scholarly journals Comparison of E-region electric fields observed with a sounding rocket and a Doppler radar in the Seek Campaign

1998 ◽  
Vol 25 (11) ◽  
pp. 1773-1776 ◽  
Author(s):  
Mamoru Yamamoto ◽  
Tetsuya Itsuki ◽  
Takeshi Kishimoto ◽  
Roland T. Tsunoda ◽  
Robert F. Pfaff ◽  
...  
Keyword(s):  
Electric Fields ◽  
Doppler Radar ◽  
Sounding Rocket ◽  
E Region

scholarly journals Electric field measurements of DC and long wavelength structures associated with sporadic-<i>E</i> layers and QP radar echoes

2005 ◽  
Vol 23 (7) ◽  
pp. 2319-2334 ◽  
Author(s):  
R. Pfaff ◽  
H. Freudenreich ◽  
T. Yokoyama ◽  
M. Yamamoto ◽  
S. Fukao ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Plasma Density ◽  
Sounding Rocket ◽  
Neutral Wind ◽  
Short Scale ◽  
Radar Echoes ◽  
E Region ◽  
Sporadic E Layer ◽  
Sporadic E

Abstract. Electric field and plasma density data gathered on a sounding rocket launched from Uchinoura Space Center, Japan, reveal a complex electrodynamics associated with sporadic-E layers and simultaneous observations of quasi-periodic radar echoes. The electrodynamics are characterized by spatial and temporal variations that differed considerably between the rocket's upleg and downleg traversals of the lower ionosphere. Within the main sporadic-E layer (95–110 km) on the upleg, the electric fields were variable, with amplitudes of 2–4 mV/m that changed considerably within altitude intervals of 1–3 km. The identification of polarization electric fields coinciding with plasma density enhancements and/or depletions is not readily apparent. Within this region on the downleg, however, the direction of the electric field revealed a marked change that coincided precisely with the peak of a single, narrow sporadic-E plasma density layer near 102.5 km. This shear was presumably associated with the neutral wind shear responsible for the layer formation. The electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 152 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10–15 km and wavevectors oriented between the NE-SW quadrants. The electric field structures had typical amplitudes of 3–5 mV/m with one excursion to 9 mV/m, and in a very general sense, were associated with perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and presumably had mapped upwards along the magnetic field from the sporadic-E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the Es-layer instability. In both cases, the same shear that formed the sporadic-E layer would provide the energy to generate the km-scale structures. Other possibilities include gravity waves or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. They also appear to have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15min later. Short scale (<100 m) electric field irregularities were also observed and were strongest in the sporadic-E region below 110km. The irregularities were organized into 2–3 layers on the upleg, where the plasma density also displayed multiple layers, yet were confined to a single layer on the downleg where the plasma density showed a single, well-defined sporadic-E peak. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving the observed waves on the upleg, but may have contributed to the growth of short scale waves on the topside of the narrow unstable density gradient observed on the downleg. The data suggest that other sources of free energy may have been important factors for the growth of the short scale irregularities. Keywords. Ionosphere (Mid-latitude ionosphere; Electric fields and currents; Ionospheric irregularities)

scholarly journals Influence of uncertainties of the empirical models for inferring the E-region electric fields at the dip equator

2016 ◽  
Vol 68 (1) ◽  
Author(s):  
Juliano Moro ◽  
Clezio Marcos Denardini ◽  
Laysa Cristina Araújo Resende ◽  
Sony Su Chen ◽  
Nelson Jorge Schuch
Keyword(s):  
Electric Fields ◽  
Empirical Models ◽  
E Region ◽  
Dip Equator

scholarly journals Equatorial E Region Electric Fields and Sporadic E Layer Responses to the Recovery Phase of the November 2004 Geomagnetic Storm

2017 ◽  
Vol 122 (12) ◽  
pp. 12,517-12,533 ◽  
Author(s):  
J. Moro ◽  
L. C. A. Resende ◽  
C. M. Denardini ◽  
J. Xu ◽  
I. S. Batista ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Electric Fields ◽  
Recovery Phase ◽  
E Region ◽  
Sporadic E Layer ◽  
Sporadic E

scholarly journals Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

2002 ◽  
Vol 20 (12) ◽  
pp. 1977-1985 ◽  
Author(s):  
R. Sridharan ◽  
C. V. Devasia ◽  
N. Jyoti ◽  
Diwakar Tiwari ◽  
K. S. Viswanathan ◽  
...  
Keyword(s):  
Electric Fields ◽  
Solar Eclipse ◽  
Equatorial Ionosphere ◽  
Hf Radar ◽  
F Region ◽  
Large Enhancement ◽  
Temporal Structures ◽  
E Region ◽  
Field Lines ◽  
Electric Fields And Currents

Abstract. The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N), India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i) the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii) significant increase in h' F immediately following the eclipse and (iii) distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F) rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities)

E region electric fields at the dip equator and anomalous conductivity effects

2013 ◽  
Vol 51 (10) ◽  
pp. 1857-1869 ◽  
Author(s):  
C.M. Denardini ◽  
H.C. Aveiro ◽  
J.H.A. Sobral ◽  
J.V. Bageston ◽  
L.M. Guizelli ◽  
...  
Keyword(s):  
Electric Fields ◽  
E Region ◽  
Dip Equator

scholarly journals Simulations of the neutral structure within the dusk side aurora

2006 ◽  
Vol 24 (10) ◽  
pp. 2519-2532
Author(s):  
H. F. Parish ◽  
L. R. Lyons
Keyword(s):  
Electric Fields ◽  
Three Dimensional ◽  
Meridional Wind ◽  
Recovery Phase ◽  
Limited Area ◽  
Neutral Winds ◽  
E Region ◽  
Linear Interactions ◽  
Simulated Wind ◽  
Equivalent Conditions

Abstract. Observations of neutral winds from rocket release experiments within the premidnight and postmidnight substorm recovery phase aurora, show very large E-region neutral winds of several hundred m/s, where winds measured on the dusk side are even larger than those on the dawn side. These large winds are also associated with strong shears, and there is evidence that some of the regions below these shears may be unstable. The mechanisms which generate this strong vertical structure are not well understood. It is also not known whether the acceleration conditions in the pre and post midnight sectors of the aurora may produce significantly different neutral responses on the dawn and dusk sides. Simulations have been performed using a three-dimensional high resolution limited area thermosphere model to try to understand the neutral structure within the dawn and dusk side aurora. When simulations are performed using auroral forcing alone, for equivalent conditions within the dawn and dusk sectors, differences are found in the simulated response on each side. When measured values of auroral forcing parameters, and background winds and tides consistent with recent observations, are used as model inputs, some of the main features of the zonal and meridional wind observations are reproduced in the simulations, but the magnitude of the peak zonal wind around 140 km tends to be too small and the maximum meridional wind around 130 km is overestimated. The winds above 120 km altitude are found to be sensitive to changes in electric fields and ion densities, as was the case for the dawn side, but the effects of background winds and tides on the magnitudes of the winds above 120 km are found to be relatively small on the dusk side. The structure below 120 km appears to be related mainly to background winds and tides rather than auroral forcing, as was found in earlier studies on the dawn side, although the peak magnitudes of simulated wind variations in the 100 to 120 km altitude range are smaller than those observed. The source of the strong shears measured around 110 km altitude on the dusk side is uncertain, but may be related to different kinds of oscillations, such as gravity waves, non migrating semidiurnal tides, or secondary oscillations produced by non linear interactions between waves.

scholarly journals 50 MHz continuous wave interferometer observations of the unstable mid-latitude E-region ionosphere

2003 ◽  
Vol 21 (7) ◽  
pp. 1589-1600 ◽  
Author(s):  
C. Haldoupis ◽  
A. Bourdillon ◽  
A. Kamburelis ◽  
G. C. Hussey ◽  
J. A. Koehler
Keyword(s):  
Electric Fields ◽  
Continuous Wave ◽  
Isotropic Turbulence ◽  
Doppler Radar ◽  
Active Regions ◽  
Field Of View ◽  
Ionosphere Plasma ◽  
First Results ◽  
Sporadic E

Abstract. In this paper we describe the conversion of SESCAT (Sporadic-E SCATter experiment), a bistatic 50 MHz continuous wave (CW) Doppler radar located on the island of Crete, Greece, to a single (east-west) baseline interferometer. The first results show that SESCAT, which provides high quality Doppler spectra and excellent temporal resolution, has its measurement capabilities enhanced significantly when operated as an interferometer, as it can also study short-term dynamics of localized scattering regions within mid-latitude sporadic E-layers. The interferometric observations reveal that the aspect sensitive area viewed by the radar often contains a few zonally located backscatter regions, presumably blobs or patches of unstable metallic ion plasma, which drift across the radar field-of-view with the neutral wind. On average, these active regions of backscatter have mean zonal scales ranging from a few kilometers to several tens of kilometers and drift with westward speeds from ~ 20 m/s to 100 m/s, and occasionally up to 150 m/s. The cross-spectral analysis shows that mid-latitude type 1 echoes occur much more frequently than has been previously assumed and they originate in single and rather localized areas of elevated electric fields. On the other hand, typical bursts of type 2 echoes are often found to result from two adjacent regions in azimuth undergoing the same bulk motion westwards but producing scatter of opposite Doppler polarity, a fact that contradicts the notion of isotropic turbulence to which type 2 echoes are attributed. Finally, quasi-periodic (QP) echoes are observed simply to be due to sequential unstable plasma patches or blobs which traverse across the radar field-of-view, sometimes in a wave-like fashion.Key words. Ionosphere (ionospheric irregularities; mid-latitude ionosphere; plasma waves and instabilities)

scholarly journals Cosmic radio noise absorption events associated with equatorward drifting arcs during a substorm growth phase

2004 ◽  
Vol 22 (5) ◽  
pp. 1675-1686 ◽  
Author(s):  
J. R. T. Jussila ◽  
A. T. Aikio ◽  
S. Shalimov ◽  
S. R. Marple
Keyword(s):  
Electron Temperature ◽  
Electric Fields ◽  
Growth Phase ◽  
Energetic Electron ◽  
Cosmic Radio ◽  
Radio Noise ◽  
Particle Precipitation ◽  
Noise Absorption ◽  
D Region ◽  
E Region

Abstract. Cosmic radio noise absorption (CNA) events associated with equatorward drifting arcs during a substorm growth phase are studied by using simultaneous optical auroral, IRIS imaging riometer and EISCAT incoherent scatter radar measurements. The CNA is generally attributed to energetic particle precipitation in the D-region. However, it has been argued that plasma irregularities or enhanced electron temperature (Te) in the E-region could also produce CNA. Both of the latter mechanisms are related to intense electric fields in the ionosphere. We present two events which occur during a substorm growth phase in the evening MLT sector. In both of the events, an auroral arc is drifting equatorward, together with a region of CNA (auroral absorption bay) located on the equatorward side and outside of the arc. Both of the events are associated with enhanced D-region electron density on the equatorward side of the auroral arc, but in the second event, a region of intense electric field and enhanced electron temperature in the E-region is also located on the equatorward side of the arc. We show that in the studied events neither plasma instabilities nor enhanced Te play a significant role in producing the measured CNA, but the CNA in the vicinity of the equatorward drifting arcs is produced by D-region energetic electron precipitation. Key words. Ionosphere (auroral ionosphere; particle precipitation; electric fields and currents)

scholarly journals Type-1 echoes from the mid-latitude E-Region ionosphere

1997 ◽  
Vol 15 (7) ◽  
pp. 908-917 ◽  
Author(s):  
C. Haldoupis ◽  
D. T. Farley ◽  
K. Schlegel
Keyword(s):  
Doppler Radar ◽  
Spectral Component ◽  
Equatorial Electrojet ◽  
Metallic Ions ◽  
Sporadic E Layers ◽  
E Region ◽  
Sporadic E ◽  
The Right

Abstract. This paper presents more data on the properties of type-1 irregularities in the nighttime mid-latitude E-region ionosphere. The measurements were made with a 50-MHz Doppler radar system operating in Crete, Greece. The type-1 echoes last from several seconds to a few minutes and are characterized by narrow Doppler spectra with peaks corresponding to wave phase velocities of 250–350 m/s. The average velocity of 285 m/s is about 20% lower than nominal E-region ion-acoustic speeds, probably because of the presence of heavy metallic ions in the sporadic-E-layers that appear to be associated with the mid-latitude plasma instabilities. Sometimes the type-1 echoes are combined with a broad spectrum of type-2 echoes; at other times they dominate the spectrum or may appear in the absence of any type-2 spectral component. We believe these echoes are due to the modified two-stream plasma instability driven by a polarization electric field that must be larger than 10 mV/m. This field is similar in nature to the equatorial electrojet polarization field and can arise when patchy nighttime sporadic-E-layers have the right geometry.

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