Ionospheric disturbances induced by substorm associated electric fields in the low-latitude F-region.

Takahashi, T.; Oya, Hiroshi; Watanabe, Shigeto

doi:10.5636/jgg.39.187

Cited by 14 publications

(8 citation statements)

References 20 publications

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“…However, there are cases when the enhancements are strongly manifested in the crest region and the critical frequency in the equatorial trough is reduced compared to quiet days. Takahashi et al (1987) have reported ionization enhancements at low latitudes during magnetic disturbed conditions. They showed that these enhancements were having an equatorial anomaly like structure having a minimum at the dip equator.…”

Section: Summary and Discussionmentioning

confidence: 99%

Airglow and other F-layer variations in the Indian sector during the geomagnetic storm of February 5–7, 2000

Mukherjee

2006

Earth Planet Sp

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A CCD based all-sky imaging system was used to monitor various nightglow emissions and hydroxyl (OH) airglow) at a low latitude station, Kolhapur (16.8 • N, 74.2 • E, dip lat 10.6• N) in India to study the characteristics of night airglow variations observed during the period of a moderate/weak geomagnetic storm with SSC (Storm Sudden Commencement) commencing at 15:42 UT (21:12 IST (Indian Standard Time = UT + 5.5 hrs)) on February 5, 2000. The images on the night of February 6 show the development of strong ionization anomaly (EIA) with bright intensity regions in OI 630-nm and the signature of rising bubbles with very low intensity. Though the signature of ionospheric plasma bubbles were not observed on the night of February 7, the OI 630-nm images showed the presence of large scale enhanced airglow moving to the southeast direction. The speed was significantly fast (∼300 m/s). There were bright intensity regions also observed in OI 557.7-nm airglow, but no intensity enhancement was seen in other mesospheric emissions (Na (589.3-nm) and hydroxyl (OH) airglow ) during this magnetic disturbance. The ionosonde observations at the nearby station, Visakhapatnam (lat. 17.67 • N, long. 83.32• E) also showed enhancement in electron density parameter ( (foF2) 2 ) at the station on each night compared to the night of February 4-5 (quiet day) around the same time interval maximizing around 23:00 IST on the night of February 7. The Total Electron Content (TEC) fluctuations obtained from GPS phase delays between two L-band signals (L1 = 1575 MHz and L2 = 1227 MHz) showed no enhancement at night at four mid latitude stations in Japan. However, noontime TEC values were enhanced on February 6 and 7 with maximum intensity occurring on February 7. It is inferred that enhanced storm time effects in the ionosphere were mainly confined to the low latitude region, the effects were subdued in the mid latitude stations.

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Section: Summary and Discussionmentioning

confidence: 99%

Airglow and other F-layer variations in the Indian sector during the geomagnetic storm of February 5–7, 2000

Mukherjee

2006

Earth Planet Sp

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“…However, the absolute magnitudes of negative ΔIRC and positive Δzonal drift driven by HAE‐SAPS are larger than that driven by LAE‐SAPS, indicating a key role of the substorm. Previous studies have reported that a westward electric field at the dayside ionosphere could be established by substorm (e.g., Takahashi et al., 1987; Wei et al., 2009). Thus, during High‐AE periods, an additional westward electric field could be generated.…”

Section: Discussionmentioning

confidence: 97%

Responses of Ionospheric Radial Currents to Subauroral Polarization Streams During Quiet Periods

Xia,

Wang,

Zhang

et al. 2024

JGR Space Physics

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Using 4 years of ionospheric radial current (IRC) from Swarm and ion velocity from the Defense Meteorological Satellite Program, our work investigates the response of IRC to the subauroral polarization streams (SAPS) during the quiet time for the first time. Both noontime (magnetic local time, MLT 11–14) inward and duskside (MLT 18–19) outward IRC get strengthened in amplitude. The noontime inward ΔIRC is attributed to the penetration westward electric field at low‐mid latitudes. It drives the poleward Hall currents and equatorward polarization electric field, which maps to the dip equator to form an inward ΔIRC at F layer. At dusk, the SAPS‐poleward electric field could directly penetrate to the low‐mid latitudes, mapping to the dip equator to drive the outward ΔIRC. The substorms‐associated westward electric field is also critical in modulation of ΔIRC, resulting in a larger inward (weaker outward) ΔIRC under high auroral electrojet (AE) index than that under low AE around noon (dusk).

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“…However, although the fountain effect has weaker strength and does not uplift the F-layer as much as necessary to form the EIA crests, it was able to spread the ionization for a few degrees on either sides of the dip equator as noted in Figure 2b. For more details about the EIA suppression during disturbed and quiet periods, see Abdu et al (1991), Fagundes et al (2016), TakahashiI et al (1987, . Figure 3 shows the day-to-day occurrence of EIA during the year of 2016, where the red bars, green bars, and white bars indicate developed EIA, not developed/absent, and geomagnetically disturbed days, respectively.…”

Section: Eia Day-to-day Variability In Three Different Longitudinal Smentioning

confidence: 99%

Section: 1029/2020ja027906mentioning

confidence: 99%

Daily and Monthly Variations of the Equatorial Ionization Anomaly (EIA) Over the Brazilian Sector During the Descending Phase of the Solar Cycle 24

et al. 2020

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It has been noticed recently that the equatorial ionization anomaly (EIA) in the Brazilian eastern, middle, and western sectors present significant longitudinal variability within a short separation due to the presence of typical magnetic field structure over South America. Therefore, the main motivation of this study is to investigate day-today and month-to-month characteristics of the EIA in three closely spaced longitudinal sectors over the Brazilian region during the year 2016 in the descending phase of the solar activity. These three longitudinal sectors are perpendicular to the magnetic equator at its largest declination over the globe. The EIA showed a semiannual variation in all sectors with a major maximum during the summer, a minimum during the winter, and secondary maximum during spring. In addition, the EIA shows its classical behavior with a trough around the magnetic equator and crests at low latitudes (from ±15°to ±20°). When the EIA is not developed, the maximum ionization is located around the dip equatorial latitudes and the anomaly crest is absent. The number of days within 1 year that showed clear EIA development in the west, middle, and east sectors is 248 (78.2%), 236 (74.4%), and 265 (83.6%), respectively. The undeveloped/absence of EIA is also found often during the months of winter, and the numbers of such days during 2016 in the west, middle, and east are 69 (21.8%), 81 (25.6%), and 52 (16.4%), respectively. Also, the shape, strength, extent, and lifetimes of EIA crest have shown significant variabilities between the three sectors during different seasons. Further, a comparative analysis is carried out on the variations of EIA crest and lifetime between GPS observations and IRI-2016 model, and the results are discussed.

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Ionospheric disturbances induced by substorm associated electric fields in the low-latitude F-region.

Cited by 14 publications

References 20 publications

Airglow and other F-layer variations in the Indian sector during the geomagnetic storm of February 5–7, 2000

Airglow and other F-layer variations in the Indian sector during the geomagnetic storm of February 5–7, 2000

Responses of Ionospheric Radial Currents to Subauroral Polarization Streams During Quiet Periods

Daily and Monthly Variations of the Equatorial Ionization Anomaly (EIA) Over the Brazilian Sector During the Descending Phase of the Solar Cycle 24

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