The seasonal and solar cycle variations of electron density gradient scale length, vertical drift and layer height during magnetically quiet days: Implications for Spread F over Trivandrum, India

Manju, G.; Devasia, C. V.; Ravindran, Sudha

doi:10.1186/bf03352986

Cited by 8 publications

(7 citation statements)

References 20 publications

(22 reference statements)

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“…The smallest values exist in March for both solar minimum (1.2 × 10 −2 km −1 ) and maximum (3.7 × 10 −3 km −1 ). These values of L max −1 (0.37–2.1 × 10 −2 km −1 ) are close to that in Mendillo et al [1992] (∼4 × 10 −2 km −1 ), but smaller than that in Ossakow et al [1979] (0.1–0.2 km −1 ) and Manju et al [2009] (0.4–1 × 10 −1 km −1 ). Furthermore, it can be found that there is not clear trend in the monthly L max −1 variations for both two solar epochs.…”

Section: Resultssupporting

confidence: 61%

“…It is noted that the values of L max −1 during solar minimum are greater than those during solar maximum. Manju et al [2009] also presented that the L −1 values are greater during solar minimum in the Indian sector. This might be because the density gradient is smaller [ Jayachandran et al , 1993] and the ambient density is greater when the F‐layer is located at higher altitude during solar maximum.…”

Section: Resultsmentioning

confidence: 87%

“…On the basis of the previous works mentioned above and in other longitudinal sectors [e.g., Jayachandran et al , 1993; Mendillo et al , 1992; Manju et al , 2009], the onset conditions of ESF chosen in the present study are PRE velocity and h ′ F , gradient density scale length, and local linear growth rate of CR‐T instability. These onset conditions are analyzed concurrently in the Peruvian sector for the first time.…”

Section: Introductionmentioning

confidence: 99%

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Occurrence and onset conditions of postsunset equatorial spread F at Jicamarca during solar minimum and maximum

Lee

2010

J. Geophys. Res.

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[1] The data of digisonde and the NRLMSISE-00 model on the occurrence of postsunset equatorial spread F (ESF) at Jicamarca during solar minimum and maximum years are used in a detailed statistical analysis. The onset conditions chosen in this study are the prereversal enhancement velocity (dhF 80 /dt), minimum virtual height of F-layer (h′F), gradient density scale length (L), and local linear growth rate (g) of collisional Rayleigh-Taylor instability. The monthly variation in ESF occurrence during solar minimum generally agrees with that during maximum. This agreement indicates that the ESF occurrence does not depend on solar activity. For the onset conditions, the differences between solar minimum and maximum exists in the monthly variations in dhF 80 /dt, h′F, and L, but not in g. This consistence in monthly g variation between two solar epochs mainly account for the solar cycle independence of ESF occurrence. Furthermore, the variations in collision frequency and recombination rate are principally responsible to the consistence in g.

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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Occurrence and onset conditions of postsunset equatorial spread F at Jicamarca during solar minimum and maximum

Lee

2010

J. Geophys. Res.

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“…(2008). The magnitude of peak vertical drift is known to control the seasonal and day-to-day variations in the occurrence of equatorial spread F (Manju et al, 2009;Tulasi Ram et al, 2006). where the magnetic field lines aligned with a geographic meridian (Burke et al, 2004;Tsunoda, 2005Tsunoda, , 2010.…”

Section: Spatial Gradient Of T Ec(t)mentioning

confidence: 99%

Spatial gradient of total electron content (TEC) between two nearby stations as indicator of occurrence of ionospheric irregularity

Dugassa¹,

Habarulema²,

Nigussie³

2018

Preprint

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Abstract. The relation between the occurrence of ionospheric irregularity and spatial gradient of total electron content (TEC) during the post-sunset hours over the equatorial region is studied. The ionospheric irregularities could pose serious challenges to satellite-based navigation and positioning applications when trans-ionospheric signals pass through them. Different instruments and techniques have been applied to study the behavior of these ionospheric irregularities. In this study, the Global positioning system (GPS) based derived total electron content (TEC) was used to investigate the spatial gradient of TEC between two nearby stations as an indicator of the occurrence of ionospheric irregularity over the East African sector. The gradient of TEC between the two stations (ASAB: 4:34° N, 114:39° E and DEBK: 3:71° N, 109:34° E, geomagnetic) located within the equatorial region of Africa were considered in this study during the year 2014. The rate of change of TEC based derived index (ROTIave) is also used to observe the correlation between the spatial gradient of TEC and the occurrence of ionospheric irregularities. The result obtained shows that most of the maximum positive/depletions in the spatial gradient of TEC observed in March and September equinoxes are more pronounced between 19:00 LT–24:00 LT as the large-scale ionospheric irregularities do. Moreover, the observed spatial gradient of TEC shows two peaks (in March and September) and they exhibit equinoctial asymmetry where the March equinox is greater than September equinox. The enhancement in the spatial gradient of TEC and ROTIave during the 15 evening time period also show similar trends but lag 1–2 hrs from the equatorial electric field (EEF). The spatial gradient of TEC between the two nearby stations could be used as an indicator of the occurrence of ionospheric irregularities.

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“…The mechanism of generation of the enhancement in vertical drift just after sunset was detailed by Farley et al (1986). The magnitude of peak vertical drift is known to control the seasonal and dayto-day variations in the occurrence of equatorial spread F (Manju et al, 2009;Tulasi Ram et al, 2006). Figure 8 depicts the quiet-monthly mean of ROTI ave (over ASAB and DEBK: red and black curves) and σ ( TEC/ long) (blue curve) in the year 2014.…”

Section: Relation Between the Equatorial Electric Fieldmentioning

confidence: 99%

Investigation of the relationship between the spatial gradient of total electron content (TEC) between two nearby stations and the occurrence of ionospheric irregularities

2019

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Abstract. The relation between the occurrence of ionospheric irregularities and the spatial gradient of total electron content (TEC) derived from two closely located stations (ASAB: 4.34∘ N, 114.39∘ E and DEBK: 3.71∘ N, 109.34∘ E, geomagnetic), located within the equatorial region, over Ethiopia, during the postsunset hours was investigated. In this study, the Global Positioning System (GPS)-derived TEC during the year 2014 obtained from the two stations were employed to investigate the relationship between the gradient of TEC and occurrence of ionospheric irregularities. The spatial gradient of TEC (ΔTEC∕Δlong) and its standard deviation over 15 min, σ(ΔTEC∕Δlong), were used in this study. The rate of change of TEC-derived indices (ROTI, ROTIave) were also utilized. Our results revealed that most of the maximum enhancement and reduction values in ΔTEC∕Δlong are noticeable during the time period between 19:00 and 24:00 LT. In some cases, the peak values in the spatial gradient of TEC are also observed during daytime and postmidnight hours. The intensity level of σ(ΔTEC∕Δlong) observed after postsunset show similar trends with ROTIave, and was stronger (weaker) during equinoctial (solstice) months. The observed enhancement of σ(ΔTEC∕Δlong) in the equinoctial season shows an equinoctial asymmetry where the March equinox was greater than the September equinox. During the postsunset period, the relation between the spatial gradient of TEC obtained from two closely located Global Navigation Satellite System (GNSS) receivers and the equatorial electric field (EEF) was observed. The variation in the gradient of TEC and ROTIave observed during the evening time period show similar trends with EEF with a delay of about 1–2 h between them. The relationship between σ(ΔTEC∕Δlong) and ROTIave correlate linearly with correlation coefficient of C=0.7975 and C=0.7915 over ASAB and DEBK, respectively. The majority of the maximum enhancement and reduction in the spatial gradient of TEC observed during the evening time period may be associated with ionospheric irregularities or equatorial plasma bubbles. In addition to latitudinal gradients, the longitudinal gradient of TEC has contributed significantly to the TEC fluctuations.

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The seasonal and solar cycle variations of electron density gradient scale length, vertical drift and layer height during magnetically quiet days: Implications for Spread F over Trivandrum, India

Cited by 8 publications

References 20 publications

Occurrence and onset conditions of postsunset equatorial spread F at Jicamarca during solar minimum and maximum

Occurrence and onset conditions of postsunset equatorial spread F at Jicamarca during solar minimum and maximum

Spatial gradient of total electron content (TEC) between two nearby stations as indicator of occurrence of ionospheric irregularity

Investigation of the relationship between the spatial gradient of total electron content (TEC) between two nearby stations and the occurrence of ionospheric irregularities

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