SM31A-1200 0800h
Observations of Earth's Bow Shock Structure from the First Chinese scientific Satellite, Double Star
New features of Earth's bow shock structure have been observed by the HIA ion experiment on the first Chinese scientific satellite, Double Star. At times of coincident apogee, the Cluster spacecraft served as monitors of the upstream condition providing information from nearly identical instruments. The combination of the orbit with an apogee approximately at 13.5 Re and data obtained in high time resolution (4s) has permitted observations of the shock structure with unprecendented detail. We present examples of laminar and turbulent shocks observed in late February and early March (2004) when the Double Star apogee was located on the sunward side skimming the shock boundary. This talk will discuss (1) evolutionary features of ion distributions of the solar wind slowdown converting almost the entire flow energy into thermal energy, (2) microscopic features that could be signifying kinetic processes at work and (3) ordering of density, bulk velocity and temperature to show the distribution of solar wind momentum and energy throughout the shock transition.
SM31A-1201 0800h
First results of the HIA instrument on the Tan Ce 1 Double Star near Equatorial Spacecraft
On December 29, 2003, the Chinese spacecraft Tan Ce 1 (TC 1), first component of the Double Star mission, has been launched with success in a low latitude orbit. In the frame of the scientific cooperation between the Academy of Sciences of China and ESA, several European instruments identical to those developed for the Cluster spacecraft were installed on board this spacecraft. The HIA (Hot Ion Analyzer) instrument on-board TC 1 is an ion spectrometer identical to the HIA sensor of the CIS instrument on-board the 4 Cluster spacecraft. This instrument has been specially adapted for TC 1. It measures the 3D distribution functions of the ions between 5 eV per q and 32 keV per q without mass discrimination. TC 1 is like a fifth Cluster to study the interaction of the solar wind with the magnetosphere and to study the storms and substorms. HIA was commissioned in February 2004. Since this period HIA has done very good measurements in the solar wind, the magnetosheath, the dayside and nightside plasma sheet, the ring current and the radiation belts. We will present the first results in coordination with the CIS Cluster measurements. These include for example ion dispersion structures in the bow shock and ion beams close to the magnetopause.
SM31A-1202 0800h
Interplanetary Shock Interaction with the Magnetosphere: Model Results
The interaction of an abrupt change in the solar wind dynamic pressure with the magnetosphere is one of the fundamental problems in space plasma physics. We employ the Bats-R-Us model with high temporal (20 s) and spatial (0.125 RE maximum) resolution to address this problem. The interaction of the interplanetary shock with the bow shock causes the latter to begin moving inward and launches a fast mode wave into the magnetosheath. The fast mode wave keeps pace with the interplanetary shock in the plane containing the interplanetary magnetic field (IMF), but moves ahead in the plane perpenedicular to the (northward) IMF. The interaction of the transmitted shock with the magnetopause causes the latter boundary to move inward and launches a fast mode wave into the magnetosphere. The fast mode wave is reflected at the plasmapause. The reflected wave further enhances outer magnetospheric magnetic field strengths, causes the magnetopause to move back outward, and is transmitted into the magnetosheath. When it reaches the bow shock it causes that boundary to move back outward also. Both the magnetopause and the bow shock move inward and outward smoothly during the entire process via a nearly global breathing mode. No large amplitude boundary waves are generated. For discontinuities oriented along the spiral IMF, the boundary motion spreads both dawnward and duskward from an initial location at post-noon local times.
SM31A-1203 0800h
Cluster investigation of the plasma depletion layer at the high-latitude dayside magnetopause
The Earth's magnetosheath consists of shocked solar wind plasma which is draped and diverted around the obstacle of the Earth's magnetic field. Unless magnetic reconnection at the dayside magnetopause occurs at a rate high enough to sustain the required flux and plasma transport, magnetic flux pile-up and associated plasma depletion is expected to occur as an inherent part of this process. Many details of when, how, and to what extent this happens are not well known. Here we report on magnetic flux pile-up and associated plasma depletion at the high-latitude dayside magnetopause observed with the constellation of the Cluster satellites. Observations from the first large-separation Cusp phase of the Cluster mission carried out during the first half of 2003 have been utilized. Near-radial separation of more than one Earth radius between pairs of spacecraft as they traverse the southern hemisphere, high-latitude magnetosheath and magnetopause is obtained at these times. This constellation allows us to distinguish between temporal and spatial variations in the field and plasma parameters and, hence, to determine unambiguously the characteristics of the plasma depletion layer at the high-latitude dayside magnetopause. Our results demonstrate that flux pile-up and plasma depletion occur for a variety of solar wind and interplanetary magnetic field conditions and exhibit complex dynamical features related to magnetopause dynamics.
SM31A-1204 0800h
Interball-1 Observations of FTEs
We present the results of a survey of FTEs in high-time resolution (6s) observations by the magnetometers on the Interball-1 spacecraft from 1995 to 1999. The orbit of Interball-1 permitted the spacecraft to observe the low- and mid-latitude (~50 degrees) dayside and flank magnetopause. We have identified more than 500 FTEs over a wide range of latitudes and longitudes. They typically exhibit amplitudes in the range from 6 to 20 nT. The direction of event motion can be determined from the sense of the magnetic field component normal to the nominal magnetopause. Both northward (+,-) and southward (-, +) moving events have been observed over the full range of latitudes covered. We present case studies of the structure of individual events and the results for event occurrence and motion as a function of solar wind conditions and location on the magnetopause. We use simultaneous Wind, Geotail, or IMP-8 observations to determine prevailing solar wind conditions and event occurrence patterns and thereby discriminate between proposed models for event generation.
SM31A-1205 0800h
Magnetic Reconnection for Southward and Northward IMF- Coordinate Observations by TC1 and Cluster on Feb.13, 2004
From 04:40 to 05:20 UT on Feb. 13, 2004, the TC1 satellite of Chinese-ESA joint Double Star Mission was located in the dayside magnetopause boundary near the equator, its GSM position was (9.5, 4.1, -0.4) RE; in the mean time the Cluster four spacecraft were traversing the southern high-latitude magnetopause region, with GSM coordinates being (7.5, 1.8, -10.2) RE. During this time interval, TC1 encountered with the magnetopause four times, the spacecraft saw two magnetic reconnection (MR) events for southward IMF, and two MR events for northward IMF; meanwhile Cluster observed a southward IMF MR and a northward IMF MR phenomenon. A preliminary analysis of these events is made in the present paper. The results are briefly summarized as follows: (1) All MR events are found to be of Component Reconnection type. In the northward IMF BZ cases a noticeably negative IMF BY component is present. (2) In southward IMF BZ cases, TC1 saw a FTE flux rope and a high-speed plasma flow in the magnetospheric low-latitude boundary layer (LLBL) in each event; while Cluster found a magnetospheric flux rope in high-latitudes. (3) For southward IMF, the reconnection structures measured by Cluster in high-latitudes and TC1 in low-latitudes were both originated from the MR process near the dayside equator. (4) In northward IMF BZ cases, the MR phenomenon observed by TC1 near the dayside equatorial plane seems to be closely related to the presence of a noticeable IMF BY. In the two events observed the X-line probably was passing through somewhere between the dayside equatorial magnetopause and the cusp region. For the 04:46-04:49 (UT) event, MR seemed to occur northward of TC1; while for the 05:16-05:18 (UT) event, MR possibly took place southward of the TC1 and northward of Cluster. (5) MR for northward IMF BZ may play a role in the formation of the LLBL and the magnetosheath boundary layer (MSBL).
SM31A-1206 0800h
Monitoring the ion Entry in the High-Altitude Cusp
The Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft in the dayside magnetosphere can detect neutral particles that are emitted in the magnetosheath flow. A recent study [Taguchi et al. JGR, 2004] has shown that the LENA emissions observed in the direction of the high-latitude sheath during relatively high dynamic pressures reflect the cusp indentation in the magnetopause shape, and that monitoring the cusp motion, which responds to the large variations of IMF Bz, is possible using LENA. In this study we report on simultaneous observations of the high-altitude cusp from IMAGE/LENA and Polar/TIDE during negative Bz of IMF, and those of the high- and low-altitude cusps from IMAGE/LENA and the SuperDARN radar for positive Bz. Analyses from the former observation have shown that the LENA high-latitude sheath emission consists of two parts: the stable emission at the higher-latitudes (which can be interpreted as the cusp indentation signal) and the lower-latitude emission, and that the appearance of this lower-latitude emission coincides with the start of the Polar observation of the cusp ion entry in similar noon meridian. This coincidence strongly suggests that the incoming cusp ions charge-exchange with the hydrogen exosphere in the entry layer. For the latter observation, we deal with an event for which emission is strong in LENA_fs field-of-view looking into the region poleward of the cusp, or the plasma mantle. During this event, the SuperDARN radar was receiving strong backscattered signals from the very high-latitude ionosphere. Comparison between the LENA and radar data shows that the reversed convection is clearly enhanced in the ionosphere in concurrence with the appearance of the LENA emission, suggesting that LENA can monitor the ion flow caused by reconnection poleward of the cusp. Detailed characteristics of the distribution of the emission will be presented, and the spatial extent of the reconnection region and its temporal variations will be discussed.
SM31A-1207 0800h
Substorms During Prolonged Northward Interplanetary Magnetic Field
We have studied substorm events under a condition of prolonged northward interplanetary magnetic field (IMF). In substorms on January 19, 1998, a series of expansion onsets and intensifications was observed by Polar UVI. The IMF remained northward for more than 20 hours before the expansion onsets, except for several very short and small southward excursions. During this period, ionospheric convection was very weak. GEOTAIL observed total pressure increases in the magnetotail at $-25>X>-30$ $R_E$, probably caused by an enhancement in the solar wind dynamic pressure and the large IMF $B_y$ component. At the substorm onsets, GEOTAIL observed fast tailward flows and southward magnetic fields, associated with plasmoids, suggesting that magnetic reconnection occurred earthward of GEOTAIL. The GOES satellites observed dipolarizations. There were no large changes in the solar wind and the IMF around the onsets. On the basis of these observations, a possible substorm mechanism will be discussed.
SM31A-1208 0800h
Correlation between Large-Amplitude Electric Field Signatures Observed by Polar and Cluster within the Terrestrial Plasma Sheet and Ground-Based Signatures of Substorm Onset
The precession of the Polar spacecraft orbit puts apogee (~9 Re) near the equator during 2000-2003 and allows correlative studies of electric fields and plasmas between Polar and the satellites of the Cluster constellation (apogee ~19 Re). This allows one to preview the sorts of radial and azimuthal alignments planned for the inner satellites of the THEMIS mission, and to better understand the relationships between the in-situ plasma and field measurements and the ground-based signatures of substorm onset. We have identified several dozen events spanning this interval where large-amplitude ($>$ 50 mV/m), temporally isolated, impulsive electric field fluctuations are identified on both Polar and Cluster. We compare the relative geomagnetic positions, timing, and amplitudes of each event as well as the relationship between those parameters and the ground-based (AE and magnetometer chain data) and orbital imaging signatures (IMAGE and Polar) of substorm onset.
SM31A-1209 0800h
Cluster/DSP observation of current sheet oscillations
Previous Cluster observations have shown that the flapping motions of the Earth's magnetotail are of internal origin and that kink-like waves are emitted from the central part of the tail and propagate toward the tail flanks. The newly launched Double Star Program (DSP) satellite allows us to investigate current sheet at 10-13 Re in the tail. Using conjunctions with Cluster we will have simultaneous observations at 10-13 and 16-19 Re of these flapping motions. In this paper, we present the first results of current sheet oscillations observed by the Cluster and Double Star satellites during the 2004 magnetotail traverses.
SM31A-1210 0800h
Signature of tail current disruption in the near-Earth plasma sheet
We investigate a sequential dipolarization event in the near-Earth plasma sheet observed by the GEOTAIL satellite on August 31, 1999, at (Xgsm, Ygsm)=(-8.3 Re, -5.1 Re), using high-time-resolution data of a fluxgate magnetometer (16-Hz sample), a search-coil magnetometer (128 Hz), and electric field (64 Hz). Two dipolarizations were observed during a short time interval of 3 min. The elevation angles of magnetic field suddenly decreased 2-4 s prior to the dipolarization. Using high-time resolution magnetic and electric field data, we found characteristic field oscillations with frequencies of 5-20 Hz and amplitudes of 1-3 mV/m at the time of the sudden decrease of elevation angle. We suggest that the sudden decrease of elevation angles prior to the dipolarization is a signature of tail current disruption, which is caused by the observed characteristic field oscillations.
SM31A-1211 0800h
Polar Observations of the Near Equatorial Plasma Sheet Near 9 RE: Radial Dynamics
In 2001, 2002 and 2003, the Polar spacecraft probed the near equatorial plasma sheet at 9 RE near local midnight. Often the magnetic field magnitude is very low in this region of space, below 5 nT. A variety of dynamic signatures are seen in the magnetic field including mirror mode waves and sudden recoveries of the field, possibly inward moving compressions, possibly associated with bursty bulk flows. We examine measurements closer to Earth at geosynchronous orbit and farther from Earth (Cluster) to determine the origin of these dynamic compressions in preparation for the THEMIS mission that will probe the region beyond Polar's apogee.
SM31A-1212 0800h
Investigation of Substorm Onset Trigging by Mutiple Satelltes
ubstorms are so complex that many issues related to them remain very controversial. Many models have been proposed to explain substorm activity. These models can be broadly classified into two categories depending on the cause of the expansion onset. The first invokes processes in the near-Earth region ($|$X$|$ $<$ 15 Re) such as current sheet disruption, instability triggered by reduction of interplanetary electric field, or some feed back instabilities near the ionosphere. The other invokes mid-tail magnetic reconnection beyond $|$X$|$ $>$ 15 Re as a source of plasma flowing earthward. Deceleration of this earthward flowing plasma and pileup of magnetic flux pileup close to the Earth is then the cause of near-Earth disturbances. A possible way to distinguish the cause of substorm expansion onset is to examine the relative timing of magnetotail disturbances. If the near-Earth region is the source region of substorm onset, a disturbance should be first observed in the near-Earth region and later in the midtail. Similarly, the opposite time delay should be observed if the mid-tail reconnection is the source of substorm expansion onset. In this study, we have identified several candidate events with chance conjuctions of GOES, GEOTAIL, POLAR, and Cluster. Data from auroral imagers, ground magnetometers, Pi 2 pulsation detectors, and synchronous particle detectors will be used to establish accurate onset times. IMF observations will be accurately time propagated by Weimer et al [2003] algorithm. The starting time of near and mid-tail disturbance from these multi-satellite observation will be compared with substorm onset time to establish a relative timing pattern during substorms.
SM31A-1213 0800h
Cluster/Double Star Observations of Substorm Dipolarization
Simultaneous observations of the inner magnetosphere and the mid tail are essential in substorm studies because of the initial local onset and the subsequent global expansion of the disturbance. Particularly, how these two key regions are linked in terms of fast flow and magnetic field dipolarizations are yet to be determined to understand the mechanism of substorm development. In this paper, we present the first analysis of substorm dipolarizations observed by Cluster and Double Star during the 2004 summer, when successive radial conjunctions between 10-12 Re and 16-19 Re were realized. By using multi-point analysis techniques, the direction and speed of the propagation is determined using Cluster and is then compared with the global propagation of the disturbances with Double Star. Recurrence of these dipolarization events enabled us to draw a more concise picture of the substorm development.
SM31A-1214 0800h
Meso-Scale Dynamics of the Near-Earth Plasma Sheet During Breakups
This study is focused on the separation of signatures of the local inner edge pseudo-breakup, breakup at full onset, and bursty flows. Sample events are presented in support of the following. A pre-breakup equator-most arc appears and intensifies at the growth phase in association with the stretching of the near-Earth magnetotail. The latter appears to be the main energy reservoir for the breakup. Sufficient stretching of the inner PS is compulsory for the arc intensification but may be not sufficient for a breakup. In some cases, the equatorial plasma sheet and arc represent a marginally stable system. Once the energy is stored in the inner plasma sheet and arc system, breakup can be triggered by various mechanisms. This can be an internal instability starting with no evident external influence (e.g., nonlinear ballooning instability). The instability of the inner PS can also start in association with the solar wind magnetic field changes (as the northward turning causing the changes of convection in the magnetosphere) or as a result of the earthward traveling perturbations of the more distant magnetotail. Externally and internally triggered breakups manifest the same signatures (onset of Pi2s, dipolarization in the near-Earth PS, vortex and electrojet expansion, etc.) When the entire PS becomes very thin, the near-Earth breakup region interacts with the NENL region. Interaction can be initiated by both the mid-tail (NENL) and near-Earth breakup activations. These two processes can also be seen virtually at the same time, suggesting that stretching of the entire magnetotail gives a start to both activations. In that sense, the question ``how does the substorm start?" may not be well posed: full onset is an interaction of the near-Earth breakup region and more distant (NENL) tail disruption in which both processes play an essential role.
SM31A-1215 0800h
A Multisatellite View of the Recovery Phase of Substorms
The growth and expansion phases of substorms have been extensively analyzed, while the recovery phase has not received as much attention by the magnetospheric research community. The recovery phase has been generally assumed to be merely a return of the system to the quiet time state, while more detailed analysis has shown it to have a fairly complex process. This study will be looking at the recovery phase in greater detail. Also, the ability to look at substorm events both telescopically and microscopically has been realized by using the CLUSTER constellation in conjunction with POLAR and various geostationary satellites. Using events from the 2002 Cluster tail season, we will be focusing on the recovery phase of substorm sequences. CLUSTER data will provide a microphysical picture of the event, while the entire radial constellation beginning with solar wind data at the L1 point, through geostationary satellites, POLAR and CLUSTER will enable us to view the macroscopic picture. We have used the Lyon-Federer-Mobarry MHD simulation code to numerically model several of these events. These observations and model comparisons are giving us a better understanding of the recovery phase of the substorms.
SM31A-1216 0800h
Cluster Observations of Earthward Flowing Plasmoid in the Tail
The energetic electrons and ions embedded in Earthward-moving plasmoid structures have been observed. These plasmoids are associated with a rotational local B$_z$ component (bi-polar) signature. Energetic electrons are found to be confined in a smaller spatial region than ions inside the plasmoid. Energetic ions and electrons seem to be a good indicator for the structure boundary. The fleet of Cluster spacecraft cross the plasmoid structure in a "first entry, last out" order (Note: when spacecraft cross a planar discontinuity, e.g. magnetopause, they will be in "first entry, first out" order). This documents the fact that the plasmoid has a non-planar nested structure. The large separation distance (around 1 R$_E$) of the Cluster satellites in October 2002 is an advantage to provide constraints on the size and shape of the plasmoid structure of interest. In addition, the plasmoid (with closed field lines) should preserve the ion composition information where it is formed. The ion composition observed in the plasmoid shows significantly lower O and He than in the ambient plasma. This implies few heavy ions are involved in the reconnection process where the plasmoid is formed. Multiple flux ropes/plasmoids observation presented in this paper can be interpreted as strong evidence for multiple X-lines.
SM31A-1217 0800h
Particle Signatures Observed by Geotail at 9-30 Re and Mapping of Auroral Regions to the Magnetosphere Without Field-Line Models
The Geotail spacecraft has often observed a rapid change of particle signatures at a geocentric distance around 10-15 Re. As the spacecraft approached the near-Earth region, particle spectra showing a low temperature, a small particle flux, and a large fluctuation in the magnetotail changed to those with a high temperature, a large flux, and a small fluctuation in the near-Earth region. This change often occurred rapidly as if there was a sharp boundary between the tail plasma sheet and the near-Earth plasma sheet. In the present paper, we call this boundary "near-Earth PS boundary (NEPS boundary)." As pointed out by recent studies, the region between the tail plasma sheet and the near-Earth plasma sheet may be a key to solving problems on dynamics of the magnetosphere [Shiokawa et al., 1998] and to studying chaotic behavior of magnetospheric particles [Zelenyi et al., 2000, 2002]. In this paper, we investigate the position of the NEPS boundary in detail and present a map showing its occurrence on the equatorial plane. We also examine characteristics of the NEPS boundary and indicate that they are very similar to characteristics of the equatorward boundary of the so-called "Wall Region" [Ashour-Abdalla et al, 1992] or "Ion Gap" [Bosqued et al, 1993; Delcourt et al., 1996], which has been observed at low altitudes. We compare the NEPS boundary with the equatorward boundary of the Wall Region (Ion Gap) identified by the low-altitude satellite Akebono. It is concluded that the boundary of the Wall Region (Ion Gap) is the field-aligned projection of the NEPS boundary detected by Geotail in the magnetosphere. This conclusion enables us to map the key region (10-15 Re) to the auroral altitudes. The result of the mapping demonstrates that the key region is projected on the latitudes of 65-70 degrees at auroral altitudes. Finally, we discuss a new method to map auroral regions to the magnetosphere without using field line models but using observed boundaries. It is suggested that this method can provide a more accurate projection of auroral regions than the method using field-line models can, especially in the radial (latitudinal) direction.
SM31A-1218 0800h
Auroral particles associated with a brightening arc
We investigated characteristics of auroral particles precipitating to a brightening arc at the initial phase of a substorm, using auroral images obtained by high-time resolution (0.25 s) all-sky TV camera, particle data obtained by the DMSP F10 spacecraft and high-latitude magnetograms. The arc brightening was observed at 0407 UT on December 30, 1994 at Fort Smith (67.0 MLAT), Canada, coincident with high-latitude Pi 2 magnetic pulsations. The event has two characteristics; 1) the brightening did not develop into global scale (pseudo-breakup), and 2) Fort Smith seemed to be duskside of the main onset region. From the simultaneous DMSP particle data, we found that the brightening arc corresponded to an electron inverted-V structure near the equatorward edge of the electron precipitation region and at ~2 deg poleward of the equatorward edge of the ion precipitation region. This fact suggests that for the present event, the pseudo-breakup of auroral substorm occurred in the inner part of the plasma sheet.
SM31A-1219 0800h
Pi2 Observations by Cluster and Ground Stations
We will present case studies of conjugate Pi2 observations by Cluster in the magnetotail ($\sim 19 R_{\rm E}$) and ground stations from the 210 meridian magnetometer chain. Comparing the magnetic field data for these events we find similar waveforms at Cluster and on the ground. Using the spatial separation of the Cluster spacecraft we can determine the propagation direction of the waves. The waves observed by Cluster are travelling tailward with velocities up to $\sim 800$ km/s. When possible, we will use the time difference between the observation on the ground and by Cluster to get an estimate of where these waves are generated.
SM31A-1220 0800h
Mass Density at L=2.5 During a Magnetic Storm: a Case Study
The inner magnetosphere plasma environment is rather dynamic and of great interest. Observational data usually come from spacecraft (e.g. particle counters, imagers) and ground-based (VLF whistlers) techniques. However, VLF receivers can also be used to monitor artificially produced whistler-mode waves that propagate in field-aligned ducts and that provide information on the electron density in the equatorial plane. Furthermore, ground magnetometers can be used to detect ULF field line resonances (FLRs) whose frequency relates to the plasma mass density in the equatorial plane. We describe an experiment using co-located magnetometers and VLF receivers to monitor mass and electron density for the same L=2.5 flux tube. We focus in particular on the variation in electron and mass density during a magnetic storm cycle. The experiments provide information on the storm-time variation in heavy ion mass loading that is compared with in situ measurements and EUV images of the He+ concentration.
SM31A-1221 0800h
Magnetospheric Radio Tomography: Theory and CLUSTER Experiments
Recent studies have shown the feasibility and scientific value of radio tomography for remote sensing Earth's magnetosphere. Radio tomography uses radio waves and phenomena known as Faraday rotation and phase/group delay that can be measured to reconstruct full images of electron density and magnetic field. Faraday rotation is the rotation of the polarization of a linearly polarized wave as it travels through the magnetospheric plasma. We present first a flexible and robust direct reconstruction method for magnetospheric radio tomography. We show that for a combined reconstruction of plasma density and magnetic field the direct reconstruction method performs as well as popular iterative methods for large number of satellites, but it performs significantly better when the number of satellites is small. The main advantages of this method are that extra information, such as in situ measurements, can be easily and flexibly incorporated into the reconstruction. We demonstrate the good performance of this method with MHD simulations in reconstructing electron density and magnetic field using constellations of relatively few satellites (11 and fewer) in a single orbit in a variety of magnetospheric regions. To validate the feasibility of the measurements behind radio tomography, we have performed three separate experiments designed using the Radio Plasma Imager (RPI) on the IMAGE spacecraft as the signal source, and the WBD instruments on the four CLUSTER spacecraft as the wave receivers. To measure Faraday rotation of the transmitted wave electric field polarization due to propagation through a magnetized plasma, RPI signals received by WBD instruments in April 2002 and May 2003 were carefully analyzed and interpreted for the three radio tomography experiments. Based on the time-varying spin modulation of the WBD received signals, and their spin-phase difference with the RPI transmitted signal, we report the measured Faraday rotation and the average electron density extracted along the wave propagation path. We demonstrate that the deduced average electron density agrees well with empirical statistical models of the northern polar region.
http://www.ee.duke.edu/~zhaiyh/publication/abstract
SM31A-1222 0800h
Multi-point Characterization of ULF Wave Energy Transport in the Magnetosphere.
There are a number of mechanisms by which global ULF oscillations can be produced in the magnetosphere. For example, during fast solar wind speed events, flow instabilities can drive surface waves on the magnetopause which in turn can drive compressional waves into the magnetosphere. Alternately, oscillations in solar wind parameters can also produce similar compressional oscillations. These compressional waves are a source of ULF wave activity throughout the magnetosphere-ionosphere system. We present event studies of global ULF wave oscillations whereby favourable radial alignment of spacecraft in the magnetosphere and conjugate measurements of field line resonances (FLRs) in the ionosphere allow the tracking of ULF wave energy in the near-Earth environment. We study an interval on the 25th November 2001 and track energy transport from the magnetopause boundary oscillations from the magnetopause through the FLR mode-conversion region and into the ionosphere. We calculate the in-situ Poynting flux to fully characterise the nature of these oscillations. Using radial alignments of multiple spacecraft (e.g. Equator-S, Geotail, Polar) and meso-scale conjugate ionospheric measurements during additional intervals, we further examine ULF wave energy transport to determine the ULF response to a range of solar wind drivers.