Future beam experiments in the magnetosphere with plasma contactors: How do we get the charge off the spacecraft?

Delzanno, Gian Luca; Borovsky, Joseph E.; Thomsen, M. F.; Moulton, J. David; MacDonald, E.

doi:10.1002/2014ja020608

Cited by 18 publications

(47 citation statements)

References 37 publications

(49 reference statements)

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“…This happens when the ions have reached the outer wall

{\overset{r}{true}}_{2}

: At this point the charge that enters the system,

Î_{b} τ

, is equal to the one that leaves the system,

Î_{i} τ

, and, considering also that the quasi‐neutral surface is static, the system is in steady state. Comparing simulations B1 and B2, one can see that the asymptotic spacecraft potential is lower for simulation B2 corresponding to a larger initial area of the contactor, confirming what was already found in Delzanno et al ().…”

Section: Resultssupporting

confidence: 87%

“…Furthermore, from Table we obtain

ψ_{sc}^{\max} \propto {((), \frac{m_{i}}{m_{e}})}^{γ}

with γ ∈[0.34,0.37]. Although expression is only based on three sets of two data points, it is consistent with the scaling law proposed in Delzanno et al (),

ψ_{sc}^{\max} \propto {((), m_{i} false/ m_{e})}^{0.4}

.…”

Section: Resultssupporting

confidence: 84%

“…This is because when the beam is turned on, the net electron contactor current is reduced to give

Î_{b} + Î_{e} ≃ Î_{i}

(Delzanno et al, ), and therefore, some (or all) contactor electrons are reabsorbed by the spacecraft. In the limit when

Î_{b} = Î_{i}

, however, the simulation results of Delzanno et al () show that the electron contactor cloud readjusts quickly and then remains constant. Thus, in our model, we use

{\overset{r}{true}}_{qn} false(τ false) = {\overset{r}{true}}_{qn, 0},

where

{\overset{r}{true}}_{qn, 0}

is a constant.…”

Section: Physics Model Of Spacecraft Potential and Contactor Dynamicsmentioning

confidence: 99%

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Spacecraft‐Charging Mitigation of a High‐Power Electron Beam Emitted by a Magnetospheric Spacecraft: Simple Theoretical Model for the Transient of the Spacecraft Potential

et al. 2018

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A spacecraft‐charging mitigation scheme necessary for the operation of a high‐power electron beam in the low‐density magnetosphere is analyzed. The scheme is based on a plasma contactor, that is, a high‐density charge‐neutral plasma emitted prior to and during beam emission and its ability to emit high ion currents without strong space‐charge limitations. A simple theoretical model for the transient of the spacecraft potential and contactor expansion during beam emission is presented. The model focuses on the contactor ion dynamics and is valid in the limit when the ion contactor current is equal to the beam current. The model is found in very good agreement with particle‐in‐cell simulations over a large parametric study that varies the initial expansion time of the contactor, the contactor current, and the ion mass. The model highlights the physics of the spacecraft‐charging mitigation scheme, indicating that the most important part of the dynamics is the evolution of the outermost ion front, which is pushed away by the charge accumulated in the system by the beam. The model can be also used to estimate the long‐time evolution of the spacecraft potential. For a short contactor expansion (0.3‐ or 0.6‐ms helium plasma or 0.8‐ms argon plasma, both with 1‐mA current) it yields a peak spacecraft potential of the order of 1–3 kV. This implies that a 1‐mA relativistic electron beam would be easily emitted by the spacecraft.

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“…This happens when the ions have reached the outer wall

{\overset{r}{true}}_{2}

: At this point the charge that enters the system,

Î_{b} τ

, is equal to the one that leaves the system,

Î_{i} τ

Section: Resultssupporting

confidence: 87%

“…Furthermore, from Table we obtain

ψ_{sc}^{\max} \propto {((), \frac{m_{i}}{m_{e}})}^{γ}

with γ ∈[0.34,0.37]. Although expression is only based on three sets of two data points, it is consistent with the scaling law proposed in Delzanno et al (),

ψ_{sc}^{\max} \propto {((), m_{i} false/ m_{e})}^{0.4}

.…”

Section: Resultssupporting

confidence: 84%

“…This is because when the beam is turned on, the net electron contactor current is reduced to give

Î_{b} + Î_{e} ≃ Î_{i}

(Delzanno et al, ), and therefore, some (or all) contactor electrons are reabsorbed by the spacecraft. In the limit when

Î_{b} = Î_{i}

, however, the simulation results of Delzanno et al () show that the electron contactor cloud readjusts quickly and then remains constant. Thus, in our model, we use

{\overset{r}{true}}_{qn} false(τ false) = {\overset{r}{true}}_{qn, 0},

where

{\overset{r}{true}}_{qn, 0}

is a constant.…”

Section: Physics Model Of Spacecraft Potential and Contactor Dynamicsmentioning

confidence: 99%

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Spacecraft‐Charging Mitigation of a High‐Power Electron Beam Emitted by a Magnetospheric Spacecraft: Simple Theoretical Model for the Transient of the Spacecraft Potential

et al. 2018

Self Cite

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“…We note that a naive view of equation would suggest that one could balance

I_{b}^{e}

by emitting an ion beam

I_{b}^{i}

of equal current,

I_{b}^{i} = I_{b}^{e}

, without the need for a contactor plasma. In practice, however, this idea does not work because for parameters of interest the ion beam current is above the Child‐Langmuir space charge limit [ Child , ] and only a small fraction of the ion beam current can really be emitted [ Wang and Lai , ; Delzanno et al , ]. On the other hand, a different strategy to enable electron beam emission in space, again based on the plasma contactor, was put forward in Delzanno et al [].…”

Section: Discussion Of Different Strategies For Electron Beam Emissiomentioning

confidence: 99%

“…One can imagine that the contactor plasma reduces the positive charge on the spacecraft by either (a) collecting ambient magnetospheric electrons or (b) emitting ions. In a prior analysis performed in vacuum [ Delzanno et al , ] it was shown that ion emission from the surface of the contactor plasma cloud into three dimensions may provide a mechanism to allow beam experiments in the magnetosphere to operate.…”

Section: Introductionmentioning

confidence: 99%

Future beam experiments in the magnetosphere with plasma contactors: The electron collection and ion emission routes

et al. 2015

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Experiments where a high-voltage electron beam emitted by a spacecraft in the low-density magnetosphere is used to probe the magnetospheric configuration could greatly enhance our understanding of the near-Earth environment. Their challenge, however, resides in the fact that the background magnetospheric plasma cannot provide a return current that balances the electron beam current without charging the spacecraft to such high potential that in practice prevents beam emission. In order to overcome this problem, a possible solution is based on the emission of a high-density contactor plasma by the spacecraft prior to and after the beam. We perform particle-in-cell simulations to investigate the conditions under which a high-voltage electron beam can be emitted from a magnetospheric spacecraft, comparing two possible routes that rely on the high-density contactor plasma. The first is an "electron collection" route, where the contactor has lower current than the electron beam and is used with the goal of connecting to the background plasma and collecting magnetospheric electrons over a much larger area than that allowed by the spacecraft alone. The second is an "ion emission" route, where the contactor has higher current than the electron beam. Ion emission is then enabled over the large quasi-spherical area of the contactor cloud, thus overcoming the space charge limits typical of ion beam emission. Our results indicate that the ion emission route offers a pathway for performing beam experiments in the low-density magnetosphere, while the electron collection route is not viable because the contactor fails to draw a large neutralizing current from the background.

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Can an electron gun solve the outstanding problem of magnetosphere‐ionosphere connectivity?

et al. 2016

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Determining the magnetic connectivity between magnetospheric phenomena and ionospheric phenomena is an outstanding problem of magnetospheric and ionospheric physics. Accurately establishing this connectivity could answer a variety of long‐standing questions. The most viable option to solve this is by means of a high‐power electron beam fired from a magnetospheric spacecraft and spotted at its magnetic footpoint in the ionosphere. This has technical difficulties. Progress has been made on mitigating the major issue of spacecraft charging. The remaining physics issues are identified, together with the need for a synergistic effort in modeling, laboratory experiments, and, ultimately, testing in space. The goal of this commentary is to stimulate awareness and interest on the magnetosphere‐ionosphere connectivity problem and possibly accelerate progress toward its solution.

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Future beam experiments in the magnetosphere with plasma contactors: How do we get the charge off the spacecraft?

Cited by 18 publications

References 37 publications

Spacecraft‐Charging Mitigation of a High‐Power Electron Beam Emitted by a Magnetospheric Spacecraft: Simple Theoretical Model for the Transient of the Spacecraft Potential

Spacecraft‐Charging Mitigation of a High‐Power Electron Beam Emitted by a Magnetospheric Spacecraft: Simple Theoretical Model for the Transient of the Spacecraft Potential

Future beam experiments in the magnetosphere with plasma contactors: The electron collection and ion emission routes

Can an electron gun solve the outstanding problem of magnetosphere‐ionosphere connectivity?

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