A laboratory experiment to examine the effect of auroral beams on spacecraft charging in the ionosphere

Siddiqui, M. Umair; Gayetsky, Lisa; Mella, M. R.; Lynch, K. A.; Lessard, M.

doi:10.1063/1.3640512

Cited by 10 publications

(14 citation statements)

References 24 publications

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“…The plasma density is n ; k B is the Boltzmann constant; m i is the ion mass; e is the fundamental electric charge; T ∥ ,

T_{⊥_{1}}

T_{⊥_{2}}

, u ∥ ,

u_{⊥_{1}}

, and

u_{⊥_{2}}

are the temperatures and drift velocities, respectively, measured with respect to the magnetic field direction. The spacecraft potential Φ sc is given by Siddiqui et al [] as

Φ_{sc} = - \frac{k_{normalB} T_{normale}}{e} \ln ((), \sqrt{\frac{m_{normali} T_{normale}}{m_{normale} T_{normali}}}) - V_{ss}

where m e is the electron mass, T i is the (isotropic) ion temperature, T e is the electron temperature (from ERPA, Figure e), and V ss is the spacecraft sphere‐to‐skin voltage difference measured by the COWBOY. The first term represents the idealized float potential of a perfectly conducting sphere; the second term is the measured difference between such a sphere (the electric field probes) and the irregular nonideal spacecraft (this term is reported positive and thus serves to further decrease the spacecraft potential).…”

Section: Discussionmentioning

confidence: 99%

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

et al. 2016

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We present an analysis of in situ measurements from the MICA (Magnetosphere‐Ionosphere Coupling in the Alfvén Resonator) nightside auroral sounding rocket with comparisons to a multifluid ionospheric model. MICA made observations at altitudes below 325 km of the thermal ion kinetic particle distributions that are the origins of ion outflow. Late flight, in the vicinity of an auroral arc, we observe frictional processes controlling the ion temperature. Upflow of these cold ions is attributed to either the ambipolar field resulting from the heated electrons or possibly to ion‐neutral collisions. We measure trueE→×trueB→ convection away from the arc (poleward) and downflows of hundreds of m s−1 poleward of this arc, indicating small‐scale low‐altitude plasma circulation. In the early flight we observe DC electromagnetic Poynting flux and associated ELF wave activity influencing the thermal ion temperature in regions of Alfvénic aurora. We observe enhanced, anisotropic ion temperatures which we conjecture are caused by transverse heating by wave‐particle interactions (WPI) even at these low altitudes. Throughout this region we observe several hundred m s−1 upflow of the bulk thermal ions colocated with WPI; however, the mirror force is negligible at these low energies; thus, the upflow is attributed to ambipolar fields (or possibly neutral upwelling drivers). The low‐altitude MICA observations serve to inform future ionospheric modeling and simulations of (a) the need to consider the effects of heating by WPI at altitudes lower than previously considered viable and (b) the occurrence of structured and localized upflows/downflows below where higher‐altitude heating rocesses are expected.

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“…The plasma density is n ; k B is the Boltzmann constant; m i is the ion mass; e is the fundamental electric charge; T ∥ ,

T_{⊥_{1}}

T_{⊥_{2}}

, u ∥ ,

u_{⊥_{1}}

, and

u_{⊥_{2}}

are the temperatures and drift velocities, respectively, measured with respect to the magnetic field direction. The spacecraft potential Φ sc is given by Siddiqui et al [] as

Φ_{sc} = - \frac{k_{normalB} T_{normale}}{e} \ln ((), \sqrt{\frac{m_{normali} T_{normale}}{m_{normale} T_{normali}}}) - V_{ss}

Section: Discussionmentioning

confidence: 99%

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

et al. 2016

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“…Comparison of T, T e , and a for 3D numerical simulations From the data given in Table I, the temperature, electron temperature, and ionization degree related to HVIGPs were numerically calculated by Eqs. (19) and (20) and listed in Table II.…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…23 e 1 will be discussed later. Equation (20) is the fitting form of the TF model given by Bell. 23 In calculation, the cgs units (length in cm, weight in g, and time in s) are adopted except for the energy and temperature which are in eV.…”

Section: Determination Of the Temperaturementioning

confidence: 99%

“…In this code, the coefficient A is chosen to be 0.02. Equations (19) and (20) are put into the self-developed 2D SPH code and then the 2D hypervelocity impacts can be numerically simulated. In the simulations, the total charges of generated plasmas were counted and compared with the empirical formula 24 to verify the accuracy of the numerical simulations.…”

Section: Simulations With the Self-developed 2d Sph Codementioning

confidence: 99%

“…The electromagnetic emissions of HVIGPs from charged spacecrafts and from the background of the space plasma have also been widely studied. [17][18][19][20][21] However, very few studies have been reported on whether the HVIGPs are in the thermodynamic equilibrium state and how their characteristics depend on the impact parameters.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical and numerical predictions of hypervelocity impact-generated plasma

Song

Ning

2014

Physics of Plasmas

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The hypervelocity impact generated plasmas (HVIGP) in thermodynamic non-equilibrium state were theoretically analyzed, and a physical model was presented to explore the relationship between plasma ionization degree and internal energy of the system by a group of equations including a chemical reaction equilibrium equation, a chemical reaction rate equation, and an energy conservation equation. A series of AUTODYN 3D (a widely used software in dynamic numerical simulations and developed by Century Dynamic Inc.) numerical simulations of the impacts of hypervelocity Al projectile on its targets at different incident angles were performed. The internal energy and the material density obtained from the numerical simulations were then used to calculate the ionization degree and the electron temperature. Based on a self-developed 2D smooth particle hydrodynamic (SPH) code and the theoretical model, the plasmas generated by 6 hypervelocity impacts were directly simulated and their total charges were calculated. The numerical results are in good agreements with the experimental results as well as the empirical formulas, demonstrating that the theoretical model is justified by the AUTODYN 3D and self-developed 2D SPH simulations and applicable to predict HVIGPs. The study is of significance for astrophysical and cosmonautic researches and safety.

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Electrostatic analyzer measurements of ionospheric thermal ion populations

Fernandes

Lynch

2016

JGR Space Physics

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We define the observational parameter regime necessary for observing low‐altitude ionospheric origins of high‐latitude ion upflow/outflow. We present measurement challenges and identify a new analysis technique which mitigates these impediments. To probe the initiation of auroral ion upflow, it is necessary to examine the thermal ion population at 200–350 km, where typical thermal energies are tenths of eV. Interpretation of the thermal ion distribution function measurement requires removal of payload sheath and ram effects. We use a 3‐D Maxwellian model to quantify how observed ionospheric parameters such as density, temperature, and flows affect in situ measurements of the thermal ion distribution function. We define the viable acceptance window of a typical top hat electrostatic analyzer in this regime and show that the instrument's energy resolution prohibits it from directly observing the shape of the particle spectra. To extract detailed information about measured particle population, we define two intermediate parameters from the measured distribution function, then use a Maxwellian model to replicate possible measured parameters for comparison to the data. Liouville's theorem and the thin‐sheath approximation allow us to couple the measured and modeled intermediate parameters such that measurements inside the sheath provide information about plasma outside the sheath. We apply this technique to sounding rocket data to show that careful windowing of the data and Maxwellian models allows for extraction of the best choice of geophysical parameters. More widespread use of this analysis technique will help our community expand its observational database of the seed regions of ionospheric outflows.

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A laboratory experiment to examine the effect of auroral beams on spacecraft charging in the ionosphere

Cited by 10 publications

References 24 publications

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

Measuring the seeds of ion outflow: Auroral sounding rocket observations of low‐altitude ion heating and circulation

Theoretical and numerical predictions of hypervelocity impact-generated plasma

Electrostatic analyzer measurements of ionospheric thermal ion populations

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