Field-aligned current associated with low-latitude plasma blobs as observed by the CHAMP satellite

Park, J.; Lühr, H.; Stolle, Claudia; Rother, M.; Min, Kyoung Wook; Michaelis, Ingo

doi:10.5194/angeo-28-697-2010

Cited by 9 publications

(11 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If we remove the model output (hereafter called “mean field”) from the CHAMP/FGM data, the remnant (hereafter called “residual field”) reflects geomagnetic fields generated by ionospheric currents. This approach has been widely used in ionospheric studies(e.g., Lühr et al [2004]; Ritter et al [2004]; Stolle et al [2006]; Park et al [2010]) and will be used again in this work. The residual field is transformed into a mean‐field aligned (MFA) system defined by the Pomme 6 model.…”

Section: Observationmentioning

confidence: 99%

Characteristics of F‐region dynamo currents deduced from CHAMP magnetic field measurements

2010

View full text Add to dashboard Cite

Using magnetic field observations of the CHAMP satellite we provide the first comprehensive study of F‐region dynamo currents as a function of season, local time, geographic longitude, and solar activity. From bipolar variations of the zonal magnetic field component the density of vertical current driven by the F‐region dynamo is deduced. The current strength is smallest around June solstice, which is attributed to a reduced F‐region Pedersen conductance caused by a lower electron density and neutral density at that season. During the hours around noon highest current densities are observed. They are flowing downward over the dip equator. A secondary peak of upward currents appears at dusk. The polarity switch occurs between15 and 16 (local time) independent of season. The noontime F‐region dynamo current peaks at longitudes connected to the South Atlantic Anomaly, which can be explained by the enhanced conductivity in the region of reduced B field. The F‐region current at dusk exhibits no peak in the longitude sector of the South Atlantic Anomaly. At noon, the F‐region dynamo currents exhibit a wave 4 longitudinal structure during equinoxes and June solstice. The wave 4 signature becomes weak during December solstice. At dusk the wave 4 signature of F‐region dynamo currents is much reduced in all seasons. This behavior can be explained by the DE3 tidal signature in the zonal wind at CHAMP altitude. F‐region dynamo currents increase linearly with the solar flux index, F10.7, during both noon and dusk time sectors. The increase in current strength with increasing F10.7 is slightly higher at dusk than at noon.

show abstract

Section: Observationmentioning

confidence: 99%

Characteristics of F‐region dynamo currents deduced from CHAMP magnetic field measurements

2010

View full text Add to dashboard Cite

show abstract

“…Ra, 52.35.Kt, 52.25.Fi Filamentary current structures associated with intermittent blobs and filaments, which propagate across magnetic fields, are observed in natural and laboratory plasmas. For example, satellites reveal current filaments aligned with the Earth magnetic field [1], which are transported with ionospheric blobs. On RFX, a reversed field pinch, insertable magnetic probes measured field aligned currents associated with plasma blobs [2].…”

mentioning

confidence: 99%

Direct Two-Dimensional Measurements of the Field-Aligned Current Associated with Plasma Blobs

et al. 2011

View full text Add to dashboard Cite

In simple magnetized toroidal plasmas, field-aligned blobs originate from ideal interchange waves and propagate radially outward under the effect of ∇B and curvature induced E × B drifts. We report on first experimental two-dimensional measurements of the field-aligned current associated with blobs, whose ends terminate on a conducting limiter. A dipolar structure of the current density is measured, which originates from ∇B and curvature induced polarization of the blob and is consistent with sheath boundary conditions. The dipole is strongly asymmetric due to the nonlinear dependence of the current density at the sheath edge upon the floating potential. Furthermore, we directly demonstrate the existence of two regimes, in which parallel currents to the sheath do or do not significantly damp charge separation and thus blob radial velocity.PACS numbers: 52.35. Ra, 52.35.Kt, 52.25.Fi Filamentary current structures associated with intermittent blobs and filaments, which propagate across magnetic fields, are observed in natural and laboratory plasmas. For example, satellites reveal current filaments aligned with the Earth magnetic field [1], which are transported with ionospheric blobs. On RFX, a reversed field pinch, insertable magnetic probes measured field aligned currents associated with plasma blobs [2]. In tokamaks, current structures associated with plasma filaments during edge localized mode (ELMs) were measured using fast imaging combined with external magnetic data on MAST [3], reciprocating magnetic probe data in the Scrape Off Layer (SOL) of ASDEX Upgrade [4] and JET tokamaks [5], and filament modeling and comparison with external coil data on DIII-D [6]. Although the field-aligned nature of these current filaments is a common feature, detailed measurements of the two-dimensional (2D) structure in the plane perpendicular to the confining field are missing, thus preventing a fuller understanding of the origin of the current itself. Furthermore, to date, the importance of parallel currents on blob propagation is only indirectly inferred by comparing experimental blob size-versus-speed scalings [7,8] with theory predictions [9].In this Letter, we report on first two-dimensional measurements of the parallel current density associated with radially propagating blobs in the open field line geometry of a simple magnetized toroidal plasma. The experiments are performed on the TORPEX device [10]. Blobs are generated from ideal interchange waves [11] and are propelled by the effective gravity force associated with ∇B and magnetic field curvature causing charge separation, polarizing the blob and a corresponding radially outwards E × B drift [7,12]. Blobs propagate in a region where both of their ends are connected to a conducting limiter, where a plasma sheath is formed. Time-resolved 2D profiles of parallel current density to the limiter are obtained using data from a single-sided Langmuir probe (LP) and from a specially designed current probe, based on an array of magnetic pick-up coils, which are conditional...

show abstract

“…In related work, Park et al (2010) has considered the reduction in the E field by a high-conductance region in order to explain observations of "plasma blobs." In that work, there is evidence that fieldaligned currents are partially closed across blobs, which are high density regions within an ESF plume (see Krall et al, 2010a, and references within).…”

Section: Discussionmentioning

confidence: 99%

Equatorial spread <I>F</I> fossil plumes

Krall

Huba

Ossakow³

et al. 2010

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. Behaviour of equatorial spread F (ESF) fossil plumes, i.e., ESF plumes that have stopped rising, is examined using the NRL SAMI3/ESF three-dimensional simulation code. We find that fossil bubbles, plasma density depletions associated with fossil plumes, can persist as highaltitude equatorial depletions even while being "blown" by zonal winds. Corresponding airglow-proxy images of fossil plumes, plots of electron density versus longitude and latitude at a constant altitude of 288 km, are shown to partially "fill in" in most cases, beginning with the highest altitude field lines within the plume. Specifically, field lines upon which the E field has fallen entirely to zero are affected and only the low altitude (≤600 km) portion if each field line fills in. This suggests that it should be possible to observe a bubble at high altitude on a field line for which the corresponding airglow image no longer shows a depletion. In all cases ESF plumes stop rising when the flux-tube-integrated ion mass density inside the upper edge of the bubble is equal to that of the nearby background, further supporting the result of Krall et al. (2010b).

show abstract

Field-aligned current associated with low-latitude plasma blobs as observed by the CHAMP satellite

Cited by 9 publications

References 26 publications

Characteristics of F‐region dynamo currents deduced from CHAMP magnetic field measurements

Characteristics of F‐region dynamo currents deduced from CHAMP magnetic field measurements

Direct Two-Dimensional Measurements of the Field-Aligned Current Associated with Plasma Blobs

Equatorial spread <I>F</I> fossil plumes

Contact Info

Product

Resources

About

Field-aligned current associated with low-latitude plasma blobs as observed by the CHAMP satellite

Cited by 9 publications

References 26 publications

Characteristics of F‐region dynamo currents deduced from CHAMP magnetic field measurements

Characteristics of F‐region dynamo currents deduced from CHAMP magnetic field measurements

Direct Two-Dimensional Measurements of the Field-Aligned Current Associated with Plasma Blobs

Equatorial spread &lt;I&gt;F&lt;/I&gt; fossil plumes

Contact Info

Product

Resources

About

Equatorial spread <I>F</I> fossil plumes