Analysis on 29 March 2006 eclipse effect on the ionosphere over Ilorin, Nigeria

Adeniyi, J.O.; Oladipo, O.A.; Radicella, S. M.; Adimula, I. A.; Olawepo, A.O.

doi:10.1029/2009ja014416

Cited by 11 publications

(4 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We will determine the physical processes driving these effects and their temporal and spatial variations through diagnostic analysis of the model outputs. We will primarily focus on the F 2 region eclipse effects where winds, ambipolar diffusion, and electric fields play significant roles, whereas the eclipse effects in the E and F 1 regions are mainly controlled by fast photochemistry and well understood (e.g., Adeniyi et al, , Rishbeth, ).…”

Section: Resultsmentioning

confidence: 99%

Physical Processes Driving the Response of the F₂ Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

et al. 2019

View full text Add to dashboard Cite

The high-resolution thermosphere-ionosphere-electrodynamics general circulation model has been used to investigate the response of F 2 region electron density (Ne) at Millstone Hill (42.61°N, 71.48°W, maximum obscuration: 63%) to the Great American Solar Eclipse on 21 August 2017. Diagnostic analysis of model results shows that eclipse-induced disturbance winds cause F 2 region Ne changes directly by transporting plasma along field lines, indirectly by producing enhanced O/N 2 ratio that contribute to the recovery of the ionosphere at and below the F 2 peak after the maximum obscuration. Ambipolar diffusion reacts to plasma pressure gradient changes and modifies Ne profiles. Wind transport and ambipolar diffusion take effect from the early phase of the eclipse and show strong temporal and altitude variations. The recovery of F 2 region electron density above the F 2 peak is dominated by the wind transport and ambipolar diffusion; both move the plasma to higher altitudes from below the F 2 peak when more ions are produced in the lower F 2 region after the eclipse. As the moon shadow enters, maximizes, and leaves a particular observation site, the disturbance winds at the site change direction and their effects on the F 2 region electron densities also vary, from pushing plasma downward during the eclipse to transporting it upward into the topside ionosphere after the eclipse. Chemical processes involving dimming solar radiation and changing composition, wind transport, and ambipolar diffusion together cause the time delay and asymmetric characteristic (fast decrease of Ne and slow recovery of the eclipse effects) of the topside ionospheric response seen in Millstone Hill incoherent scatter radar observations. Key Points:• Changes in winds, composition, and diffusion play significant roles in temporal and spatial variations of the eclipse effects on F 2 region • The recovery of F 2 region electron density above the F 2 peak is dominated by the transport due to winds and ambipolar diffusion • Observations and model show time delay and asymmetric (fast decrease and slow recovery) response of topside plasma density to the eclipse The Millstone Hill ISR conducted 5-day observations centered on 21 August 2017. In this study, we used the zenith antenna data of electron density (Ne) profiles from interleaved 480-μs single pulse measurements above 250 km (black solid squares in Figures 1c-1f) and alternating code measurements below 250 km (gray solid circles in Figures 1c-1f). This allows for appropriate data quality in different altitude ranges. We have calibrated ISR Ne against the digisonde data.The TIEGCM solves time-dependent momentum, energy, and continuity equations for the neutrals and energy and continuity equations for the ions of the coupled I-T system on a global grid (Qian et al., 2014;Richmond et al., 1992;Roble et al., 1988). Recently, the TIEGCM V2.0 has been upgraded to high resolution with a 0.625°× 0.625°geographic latitude-longitude grid and 1/4 scale height in the vertical pressure coordinates to facil...

show abstract

Section: Resultsmentioning

confidence: 99%

Physical Processes Driving the Response of the F₂ Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

et al. 2019

View full text Add to dashboard Cite

show abstract

“…In Figure 4b, the N m F 2 increased during the eclipse period, but the magnitude is more reduced compared to that observed in Figure 4c. These changes in magnitude can be attributed to the effect of solar activity, since solar radiation is lower at low solar activity [Adeniyi et al, 2009]. The most obvious is between an interval of 10:00 LT and 18:00 LT, when the electron density increases around 16:00 LT presunset.…”

Section: Peak Electron Density Observationmentioning

confidence: 97%

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

2015

View full text Add to dashboard Cite

The response of the vertical plasma drift (Vz) and the electron density (NmF2) during different solar eclipses was investigated. The diurnal values of the direct scaled measurement of F2 peak height and the one derived from M(3000) F2 data, acquired over an equatorial/low‐latitude stations, have been used to determine the vertical plasma drift. The ionosphere during a solar eclipse is significantly affected by the E × B vertical drift; the large depletion of electron density at low altitudes can be transported to high altitudes through the plasma vertical drift. The loss in ionization density during the eclipse phase decreases the electron density, which was accompanied by rapid increase in hmF2. This deviation in the NmF2 during eclipse compared to control days can be related to the increase in the loss rate due to recombination, as a result of reduction in thermal energy. However, the maximum reduction in NmF2 is not synchronous with the time of maximum totality but some minutes later. The differences in the solar epochs may contribute to the observed relative changes in the ionospheric F2 region behavior during the eclipse window. Lastly, it is very difficult to separate the influence of magnetic disturbances from solar eclipse. The deviation in NmF2 is higher during magnetic disturbed days than the quiet day. The reverse is the case for hmF2 observation. However, the NmF2 variation increases with an increase in solar activity.

show abstract

“…The reason for a steeper foF2 reduction rate over KTB was most likely the higher initial foF2 (and NmF2) value at the start of the eclipse, which resulted in a higher recombination rate in the absence of photoionization, viz. dN/dt = −α N 2 in the ionization balance equation (Rishbeth, 1963(Rishbeth, , 1968Rishbeth and Garriott, 1969;Adeniyi et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…The average rate of foF1 reduction over KTB was −16 el cm −3 /s, and that over PTK was −29 el cm −3 /s. The much steeper foF1 reduction rate over PTK was most likely due to a higher initial foF1 value, which resulted in a higher recombination rate (dN/dt = −α N 2 ) in the absence of photoionization (Cheng et al, 1992;Adeniyi et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Ionosonde and GPS Total Electron Content Observations during the 26 December 2019 Annular Solar Eclipse over Indonesia

Harjosuwito

Husin

Dear

et al. 2022

Preprint

View full text Add to dashboard Cite

Abstract. We report our investigation of ionospheric effects due to the passage of an annular solar eclipse over Southeast Asia on 26 December 2019, using multiple set of observations. Two ionosondes (one at Kototabang and another at Pontianak) were used to measure dynamical changes in the ionospheric layer during the event. A network of ground-based GPS receiver stations in Indonesia were used to derive the distribution of total electron content (TEC) over the region. In addition, extreme ultraviolet (EUV) images of the Sun from the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory (SDO) satellite were also analyzed to determine possible impacts of solar active regions on the changes that occurred in the ionosphere during the eclipse. We found −1.67 MHz and −1.58 MHz reduction (23.2 % and 22.4 % relative reduction) in foF2 during the solar eclipse over Kototabang and Pontianak, respectively. The respective TEC reduction over Kototabang and Pontianak during the eclipse was −4.34 TECU and −5.45 TECU (24.9 % and 27.9 % relative reduction). Overall, there was 34–36 minutes delay from maximum eclipse until minimum foF2 was reached at these two locations. The corresponding time delays for eclipse-related TEC reduction at these two locations were 40 minutes and 16 minutes, respectively. The ionospheric F-layer was found to descend with a speed of 9–19 m/s during the first half of the eclipse period. We also found an apparent rise of the ionospheric F-layer height near the end of the solar eclipse period, equivalent to vertical drift velocity of 44–47 m/s. The GPS TEC data mapping along a set of cross-sectional cut lines indicate that the greatest TEC reduction actually occurred to the north of the solar eclipse path, opposite of the direction from which the lunar shadow fell. As the central path of the solar eclipse was located just to the north of the southern equatorial ionization anomaly (EIA) crest, it is suspected that such a peculiar TEC reduction pattern was caused by plasma flow associated with the equatorial fountain effect. Net perturbations of TEC were also computed and analyzed, which revealed the presence some wavelike fluctuations associated with the solar eclipse event. Some of the observed TEC perturbation patterns that propagated with a velocity matching the lunar shadow may be explained in terms of non-uniform EUV illumination that arose as various active regions on the Sun went obstructed and unobstructed during the eclipse. The remaining wavelike features are likely to be traveling ionospheric disturbances (TIDs) driven by acoustic-gravity waves (AGWs), generated by the passage of the solar eclipse on top of other diurnal factors.

show abstract

Analysis on 29 March 2006 eclipse effect on the ionosphere over Ilorin, Nigeria

Cited by 11 publications

References 16 publications

Physical Processes Driving the Response of the F₂ Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

Physical Processes Driving the Response of the F₂ Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

Ionosonde and GPS Total Electron Content Observations during the 26 December 2019 Annular Solar Eclipse over Indonesia

Contact Info

Product

Resources

About

Analysis on 29 March 2006 eclipse effect on the ionosphere over Ilorin, Nigeria

Cited by 11 publications

References 16 publications

Physical Processes Driving the Response of the F2 Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

Physical Processes Driving the Response of the F2 Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

Ionosonde and GPS Total Electron Content Observations during the 26 December 2019 Annular Solar Eclipse over Indonesia

Contact Info

Product

Resources

About

Physical Processes Driving the Response of the F₂ Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

Physical Processes Driving the Response of the F₂ Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill