scholarly journals Statistical Study of Ionospheric Equivalent Slab Thickness at Guam Magnetic Equatorial Location

2021 ◽  
Vol 13 (24) ◽  
pp. 5175
Author(s):  
Yuqiang Zhang ◽  
Zhensen Wu ◽  
Jian Feng ◽  
Tong Xu ◽  
Zhongxin Deng ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Magnetic Activity ◽  
Equatorial Region ◽  
Topside Ionosphere ◽  
Slab Thickness ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Time Period ◽  
Storm Effect

The ionospheric equivalent slab thickness (τ) is defined as the ratio of the total electron content (TEC) to the F2-layer peak electron density (NmF2), and it is a significant parameter representative of the ionosphere. In this paper, a comprehensive statistical analysis of the diurnal, seasonal, solar, and magnetic activity variations in the τ at Guam (144.86°E, 13.62°N, 5.54°N dip lat), which is located near the magnetic equator, is presented using the GPS-TEC and ionosonde NmF2 data during the years 2012–2017. It is found that, for geomagnetically quiet days, the τ reaches its maximum value in the noontime, and the peak value in winter and at the equinox are larger than that in summer. Moreover, there is a post-sunset peak observed in the winter and equinox, and the τ during the post-midnight period is smallest in equinox. The mainly diurnal and seasonal variation of τ can be explained within the framework of relative variation of TEC and NmF2 during different seasonal local time. The dependence of τ on the solar activity shows positive correlation during the daytime, and the opposite situation applies for the nighttime. Specifically, the disturbance index (DI), which can visually assess the relationship between instantaneous τ values and the median, is introduced in the paper to quantitatively describe the overall pattern of the geomagnetic storm effect on the τ variation. The results show that the geomagnetic storm seems to have positive effect on the τ during most of the storm-time period at Guam. An example, on the 1 June 2013, is also presented to analyze the physical mechanism. During the positive storms, the penetration electric field, along with storm time equator-ward neutral wind, tends to increase upward drift and uplift F region, causing the large increase in TEC, accompanied by a relatively small increase in NmF2. On the other hand, an enhanced equatorward wind tends to push more plasma, at low latitudes, into the topside ionosphere in the equatorial region, resulting in the TEC not undergoing severe depletion, as with NmF2, during the negative storms. The results would complement the analysis of τ behavior during quiet and disturbed conditions at equatorial latitudes in East Asia.

scholarly journals Climatology of ionospheric slab thickness

2004 ◽  
Vol 22 (1) ◽  
pp. 25-33 ◽  
Author(s):  
B. Jayachandran ◽  
T. N. Krishnankutty ◽  
T. L. Gulyaeva
Keyword(s):  
High Latitude ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Magnetic Activity ◽  
Slab Thickness ◽  
Electron Content ◽  
Night Time ◽  
Total Electron ◽  
Ionospheric Physics ◽  
F Region

Abstract. The ionospheric slab thickness τ defined as a ratio of the total electron content (TEC) to the F-region peak electron density (NmF2) has been analysed during the solar maximum (1981) and minimum (1985) phases of an intense, the 21st, solar cycle. Hourly values of TEC and NmF2 collected at Hawaii (low-latitude), Boulder (mid-latitude) and Goosebay (high-latitude) are used in the study. Climatology of the slab thickness is described by the diurnal, seasonal, solar and magnetic activity variations of τ for the different latitude zones. It is found that, for magnetically quiet days of solar maximum, increased ionization of NmF2 and TEC during the daytime is accompanied by an increased thickness of the ionosphere compared to the night-time for non-auroral latitudes. However, the reverse is found to be true during the solar minimum compensating TEC against a weak night-time ionization of NmF2. For the high-latitude the night-time slab thickness is higher compared to the daytime for both the solar phases. Ratios of daily peak to minimum values of slab thickness vary from 1.3 to 3.75 with the peaks of τ often observed at pre-sunrise and post-sunset hours. The average night-to-day ratios of τ vary from 0.68 to 2.23. The day-to-day variability of τ, expressed in percentage standard deviation, varies from 10% by day (equinox, high-latitude) to 67% by night (summer, mid-latitude) during solar minimum and from 10% by day (winter and equinox, mid-latitude) to 56% by night (equinox, high-latitude) during solar maximum. A comprehensive review of slab thickness related literature is given in the paper. Key words. Ionospheric physics

scholarly journals Morphology in the total electron content under geomagnetic disturbed conditions: results from global ionosphere maps

2007 ◽  
Vol 25 (7) ◽  
pp. 1555-1568 ◽  
Author(s):  
Zhao Biqiang ◽  
Wan Weixing ◽  
Liu Libo ◽  
Mao Tian
Keyword(s):  
Geomagnetic Storm ◽  
Local Time ◽  
Statistical Study ◽  
Electron Content ◽  
Geomagnetic Disturbances ◽  
Total Electron ◽  
Summer Hemisphere ◽  
Storm Effect ◽  
Time Variations ◽  
Winter Hemisphere

Abstract. Using 8-year global ionosphere maps (GIMs) of TEC products from the Jet Propulsion Laboratory (JPL), we make a statistical study on the morphology of the global ionospheric behaviors with respect to the geomagnetic disturbances. Results show that the behaviors of TEC during geomagnetic storm present clear seasonal and local time variations under geomagnetic control in a similar way as those of NmF2 (Field and Rishbeth, 1997). A negative phase of TEC occurs with high probability in the summer hemisphere and most prominent near the geomagnetic poles, while a positive phase is obvious in the winter hemisphere and in the far pole region. A negative storm effect toward lower latitudes tends to occur from post-midnight to the morning sector and recedes to high latitude in the afternoon. A positive storm effect is separated by geomagnetic latitudes and magnetic local time. Furthermore, ionospheric responses at different local time sectors with respect to the storm commencement shows very different developing processes corresponding to the evolution of the geomagnetic storm. A daytime positive storm effect is shown to be more prominent in the American region than those in the Asian and European regions, which may suggest a longitudinal effect of the ionospheric storm.

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 TEC variations during low solar activity period (2005–2007) near the Equatorial Ionospheric Anomaly Crest region in India

2009 ◽  
Vol 27 (3) ◽  
pp. 1047-1057 ◽  
Author(s):  
Mala S. Bagiya ◽  
H. P. Joshi ◽  
K. N. Iyer ◽  
M. Aggarwal ◽  
S. Ravindran ◽  
...  
Keyword(s):  
Solar Activity ◽  
Geomagnetic Storm ◽  
Activity Period ◽  
Electron Content ◽  
Ionospheric Storm ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Short Period ◽  
Storm Effect ◽  
Solar Activity Period

Abstract. The dual frequency signals from the GPS satellites recorded at Rajkot (22.29° N, 70.74° E, Geographic, 14.03° N Geomagnetic) near the Equatorial ionization anomaly crest in India have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007. In this study, we describe the diurnal and seasonal variations of TEC, solar activity dependence of TEC and effects of a space weather related event, a geomagnetic storm on TEC. The diurnal variation of TEC shows pre-dawn minimum for a short period of time, followed by a steep early morning increase and then reaches maximum value between 14:00 LT and 16:00 LT. The mean diurnal variations during different seasons are brought out. It is found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation. TEC values have been decreasing since 2005, onwards showing positive correlation with solar activity. TEC variations during the geomagnetic storm commencing 24 August 2005 with Dst=−216 nT are analysed. TEC shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day. The equatorial Electrojet control on the development of the equatorial anomaly is also demonstrated.

scholarly journals Enhanced variability in the topside ionosphere

1995 ◽  
Vol 38 (3-4) ◽  
Author(s):  
T. Gulyaeva ◽  
P. Spalla
Keyword(s):  
Solar Activity ◽  
Faraday Rotation ◽  
Solar Minimum ◽  
High Solar Activity ◽  
Dynamic Processes ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Rotation Method

Variability of total electron content (TEC) observed by the Faraday rotation method at Florence has been stud- ied with the same technique applied independently to the ionospheric parameters foF2 and M(3000)F2 of the ground-based vertical-incidence sounding database (VID). Results of daily and monthly TEC disturbance indices at sub-ionospheric point are compared with variability of the ionosphere at Rome and Gibilmanna (de- duced from VID) for a period of 1976 to 1991. During moderate and high solar activity the variability of TEC is greater than the variability of VID, whereas during solar minimum the situation is opposite. In this context joint TEC and VID observations distinguish either the F region peak or the topside ionosphere heights where the dynamic processes dominate at different times.

scholarly journals The ionospheric response in the Brazilian sector during the super geomagnetic storm on 20 November 2003

2007 ◽  
Vol 25 (4) ◽  
pp. 863-873 ◽  
Author(s):  
F. Becker-Guedes ◽  
Y. Sahai ◽  
P. R. Fagundes ◽  
E. S. Espinoza ◽  
V. G. Pillat ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Recovery Phase ◽  
Peak Height ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Station ◽  
Ionospheric Response ◽  
F Region ◽  
The Difference ◽  
Ionospheric Sounding

Abstract. A very intense geomagnetic storm (superstorm) began with storm sudden commencement (SSC) at 08:03 UT on 20 November 2003, as a result of the coronal mass ejection (CME) by sunspot 484 hurled into space on 18 November 2003. The geomagnetic storm attained |Dst|max=472 nT at 20:00 UT (20 November). In this paper we present the simultaneous ionospheric sounding observations, using the Canadian Advanced Digital Ionosondes (CADIs), carried out from Palmas (PAL; 10.2° S, 48.2° W; dip latitude 5.5° S; a near equatorial station) and São José dos Campos (SJC; 23.2° S, 45.9° W; dip latitude 17.6° S; station located under the crest of equatorial ionospheric anomaly), Brazil. In addition, total electron content (TEC) measurements from several GPS receiving stations in the Brazilian sector during this storm are presented. The simultaneous ionospheric sounding observations carried out at SJC and PAL, and TEC observations on 3 consecutive days viz., 19 November (quiet), 20 November (disturbed) and 21 November (recovery phase) are presented. Salient features from the ionospheric observations in the Brazilian sector during the superstorm are discussed. The difference in the observed ionospheric response at the two stations (PAL and SJC) is considerable. This is not surprising given that PAL is close to the magnetic equator and SJC is near the crest of the equatorial ionospheric anomaly (EIA). It should be pointed out that soon after the SSC (about 4 h later), the F-region critical frequency (foF2), the F-region peak height (hpF2), and variations of virtual heights at different frequencies (iso-frequency plots) all show wavelike oscillations of the F-region during daytime at both the ionospheric sounding stations. Unusual rapid uplifting of F-region at PAL was observed during both the main and recovery phases of the storm.

scholarly journals Topside Ionosphere and Plasmasphere Modelling Using GNSS Radio Occultation and POD Data

2021 ◽  
Vol 13 (8) ◽  
pp. 1559
Author(s):  
Fabricio S. Prol ◽  
M. Mainul Hoque
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Radio Occultation ◽  
Geomagnetic Latitude ◽  
Low Earth Orbit ◽  
Activity Level ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
Solar Activity Level

A 3D-model approach has been developed to describe the electron density of the topside ionosphere and plasmasphere based on Global Navigation Satellite System (GNSS) measurements onboard low Earth orbit satellites. Electron density profiles derived from ionospheric Radio Occultation (RO) data are extrapolated to the upper ionosphere and plasmasphere based on a linear Vary-Chap function and Total Electron Content (TEC) measurements. A final update is then obtained by applying tomographic algorithms to the slant TEC measurements. Since the background specification is created with RO data, the proposed approach does not require using any external ionospheric/plasmaspheric model to adapt to the most recent data distributions. We assessed the model accuracy in 2013 and 2018 using independent TEC data, in situ electron density measurements, and ionosondes. A systematic better specification was obtained in comparison to NeQuick, with improvements around 15% in terms of electron density at 800 km, 26% at the top-most region (above 10,000 km) and 26% to 55% in terms of TEC, depending on the solar activity level. Our investigation shows that the developed model follows a known variation of electron density with respect to geographic/geomagnetic latitude, altitude, solar activity level, season, and local time, revealing the approach as a practical and useful tool for describing topside ionosphere and plasmasphere using satellite-based GNSS data.

scholarly journals EFEK CME HALO PENUH PADA IONOSFER LINTANG RENDAH DARI DATA GPS BAKO DI CIBINONG [EFFECT OF FULL HALO CME ON LOW LATITUDE IONOSPHERE FROM BAKO GPS DATA IN CIBINONG]

2018 ◽  
Vol 15 (1) ◽  
pp. 51
Author(s):  
Fakhrizal Muttaqien ◽  
Buldan Muslim
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Geomagnetic Disturbance ◽  
Main Phase ◽  
Gps Data ◽  
Electron Content ◽  
Ionospheric Storm ◽  
Total Electron ◽  
Dst Index ◽  
Software Analysis

A full halo coronal mass ejections (CMEs) are most energetic solar events that eject huge amount of mass and magnetic fields into heliosphere with 360o angular angle. The full halo CME effect on the ionosphere can be determined from the ionospheric total electron content (TEC) derived from GPS data. GPS data from BAKO station in Cibinong, satellite orbital data (brcd files) and intrumental bias data (DCB files) have been used to obtain TEC using GOPI software. Analysis of  the full halo CME data, Dst index, and TEC during October 2003 and February 2014 showed that the full halo CME could cause ionospheric disturbances called ionospheric storms. Magnitude and time delay of the ionospheric storms  depended on the full halo CME speed. For the high-speed full halo CME, the negative ionospheric storm generally occured during recovery phase of the geomagnetic storm. When the initial phase of geomagnetic disturbance with increasing Dst index more than +30 nT, the ionospheric storm occured during main phase of geomagnetic disturbance although the main phase of geomagnetic disturbance did not reach geomagnetic storm condition. ABSTRAKCoronal mass ejection  (CME) halo penuh merupakan peristiwa matahari  berenergi tinggi, yang menyemburkan massa dan medan magnet ke heliosfer dengan sudut angular sebesar 360º. Efek  CME halo penuh pada ionosfer dapat diketahui dari Total Electron Content (TEC). Data GPS BAKO di Cibinong, data orbit satelit (file brcd) dan data bias instrumental (file DCB) dapat digunakan untuk penentuan TEC menggunakan software GOPI. Analisis data CME halo penuh, indeks Dst, dan TEC selama bulan Oktober 2003 dan Februari 2014 menunjukkan bahwa CME halo penuh dapat menimbulkan gangguan ionosfer yang disebut badai ionosfer. Besar dan selang waktu badai ionosfer setelah terjadinya CME, tergantung pada kelajuan CME halo penuh. Untuk CME halo penuh berkelajuan tinggi, badai ionosfer negatif umumnya terjadi pada fase pemulihan badai geomagnet. Jika fase awal gangguan geomagnet diawali dengan peningkatan indeks Dst melebihi +30 nT, maka badai ionosfer dapat terjadi pada fase utama gangguan geomagnet walau gangguan geomagnet setelah  fase awal tidak mencapai kondisi badai geomagnet. 

Sign in / Sign up

Export Citation Format

Share Document