14 research outputs found
A Model For Rapid Charging Events on International Space Station
No full textSurface charging by plasma can be a serious issue for any spacecraft. Though significant charging is not observed in all spacecrafts at all times, it only requires a single episode of extreme charging to result in serious damage. The International Space Station (ISS) is an interesting platform to study these charging effects because of its size and relatively high voltage systems. Of the many kinds of charging observed on ISS, the rapid charging events during solar eclipse exit in a low-density ionosphere is not yet understood. This report is an investigation to understand this phenomenon. This report proposes a simple linear model of this nonlinear charging that takes into account the capacitive and resistive natures of conducting and oxidized surfaces is sufficient to describe the phenomenon
Altitudinal Variability of Quiet-Time Plasma Drifts in the Equatorial Ionosphere
No full textIn the modern world, we increasingly depend on space-based systems for our communication, positioning, and navigation systems. These systems depend on electromagnetic waves propagating through the ionosphere. The ionosphere is the medium in the upper atmosphere where, due to presence of the charged atomic and molecular particles and electrons collectively known as plasma, it influences the traveling electromagnetic waves following laws of electrodynamics. Improved models for predicting space weather conditions require improved knowledge of the drifts of these plasmas in the ionosphere. This study is focused on climatology of the altitudinal variations of these plasma drifts in the equatorial latitudes. We used vertical and zonal plasma drift data measured by Jicamarca radars from 150 km to about 600 km altitude in bimonthly bins. One of the objectives of this study is to understand the relationship between E- and F-region drifts during the daytime. The vertical drifts, in general increase with altitude in the morning hours and decrease with altitude in the afternoon. The vertical drifts change mostly linearly from E- to F-region altitudes except in the morning hours of May-June when the gradients are very small. The zonal drifts, on the other hand, show large nonlinear decrease with altitude at the lower altitudes and then slowly decrease with increasing height. We also observed occasional exceptions to these general patterns, especially in the morning hours of March-April and May-June. The E-region zonal drifts show more day-to-day variability compared to higher altitudes. The altitudinal variations during the special periods, known as sudden stratospheric warming periods, have also been studied. While the altitudinal variations do not change much for vertical drifts, the sudden stratospheric events do not seem to affect zonal drifts much.
We also presented altitudinal variations of vertical plasma drifts during late afternoon and evening time when these variations change more rapidly compared to the daytime. For the first time, we presented observations of drifts up to 2000 km altitude. We found that during the evening prereversal enhancement, the drifts increase with altitude up to the F-region peak, above which the drifts decrease with altitude until a height from where they become height independent. This transition from height-dependent to height-independent drifts seems to increase with increasing solar flux. We also addressed the relationship between the vertical and zonal plasma drifts and how the time derivatives of zonal drifts balance the altitudinal gradients of vertical plasma drifts. Neglecting these altitudinal variations would violate the curl-free condition of the electric field in the ionosphere; and thus, these variations are important to be incorporated in the present ionospheric models to improve space weather predictions
Altitudinal Gradients of Plasma Drifts in The Equatorial Ionosphere
No full textThe Earth\u27s ionosphere is the weakly ionized region of the upper atmosphere extending from about 90 km to 800 km. Electrodynamic processes driven by ionospheric electric fields can significantly affect the propagation of radiowaves used in communication, navigation and space based positioning systems, especially in the equatorial region. These processes can be highly variable over space and time and can introduce errors in the transmitted information. One of the ways to understand this equatorial ionospheric electrodynamics is to monitor the vertical and zonal drifts of the plasma in the ionosphere. Traditionally, these drifts were studied in a height averaged sense or a single altitude satellite data neglecting the altitudinal variations in the drifts/electric fields. Also neglecting these gradients contradicts with the irrotational condition of the electric field in the ionosphere. We present results on the climatology and local time variations of equatorial electric field height gradients with emphasis on evening time variations when these gradients change rapidly
Moment Calculations For Low Energy Ions In Jupiter\u27s Magnetotail From Nasa\u27s New Horizons Mission
No full textJupiter\u27s magnetosphere and magnetotail is the largest cohesive structure in our solar system which extends to the orbit of Saturn. One of NASA\u27s objectives is to understand how universal bodies interact with its surroundings. The New Horizons (NH) mission is the first satellite to traverse axially through the Jovian magnetotail and obtain in-situ data. The Solar Wind Around Pluto (SWAP) instrument onboard NH measured low energy ions from 35eV to 7.5 keV in the Jovian magnetotail during its fly-by. We analyzed SWAP data from 500-1750 Jovian radii (RJ) when the spacecraft was spinning. A 3D phase-space density fitting procedure was constructed to calculate fluid moments, such as densities, velocities, Mach numbers, temperatures, and thermal pressures, to better understand the ion characteristics in the magnetotail. The results indicate that Jupiter\u27s magnetotail is a highly dynamic region with tremendous variations
Variable Responses of Equatorial Ionosphere During Undershielding and Overshielding Conditions
No full textSignificance of IMF By and Substorms on Ionospheric Electric Fields: New Results
No full text15th MST Radar Workshop
Session M3: Ionospheric irregularities and IS experiments
May 27 (Sat), Poster Sessionconference objec
Distinctly Different responses of Equatorial F region during Undershielding and Overshielding Conditions
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Daytime plasma drifts in the equatorial lower ionosphere
No full textWe have used extensive radar measurements from the Jicamarca Observatory during low solar flux periods to study the quiet time variability and altitudinal dependence of equatorial daytime vertical and zonal plasma drifts. The daytime vertical drifts are upward and have largest values during September-October. The day-to-day variability of these drifts does not change with height between 150 and 600 km, but the bimonthly variability is much larger in the F region than below about 200 km. These drifts vary linearly with height generally increasing in the morning and decreasing in the afternoon. The zonal drifts are westward during the day and have largest values during July-October. The 150 km region zonal drifts have much larger day-to-day, but much smaller bimonthly variability than the F region drifts. The daytime zonal drifts strongly increase with height up to about 300 km from March through October, and more weakly at higher altitudes. The December solstice zonal drifts have generally weaker altitudinal dependence, except perhaps below 200 km. Current theoretical and general circulation models do not reproduce the observed altitudinal variation of the daytime equatorial zonal drifts. © 2015 American Geophysical Union. All Rights Reserved
