Quiet time F2-layer disturbances: seasonal variations of the occurrence in the daytime sector

Михайлов, А. А.; Depueva, A. Kh.; Depuev, V.

doi:10.5194/angeo-27-329-2009

Cited by 23 publications

(18 citation statements)

References 44 publications

(59 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Of course, during the night, recombination naturally causes such a depletion. However, it is well established that during times of low geomagnetic activity, the density within the ionosphere can fluctuate substantially, between about 25% and 40% on scales of a few hours to several days [Forbes et al, 2000;Mikhailov et al, 2007Mikhailov et al, , 2009. It may be that during our VLA observations, larger than average nighttime depletions occurred as a result of quiet time variability caused by forcing from the lower atmosphere via planetary waves, gravity waves, and/or tides [Chen, 1992;Rishbeth and Medillo, 2001;Liu et al, 2010].…”

Section: Discussionmentioning

confidence: 82%

Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere

Helmboldt¹,

Intema²

2012

Radio Science

View full text Add to dashboard Cite

[1] We present the results of a multiscale analysis of TEC fluctuations using a roughly five-hour observation of the bright radio source Virgo A with the Very Large Array (VLA) at 74 MHz in its B configuration. Our analysis combines data sensitive to fine-scale structure ($10 km and <0.001 TECU in amplitude) along the line of sight to Virgo A as well as larger structures (hundreds of km) observed using several ($30) moderately bright sources in the field of view. The observations span a time period from midnight to dawn local time during 1 March 2001. Several groups of magnetic eastward directed (MED), wavelike disturbances were identified and determined to be located within the plasmasphere (2.1 < L < 2.9). We have also detected evidence of non-wavelike structures associated with these disturbances which are propagating roughly toward magnetic north. These likely represent a non-uniform density flow from the plasmasphere toward the nighttime ionosphere. AE and K p indices and GPS TEC data indicate that during the observations, there were low levels of geomagnetic activity accompanied by somewhat localized depletions in ionospheric density. Thus, the observed plasmaspheric disturbance may be part of a flow triggered by these ionospheric depletions, likely associated with forcing from the lower atmosphere which is typically more prominent during quiet geomagnetic conditions. In addition, we have also observed several roughly westward directed and southeast directed waves located within the ionosphere. They are coincident in time with the plasmaspheric disturbances and may be related to the deposition of material onto the nighttime ionosphere.Citation: Helmboldt, J. F., and H. T. Intema (2012), Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere, Radio Sci., 47, RS0K03,

show abstract

Section: Discussionmentioning

confidence: 82%

Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere

Helmboldt¹,

Intema²

2012

Radio Science

View full text Add to dashboard Cite

show abstract

“…For the meteorological influences, Mendillo et al (1998) tried to estimate to what degree the F-layer variability could be attributed to the troposphere and lower stratosphere by using the NCAR (National Center for Atmospheric Research) coupled CCM3/TIME-GCM (Community Climate Model-3/Thermospere-IonosphereMesosphere-Electrodynamics General Circulation Model; Roble and Ridley, 1994). Mikhailov et al (2007Mikhailov et al ( , 2009 showed that synchronous variation of electron density can be observed during geomagnetic quiet day in both E-and F-region. Such variability is considered to be caused by perturbation originating from lower atmosphere.…”

Section: Description Of the Similar-parameters Interpolation Methodsmentioning

confidence: 99%

Modeling ionospheric <I>fo</I>F2 by using empirical orthogonal function analysis

et al. 2011

View full text Add to dashboard Cite

Abstract.A similar-parameters interpolation method and an empirical orthogonal function analysis are used to construct empirical models for the ionospheric foF2 by using the observational data from three ground-based ionosonde stations in Japan which are Wakkanai (Geographic 45.4 • N, 141.7 • E), Kokubunji (Geographic 35.7 • N, 140.1 • E) and Yamagawa (Geographic 31.2 • N, 130.6 • E) during the years of [1971][1972][1973][1974][1975][1976][1977][1978][1979][1980][1981][1982][1983][1984][1985][1986][1987]. The impact of different drivers towards ionospheric foF2 can be well indicated by choosing appropriate proxies. It is shown that the missing data of original foF2 can be optimal refilled using similar-parameters method. The characteristics of base functions and associated coefficients of EOF model are analyzed. The diurnal variation of base functions can reflect the essential nature of ionospheric foF2 while the coefficients represent the long-term alteration tendency. The 1st order EOF coefficient A 1 can reflect the feature of the components with solar cycle variation. A 1 also contains an evident semi-annual variation component as well as a relatively weak annual fluctuation component. Both of which are not so obvious as the solar cycle variation. The 2nd order coefficient A 2 contains mainly annual variation components. The 3rd order coefficient A 3 and 4th order coefficient A 4 contain both annual and semi-annual variation components. The seasonal variation, solar rotation oscillation and the small-scale irregularities are also included in the 4th order coefficient A 4 . The amplitude range and developing tendency of all these coefficients depend on the level of solar activity and geomagnetic activity. The reliability and validity of EOF model are verified by comparison with observational data and with International Reference Ionosphere (IRI). The agreement between observations and EOF model is quite well, indicating that the EOF model can reflect the major changes and the temporal distribution characteristicsCorrespondence to: D.-H. Zhang (zhangdh@pku.edu.cn) of the mid-latitude ionosphere of the Sea of Japan region. The error analysis processes imply that there are seasonal anomaly and semi-annual asymmetry phenomena which are consistent with pre-existing ionosphere theory.

show abstract

“…The initial phase is observed to be recorded with an intense ionospheric storm despite the low geomagnetic storm activity at the period. This follows the fact that the variations of F2 layer quite disturbances have different formation mechanism and have been interpreted to the concept of thermosphere-ionosphere interaction (Mikhailov et al 2009). …”

Section: Resultsmentioning

confidence: 96%

On the effects of geomagnetic storms and pre storm phenomena on low and middle latitude ionospheric F2

Adekoya

Chukwuma

Bakare

et al. 2012

Astrophys Space Sci

View full text Add to dashboard Cite

This paper presents some features of the ionospheric response observed in equatorial and mid-latitudes region to two strong geomagnetic storms, occurring during Oct. 19-23, 2001 and May 13-17, 2005 and to understand the phenomena of pre-storm that lead to very intense geomagnetic storms. The result point to the fact that pre-storm phenomena that leads to intense ionospheric storm are; large southward turning of interplanetary magnetic field Bz, high electric field, increase in flow speed stream, increase in proton number density, high pressure ram and high plasma beta. The magnitude of Bz turning into southward direction from northward highly depends upon the severity of the storm and the variation in F2 layer parameter at the time of geomagnetic storm are strongly dependent upon the storm intensity. A detailed analysis of the responses of the ionosphere shows that during the storm periods, foF2 values depleted simultaneously both in the equatorial and mid latitude. Observation also shows that low to moderate variations in ionospheric F2 at the pre-storm period may signal the upcoming of large ionospheric disturbances at the main phase. The ionospheric F2response for low and mid latitude does not show any significant differences during the storm main phase and the prestorm period. The ionospheric response during the pre-storm period is thought very puzzling. The period is observed to be depleted throughout with low-moderate effect across all the stations in the low and mid latitude.

show abstract

Quiet time F2-layer disturbances: seasonal variations of the occurrence in the daytime sector

Cited by 23 publications

References 44 publications

Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere

Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere

Modeling ionospheric <I>fo</I>F2 by using empirical orthogonal function analysis

On the effects of geomagnetic storms and pre storm phenomena on low and middle latitude ionospheric F2

Contact Info

Product

Resources

About

Quiet time F2-layer disturbances: seasonal variations of the occurrence in the daytime sector

Cited by 23 publications

References 44 publications

Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere

Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere

Modeling ionospheric &lt;I&gt;fo&lt;/I&gt;F2 by using empirical orthogonal function analysis

On the effects of geomagnetic storms and pre storm phenomena on low and middle latitude ionospheric F2

Contact Info

Product

Resources

About

Modeling ionospheric <I>fo</I>F2 by using empirical orthogonal function analysis