Possibility of detecting Ionospheric Drifts from the Occurrence of Spread F Echoes at Low Latitudes

The generation mechanism for the ionization irregularities in the upper atmosphere which are responsible for radio star scintillations is considered. The general belief that scintillations are related to the spread-F phenomenon observed on ionosonde recordings is found to be an inadequate explanation for the scintillations at 53 Mc/s recorded at Ottawa. An examination of the Ottawa recordings shows that there is a definite association, both in time of occurrence and geographical location, with those ionospheric disturbances that are usually considered to be due to incoming solar particles. Since other workers at more southerly geomagnetic latitudes have associated their scintillation observations with the spread-F phenomenon which they consider to be independent of auroral activity, it would appear that two mechanisms, at least, are responsible for the radio star fluctuations: namely, the precipitation of solar corpuscles and a mechanism linked with the spread-F phenomenon. The former seems to predominate at high latitudes, the latter is probably predominant at low latitudes, while both mechanisms probably are operative in middle latitudes.

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Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

Annales Geophysicae ◽

10.5194/angeo-22-3241-2004 ◽

2004 ◽

Vol 22 (9) ◽

pp. 3241-3250 ◽

Cited By ~ 26

Author(s):

D. Pallamraju ◽

S. Chakrabarti ◽

C. E. Valladares

Keyword(s):

Gravity Wave ◽

Magnetic Storm ◽

Geomagnetic Storm ◽

Local Time ◽

Direct Effect ◽

Spatial Structures ◽

Low Latitude ◽

Equatorial Ionization Anomaly ◽

Low Latitudes ◽

Spread F

Abstract. We describe the effect of the 6 November 2001 magnetic storm on the low latitude thermospheric composition. Daytime red line (OI 630.0nm) emissions from Carmen Alto, Chile showed anomalous 2-3 times larger emissions in the morning (05:30-08:30 Local Time; LT) on the disturbed day compared to the quiet days. We interpret these emission enhancements to be caused due to the increase in neutral densities over low latitudes, as a direct effect of the geomagnetic storm. As an aftereffect of the geomagnetic storm, the dayglow emissions on the following day show gravity wave features that gradually increase in periodicities from around 30min in the morning to around 100min by the evening. The integrated dayglow emissions on quiet days show day-to-day variabilities in spatial structures in terms of their movement away from the magnetic equator in response to the Equatorial Ionization Anomaly (EIA) development in the daytime. The EIA signatures in the daytime OI 630.0nm column-integrated dayglow emission brightness show different behavior on days with and without the post-sunset Equatorial Spread F (ESF) occurrence.

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Simultaneous 6300 Å airglow and radar observations of ionospheric irregularities and dynamics at the geomagnetic equator

Annales Geophysicae ◽

10.5194/angeo-36-473-2018 ◽

2018 ◽

Vol 36 (2) ◽

pp. 473-487 ◽

Cited By ~ 6

Author(s):

Dustin A. Hickey ◽

Carlos R. Martinis ◽

Michael Mendillo ◽

Jeffrey Baumgardner ◽

Joei Wroten ◽

...

Keyword(s):

Plasma Temperature ◽

Radar Data ◽

Ionospheric Irregularities ◽

Group Separation ◽

Plasma Parameters ◽

Zonal Winds ◽

Fabry Perot ◽

Low Latitudes ◽

Spread F ◽

Plasma Depletions

Abstract. In March 2014 an all-sky imager (ASI) was installed at the Jicamarca Radio Observatory (11.95∘ S, 76.87∘ W; 0.3∘ S MLAT). We present results of equatorial spread F (ESF) characteristics observed at Jicamarca and at low latitudes. Optical 6300 and 7774 Å airglow observations from the Jicamarca ASI are compared with other collocated instruments and with ASIs at El Leoncito, Argentina (31.8∘ S, 69.3∘ W; 19.8∘ S MLAT), and Villa de Leyva, Colombia (5.6∘ N, 73.52∘ W; 16.4∘ N MLAT). We use Jicamarca radar data, in incoherent and coherent modes, to obtain plasma parameters and detect echoes from irregularities. We find that ESF depletions tend to appear in groups with a group-to-group separation around 400–500 km and within-group separation around 50–100 km. We combine data from the three ASIs to investigate the conditions at Jicamarca that could lead to the development of high-altitude, or topside, plumes. We compare zonal winds, obtained from a Fabry–Pérot interferometer, with plasma drifts inferred from the zonal motion of plasma depletions. In addition to the ESF studies we also investigate the midnight temperature maximum and its effects at higher latitudes, visible as a brightness wave at El Leoncito. The ASI at Jicamarca along with collocated and low-latitude instruments provide a clear two-dimensional view of spatial and temporal evolution of ionospheric phenomena at equatorial and low latitudes that helps to explain the dynamics and evolution of equatorial ionospheric/thermospheric processes. Keywords. Ionosphere (equatorial ionosphere; ionospheric irregularities; plasma temperature and density)

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Ionosonde observations of daytime spread F at low latitudes

Journal of Geophysical Research Space Physics ◽

10.1002/2016ja023123 ◽

2016 ◽

Vol 121 (12) ◽

pp. 12,093-12,103 ◽

Cited By ~ 9

Author(s):

Chunhua Jiang ◽

Guobin Yang ◽

Jing Liu ◽

Tatsuhiro Yokoyama ◽

Tharadol Komolmis ◽

...

Keyword(s):

Low Latitudes ◽

Spread F

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Variational electric fields at low latitudes and their relation to spread-F and plasma irregularities

Journal of Atmospheric and Terrestrial Physics ◽

10.1016/s0021-9169(77)90139-8 ◽

1977 ◽

Vol 39 (3) ◽

pp. 247-262 ◽

Cited By ~ 22

Author(s):

J.A. Holtet ◽

N.C. Maynard ◽

J.P. Heppner

Keyword(s):

Electric Fields ◽

Plasma Irregularities ◽

Low Latitudes ◽

Spread F

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Imaging science at El Leoncito, Argentina

Annales Geophysicae ◽

10.5194/angeo-24-1375-2006 ◽

2006 ◽

Vol 24 (5) ◽

pp. 1375-1385 ◽

Cited By ~ 35

Author(s):

C. Martinis ◽

J. Baumgardner ◽

S. M. Smith ◽

M. Colerico ◽

M. Mendillo

Keyword(s):

Gravity Waves ◽

Conjugate Point ◽

South American ◽

Vertical Temperature ◽

Equatorial Ionization Anomaly ◽

Atmospheric Disturbances ◽

Low Latitudes ◽

Imaging Science ◽

Spread F ◽

Rayleigh Taylor Instability

Abstract. Thermospheric and mesospheric structures are studied using an all-sky imager located at El Leoncito, Argentina (31.8° S, 69.3° W, –18° mag lat). This site has relatively high geographic latitude for a location under the crest of the equatorial ionization anomaly (EIA), and thus observations can be used to study the intrusion of several equatorial processes into the midlatitude domain. In addition, it has a conjugate point close to the field of view of our companion imager at Arecibo, PR, allowing for the study of inter-hemispheric effects. Four types of phenomena were studied using 630.0 nm and 777.4 nm observations: (1) highly-structured airglow depletions associated with the Rayleigh-Taylor instability/equatorial spread-F (RTI/ESF) process, (2) brightness waves (BW) associated with the midnight temperature maximum (MTM), (3) strong airglow enhancements associated with the positive phase of ionospheric storms, and (4) simple (non-structured) bands of airglow depletions with characteristics matching a Perkins-like instability. Using 557.7 nm mesospheric observations, a fifth category of study deals with gravity waves probably generated by lower atmospheric disturbances, and mesospheric bores related to strong vertical temperature gradients. While ESF depletions and BW events are detected fairly frequently, the mid-latitude bands are not, and thus their successful imaging at El Leoncito offers the first example of the coupling from mid-latitudes to low-latitudes in the South American longitude sector. Preliminary results on these features are presented in this paper. Taken together, these five types of optical structures offer the opportunity to investigate coupling, both in altitude and latitude, of aeronomic processes at low latitudes in an under-sampled longitude sector in the Southern Hemisphere.

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