Variability of total electron content near the crest of the equatorial anomaly during moderate geomagnetic storms

Chakraborty, Sumanjit; Hajra, Rajkumar

doi:10.1016/j.jastp.2010.05.006

Cited by 10 publications

(6 citation statements)

References 50 publications

(35 reference statements)

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“…From July 30 to August 4, last recovery period, TEC values depleted compared to July 29. These results are in agreement with those of Chakraborty and Hajra (2010) which showed that in general, in the equatorial region, positive and negative storms occurred (increase and decrease in TEC values). In addition, during the main phase, we note the disappearance of the PRE signature of fluctuations in the equatorial electrojet intensity and the rise of an equatorial counter-electrojet during the recovery phase.…”

Section: Discussionsupporting

confidence: 93%

“…According to these authors, geomagnetic storms cause an increase in electron density or in total electron content (TEC) at some stations and also affect electrodynamics. In general, in low latitudes in the equatorial region, positive storms occur (increase in TEC values) and negative storms (decrease in TEC values) (Chakraborty and Hajra, 2010) compared to the monthly mean or median. The equatorial ionosphere presents some particularities as :…”

Section: Introductionmentioning

confidence: 98%

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Total electron content response to two moderate geomagnetic storms in July 2003 at Niamey Station in Niger

Zoundi¹,

ephane²,

Drabo³

et al. 2021

Sci. Res. Essays

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The present paper reviews CODG TEC response to the moderate storm of July 26, 2003 and that of July 29 at Niamey station in West African equatorial station (Geo Lat 13° 28'45.3 "N; Geo long: 02° 10'59.5" E) in Niger. These two moderate geomagnetic storms are of solar wind origin. The study showed an increase in CODG TEC values during the initial phase of the storm and a decrease in CODG TEC values during the main and recovery phases of the storm. In general, in the equatorial region, positive and negative storms occurred (increase and decrease in TEC values). Here we highlight the prereversal enhancement (PRE), a particularity of the equatorial ionosphere. Our investigations show M, B and R profiles in addition to the well-known dome profile in the variation of the CODG TEC in Niamey. This work suggests a variation of the equatorial electrojet intensity during the storm recovery phase, the appearance of the counter-electrojet as well as a disturbance of the ExB drift. This study is local, in the equatorial region in the West African sector. Data are needed to corroborate some hypotheses such as changes in profiles associated with the presence or absence of electrojet and counter-electrojet currents. We advocate for a new IHY for Africa and for data exchange between researchers.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 98%

Total electron content response to two moderate geomagnetic storms in July 2003 at Niamey Station in Niger

Zoundi¹,

ephane²,

Drabo³

et al. 2021

Sci. Res. Essays

View full text Add to dashboard Cite

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“…This is shown in Figure (bottom). The solar cycle dependence of geomagnetic storms of varying intensity has been previously studied [ Sugiura , ; Gonzalez and Tsurutani , ; Gonzalez et al ., ; Chakraborty and Hajra , ; Hajra et al ., ; Echer et al ., , , ; Hajra , ], and we reproduce their results here. While the geomagnetic storms are found to occur during all phases of the solar cycle, peak occurrence of intense storms is concentrated around the F 10.7 solar cycle peaks.…”

Section: Resultsmentioning

confidence: 99%

Supersubstorms (SML < −2500 nT): Magnetic storm and solar cycle dependences

et al. 2016

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We study extremely intense substorms with SuperMAG AL (SML) peak intensities < −2500 nT (“supersubstorms”/SSSs) for the period from 1981 to 2012. The SSS events were often found to be isolated SML peaks and not statistical fluctuations of the indices. The SSSs occur during all phases of the solar cycle with the highest occurrence (3.8 year−1) in the descending phase. The SSSs exhibited an annual variation with equinoctial maximum altering between spring in solar cycle 22 and fall in solar cycle 23. The occurrence rate and strength of the SSSs did not show any strong relationship with the intensity of the associated geomagnetic storms. All SSS events were associated with strong southward interplanetary magnetic field Bs component. The Bs fields were part of interplanetary magnetic clouds in 46% and of interplanetary sheath fields in 54% of the cases. About 77% of the SSSs were associated with small regions of very high density solar wind plasma parcels or pressure pulses impinging upon the magnetosphere. Comments on how SSS events may cause power outages at Earth are discussed at the end of the paper.

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“…The solar cycle dependence of HILDCAAs depicted here is different from the reported solar cycle dependence of intense (Dst < −100 nT) geomagnetic storms [ Gonzalez et al ., , , ; Alves et al ., ; Tsurutani et al ., ; Echer et al ., , , ; Chakraborty and Hajra , ; Hajra , ]. The largest occurrence of the storms is at and around solar maximum.…”

Section: Resultsmentioning

confidence: 99%

Solar cycle dependence of High‐Intensity Long‐Duration Continuous AE Activity (HILDCAA) events, relativistic electron predictors?

et al. 2013

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[1] High-Intensity, Long-Duration, Continuous AE Activity (HILDCAA) events are studied using long-term geomagnetic and solar wind/interplanetary databases. We use the strict definition of a HILDCAA event, that it occurs outside of the main phase of a magnetic storm, the peak AE is >1000 nT, and the duration is at least 2 days long. One hundred thirty-three events have been identified from the AE indices in the 1975 to 2011 interval, a~3½ solar cycle span. Of the 133 events, 99 had simultaneous interplanetary data available. The overwhelmed majority (94%) of these latter cases were associated with high-speed solar wind stream (HSS) events. The remaining 6% of the cases occurred after the passage of interplanetary coronal mass ejections (ICMEs). The HSS-related events were typically associated with large interplanetary magnetic field (IMF) Bz variances. The ICME-related events were characterized by steady southward Bz intervals or low-frequency fluctuations, both of which we view as possible different interplanetary phenomena. HILDCAA events have been found to have their largest occurrence frequency in the solar cycle descending phase (~6.8/year) with the second largest at solar minimum (~3.5/year). The occurrence frequencies were considerably lower in the ascending phase (~2.5/year) and at solar maximum (~2.2/year). Thus, HILDCAAs can occur during all phases of the solar cycle, with the descending phase approximately three times more likely to have an event than at solar maximum and the ascending phase. The HILDCAA events that occurred in the declining phase and at solar minimum were >20% longer in duration than those in the ascending phase and solar maximum, respectively. The events during the recent solar and geomagnetic minima, 2007-2009, were, on the average,~17% and 14% weaker in peak AE than the events during the previous two minima of 1995-1997 and 1985-1987, respectively. The recent minimum events were~35% and 41% shorter in durations, respectively, than the events during those previous minima. The yearly occurrence of the events exhibited statistically significant correlation (>0.70) with yearly average speed and number of HSSs. No seasonal dependence of HILDCAA was noted.

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Variability of total electron content near the crest of the equatorial anomaly during moderate geomagnetic storms

Cited by 10 publications

References 50 publications

Total electron content response to two moderate geomagnetic storms in July 2003 at Niamey Station in Niger

Total electron content response to two moderate geomagnetic storms in July 2003 at Niamey Station in Niger

Supersubstorms (SML < −2500 nT): Magnetic storm and solar cycle dependences

Solar cycle dependence of High‐Intensity Long‐Duration Continuous AE Activity (HILDCAA) events, relativistic electron predictors?

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