Diurnal and seasonal variations of F2 layer characteristics over Irkutsk during the decrease in solar activity in 2003–2006: Observations and IRI-2001 model predictions

Ratovsky, Konstantin; Oinats, Alexey; Medvedev, Andrey

doi:10.1016/j.asr.2008.09.029

Cited by 19 publications

(14 citation statements)

References 16 publications

(22 reference statements)

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“…Generally, median data are not well correlated with the solar activity intra year variations (from 27 days to 1 year) with the exception of December daytime. This fact is in agreement with our previous studies (Ratovsky et al, 2009) where the difference between the observed f o F 2 medians and IRI prediction was found to be poorly correlated with the F 10.7 intra year variations. Finally, we selected the 1-year running mean of daily F 10.7 as a solar activity proxy input for LEMI.…”

Section: Lemi Construction Techniquesupporting

confidence: 82%

“…3(b)), the diurnal maximum of the summer N m F 2D is seen at prenoon and noon hours, rather than in the evening, which makes the evening and prenoon maxima of N m F 2 comparable to each other with increasing solar activity. This disagreement between the IRI-predicted and the observed summer diurnal behavior of f o F 2 was discussed previously by Ratovsky et al (2009). The Irkutsk summer diurnal behavior of the N m F 2D slope differs from the Millstone Hill behavior (Lei et al, 2005), where the summer N m F 2D varies only weakly during the day (2-3 10 5 cm −3 /100 s.f.u.).…”

Section: N M F 2 Morphologymentioning

confidence: 67%

“…The authors explained this phenomenon by suggesting that the nighttime recombination rate increases faster than the nighttime influx from the plasmasphere with increasing solar activity. Ratovsky et al (2009) observed that the solar activity dependence of the diurnal f o F 2 minimum at Irkutsk is much weaker than the IRI prediction. This disagreement manifests itself in the difference between the postmidnight N m F 2D obtained with LEMI and IRI.…”

Section: N M F 2 Morphologymentioning

confidence: 89%

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Local empirical model of ionospheric plasma density derived from Digisonde measurements at Irkutsk

Ratovsky

Oinats

2011

Earth Planet Sp

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Ionogram data from routine ionospheric observations in Irkutsk, Russia using a DPS-4 Digisonde sounder were hand-scaled for the 6-year period from December 2002 to December 2008 to derive a local empirical model of the electron density distribution in the bottomside ionosphere that provides a comprehensive description of the diurnal, seasonal, and solar activity variations of the major ionospheric characteristics. The paper describes the technique for building the local empirical model and the results of comparing its diurnal, seasonal, and solar activity specifications with the standard IRI-2007 climatological model for the same period of time, and retrospective observational data from the Millstone Hill incoherent scatter radar and a collocated Digisonde (1989Digisonde ( -1990Digisonde ( , 1998Digisonde ( -2004. Reasoning for the observed differences between the three datasets is then provided in terms of background physical phenomena. Primary focus of the paper is the behavior of three F 2 layer characteristics: the F 2 peak density (N m F 2 ), the peak height (h m F 2 ) and the bottomside thickness (B 0 ).

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Section: Lemi Construction Techniquesupporting

confidence: 82%

Section: N M F 2 Morphologymentioning

confidence: 67%

Section: N M F 2 Morphologymentioning

confidence: 89%

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Local empirical model of ionospheric plasma density derived from Digisonde measurements at Irkutsk

Ratovsky

Oinats

2011

Earth Planet Sp

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“…In Africa, the variations of the F 2 peak parameters obtained by the ionosonde at Ouagadougou (12.4 • N, 1.5 • S, 294.6 • E), Argentina (Batista and Abdu, 2004;Bertoni et al, 2006;Lee and Reinisch, 2006;Lee et al, 2008;Ezquer et al, 2008). In Europe, Ratovsky et al (2009) compared the observed ionospheric data with the IRI model at Irkutsk (52.3 • N, 104.3 • E), Russia. In Asia, Zhang et al (2007), Sethi et al (2007), Chuo and Lee (2008), Ayub et al (2009), Wichaipanich et al (2010 Fig.…”

Section: Introductionmentioning

confidence: 99%

Thailand low and equatorial F 2-layer peak electron density and comparison with IRI-2007 model

et al. 2012

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Ionosonde measurements obtained at two Thailand ionospheric stations, namely Chumphon (10.72 • N, 99.37• E, dip 3.0• N) and Chiang Mai (18.76 • N, 98.93• E, dip 12.7• N) are used to examine the variation of the F 2 -layer peak electron density (N m F 2 ) which is derived from the F 2 -layer critical frequency, f o F 2 . Measured data from September 2004 to August 2005 (a period of low solar activity) are analyzed based on the diurnal and seasonal variation and then compared with IRI-2007 model predictions. Our results show that, in general, the diurnal and seasonal variations of the N m F 2 predicted by the IRI (URSI and CCIR options) model show a feature generally similar to the observed N m F 2 . Underestimation mostly occurs in all seasons except during the September equinox and the December solstice at Chumphon, and the September equinox and the March equinox at Chiang Mai, when they overestimate those measured. The best agreement between observation and prediction occurs during the pre-sunrise to post-sunrise hours. The best agreement of the %PD values of both the options occurs during the March equinox, while the agreement is the worst during the September equinox. The N m F 2 values predicted by the CCIR option show a smaller range of deviation than the N m F 2 values predicted by the URSI option. During post-sunset to morning hours (around 21:00-09:00 LT), the observed N m F 2 at both stations are almost identical for the periods of low solar activity. However, during daytime, the observed N m F 2 at Chumphon is lower than that at Chiang Mai. The difference between these two stations can be explained by the equatorial ionospheric anomaly (EIA). These results are important for future improvements of the IRI model for N m F 2 over Southeast Asia, especially for the areas covered by Chumphon and Chiang Mai stations.

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“…On the average, a June solstice to December solstice difference of 90 km is observed in daytime hmF2 but the difference is less perceptible in the nighttime. In December solstice, the midnight values of hmF2 are higher than those of daytime maximum hmF2 and this behavior is reminiscent of mid-latitude stations (Mikhailov and Marin 2001;Liu et al 2007b;Ratovsky and Oinats 2009). It has been reported by number of workers that in the Indian zone, the crest of the EIA recedes in December solstice to~10°N geomagnetic (Rastogi et al 1972;Bhuyan et al 2003;Chakrabarty and Hajra 2009).…”

Section: The Variation Of Nmf2 With Equatorial Electrojet Strengthmentioning

confidence: 95%

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

2015

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The characteristics of the F2 layer parameters NmF2 and hmF2 over Dibrugarh (27.5°N, 95°E, 17°N geomagnetic, 43°dip) measured by a Canadian Advanced Digital Ionosonde (CADI) for the period of August 2010 to July 2014 are reported for the first time from this low mid-latitude station lying within the daytime peak of the longitudinal wave number 4 structure of equatorial anomaly (EIA) around the northern edge of anomaly crest. Equinoctial asymmetry is clearly observed at all solar activity levels whereas the midday winter anomaly is observed only during high solar activity years and disappears during the temporary dip in solar activity in 2013 but forenoon winter anomaly can be observed even at moderate solar activity. The NmF2/hmF2 variations over Dibrugarh are compared with that of Okinawa (26.5°N, 127°E, 17°N geomagnetic), and the eastward propagation speed of the wave number 4 longitudinal structure from 95°E to 127°E is estimated. The speed is found to be close to the theoretical speed of the wave number 4 (WN4) structure. The correlation of daily NmF2 over Dibrugarh and Okinawa with solar activity exhibits diurnal and seasonal variations. The highest correlation in daytime is observed during the forenoon hours in equinox. The correlation of daily NmF2 (linear or non-linear) with solar activity exhibits diurnal variation. A tendency for amplification with solar activity is observed in the forenoon and late evening period of March equinox and the postsunset period of December solstice. NmF2 saturation effect is observed only in the midday period of equinox. Non-linear variation of neutral composition at higher altitudes and variation of recombination rates with solar activity via temperature dependence may be related to the non-linear trend. The noon time maximum NmF2 over Dibrugarh exhibits better correlation with equatorial electrojet (EEJ) than with solar activity and, therefore, new low-latitude NmF2 index is proposed taking both solar activity and EEJ strength into account.

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Diurnal and seasonal variations of F2 layer characteristics over Irkutsk during the decrease in solar activity in 2003–2006: Observations and IRI-2001 model predictions

Cited by 19 publications

References 16 publications

Local empirical model of ionospheric plasma density derived from Digisonde measurements at Irkutsk

Local empirical model of ionospheric plasma density derived from Digisonde measurements at Irkutsk

Thailand low and equatorial F 2-layer peak electron density and comparison with IRI-2007 model

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

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