Solar cycle variations of the Cluster spacecraft potential and its use for electron density estimations

Lybekk, B.; Pedersen, Å.; Haaland, Stein; Svenes, K.; Fazakerley, A. N.; Masson, A.; Taylor, M. G. G. T.; Trotignon, Jean-Gabriel

doi:10.1029/2011ja016969

Cited by 57 publications

(106 citation statements)

References 36 publications

(31 reference statements)

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“…The probe-toprobe separation is 88 m. The instrument can be used to obtain the electric field by taking the potential difference between two probes. We also use measurements of the potential difference between the probes and spacecraft, often refereed to as the spacecraft potential, to estimate the plasma density , Lybekk et al 2012.…”

Section: The Way To a Solutionmentioning

confidence: 99%

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Previously hidden low-energy ions: a better map of near-Earth space and the terrestrial mass balance

André

2015

Phys. Scr.

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This is a review of the mass balance of planet Earth, intended also for scientists not usually working with space physics or geophysics. The discussion includes both outflow of ions and neutrals from the ionosphere and upper atmosphere, and the inflow of meteoroids and larger objects. The focus is on ions with energies less than tens of eV originating from the ionosphere. Positive low-energy ions are complicated to detect onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. We have invented a technique to observe low-energy ions based on the detection of the wake behind a charged spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the ion density and the outward flux in large volumes in the magnetosphere. The global outflow is of the order of 10 26 ions s -1 . This is a significant fraction of the total number outflow of particles from Earth, and changes plasma processes in near-Earth space. We compare order of magnitude estimates of the mass outflow and inflow for planet Earth and find that they are similar, at around 1 kg s −1 (30 000 ton yr −1 ). We briefly discuss atmospheric and ionospheric outflow from other planets and the connection to evolution of extraterrestrial life.

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Section: The Way To a Solutionmentioning

confidence: 99%

“…The plasma density can be estimated by calibrating observations of the spacecraft potential obtained by the Cluster EFW instrument , Svenes et al 2008, Lybekk et al 2012, Haaland et al 2012b.…”

Section: The Solutionmentioning

confidence: 99%

Previously hidden low-energy ions: a better map of near-Earth space and the terrestrial mass balance

André

2015

Phys. Scr.

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“…The slopes of the fitted lines are slightly variable, which is most likely owing to some scatter in the data. As pointed out by and later by Lybekk et al (2012), the downward trend of the spacecraft potential correlates with solar activity. Looking at the 10.7 cm radio flux progression in the last solar cycle it becomes evident that the period 2001 to 2004 was in the declining phase.…”

Section: Principle Of Active Spacecraft Potential Controlmentioning

confidence: 99%

“…The correlation between spacecraft potential and solar activity has been further elaborated by Lybekk et al (2012). These authors studied the photo-emission current escaping from the spacecraft (I phs ) as a function of the spacecraft potential (more exactly, of V s − V p ) for Cluster in the years 2001 to 2006.…”

Section: Principle Of Active Spacecraft Potential Controlmentioning

confidence: 99%

“…Flux and energy spectrum of photoelectrons emitted from spacecraft surfaces have been studied by numerous authors for various spacecraft, among them ISEE (Escoubet et al 1997), Geotail (Nakagawa et al 2000), and Cluster (Lybekk et al 2012). It appears as a common feature, as for example stated by Pedersen (1995), that photoelectrons created by solar EUV radiation exist in two regimes, one at energies near 1 eV and another one at 5-15 eV, whereby the flux of the population at lower energy is approximately an order of magnitude higher than that of the latter.…”

Section: Principle Of Active Spacecraft Potential Controlmentioning

confidence: 99%

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Active Spacecraft Potential Control Investigation

et al. 2014

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In tenuous plasma the floating potential of sunlit spacecraft reaches tens of volts, positive. The corresponding field disturbs measurements of the ambient plasma by electron and ion sensors and can reduce micro-channel plate lifetime in electron detectors owing to large fluxes of attracted photoelectrons. Also the accuracy of electric field measurements may suffer from a high spacecraft potential. The Active Spacecraft Potential Control (ASPOC) neutralizes the spacecraft potential by releasing positive charge produced by indium ion emitters. The method has been successfully applied on other spacecraft such as Cluster and Double Star. Two ASPOC units are present on each spacecraft. Each unit contains four ion emitters, whereby one emitter per instrument is operated at a time. ASPOC for the Magnetospheric Multiscale (MMS) mission includes new developments in the design of the emitters and the electronics. New features include the use of capillaries instead of needles, new materials for the emitters and their internal thermal insulators, an extended voltage and current range of the electronics, both for ion emission and heating purposes, and a more capable control software. This enables lower spacecraft potentials, higher reliability, and a more uniform potential structure in the spacecraft's sheath compared to previous missions. Results from on-ground testing demonstrate compliance with requirements. Model calculations confirm the findings from previous applications that the plasma measurements will

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Photoelectron‐mediated spacecraft potential fluctuations

et al. 2014

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Electric field fluctuations such as those due to plasma waves in Earth's magnetosphere may modulate photoelectrons emitted from spacecraft surface, causing fluctuations in spacecraft potential. We experimentally investigate such photoelectron-mediated spacecraft potential fluctuations. The photoelectric charge of a spacecraft model is found to increase with increasing applied electric field as more photoelectrons escape the spacecraft model surface and dissipates with a decrease in the electric field through collection of ambient plasma electrons. When the applied electric field is driven to oscillate at a frequency lower than the response frequency of the spacecraft model, the surface potential follows the electric field oscillations. The spacecraft model maintains an approximately constant potential if the electric field oscillations are driven at a much higher frequency. When a high-frequency electric field modulated by a low-frequency envelope is applied, rectified oscillations in the potential of the spacecraft model are observed. Our experimental results indicate that photoelectron-mediated wave rectifications must be taken into account when spacecraft potential fluctuations are used to infer plasma density structures.

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Solar cycle variations of the Cluster spacecraft potential and its use for electron density estimations

Cited by 57 publications

References 36 publications

Previously hidden low-energy ions: a better map of near-Earth space and the terrestrial mass balance

Previously hidden low-energy ions: a better map of near-Earth space and the terrestrial mass balance

Active Spacecraft Potential Control Investigation

Photoelectron‐mediated spacecraft potential fluctuations

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