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Found 3 entries in the Bibliography.
Showing entries from 1 through 3
| 2019 |
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Satellite-based direct electric field measurements deliver crucial information for space science studies. Yet they require meticulous design and calibration. In-flight calibration of double-probe instruments is usually presented in the most common case of tenuous plasmas, where the presence of an electrostatic structure surrounding the charged spacecraft alters the geophysical electric field measurements. To account for this effect and the uncertainty in the boom length, the measured electric field is multiplied by a parameter called the shorting factor (sf). In the plasmasphere, the Debye length is very small in comparison with spacecraft dimension, and there is no shorting of the electric field measurements (sf = 1). However, the electric field induced by spacecraft motion greatly exceeds any geophysical electric field of interest in the plasmasphere. Thus, the highest level of accuracy in calibration is required. The objective of this work is to discuss the accuracy of the setting sf = 1 and therefore to examine the accuracy of Van Allen Probes electric field measurements below L = 2. We introduce a method to determine the shorting factor near perigee. It relies on the idea that the value of the geophysical electric field measured in the Earth\textquoterights rotating frame of reference is independent of whether the spacecraft is approaching perigee or past perigee, that is, it is independent of spacecraft velocity. We obtain that sf = 0.994 \textpm 0.001. The resulting margins of errors in individual electric drift measurements are of the order of \textpm0.1\% of spacecraft velocity (a few meters per second). Published by: Earth and Space Science Published on: 04/2019 YEAR: 2019 DOI: 10.1029/2018EA000550 DC electric field; double probe instrument; electric drift; plasmasphere; shorting factor; Van Allen Probes |
| 2018 |
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Magnetic activity dependence of the electric drift below L=3 More than two years of magnetic and electric field measurements by the Van Allen Probes are analyzed with the objective of determining the average effects of magnetic activity on the electric drift below L=3. The study finds that an increase in magnetospheric convection leads to a decrease in the magnitude of the azimuthal component of the electric drift, especially in the night-side. The amplitude of the slowdown is a function of L, local time MLT, and Kp, in a pattern consistent with the storm-time dynamics of the ionosphere and thermosphere. To a lesser extent, magnetic activity also alters the average radial component of the electric drift below L=3. A global picture for the average variations of the electric drift with Kp is provided as a function of L and MLT. It is the first time that the signature of the ionospheric disturbance dynamo is observed in near-equatorial electric drift measurements. Published by: Geophysical Research Letters Published on: 04/2018 YEAR: 2018 DOI: 10.1029/2018GL077873 electric drift; electric field; Inner radiation belt; ionospheric disturbance dynamo; plasmasphere; subcorotation; Van Allen Probes |
| 2016 |
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The electric drift E \texttimes B/B2 plays a fundamental role for the description of plasma flow and particle acceleration. Yet it is not well-known in the inner belt and slot region because of a lack of reliable in situ measurements. In this article, we present an analysis of the electric drifts measured below L ~ 3 by both Van Allen Probes A and B from September 2012 to December 2014. The objective is to determine the typical components of the equatorial electric drift in both radial and azimuthal directions. The dependences of the components on radial distance, magnetic local time, and geographic longitude are examined. The results from Van Allen Probe A agree with Van Allen Probe B. They show, among other things, a typical corotation lag of the order of 5 to 10\% below L ~ 2.6, as well as a slight radial transport of the order of 20 m s-1. The magnetic local time dependence of the electric drift is consistent with that of the ionosphere wind dynamo below L ~ 2 and with that of a solar wind-driven convection electric field above L ~ 2. A secondary longitudinal dependence of the electric field is also found. Therefore, this work also demonstrates that the instruments on board Van Allen Probes are able to perform accurate measurements of the electric drift below L ~ 3. Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023613 electric drift; electric field; Inner radiation belt; plasmasphere; subcorotation; Van Allen Probes |
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