Comparison of the characteristics of ionospheric parameters obtained from FORMOSAT-3 and digisonde over Ascension Island

Abstract. Electron density profile data obtained from the FORMOSAT-3 radio occultation (RO) measurements over Ascension Island are used to study the bottomside thickness parameter B0 in the International Reference Ionosphere (IRI) model, scale height around the F region peak height, and other F2 region parameters. The RO data were collected when the radio occultation occurred at Ascension Island (345.6° E, 8.0° S) during the solar minimum activity period from May 2006 to April 2008. Results show that the B0 values are in moderate agreement with the ground-based observations in the equinox period (correlation coefficient r = 0.682) and winter (r = 0.570), with a strong correlation in summer (r = 0.750). The seasonal and diurnal variations in B0 over Ascension Island show peak values during the daytime and in winter. In addition, the B0 values were underestimated and overestimated in the RO measurements during the daytime and nighttime, respectively. Moreover, the comparison of scale heights shows that scale heights obtained from the retrieved data and digisonde observations are weakly correlation in all three seasons. Furthermore, although the effective scale height (HT) values were reverse of those obtained from the RO measurements and are higher during the nighttime than in the daytime, they are in good agreement with those from ground-based observations. This paper also provides a comprehensive discussion of the effect of the asymmetric ionospheric electron density profiles on RO measurements.

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New topside ionosphere model based on Vary-Chap function using radio occultation and topside sounder data

10.5194/egusphere-egu2020-12822 ◽

2020 ◽

Author(s):

Mengjie Wu

Keyword(s):

Electron Density ◽

Radio Occultation ◽

Satellite System ◽

Electron Density Profile ◽

Scale Height ◽

Topside Ionosphere ◽

Ionosphere Model ◽

Ionospheric Models ◽

Electron Density Profiles ◽

Global Navigation Satellite

The Global Navigation Satellite System (GNSS) radio occultation and topside sounder provide materials&#160;for the validation of a mathematical description&#160;of the&#160;topside ionosphere up to satellite altitude. An attempt to represent the topside electron density profile is using &#945;-Chapman function with a continuously varying scale height. In this study, the Vary-Chap scale height profiles are obtained based on Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) electron density profiles from 1 January 2008 to 31 December 2013 and fitted by a shape function composed of two weighted patterns&#160;representing&#160;the ion and electron&#160;contributions&#160;of lower and higher altitudes. The topside profiles of ISIS-1 data are used to define the transition height of different ions. The associated fitting parameters are analyzed to reveal their temporal and spatial features and variations along with enhancement of solar activity. Their prominent dependence on latitudes, longitudes, the local time, the season, and the solar cycle facilitates modeling of the Vary-Chap scale height in constructing empirical topside ionospheric models.

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Accuracy assessment of the quiet-time ionospheric F2 peak parameters as derived from COSMIC-2 multi-GNSS radio occultation measurements

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2020080 ◽

2021 ◽

Vol 11 ◽

pp. 18

Author(s):

Iurii Cherniak ◽

Irina Zakharenkova ◽

John Braun ◽

Qian Wu ◽

Nicholas Pedatella ◽

...

Keyword(s):

Electron Density ◽

Radio Occultation ◽

Electron Density Profile ◽

Equatorial Region ◽

Quality Data ◽

Quiet Time ◽

Density Profiles ◽

Middle Latitudes ◽

Receiver System ◽

Electron Density Profiles

The Constellation Observing System for Meteorology, Ionosphere, and Climate 2 (COSMIC-2) mission was launched into a low-inclination (24°) orbit on June 25, 2019. Six satellites, each with an advanced Tri-GNSS Radio-Occultation Receiver System (TGRS), provide a global and uniform data coverage of the equatorial region with several thousand electron density profiles daily. The COSMIC-2 electron density profiles, and specifically the derived ionospheric F2 peak parameters, are properly validated in this study with reliable “truth” observations. For this purpose, we used manually scaled ionograms from 29 ground-based ionosondes located globally at low and middle latitudes. For this validation campaign, we considered only geomagnetically quiet conditions in order to establish benchmark level of the new mission’s ionospheric observation quality and to evaluate the operational capability of the COSMIC-2 Radio Occultation (RO) payload at the background of normal day-to-day variability of the ionosphere. For reliable colocations between two independent techniques, we selected only COSMIC-2 RO profiles whose F2 peak point coordinates were within 5° of the closest ionosonde. Our comparison of the ionospheric F2 peak height (hmF2) derived from COSMIC-2 RO and ground-based ionosonde measurements showed a very good agreement, with a mean of ~5 and ~2 km at low and middle latitudes, respectively, while RMS error was of ~23 and ~14 km, respectively. That range corresponds to a deviation of only 6–9% from the reference, ionosonde observations. Examination of representative collocation events with multiple (2–5) simultaneous RO tracks near the same ionosonde with different RO geometry, multi-satellite and multi-GNSS combination give us observational evidence that COSMIC-2 RO-based EDPs derived from GPS and GLONAS links show good self-consistency in terms of the ionospheric F2 peak values and electron density profile shape. We can conclude that COSMIC-2 provides high quality data for specification the ionospheric electron density at the F2 peak region.

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Vertical electron density and topside effective scale height (HT) variations over the Indian equatorial and low latitude stations

Annales Geophysicae ◽

10.5194/angeo-29-1861-2011 ◽

2011 ◽

Vol 29 (10) ◽

pp. 1861-1872 ◽

Cited By ~ 33

Author(s):

K. Venkatesh ◽

P. V. S. Rama Rao ◽

P. L. Saranya ◽

D. S. V. V. D. Prasad ◽

K. Niranjan

Keyword(s):

Diurnal Variation ◽

Electron Density ◽

Scale Height ◽

Electron Content ◽

Iri Model ◽

Night Time ◽

Low Latitude ◽

Density Profiles ◽

Gps Tec ◽

Electron Density Profiles

Abstract. Understanding the vertical electron density profile, which is the altitudinal variation of ionospheric electron density distribution is an important aspect for the ionospheric investigations. In this paper, the bottom-side electron density profiles derived from ground based ionosonde data and the ROCSAT-1 in-situ electron density data were used to determine the estimates of the topside electron density profiles using α-Chapman function over an equatorial station Trivandrum (8.47° N, 76.91° E) and a low latitude station Waltair (17.7° N, 83.3° E) in the Indian region. The reconstructed electron density profiles are compared with IRI (2007) model derived vertical electron density profiles which resulted in significant deviations between the two different profiles. Both the reconstructed electron density profiles and the IRI model derived profiles are integrated independently to derive the Total Electron Content (TEC) values which are compared with GPS derived TEC values. TEC values derived from the reconstructed electron density profiles give better estimates with the GPS-TEC compared to those of IRI model derived TEC values. Compared to the GPS-TEC, the IRI model is underestimating the TEC values during day-time and is overestimating during night-time at both the stations. The percentage deviations of IRI derived TEC from GPS-TEC are larger compared to those between reconstructed profile derived TEC and GPS-TEC. F2-layer peak electron density, peak height and electron density at ROCSAT altitudes (≈600 km) are used to derive the effective scale heights (HT) of the topside ionosphere during the period from July 2003 to June 2004. The diurnal and seasonal variations of HT and E×B drift velocities are presented in this paper. The diurnal variation of the effective scale height (HT) shows peak values around noon hours with higher values during day-time and lower values during night-time both at Trivandrum and Waltair. The E×B drift velocities at both the places also have shown a clear diurnal variation with a negative peak around 04:00 LT and maximum during day-time hours. The higher and lower values of HT seem to be associated with positive and negative phases of the E×B drift velocities, respectively.

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Electron density profiles probed by radio occultation of FORMOSAT-7/COSMIC-2 at 520 and 800 km altitude

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-1615-2015 ◽

2015 ◽

Vol 8 (2) ◽

pp. 1615-1627

Author(s):

J. Y. Liu ◽

C. Y. Lin ◽

H. F. Tsai

Keyword(s):

Electron Density ◽

Density Profile ◽

Radio Occultation ◽

System Simulation ◽

Electron Density Profile ◽

Abel Inversion ◽

Simulation Experiments ◽

Density Profiles ◽

Satellite Altitude ◽

Electron Density Profiles

Abstract. The FORMOSAT-7/COSMIC-2 (F7/C2) will ultimately place 12 satellites in orbit with two launches with 24° inclination and 520 km altitude in 2016 and with 72° inclination and 800 km altitude in 2019. In this study, we examine the electron density probed at the two satellite altitudes 500 and 800 km by means of FORMOSAT-3/COSMIC (F3/C) observations at the packing orbit 500 km altitude and mission orbit 800 km altitude, as well as observing system simulation experiments (OSSE). The electron density derived from 500 and 800 km satellite altitude of the F3/C observation and the OSSE confirm that the standard Abel inversion can correctly derive the electron density profile.

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A High Latitude Model for the E Layer Dominated Ionosphere

Remote Sensing ◽

10.3390/rs13183769 ◽

2021 ◽

Vol 13 (18) ◽

pp. 3769

Author(s):

Sumon Kamal ◽

Norbert Jakowski ◽

Mohammed Mainul Hoque ◽

Jens Wickert

Keyword(s):

Electron Density ◽

Geomagnetic Latitude ◽

Peak Height ◽

Electron Density Profile ◽

Radio Waves ◽

Occurrence Probability ◽

Satellite Mission ◽

Primary Relationships ◽

Future Prediction ◽

Electron Density Profiles

Under certain conditions, the ionization of the E layer can dominate over that of the F2 layer. This phenomenon is called the E layer dominated ionosphere (ELDI) and occurs mainly in the auroral regions. In the present work, we model the variation of the ELDI for the Northern and Southern Hemispheres. Our proposed Neustrelitz ELDI Event Model (NEEM) is an empirical, climatological model that describes ELDI characteristics by means of four submodels for selected model observables, considering the dependencies on appropriate model drivers. The observables include the occurrence probability of ELDI events and typical E layer parameters that are important to describe the propagation medium for High Frequency (HF) radio waves. The model drivers are the geomagnetic latitude, local time, day of year, solar activity and the convection electric field. During our investigation, we found clear trends for the model observables depending on the drivers, which can be well represented by parametric functions. In this regard, the submodel NEEM-N characterizes the peak electron density NmE of the E layer, while the submodels NEEM-H and NEEM-W describe the corresponding peak height hmE and the vertical width wvE of the E layer electron density profile, respectively. Furthermore, the submodel NEEM-P specifies the ELDI occurrence probability %ELDI. The dataset underlying our studies contains more than two million vertical electron density profiles covering a period of almost 13 years. These profiles were derived from ionospheric GPS radio occultation observations on board the six COSMIC/FORMOSAT-3 satellites (Constellation Observing System for Meteorology, Ionosphere and Climate/Formosa Satellite Mission 3). We divided the dataset into a modeling dataset for determining the model coefficients and a test dataset for subsequent model validation. The normalized root mean square deviation (NRMS) between the original and the predicted model observables yields similar values across both datasets and both hemispheres. For NEEM-N, we obtain an NRMS varying between 36.1% and 47.1% and for NEEM-H, between 6.1% and 6.3%. In the case of NEEM-W, the NRMS varies between 38.5% and 41.1%, while it varies between 56.5% and 60.3% for NEEM-P. In summary, the proposed NEEM utilizes primary relationships with geophysical and solar wind observables, which are useful for describing ELDI occurrences and the associated changes of the E layer properties. In this manner, the NEEM paves the way for future prediction of the ELDI and of its characteristics in technical applications, especially from the fields of telecommunications and navigation.

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A complete solar cycle (2006–2016) studies of scale heights derived using COSMIC radio occultation retrieved electron density profiles

Journal of Atmospheric and Solar-Terrestrial Physics ◽

10.1016/j.jastp.2018.11.010 ◽

2019 ◽

Vol 182 ◽

pp. 101-118 ◽

Cited By ~ 1

Author(s):

G. Uma ◽

P.S. Brahmanandam ◽

S. Tulasi Ram ◽

K.-H. Wu ◽

Y.H. Chu

Keyword(s):

Solar Cycle ◽

Electron Density ◽

Radio Occultation ◽

Cosmic Radio ◽

Density Profiles ◽

Electron Density Profiles

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Variations of topside ionospheric scale heights over Millstone Hill during the 30-day incoherent scatter radar experiment

Annales Geophysicae ◽

10.5194/angeo-25-2019-2007 ◽

2007 ◽

Vol 25 (9) ◽

pp. 2019-2027 ◽

Cited By ~ 36

Author(s):

L. Liu ◽

W. Wan ◽

M.-L. Zhang ◽

B. Ning ◽

S.-R. Zhang ◽

...

Keyword(s):

Electron Density ◽

Thermal Structure ◽

Plasma Temperature ◽

Scale Height ◽

Incoherent Scatter Radar ◽

Density Profiles ◽

Incoherent Scatter ◽

Scatter Radar ◽

Vertical Scale ◽

Electron Density Profiles

Abstract. A 30-day incoherent scatter radar (ISR) experiment was conducted at Millstone Hill (288.5° E, 42.6° N) from 4 October to 4 November 2002. The altitude profiles of electron density Ne, ion and electron temperature (Ti and Te), and line-of-sight velocity during this experiment were processed to deduce the topside plasma scale height Hp, vertical scale height VSH, Chapman scale height Hm, ion velocity, and the relative altitude gradient of plasma temperature (dTp/dh)/Tp, as well as the F2 layer electron density (NmF2) and height (hmF2). These data are analyzed to explore the variations of the ionosphere over Millstone Hill under geomagnetically quiet and disturbed conditions. Results show that ionospheric parameters generally follow their median behavior under geomagnetically quiet conditions, while the main feature of the scale heights, as well as other parameters, deviated significantly from their median behaviors under disturbed conditions. The enhanced variability of ionospheric scale heights during the storm-times suggests that the geomagnetic activity has a major impact on the behavior of ionospheric scale heights, as well as the shape of the topside electron density profiles. Over Millstone Hill, the diurnal behaviors of the median VSH and Hm are very similar to each other and are not so tightly correlated with that of the plasma scale height Hp or the plasma temperature. The present study confirms the sensitivity of the ionospheric scale heights over Millstone Hill to thermal structure and dynamics. The values of VSH/Hp tend to decrease as (dTp/dh)/Tp becomes larger or the dynamic processes become enhanced.

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