Showing papers on "TEC published in 1996"

Global ionosphere perturbations monitored by the Worldwide GPS Network

Abstract: For the first time, measurements from the Global Positioning System (GPS) worldwide network are employed to study the global ionospheric total electron content (TEC) changes during a magnetic storm (November 26, 1994). These measurements are obtained from more than 60 world-wide GPS stations which continuously receive dual-frequency signals. Based on the delays of the signals, we have generated high resolution global ionospheric maps (GIM) of TEC at 15 minute intervals. Using a differential method comparing storm time maps with quiet time maps, we find that significant TEC increases (the positive effect) are the major feature in the winter hemisphere during this storm (the maximum percent change relative to quiet times is about 150%). During this particular storm, there is almost no negative phase. A traveling ionospheric disturbance (TID) event is identified that propagates from the northern subauroral region to lower latitudes (down to about 30°N) at a speed of ∼460 m/s. This TID is coincident with significant increases in the TEC around the noon sector. We also find that another strong TEC enhancement occurs in the pre-dawn sector in the northern hemispheric subauroral latitudes, in the beginning of the storm main phase. This enhancement then spreads into almost the entire nightside. The nighttime TEC increase in the subauroral region is also noted in the southern hemisphere, but is less significant. These preliminary results indicate that the differential mapping method, which is based on GPS network measurements, appears to be a powerful tool for studying the global pattern and evolution process of the entire ionospheric perturbation.

Total Electron Content Obtained by Using the Global Positioning System

Abstract: A procedure is introduced to obtain the balance of measurements of differential group delays and differential carrier phase lead characteristics, both phenomena being due to the ionospheric total electron content(TEC)along the ray path from a Global Positioning System (GPS) satellite. It has been demonstrated that utilizing the measurement of both pseudorange and carrier phase recorded by genetic GPS receivers, the precision of the vertical TEC derived when the anti-spoofing (AS)is on can be as good as that derived when it is off. Combining the data of a network of four GPS receivers, a TEC map is reconstructed which can be employed to examine the ionospheric latitude/longitude structure and dynamics in the Taiwan area.

Characteristics of thermally expanded core fiber

Abstract: Thermally expanded core (TEC) fiber is expected to reduce fiber-to-fiber and fiber-to-laser diode connection loss This paper describes the characteristics of TEC fiber theoretically and experimentally We reveal theoretically that when fabricating TEC fiber the mode field diameter (MFD) is enlarged more effectively by increasing the heating temperature rather than the heating time In the 1300-1600/spl deg/C temperature range with heating times between 0 and 60 min, it is necessary to control the temperature accurately so that no deviation from the target temperature is more than /spl plusmn/30/spl deg/C This is in order to ensure that any connection loss caused by MFD mismatch is less than 01 dB We show experimentally that the propagation loss of TEC fiber is dependent on the heating region and wavelength by using a micro burner with a propane/oxygen flame Based on the relationship between the loss characteristics and the expanded MFD, we suggest a method for nondestructively measuring the MFD in TEC fibers

Chemical Conditions Conducive to the Release of Mobile Colloids from Ultisol Profiles

Abstract: The objective of this study was to determine how soil pH (4.3-6.9), low total electrolyte concentration (TEC, 0.4-2.8 mol{sub c} m{sup -3}) and low Na adsorption ratios (SAR, 0.3-1.8 [mol{sub c} m{sup -3}]{sup 0.5}) affected the concentration of mobile colloids released from 13.5-m{sup 3} reconstructed Ultisol profiles. Critical flocculation concentration (CFC, the minimum TEC to induce flocculation of a clay suspension) tests were conducted using the water-dispersible clay fraction of the Ap horizon of these profiles, which is the primary source for the mobile colloids. Surface soil pH, TEC, and SAR levels of the profiles that released high concentrations of colloids fell within the dispersion domain identified by the laboratory CFC tests. The effect of SAR on dispersion appears to be a continuum that approaches zero, and this effect is significantly (P = 0.01) dependent on TEC. This dispersible nature of these soils is in part attributed to their very low TEC, generally < 2 mol{sub c} m{sup -3}, which results from low concentrations of weatherable minerals. The TEC of 10 of the 13 profiles were < 2 mol{sub c} m{sup -3}, the CFC for SAR = 1 (mol{sub c} m{sup -3}){sup 0.5}, indicating that if the pH is notmore » limiting (pH greater than = 6.0), colloidal dispersion will occur. 24 refs.« less

A new approach to optimum design in thermoelectric cooling systems

Abstract: A thermoelectric cooling system usually consists of a thermoelectric cooler (TEC) and heat exchangers at the cold side and the hot side. Heat exchangers in TEC systems are designed to minimize their thermal resistance under restrictions such as the size of the system and heat transfer method, because as the thermal resistances of heat exchangers increase, the performance of TEC systems decreases. In the TEC system in which thermal resistance of heat exchangers is minimized, the optimum TEC is analyzed to maximize the coefficient of performance (COP) and the exergetic efficiency in absorbing a given heat load. The effects of the thermal resistance of heat exchangers on the performance of the TEC system and the design parameters of that system are also investigated. To discuss these matters, dimensionless entropy flow equations of the TEC system are introduced, and the COP and the exergetic efficiency are expressed as a function of dimensionless quantities by using these dimensionless equations.

Relationships between GPS-signal propagation errors and EISCAT observations

Abstract: When travelling through the ionosphere the signals of space-based radio navigation systems such as the Global Positioning System (GPS) are subject to modifica- tions in amplitude, phase and polarization. In particular, phase changes due to refraction lead to propagation er- rors of up to 50 m for single-frequency GPS users. If both the L1 and the L2 frequencies transmitted by the GPS satellites are measured, first-order range error contribu- tions of the ionosphere can be determined and removed by di⁄erence methods. The ionospheric contribution is pro- portional to the total electron content (TEC) along the ray path between satellite and receiver. Using about ten Euro- pean GPS receiving stations of the International GPS Service for Geodynamics (IGS), the TEC over Europe is estimated within the geographic ranges!20i4j440iE and 32.5i4/470iN in longitude and latitude, respec- tively. The derived TEC maps over Europe contribute to the study of horizontal coupling and transport proces- ses during significant ionospheric events. Due to their comprehensive information about the high-latitude ionosphere, EISCAT observations may help to study the influence of ionospheric phenomena upon propagation errors in GPS navigation systems. Since there are still some accuracy limiting problems to be solved in TEC determination using GPS, data comparison of TEC with vertical electron density profiles derived from EISCAT observations is valuable to enhance the accuracy of propagation-error estimations. This is evident both for absolute TEC calibration as well as for the conversion of ray-path-related observations to vertical TEC. The com- bination of EISCAT data and GPS-derived TEC data enables a better understanding of large-scale ionospheric processes.

Solar cycle variations of the equatorial ionospheric anomaly in total electron content in the Asian region

Abstract: Daily equatorial ionospheric anomaly (EIA) contour charts in total electron content (TEG) were obtained by receiving simultaneously two coherent radio signals transmitted from the U.S. Navy Navigation Satellite System satellite at Lunping Observatory (25.00°N, 121.17°E) from September 1985 to December 1994. The latitude, occurrence time, and strength of the most developed EIA crest obtained from daily TEC contour charts have been used to study the solar cycle variations of EIA in the Asian region. No significant solar cycle effect can be seen in the occurrence time and latitude of the most developed EIA crest. Seasonally, the winter crest appears larger and earlier than the summer crest, and the summer crest appears in lower latitude than other seasons. These seasonal changes are mainly accounted for by the effect of daytime meridional wind. The strength of EIA crest increases with the increasing of solar activity and exhibits winter anomaly with the winter strength larger than the summer one Positive correlation is found between the 12-month smoothed EIA crest strength and sunspot number. No saturation effect can be seen during the high solar activity period. The 12-month smoothed EIA crest strength exhibits a hysteresis variation about the solar cycle variation. Monthly mean TEC contour charts for the latitude from 15°N to 35°N are also obtained from those daily contour charts. By using linear regression analysis, the monthly mean TEC I at a given month is linearly correlated with smoothed sunspot number R by a formula I = A + BR. These results can be used to construct the monthly EIA contour chart in TEC for any given sunspot number.

An Assessment of Predicted and Measured Ionospheric Total Electron Content Using a Regional GPS Network

Abstract: The signals from the satellites of the Navstar Global Positioning System (GPS) must travel through the earth's ionosphere on their way to GPS receivers on or near the earth's surface. To achieve the highest possible positioning accuracies from GPS, one must correct for the carrier phase advance and pseudorange group delay imposed on the signals by the ionosphere. Whereas these effects may be considered a nuisance by most GPS users, they will provide the ionospheric community with an opportunity to use GPS as a tool to better understand the plasma surrounding the earth. The dispersive nature of the ionosphere makes it possible to measure its total electron content (TEC) using dualfrequency GPS observations collected by permanent networks of receivers. One such network is that of the International GPS Service for Geodynamics (IGS). We have used dual-frequency GPS pseudorange and carrier phase observations from six European stations in this network to derive regional TEC values. In this research, we investigated the effect of using different elevation cutoff angles and ionospheric shell heights on TEC estimates and satellite-receiver instrumental biases. We found that using different elevation cutoff angles had an impact on TEC estimates at the 2 TEC unit (TECU) level. We also discovered that using different ionospheric shell heights has an effect on the ionospheric TEC estimates at about the 2 TECU level depending on geographic location and time of the day. We found no significant changes in the bias estimates using different elevation cutoff angles. We compared our TEC estimates with TEC predictions obtained by using the International Reference Ionosphere 1990 (IRI90) model. The results of this comparison are similar to those of other studies that were conducted using data sets at low solar activity times. After processing the data from the 6 European stations collected over a 7 day period, we were able to follow highly varying ionospheric conditions associated with geomagnetic disturbances.

Simultaneous Global Positioning System and radar observations of equatorial spread F at Kwajalein

Abstract: GPS satellites broadcast at two frequencies (Ll of 1575.42 MHz and L2 of 1227.6 MHz). The dispersive property of the ionosphere is frequently used to correct positional measurements for ionospheric effects. Independent measurements at the two frequencies can also be combined to form a relative ionospheric delay and a measure of the total electron content (TEC) which is uncertain by an additive constant. In a previous paper (Musman et al., 1990) estimates of this offset were utilized in constructing models of the time history of the equivalent zenith delay at Westford, Massachusetts. An ionospheric model composed of uniform shells whose electron density changes slowly in a typical diurnal pattern would produce relative ionospheric delays with a simple u-shaped or j-shaped curve. Most of the change in delay would be a result of changes in geometry between the observer and the satellite. Departures from a simple pattern are indicative of ionospheric disturbances and the influence of the protonosphere. From GPS data alone, it is ambiguous whether these disturbances are due to spatial structures, temporal changes, or some combination of the two. Equatorial spread F (ESF) refers to a variety of equatorial ionospheric disturbances, some of which are associated with rising plasma plumes having low electron density and a high degree of turbulence. This phenomenon occurs primarily between local sunset and local midnight at sites within about 15° of the magnetic equator. In some seasons, disturbances can occur during two out of three evenings, while at other times it can be much quieter. GPS observations at Kwajalein (9°N latitude) reported here for August 14, 1990, show severe ionospheric disruption. Two independent and simultaneous sets of radar observations confirm the presence of ESF and reveal quite a bit about the spatial and temporal conditions which affect the system. GPS observations on August 15, 1990, when no ESF was present are much quieter. We find that tens of minute variations in the TEC correspond to the motion of large scale features across the GPS field of view. More severe GPS effects are seen to be collocated with turbulent low density plumes which rise rapidly to high altitudes and drift west to east across the GPS line of sight. Severe disruption can occur in moderately sophisticated GPS systems during such events, at least near solar maximum.

Tec protein-tyrosine kinase is an effector molecule of Lyn protein-tyrosine kinase.

Abstract: The Tec family is a recently emerging subfamily among nonreceptor type protein-tyrosine kinases (PTKs) consisting of Tec, Txk, Btk, Bmx, and Itk/Tsk/Emt. They have a long amino-terminal unique region containing a pleckstrin homology domain and a Tec-homology domain. We could previously show that, through the Tec-homology domain, Tec is bound to Lyn kinase both in vitro and in vivo. Because Tec is coexpressed with Lyn in many hematopoietic cell types, it has been intriguing to investigate the biological role of the Tec-Lyn association. Here we demonstrate that Lyn can phosphorylate tyrosine residues of the Tec protein, and thereby activate Tec in 3T3 fibroblasts. However, coexpression of Tec has little effect on the phospho-tyrosine-contents of Lyn. By using the in vitro kinase assay and the yeast system, we could prove that the Tec protein is a direct substrate of the Lyn kinase both in vitro and in vivo. From this evidence we conclude that Tec acts downstream of Lyn in intracellular signaling pathways. T...

Improved short‐term predictions of ƒ0F2 using GPS time delay measurements

Abstract: Reliable HF communications along short-, medium- and long-range paths require propagation assessment. Such assessment could be facilitated with the monitoring of ionospheric characteristics by continuously available passive means, i.e., measurement of the total electron content (TEC) using satellite-emitted signals without a need for burdening the electromagnetic spectrum. With ubiquitous Global Positioning System (GPS) providing instantaneous time delay, or equivalently, TEC, values when needed, an assessment of HF propagation conditions may be available on a near-real-time basis. Both TEC and the peak electron density of the ionosphere, which determines the ordinary upper frequency limit (ƒ0F2( for HF sky wave vertical propagation, vary strongly with solar and geomagnetic parameters. Their ratio, the equivalent slab thickness, may vary to a lesser degree and hence be modeled with greater accuracy. A slab thickness model combined with real-time TEC measurement anywhere on the globe may possibly yield an improved HF parameter prediction algorithm. To test the efficacy of the hypothesis, one has to ascertain the correlation, as exhibited by the correlation coefficient, between the TEC daily variability about the monthly mean and the ƒ0F2 variability. To determine such correlation, a study compared Faraday TEC data as well as GPS-generated TEC data collected in Israel and with corresponding ƒ0F2 values obtained from vertical sounder measurements near the appropriate subionospheric location in Cyprus. The analysis shows that for large percentages of the time, very good correlation exists between TEC and ƒ0F2 short-term variations. The correlation coefficient varies between 0.7 or better during winter and summer months to about 0.5–0.6 during equinox months. A study of the diurnal dependence of the correlation indicates that a better correlation exists during daytime than nighttime. There was no indication that the coefficient is dependent on geomagnetic activity or on protonospheric electron content during the period of this study.

Bone marrow-derived cells fail to induce positive selection in thymus reaggregation cultures.

Abstract: The requirements for inducing positive selection of T cells were examined in thymus reaggregation cultures, a system in which dispersed populations of immature CD4+8+ cells and purified thymic epithelial cells (TEC) are reaggregated in tissue culture. Studies with TEC from mice selectively lacking major histocompatibility complex (MHC) class I (I-II+), class II (I+II-), or both class I and II (I-II-) molecules showed that class II expression was essential for the differentiation of CD4+8+ cells into CD4+8- cells. Unexpectedly, the generation of TCRhi CD4-8+ cells from CD4+8+ cells was apparent with I-II+ TEC but not with I-II- TEC, perhaps reflecting cross-reactive specificity of CD4-8+ cells for class II molecules. Significantly, the failure of I-II- TEC to generate TCRhi CD4+8- or CD4-8+ cells could not be overcome by adding MHC+ bone marrow-derived cells. These findings, together with experiments on purified subsets of TEC, suggest that positive selection in thymus reaggregation cultures is an exclusive property of cortical TEC.

Self-contained refrigeration device for fruit

Abstract: A self-contained storage and display unit intended to be used for fruit. Cooling of the device is accomplished by the use of commercially available thermoelectric cooling (TEC) chips. A heat sink is included to dissipate the heat generated by the TEC chips. The rate of fresh air flow through the storage area can be controlled by the user to speed or slow the ripening rate of the fruit.

Deletion of Src Homology 3 Domain Results in Constitutive Activation of Tec Protein‐Tyrosine Kinase

Abstract: Tec protein-tyrosine kinase (PTK) is the prototype of a new subfamily of non-receptor type PTKs, and is abundantly expressed in hematopoietic tissues We have revealed that Tec is inducibly tyrosine-phosphorylated and activated by stimulation with a wide range of cytokines To get more insight into the signaling mechanism through Tec, we have generated a constitutively active form of Tec PTK Deletion of the Src homology (SH) 3 domain gave rise to a hyperphosphorylated and activated Tec kinase (Tec deltaSH3) The activity of Tec deltaSH3 was confirmed in 293 cells, as well as in cytokine-dependent hematopoietic cells (BA/F3) Tec deltaSH3 should be a useful tool to study the in vivo substrates of Tec PTK

Test of GPS for permanent ionospheric TEC monitoring at high latitudes

Abstract: . The Global Positioning System (GPS) observables are affected by the ionosphere. The dispersive nature of this effect and the use of two frequencies in the GPS observations make possible to measure the ionospheric total electron content (TEC) from dual frequency GPS data. In this work we test the concept of permanent monitoring of TEC using a network of GPS receivers at high latitudes. We have used GPS data from five permanent receivers in Scandinavia, from 1-30 January 1994, with geographic latitudes ranging from 57.4°N to 78.9°N. The results show the capability of the method to monitor the evolution of TEC as a function of time and geographical location. We have detected night-time enhancements almost every night for some of the stations, and we have also been able to produce maps of the instantaneous TEC as a function of both latitude and longitude around the GPS network. We also present some of the current limitations in the use of GPS for estimating TEC at high latitudes such as the difficulties in solving for cycle-slips, and the necessity of reliable values for the receiver and satellite differential instrumental biases.

TEC as electric generator in an automobile catalytic converter

Abstract: Modern cars use more and more electric power due to more on-board electric systems. A modern car may be equipped with an electric generator (generally an alternator) with an output current of maximum 60-90 A at 12 V. A belt driven generator has a rather low total efficiency and so it is interesting to find alternative solutions for this electricity generation problem. One possible energy source for electricity generation is to use the waste heat from the car's engine, which generally is as much as much as 80% of the total energy from the combustion of the gasoline. Maybe the best location to tap the excess heat is the catalytic converter (Cat) in the exhaust system or perhaps at the exhaust pipes close to the engine. The Cat must be kept within a certain temperature interval. Large amounts of heat are dissipated through the walls of the Cat. A thermionic energy converter (TEC) in a coaxial form could conveniently be located around the ceramic cartridge of the Cat. Since the TEC is a rather good heat insulator before it reaches its working temperature, the Cat will reach working temperature faster and its final temperature can be controlled better when encapsulated in a concentric TEC arrangement. It is also possible to regulate the temperature of the Cat and the TEC by controlling the electrical load of the TEC. The possible working temperatures of present and future Cats appear very suitable for the authors' new low work function collector TEC, which has been demonstrated to work down to 470 K.

Optimum design in thermoelectric cooling systems

Abstract: An optimum design is investigated to maximize the coefficient of performance (COP) for a thermoelectric cooling system (TEC system) which consists of a thermoelectric cooler (TEC) and heat-exchangers at the cold side and the hot side. Optimizing a TEC in the TEC system for the maximum COP can be performed by using the balance equations of nondimensional entropy flow, when the thermal resistances of heat-exchangers for a TEC system are given and the system operates under a constant temperature difference. In these equations, the COP of the TEC system becomes a function of nondimensional thermal resistance of the cold side heat-exchanger and nondimensional entropy flow at the cold side of the TEC system. Therefore the COP of the TEC system is shown as a contour graph on these two variables. By using this graph, not only TEC design parameters for the maximum COP of the TEC system can be determined, but the degrading effect by thermal resistances of the TEC system on the COP can also be evaluated.

TEC policy failure: evidence from the baseline follow-up studies

Abstract: Jones, M. R. (1996). TEC policy failure: evidence from the baseline follow-up studies. Regional Studies, 30 (5), 509-515.

Effect of Fatigue Damage in Woven Composites on Thermo-Mechanical Properties and Residual Compressive Strength

Abstract: The long term mechanical and thermal fatigue of a Celion G30-500/ PMR-15 woven composite system is investigated to study the interrelationship between thermo-mechanical properties, namely the thermal expansion coefficent (TEC) and the compressive strength. Qualitative trends in the experimental data generated by either thermal or mechanical loadings are shown to be similar to properties predicted by a shear lag based model. Residual compressive strength measurements (IITRI fixture) conducted on specimens subjected to tension-tension fatigue cycling indicate that this material property is sensitive to cracks and delaminations which form during mechanical cycling. Measured compressive strength degradation is as large as 49% for this material undergoing mechanical fatigue cycling with TEC degradation as large as 61%. Experimental results show that a correlation exists between TEC measurements and compressive strength. This correlation suggests that TEC measurements may be used as a damage evaluation technique.

Human thymic epithelial cells present superantigens to T-cell lines and thymocytes.

Abstract: It is generally accepted that thymic epithelial cells (TEC) act as accessory cells in positive selection of pre-T cells. However, our knowledge of the antigen presentation and accessory cell function to human TEC is limited. Here we present results obtained by the use of serum-free cultured human TEC, showing that IFN-gamma-treated TEC are able to support T-cell-mediated responses to the bacterial superantigens (Sag) SEA and SEB, even at very low Sag concentrations. T-cell responses to TEC-presented Sags were dependent on the presence of the adhesion molecules ICAM-1, ICAM-2, LFA-1, and LFA-3, but not on CD4 and CD8 molecules. There is a low but significant expression of B7 molecules on human TEC, and treatment of TEC with anti-B7.1 and anti-B7.2 antibodies before Sag pulsing leads to decreased Sag responses, indicating a significant importance of B7 molecules on TEC. Both CD4+ T-cell lines and CD4+ as well as CD8+ subpopulations of thymocytes showed significant responses, whereas nonseparated thymocytes, CD4+8+, and CD4-CD8- thymocytes did not respond or showed very low responses. In conclusion, the present results demonstrate that cultured human TEC are able to present Sag to thymocytes.

Pre/post-filter for performance improvement of transform coding

Abstract: A technique for generating independent transform coefficients from any p -dependent signal has been developed. Since these coefficients are independent, the Lloyd-Max quantization efficiency is improved. In addition, these coefficients are shown to be Gaussian distributed. Therefore, the probability density function estimate is bypassed during the quantizer design. An all-pass (encryption) pre-filter is required by the proposed technique, and the filtered signal is obtained efficiently by an algorithm developed in this paper. An added benefit of this technique is the compatibility and higher security with respect to the conventional transform coding (TC), and the method is called the transform encryption coding (TEC). In addition, a post-filter is necessary for signal reconstruction. Due to the all-pass nature of the pre/post-filtering process, the mean-square quantization error for the complete process is equal to that for the intermediate independent Gaussian transform coefficients. Simulation results show TEC achieves about 1 dB coding gain compared with TC. Coded images without blocking effects are obtained at 0.5 bit/pixel (bpp) using TEC. The image quality is similar to that obtained by TC at 1 bpp. Even at 0.35 bpp, TEC performs in the same way as the recent ‘DCT/DST’ technique of Rose et al. (1990) and shows no blocking effects. Most significantly, TEC encoded image is insensitive and robust to the channel noise.

Ionospheric disturbances during low‐latitude auroral events and their association with magnetospheric processes

Abstract: Ionospheric disturbances associated with low-latitude auroral events that occurred during geomagnetic storms on October 21, 1989, and May 10, 1992, are investigated from measurements of the total electron content (TEC) by the U.S. Navy Navigation Satellite System (NNSS) and ionosonde data from the Japanese meridian chain. Features of the ionospheric disturbances are then associated with the progression of geomagnetic disturbances during the storms. After the onset of the main phase of each storm, anomalous TEC distributions characterized by depressed TEC distributions on the high-latitude side (> 35° geographic latitude) and an enhanced equatorial ionization anomaly (EIA) on the low-latitude side (<35° geographic latitude) were observed over Japan both by the NNSS and by the meridian chain of ionosonde stations. This enhancement of the EIA suggests the penetration of magnetospheric electric fields during the storms. Corresponding to the anomalous TEC decreases in the northern part of Japan, ionosonde stations in this region observed specific disturbances of ionospheric variation characterized by simultaneous decreases of ƒ0F2 and increases of h′F. These features of ionospheric variations on the high-latitude side can be attributed to the upward escape of ionospheric plasma caused by the heating and evacuation mechanisms, which are induced by depletion of the plasmasphere and the resulting access of ring current particles to low latitudes. After the appearance of the characteristic ionospheric variations mentioned above, low-latitude aurorae were observed at the maximum development stage of the Dst, associated with the recovery of midlatitude geomagnetic horizontal (H) components. Prior to the appearance of the low-latitude aurorae, magnetic disturbances in the auroral region increased with the decrease of midlatitude H components, as a natural consequence of magnetic storms. However, they showed a recovery before the start of the low-latitude aurorae, while the magnitude of the low-latitude magnetic field continued to decrease. These observed features of the magnetic disturbances suggest that the position of the auroral oval shifted toward the equator before the appearance of the low-latitude aurorae. Consequently, these observations are consistent with the plasmapause and auroral zone moving toward the equator before the onset of low-latitude aurorae. We conclude that the convection electric field penetrating toward low latitudes causes the enhancement of the EIA, the shrinkage of the plasmasphere, and the penetration of high-energy particles toward the low-latitude region.