scholarly journals Imaging observations of nighttime mid-latitude F-region field-aligned irregularities by an MU radar ultra-multi-channel system

2008 ◽  
Vol 26 (8) ◽  
pp. 2345-2352 ◽  
Author(s):  
S. Saito ◽  
M. Yamamoto ◽  
H. Hashiguchi
Keyword(s):  
Radar Imaging ◽  
Doppler Velocity ◽  
Electron Content ◽  
Imaging Analysis ◽  
Channel System ◽  
Total Electron ◽  
F Region ◽  
Mu Radar ◽  
Scale Structures ◽  
Field Aligned Irregularities

Abstract. Mid-latitude F-region field-aligned irregularities (FAIs) were studied by using the middle-and-upper atmosphere (MU) radar ultra-multi-channel system with the radar imaging technique. On 12 June 2006, F-region FAI echoes with a period of about one hour were observed intermittently. These echoes were found to be embedded in medium-scale traveling ionospheric disturbances (MSTIDs) observed as variations of total electron content (TEC). The echoes drifting away from (toward) the radar were observed in the depletion (enhancement) phase of the MSTID. The Doppler velocity of the echoes is consistent with the range rates in the the range-time-intensity (RTI) maps. Fine scale structures with a spatial scale of 10 km or less were found by the radar imaging analysis. Those structures with positive Doppler velocities (moving away from the radar) appeared to drift north- (up-) westward, and those with negative Doppler velocities south- (down-) eastward approximately along the wavefronts of the MSTID. FAIs with positive Doppler velocities filling TEC depletion regions were observed.

scholarly journals Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill

2000 ◽  
Vol 18 (1) ◽  
pp. 111-119 ◽  
Author(s):  
J. C. Foster ◽  
J. M. Holt ◽  
L. J. Lanzerotti
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Ionospheric Disturbance ◽  
Geomagnetic Disturbance ◽  
Oscillatory Behavior ◽  
Doppler Velocity ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Magnetic Field Variations

Abstract. Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor ~2) near the 320 km Shuttle orbital altitude persisted for ~35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of ~6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a ~80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar ~80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (~95 s period) accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID) launched by the enhanced auroral activity. The most reasonable conclusion is that the ionospheric oscillations were a result of the coincident geomagnetic disturbance. The pronounced depletion of the bottomside ionosphere, however, accentuated the oscillatory behavior during the interval following the Shuttle OMS burn..Key words. Ionosphere (active experiments; ionospheric disturbances) · Magnetospheric physics (storms and substorms)

scholarly journals Study of Equatorial Plasma Bubbles Using ASI and GPS Systems

2020 ◽  
Author(s):  
Dada P. Nade ◽  
Swapnil S. Potdar ◽  
Rani P. Pawar
Keyword(s):  
Electron Content ◽  
Gps Receiver ◽  
Plasma Bubble ◽  
Low Latitude ◽  
Total Electron ◽  
Plasma Irregularities ◽  
Plasma Bubbles ◽  
F Region ◽  
Equatorial Plasma Bubbles ◽  
Background Density

The plasma irregularities have been frequently observed in the F-region, at low latitude regions, due to the instability processes occurring in the ionosphere. The depletions in electron density, as compared to the background density, is a signature of the plasma irregularities. These irregularities are also known as the “equatorial plasma bubble” (EPB). These EPBs can measure by the total electron content (TEC) using GPS receiver and by images of the nightglow OI 630.0 nm emissions using all sky imager (ASI). The current chapter is based on the review on the signature of the EPBs in TEC and ASI. measurements. We have also discussed the importance of the study of EPBs.

scholarly journals Equatorial scintillations in relation to the development of ionization anomaly

2006 ◽  
Vol 24 (5) ◽  
pp. 1429-1442 ◽  
Author(s):  
S. Ray ◽  
A. Paul ◽  
A. DasGupta
Keyword(s):  
Subsequent Development ◽  
Equatorial Electrojet ◽  
Equatorial Region ◽  
Magnetic Equator ◽  
Electron Content ◽  
Navigation Systems ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
F Region ◽  
L Band

Abstract. The irregularities in the electron density distribution of the ionosphere over the equatorial region frequently disrupt space-based communication and navigation links by causing severe amplitude and phase scintillations of signals. Development of a specification and forecast system for scintillations is needed in view of the increased reliance on space-based communication and navigation systems, which are vulnerable to ionospheric scintillations. It has been suggested in recent years that a developed equatorial anomaly in the afternoon hours, with a steep gradient of the F-region ionization or Total Electron Content (TEC) in the region between the crest and the trough, may be taken as a precursor to scintillations on transionospheric links. Latitudinal gradient of TEC measured using Faraday Rotation technique from LEO NOAA 12/14 transmissions during the afternoon hours at Calcutta shows a highly significant association with L-band scintillations recorded on the INMARSAT link, also from Calcutta, during the equinoxes, August through October 2000, and February through April 2001. The daytime equatorial electrojet is believed to control the development of the equatorial anomaly and plays a crucial role in the subsequent development of F-region irregularities in the post-sunset hours. The diurnal maximum and integrated value (integrated from the time of onset of plasma influx to off-equatorial latitudes till local sunset) of the strength of the electrojet in the Indian longitude sector shows a significant association with post-sunset L-band scintillations recorded at Calcutta during the two equinoxes mentioned earlier. Generation of equatorial irregularities over the magnetic equator in the post-sunset hours is intimately related to the variation of the height of the F-layer around sunset. Ionosonde data from Kodaikanal, a station situated close to the magnetic equator, has been utilized to calculate the vertical drift of the F-layer over the magnetic equator for the period August through October 2000. The post-sunset F-region height rise over the magnetic equator shows a remarkable correspondence with the occurrence of scintillations at Calcutta located near the northern crest of the equatorial anomaly. Existence of a flat-topped ionization distribution over the magnetic equator around sunset has been suggested as a possible indication of occurrence of post-sunset scintillations. Width of the latitudinal distribution of ionization obtained from DMSP satellite shows some correspondence with post-sunset L-band scintillations. During the period of observation of the present study (August through October 2000, and February through April 2001), it has been observed that although the probability of occurrence of scintillations is high on days with flat-topped ion density variation over the equator, there are cases when no scintillations were observed even when a pronounced flat top variation was recorded.

scholarly journals Ionospheric effects on the F region during the sunrise for the annular solar eclipse over Taiwan on 21 May 2012

2013 ◽  
Vol 31 (11) ◽  
pp. 1891-1898 ◽  
Author(s):  
Y. J. Chuo
Keyword(s):  
Solar Eclipse ◽  
Peak Height ◽  
Scale Height ◽  
Rate Of Change ◽  
Slab Thickness ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Northern Pacific ◽  
Annular Solar Eclipse

Abstract. On 21 May 2012 (20:56, Universal Time; UT, on 20 May), an annular solar eclipse occurred, beginning at sunrise over southeast China and moving through Japan, sweeping across the northern Pacific Ocean, and completing its passage over the western United States at sunset on 20 May 2012 (02:49 UT, 21 May). We investigated the eclipse area in Taiwan, using an ionosonde and global positioning system (GPS) satellite measurements. The measurements of foF2, hmF2, bottomside scale height around the peak height (Hm), and slab thickness (B0) were collected at the ionosonde station at Chung-Li Observatory. In addition, we calculated the total electron content (TEC) to study the differences inside and outside the eclipse area, using 3 receivers located at Marzhu (denoted as MATZ), Hsinchu (TNML), and Henchun (HENC). The results showed that the foF2 values gradually decreased when the annularity began and reached a minimum level of approximately 2.0 MHz at 06:30 LT. The hmF2 immediately decreased and then increased during the annular eclipse period. The TEC variations also appeared to deplete in the path of the eclipse and opposite the outside passing area. Further, the rate of change of the TEC values (dTEC / dt measured for 15 min) was examined to study the wave-like fluctuations. The scale height near the F2 layer peak height (Hm) also decreased and then increased during the eclipse period. To address the effects of the annular eclipse in the topside and bottomside ionosphere, this study provides a discussion of the variations between the topside and bottomside ionospheric parameters during the eclipse period.

scholarly journals MODEL OF MID-AND LOW-LATITUDE F REGION IONOSPHERE AND PROTONOSPHERE

1981 ◽  
Vol 20 (1) ◽  
pp. 11-39
Author(s):  
A. Tan ◽  
S. T. Wu
Keyword(s):  
Drift Velocity ◽  
Loss Rate ◽  
Electron Content ◽  
Low Latitude ◽  
Ion Density ◽  
Total Electron ◽  
F Region ◽  
Latitude Station ◽  
Nocturnal Increase ◽  
Radio Beacon

The coupled continuity and momentum equations of O+ and H+ ions in the F region and the protonosphere are solved for a mid-latitude station (Arecibo) and a low-latitude station (Jicamarca) to investigate the diurnal behavior of the peak electron density NmF2, the height of the peak HmF2, the O+-H+ transition height Htr and the transition level ion density Ntr. The effects of the neutral wind on the NmF2, HmF2 Ntr and Htr curves above Arecibo are more important than and generally in the opposite direction of those of a sinusoidal elctromagnetic drift. the electromagnetic drift plays a fa-reaching role in shaping the ionospheric and protonospheric profiles at Jicamarca.  An upward drift that peaks during the day produces a 'valey' in the NmF2 curve, while an upward drift that stays constant during ost of the day produces a 'plateau'.  The nighttime decay in Nmf2 is due to the conbined effects of a slow downward drift and chemical recombination.  A nocturnal increase in NmF2 is due to a sufficiently large downward drift when the resultant 'squeezing' of the field tubes overcomes the O+ loss rate.  The diurnal variations of HmF2 and Htr tend to follow that of the upward drift velocity pattern, with gradients somewhat smoothed.  A downward reversal of the drift at sunset causes and enhancement in the post-sunset Ntr. Finally, the applicability of the model to the study of the total electron content measurements of the ATS-6 radio beacon experiments at Ootacamund is demonstrated.  By comparing with the observed values, the probable drift velocities over Ootacamund are determined for October and December, 1975.  The drift velocity patterns show broad similitarities with those observed over Jicamarca.

scholarly journals Electron density profile modeling

1996 ◽  
Vol 39 (3) ◽  
Author(s):  
R. G. Ezquer ◽  
M. Mosert de Gonzalez ◽  
T. Heredia
Keyword(s):  
Electron Density ◽  
Characteristic Point ◽  
Base Point ◽  
Electron Density Profile ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Bottom Side ◽  
The Difference ◽  
Good Agreement

The Base Point Model (BPM) is used to model the electron density (N) profile in the ionosphere, This model assumes two Chapman profile expressions one for the bottomside and one for the topside, and requires a characteristic point called "F region base point". The comparison among the modeled and experimental bottom-side N profiles obtained from Tucuman (26,9°S; 65.4°W) ionosonde shows that, in general, there is a very good agreement within 30 km below the height of the maximum N(hm). Cases with a very good agreement for the entire N-profile are observed. The study of the electron content below hm and the Total Electron Content (TEC) measured over Tucuman shows that, the difference among predicted and measured TEC is due to the disagreement in the topside N-profile more than that observed in the bottomside N-profile.

scholarly journals Comparison of volcanic explosions in Japan using impulsive ionospheric disturbances

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Mokhamad Nur Cahyadi ◽  
Eko Yuli Handoko ◽  
Ririn Wuri Rahayu ◽  
Kosuke Heki
Keyword(s):  
Wave Speed ◽  
Volcanic Eruptions ◽  
Satellite System ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Gnss Receivers ◽  
Explosive Volcanic Eruptions ◽  
Global Navigation Satellite ◽  
Volcanic Explosions

AbstractUsing the ionospheric total electron content (TEC) data from ground-based Global Navigation Satellite System (GNSS) receivers in Japan, we compared ionospheric responses to five explosive volcanic eruptions 2004–2015 of the Asama, Shin-Moe, Sakurajima, and Kuchinoerabu-jima volcanoes. The TEC records show N-shaped disturbances with a period ~ 80 s propagating outward with the acoustic wave speed in the F region of the ionosphere. The amplitudes of these TEC disturbances are a few percent of the background absolute vertical TEC. We propose to use such relative amplitudes as a new index for the intensity of volcanic explosions. Graphical Abstract

The hemispheric asymmetry of ionospheric lunitidal signatures during Sudden Stratospheric Warmings in the eastern Asian and American sectors

2021 ◽  
Author(s):  
Jing Liu ◽  
Donghe Zhang ◽  
Larisa Goncharenko ◽  
Shun-Rong Zhang ◽  
Maosheng He ◽  
...  
Keyword(s):  
Hemispheric Asymmetry ◽  
Field Configuration ◽  
Weddell Sea ◽  
Electron Content ◽  
Total Electron ◽  
Total Electron Content Data ◽  
Vertical Coupling ◽  
F Region ◽  
Weddell Sea Anomaly ◽  
Plasma Distribution

<p>During Sudden Stratospheric Warming events, the ionosphere exhibits phase-shifted semi-diurnal perturbations, which are typically attributed to vertical coupling associated with the semi-diurnal lunar tide (M2). Our understanding of ionospheric responses to M2 is limited. This study focuses on fundamental vertical coupling processes associated with the latitudinal extent and hemispheric asymmetry of ionospheric M2 signatures, using total electron content data from the eastern Asian and American sectors. Our results illustrate that the asymmetry maximizes at around 15°N and 20°S magnetic latitudes. In the southern hemisphere, the M2-like signatures extend deep into midlatitude and, in the American sector, encounter the Weddell Sea Anomaly. The M2 amplitude is larger in the northern hemisphere and such asymmetry is more distinct in the eastern Asian sector. The hemispheric asymmetry of M2 signatures in the low latitude can be primarily explained by the trans-equatorial wind modulation of the equatorial plasma fountain. Other physical processes could also be relevant, including hemispheric asymmetry of the M2 below the F region, the ambient thermospheric composition and ionospheric plasma distribution, and the geomagnetic field configuration.</p>

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