative contribution of both lobe reconnection and dayside/nightisde reconnection to the ionospheric convection pattern. Using this segmentation technique we can get new quantitative insights into the importance of the various mechanisms that affect the lobe reconnection rate. In this presentation we will describe the technique and show results of analysis of periods when the IMF is mainly in the dawn-dusk direction. Our quantification of the average lobe reconnection rate during various conditions yields quantitative knowledge of the importance of the lobe reconnection process, which can act independently in the two hemispheres. We will specifically constrain the influence from parameters such as the dipole tilt angle and the product of IMF transverse component and solar wind velocity.&lt;/p&gt;

The response of ionospheric convection in the polar cap to substorm activity

1995 ◽  
Vol 13 (2) ◽  
pp. 147-158 ◽  
Author(s):  
M. Lester ◽  
M. Lockwood ◽  
T. K. Yeoman ◽  
S. W. H. Cowley ◽  
H. Lühr ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Neutral Line ◽  
Flow Reversal ◽  
Polar Cap ◽  
Substorm Current Wedge ◽  
Expansion Phase ◽  
Ionospheric Convection ◽  
Eiscat Radar ◽  
Current Wedge

Abstract. We report multi-instrument observations during an isolated substorm on 17 October 1989. The EISCAT radar operated in the SP-UK-POLI mode measuring ionospheric convection at latitudes 71°λ-78°λ. SAMNET and the EISCAT Magnetometer Cross provide information on the timing of substorm expansion phase onset and subsequent intensifications, as well as the location of the field aligned and ionospheric currents associated with the substorm current wedge. IMP-8 magnetic field data are also included. Evidence of a substorm growth phase is provided by the equatorward motion of a flow reversal boundary across the EISCAT radar field of view at 2130 MLT, following a southward turning of the interplanetary magnetic field (IMF). We infer that the polar cap expanded as a result of the addition of open magnetic flux to the tail lobes during this interval. The flow reversal boundary, which is a lower limit to the polar cap boundary, reached an invariant latitude equatorward of 71°λ by the time of the expansion phase onset. A westward electrojet, centred at 65.4°λ, occurred at the onset of the expansion phase. This electrojet subsequently moved poleward to a maximum of 68.1°λ at 2000 UT and also widened. During the expansion phase, there is evidence of bursts of plasma flow which are spatially localised at longitudes within the substorm current wedge and which occurred well poleward of the westward electrojet. We conclude that the substorm onset region in the ionosphere, defined by the westward electrojet, mapped to a part of the tail radially earthward of the boundary between open and closed magnetic flux, the "distant" neutral line. Thus the substorm was not initiated at the distant neutral line, although there is evidence that it remained active during the expansion phase. It is not obvious whether the electrojet mapped to a near-Earth neutral line, but at its most poleward, the expanded electrojet does not reach the estimated latitude of the polar cap boundary.

Correction to “Effect of high-latitude ionospheric convection in Sun-aligned polar cap arcs”

1994 ◽  
Vol 99 (A7) ◽  
pp. 13281 ◽  
Author(s):  
J. J. Sojka ◽  
L. Zhu ◽  
D. J. Crain ◽  
R. W. Schunk
Keyword(s):  
High Latitude ◽  
Polar Cap ◽  
Ionospheric Convection

scholarly journals Magnetospheric convection from Cluster EDI measurements compared with the ground-based ionospheric convection model IZMEM

2009 ◽  
Vol 27 (8) ◽  
pp. 3077-3087 ◽  
Author(s):  
M. Förster ◽  
Y. I. Feldstein ◽  
S. E. Haaland ◽  
L. A. Dremukhina ◽  
L. I. Gromova ◽  
...  
Keyword(s):  
High Latitude ◽  
Electric Potential ◽  
Potential Distribution ◽  
Spatial And Temporal Variation ◽  
Convection Pattern ◽  
Polar Cap ◽  
Ionospheric Convection ◽  
Electric Potential Distribution ◽  
Convection Model ◽  
The Imf

Abstract. Cluster/EDI electron drift observations above the Northern and Southern polar cap areas for more than seven and a half years (2001–2008) have been used to derive a statistical model of the high-latitude electric potential distribution for summer conditions. Based on potential pattern for different orientations of the interplanetary magnetic field (IMF) in the GSM y-z-plane, basic convection pattern (BCP) were derived, that represent the main characteristics of the electric potential distribution in dependence on the IMF. The BCPs comprise the IMF-independent potential distribution as well as patterns, which describe the dependence on positive and negative IMFBz and IMFBy variations. The full set of BCPs allows to describe the spatial and temporal variation of the high-latitude electric potential (ionospheric convection) for any solar wind IMF condition near the Earth's magnetopause within reasonable ranges. The comparison of the Cluster/EDI model with the IZMEM ionospheric convection model, which was derived from ground-based magnetometer observations, shows a good agreement of the basic patterns and its variation with the IMF. According to the statistical models, there is a two-cell antisunward convection within the polar cap for northward IMFBz+≤2 nT, while for increasing northward IMFBz+ there appears a region of sunward convection within the high-latitude daytime sector, which assumes the form of two additional cells with sunward convection between them for IMFBz+≈4–5 nT. This results in a four-cell convection pattern of the high-latitude convection. In dependence of the ±IMFBy contribution during sufficiently strong northward IMFBz conditions, a transformation to three-cell convection patterns takes place.

scholarly journals Testing nowcasts of the ionospheric convection from the expanding and contracting polar cap model

Space Weather ◽  
2017 ◽  
Vol 15 (4) ◽  
pp. 623-636 ◽  
Author(s):  
M.-T. Walach ◽  
S. E. Milan ◽  
T. K. Yeoman ◽  
B. A. Hubert ◽  
M. R. Hairston
Keyword(s):  
Polar Cap ◽  
Ionospheric Convection ◽  
Cap Model
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