60 research outputs found
Artificial plasma experiments. Chemical release observations associated with the CRRES program
This report submitted is the final report and covers work performed under the contract for the period Apr. 12, 1985 - Dec. 23, 1993. The CRRES program investigated earth plasma environment by active experiments in which metal vapors were injected into the upper atmosphere and magnetosphere. The vapor clouds perturb the ambient ionospheric / magnetospheric environment and the effects could be monitored by passive observing instruments. Our part of the CRRES program, the Artificial Plasma Experiment program, was a ground based and aircraft based investigation to observe artificial chemical releases by optical techniques
Measurement of precipitation induced FUV emission and Geocoronal Lyman Alpha from the IMI mission
This final report describes the activities of the Lockheed Martin Palo Alto Research Laboratory in studying the measurement of ion and electron precipitation induced Far Ultra-Violet (FUV) emissions and Geocoronal Lyman Alpha for the NASA Inner Magnetospheric Imager (IMI) mission. this study examined promising techniques that may allow combining several FUV instruments that would separately measure proton aurora, electron aurora, and geocoronal Lyman alpha into a single instrument operated on a spinning spacecraft. The study consisted of two parts. First, the geocoronal Lyman alpha, proton aurora, and electron aurora emissions were modeled to determine instrument requirements. Second, several promising techniques were investigated to determine if they were suitable for use in an IMI-type mission. Among the techniques investigated were the Hydrogen gas cell for eliminating cold geocoronal Lyman alpha emissions, and a coded aperture spectrometer with sufficient resolution to separate Doppler shifted Lyman alpha components
An Evening Sector Ps 6 - Omega Band Event
Article draft. Author list indicative and roughly corresponds to amount of contribution to the article to date.Abstract. Ps 6 magnetic disturbances and associated optical
forms known as omega bands are usually associated
with the morning sector. Some evidence for similar phenomenology
in the evening sector has been presented by
Solovyev et al. (1999). We confirm and extend those results
with high time resolution magnetic and imaging observations
from Athabasca University Geophysical Observatory
for an event that took place on July 27, 2003, along with conjugate
hemisphere imaging from the Polar spacecraft. The
observed signatures indicate sunward drift (westward in the
evening sector). Magnetic perturbations feature negative Y
and transitional Z indicating westward passage of poleward
equivalent currents overhead. As has been suggested by Connors
et al. (2003) to be often the case for morning sector Ps
6/omega bands, initiation of the evening sector event coincided
with substorm onset. From optical and magnetic data
we obtain consistent results for the drift rate of the forms,
which changed during the event. An inner magnetospheric
source is suggested, with triggering of the onset by an increase
in solar wind speed
Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP
Recent imager and radar observations in the nightside polar cap have shown evidence that polar cap patches are associated with localized flow channels. To understand how flow channels propagate from the dayside auroral oval into the polar cap, we use an all-sky imager in Antarctica and DMSP (F13, F15, F16, F17 and F18) to determine properties of density and flows associated with dayside polar cap patches. We identified 50 conjunction events during the southern winter seasons of 2007–2011. In a majority (45) of events, longitudinally narrow flow enhancements directed anti-sunward are found to be collocated with the patches, have velocities (up to a few km/s) substantially larger than the large-scale background flows (~500 m/s) and have widths comparable to patch widths (~400 km). While the patches start with poleward moving auroral forms (PMAFs) as expected, many PMAFs propagate azimuthally away from the noon over a few hours of MLT, resulting in formation of polar cap patches quite far away from the noon, as early as ~6 MLT. The MLT separation from the noon is found to be proportional to the IMF |By|. Fast polar cap flows of \u3e~1500 m/s are predominantly seen during large IMF |By| and small |Bz|. The presence of fast, anti-sunward flow channels associated with the polar cap patches suggests that the flow channels form in the dayside auroral oval through transient reconnection and can be the source of flow channels propagating into the polar cap
TIMED Imaging Photometer Experiment (TIPE)
This document contains a summary of the TIMED Imaging Photometer Experiment (TIPE) instrument study at the time of the termination of project due to TIPE being de-selected from the Thermosphere, Ionosphere and Mesosphere Energetics and Dynamics (TIMED) mission
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Near-Earth initiation of a terrestrial substorm
Despite the characterization of the auroral substorm more than 40 years ago, controversy still surrounds the processes triggering substorm onset initiation. That stretching of the Earth's magnetotail following the addition of new nightside magnetic flux from dayside reconnection powers the substorm is well understood; the trigger for explosive energy release at substorm expansion phase onset is not. Using ground-based data sets with unprecedented combined spatial and temporal coverage, we report the discovery of new localized and contemporaneous magnetic wave and small azimuthal scale auroral signature of substorm onset. These local auroral arc undulations and magnetic field signatures rapidly evolve on second time scales for several minutes in advance of the release of the auroral surge. We also present evidence from a conjugate geosynchronous satellite of the concurrent magnetic onset in space as the onset of magnetic pulsations in the ionosphere, to within technique error. Throughout this time period, the more poleward arcs that correspond to the auroral oval which maps to the central plasma sheet remain undisturbed. There is good evidence that flows from the midtail crossing the plasma sheet can generate north-south auroral structures, yet no such auroral forms are seen in this event. Our observations present a severe challenge to the standard hypothesis that magnetic reconnection in stretched magnetotail fields triggers onset, indicating substorm expansion phase initiation occurs on field lines that are close to the Earth, as bounded by observations at geosynchronous orbit and in the conjugate ionosphere
Time Evolution of the Substorm Current Wedge from Ground and Space-based Magnetic Fields
PDF of a posterOver the past several years, intensive efforts have resulted in a significant
improvement in the ground instrumentation for auroral studies in North America. A
major part of this is due to the THEMIS ground program, both in the U.S. and in Canada.
The THEMIS Ground-Based Observatory network has fielded 10 additional
magnetometers in Canada and Alaska. Further THEMIS magnetometers are part of the
GEONS outreach effort, found in the continental U.S. and Alaska. Athabasca University
initiatives and collaborations have made yet further magnetometer data available, most
notably from a new network of instruments in central Alberta. Several stations of the
University of Tokyo STEP network remain operational, and some have been upgraded.
There is finally a dense enough set of magnetic data that techniques based on forward
modeling, and most relevant to the opportunity afforded by THEMIS, Automated
Regional Modeling (ARM), can be reliably used. These techniques specify where net
field-aligned current (FAC) and ionospheric electric current flow are located. In some
cases the Pedersen system can also be included based on data. Even when it is not, it can
be considered collocated with electrojet locations given by ARM. The extension into
space of the FAC (net or Pedersen) allows comparison with the perturbations observed at
THEMIS. We present results from an event on March 13, 2007, during which THEMIS
in its early orbital configuration was over central North America, clear weather prevailed,
and a substorm took place whose perturbations were ideally suited for inversion using
ARM. At about 5 UT, activations were detected from the ground with magnetic
perturbations also detected from THEMIS above the affected stations. The ground
perturbations are very well represented by a three-dimensional substorm current wedge
(SCW) system, and perturbations in space indicate radial propagation at a time when the
electrojet was expanding poleward. Little longitudinal propagation of the SCW is
suggested by the ground data
Time Evolution of the Substorm Current Wedge from Ground and Space-based Magnetic Fields
Poster SM23A-1188 at AGU Fall Meeting 2007. Updated version of a poster from STAMMS-2, presented in September.Over the past several years, intensive efforts have resulted in a significant improvement in the ground instrumentation for auroral studies in North America. A major part of this is due to the THEMIS ground program, both in the U.S. and in Canada. The THEMIS Ground-Based Observatory network has fielded 10 additional magnetometers in Canada and Alaska. Further THEMIS magnetometers are part of the GEONS outreach effort, found in the continental U.S. and Alaska. Athabasca University initiatives and collaborations have made yet further magnetometer data available, most notably from the new AUTUMN network of instruments in central Alberta, and others in Quebec. Several stations of the University of Tokyo STEP network remain operational, and some have been upgraded. There is finally a dense enough set of magnetic data that techniques based on forward modeling, and most relevant to the opportunity afforded by THEMIS, Automated Regional Modeling (ARM), can be reliably used. These techniques specify where net field-aligned current (FAC) and ionospheric electric current flow are located. In some cases the Pedersen system can also be included based on data. Even when it is not, it can be considered collocated with electrojet locations given by ARM. The extension into space of the FAC (net or Pedersen) allows comparison with the perturbations observed at THEMIS. We present results from an event on March 13, 2007, during which THEMIS in its early orbital configuration was magnetically conjugate to central North America, clear weather prevailed, and a substorm took place whose perturbations were ideally suited for inversion using ARM. At about 5 UT, activations were detected from the ground with magnetic perturbations also detected from THEMIS. The ground perturbations are well represented by a three-dimensional substorm current wedge (SCW) system, and perturbations in space indicate radial propagation at a time when the electrojet expanded poleward. Little longitudinal propagation of the SCW is suggested by the ground data.Canada Research Chairs
Canada Foundation for Innovation
NSERC
Athabasca Universit
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Timing and localization of ionospheric signatures associated with substorm expansion phase onset
In this paper, we present case studies of the optical and magnetic signatures of the characteristics of the first minute of substorm expansion phase onset observed in the ionosphere. We find that for two isolated substorms, the onset of magnetic pulsations in the 24–96 s period wavelet band are colocated in time and space with the formation and development of small-scale optical undulations along the most equatorward preexisting auroral arc prior to auroral breakup. These undulations undergo an inverse spatial cascade into vortices prior to the release of the westward traveling surge. We also present a case study of a multiple activation substorm, whereby discrete onsets of ULF wave power above a predetermined quiet time threshold are shown to be associated with specific optical intensifications and brightenings. Moreover, in the multiple activation substorm event, we show that neither the formation of the small-scale undulations nor the formation of similar structures along a north–south aligned arc is sufficient to produce auroral breakup associated with expansion phase onset. It is only ∼10 min after these two disparate activation regions initiate that auroral breakup and the subsequent formation of a westward traveling surge occur. We discuss the implications of these results in terms of the triggering mechanisms likely to be occurring during these specific events
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