Sporadic E-Region Ionization at Watheroo Magnetic Observatory 1938-1944

Abstract. The electron temperature (Te), electron density (Ne), and two components of the electric field were measured from the height of 90 km to 150 km by one of the sounding rockets launched during the SEEK-2 campaign. The rocket went through sporadic E layer (Es) at the height of 102 km–109 km during ascent and 99 km–108 km during decent, respectively. The energy density of thermal electrons calculated from Ne and Te shows the broad maximum in the height range of 100–110 km, and it decreases towards the lower and higher altitudes, which implies that a heat source exists in the height region of 100 km–110 km. A 3-D picture of Es, that was drawn by using Te, Ne, and the electric field data, corresponded to the computer simulation; the main structure of Es is projected to a higher altitude along the magnetic line of force, thus producing irregular structures of Te, Ne and electric field in higher altitude.

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Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany

10.5194/egusphere-egu21-12929 ◽

2021 ◽

Author(s):

Mani Sivakandan ◽

Jorge L Chau ◽

Carlos Martinis ◽

Yuichi Otsuka ◽

Jens Mielich ◽

...

Keyword(s):

Gps Tec ◽

F Region ◽

Perkins Instability ◽

Sporadic E Layers ◽

Spread F ◽

E Region ◽

Sporadic E ◽

Low Latitude Ionosphere ◽

Atmospheric Gravity

Northwest to southeast phase fronts with southwestward moving features are commonly observed in the nighttime midlatitude ionosphere during the solstice months at low solar activity. These features are identified as nighttime MSTIDs (medium scale traveling ionospheric disturbances). Initially, they were considered to be a manifestation of neutral atmospheric gravity waves. Later on, investigations showed that the nighttime MSTIDs are electrified in nature and mostly confined to the mid and low latitude ionosphere. Although the overall characteristics of the nighttime MSTIDs are mostly well understood, the causative mechanisms are not well known. Perkins instability mechanism was believed to be the cause of nighttime MSTIDs, however, the growth rate of the instability is too small to explain the perturbations observed. Recently, model simulations and observational studies suggest that coupling between sporadic-E layers and other type of E-region instabilities, and the F region may be relevant to explain the generation of the MSTIDs.In the present study simultaneous observation from OI 630 nm all-sky airglow imager, GPS-TEC, ionosonde and Meteor radars, are used to investigate the role of E and F region coupling on the generation of MSTIDs .Nighttime MSTIDs observed on three nights (14 March 2020, 23 March 2020 and 28 May 2020) in the OI 630 nm airglow images over Kuehlungsborn (54&#176;07'N; 11&#176;46'E, 53.79N&#160; mag latitude), Germany, are presented. Simultaneous detrended GPS-TEC measurements also shows presence of MSTIDs on these nights. In addition, simultaneous ionosonde observations over Juliusruh (54&#176;37.7'N 13&#176;22.5'E) show spread-F in the ionograms as well as sporadic-E layer occurrence.&#160; Furthermore, we also investigate the MLT region wind variations during these nights. The role of Es-layers and the interplay between the winds and Es-layers role on the generation of the MSTIDs will be discussed in detail in this presentation.&#160;

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Some Aspects of Gyro?Splitting in the Ionosphere

Australian Journal of Physics ◽

10.1071/ph620025 ◽

1962 ◽

Vol 15 (1) ◽

pp. 25 ◽

Cited By ~ 7

Author(s):

GG Bowman

Keyword(s):

Geomagnetic Latitude ◽

Mode Propagation ◽

E Region ◽

Sporadic E

Ionograms for Hobart (geomagnetic latitude 52 oS.), showing x-mode propagation below the electron gyro frequency, were examined. Detailed analyses of some ionograms were made. Strong reflections for this particular propagation seem dependent on the amount of ionization, between the sporadic E level and 180 km, being reduced to a sufficiently low value. It is suggested that this can be achieved, in the sporadic E region, by the concentration of existing ionization; this concentration producing the sporadic E reflections.

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Morphological study of the field-aligned E-layer irregularities observed by the Gadanki VHF radar

Annales Geophysicae ◽

10.5194/angeo-22-3799-2004 ◽

2004 ◽

Vol 22 (11) ◽

pp. 3799-3804 ◽

Cited By ~ 1

Author(s):

C. J. Pan ◽

P. B. Rao

Keyword(s):

Geomagnetic Latitude ◽

Spectral Width ◽

Statistical Characteristics ◽

Low Latitude ◽

Vhf Radar ◽

Lower Altitude ◽

Radar Echoes ◽

E Region ◽

Sporadic E ◽

Total Observation

Abstract. We report on the field-aligned irregularities observed in the low-latitude sporadic E-layer (Es) with the Gadanki (13.5° N, 79.2° E; geomagnetic latitude 6.3° N) VHF radar. The radar was operated intermittently for 15 days during the summer months in 1998 and 1999, for both daytime and nighttime observation. The total observation periods are 161h for the nighttime and 68h for the daytime. The observations were used to study the percentage of occurrence of the E-region echoes for both daytime and nighttime. The statistical characteristics of the mean radial velocity and spectral width are presented for three cases based on the echo occurrence characteristics and the altitude of observations (from 90 to 140km ranges), namely, the lower E-region daytime (90-110km), the lower E-region nighttime (90-105km) and the upper E-region nighttime (105-140km) echoes. The results are compared with that of Piura, a low-latitude station located at about the same geomagnetic latitude, but to the south of the equator. By comparing the behaviors of the lower E-region radar echoes of the summer months between Gadanki and Piura, we find that the lower altitude echoes below about 100km are rarely reported in Piura but commonly seen in Gadanki. Features of the nighttime echoes observed by these two radars are quite similar but daytime FAI echoes are again seldom detected by Piura.

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

Annales Geophysicae ◽

10.1007/s00585-997-0908-2 ◽

1997 ◽

Vol 15 (7) ◽

pp. 908-917 ◽

Cited By ~ 1

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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Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

Annales Geophysicae ◽

10.5194/angeo-19-59-2001 ◽

2001 ◽

Vol 19 (1) ◽

pp. 59-69 ◽

Cited By ~ 10

Author(s):

H. Chandra ◽

S. Sharma ◽

C. V. Devasia ◽

K. S. V. Subbarao ◽

R. Sridharan ◽

...

Keyword(s):

Meteor Shower ◽

Low Latitude ◽

Equatorial Station ◽

Radio Science ◽

Ionospheric Physics ◽

Transmitter Power ◽

Multiple Structures ◽

E Region ◽

Sporadic E Layer ◽

Sporadic E

Abstract. Rapid radio soundings were made over Ahmedabad, a low latitude station during the period 16–20 November 1998 to study the sporadic-E layer associated with the Leonid shower activity using the KEL Aerospace digital ionosonde. Hourly ionograms for the period 11 November to 24 November were also examined during the years from 1994 to 1998. A distinct increase in sporadic-E layer occurrence is noticed on 17, 18 and 19 November from 1996 to 1998. The diurnal variations of f0Es and fbEs also show significantly enhanced values for the morning hours of 18 and 19 November 1998. The ionograms clearly show strong sporadic-E reflections at times of peak shower activity with multiple traces in the altitude range of 100–140 km in few ionograms. Sporadic-E layers with multiple structures in altitude are also seen in some of the ionograms (quarter hourly) at Thumba, situated near the magnetic equator. Few of ionograms recorded at Kodaikanal, another equatorial station, also show sporadic- E reflections in spite of the transmitter power being significantly lower. These new results highlighting the effect of intense meteor showers in the equatorial and low latitude E-region are presented.Key words. Ionosphere (equatorial ionosphere) – Radio science (ionospheric physics)

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Multistation digisonde observations of equatorial spread F in South America

Annales Geophysicae ◽

10.5194/angeo-22-3145-2004 ◽

2004 ◽

Vol 22 (9) ◽

pp. 3145-3153 ◽

Cited By ~ 39

Author(s):

B. W. Reinisch ◽

M. Abdu ◽

I. Batista ◽

G. S. Sales ◽

G. Khmyrov ◽

...

Keyword(s):

South America ◽

Field Line ◽

Magnetic Equator ◽

Simple Correlation ◽

Equatorial Spread F ◽

F Region ◽

Sporadic E Layers ◽

Spread F ◽

E Region ◽

Sporadic E

Abstract. Directional ionogram and F-region drift observations were conducted at seven digisonde stations in South America during the COPEX campaign from October to December 2002. Five stations in Brazil, one in Argentina, and one in Peru, monitored the ionosphere across the continent to study the onset and development of F-region density depletions that cause equatorial spread F (ESF). New ionosonde techniques quantitatively describe the prereversal uplifting of the F layer at the magnetic equator and the eastward motion of the depletions over the stations. Three of the Brazilian stations were located along a field line with a 350-km apex over the equator to investigate the relation of the occurrence of ESF and the presence of sporadic E-layers at the two E-region intersections of the field line. No simple correlation was found.

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