Occurrence characteristics of low latitude ionosphere irregularities observed by impedance probe on board the Hinotori satellite.

Watanabe, Shigeto; Oya, Hiroshi

doi:10.5636/jgg.38.125

Cited by 105 publications

(135 citation statements)

References 35 publications

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“…Since the memory of the recorder on board the satellite was limited, only 4 to 6 orbits of data per day were transmitted to the data acquisition station at the Kagoshima Space Center. The electron density and electron temperature were measured by an impedance probe in an upper resonance mode (Watanabe and Oya, 1986) and a resonance recti®cation probe (Hirao and Oyama, 1970), respectively. The relative error of the electron density measurements is about 10% and the maximum error of the electron temperature is about 50 K. It should be pointed out that normally the F2 layer peak of the ionosphere is lower than the altitude of the satellite (600 km), although the peak might occasionally move to above 600 km around equator during the postsunset period (Su et al, 1997).…”

Section: Data Analysis and Resultsmentioning

confidence: 99%

Yearly variations in the low-latitude topside ionosphere

Bailey

Oyama

2000

Ann. Geophys.

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Abstract. Observations made by the Hinotori satellite have been analysed to determine the yearly variations of the electron density and electron temperature in the lowlatitude topside ionosphere. The observations reveal the existence of an equinoctial asymmetry in the topside electron density at low latitudes, i.e. the density is higher at one equinox than at the other. The asymmetry is hemisphere-dependent with the higher electron density occurring at the March equinox in the Northern Hemisphere and at the September equinox in the Southern Hemisphere. The asymmetry becomes stronger with increasing latitude in both hemispheres. The behaviour of the asymmetry has no signi®cant longitudinal and magnetic activity variations. A mechanism for the equinoctial asymmetry has been investigated using CTIP (coupled thermosphere ionosphere plasmasphere model). The model results reproduce the observed equinoctial asymmetry and suggest that the asymmetry is caused by the north-south imbalance of the thermosphere and ionosphere at the equinoxes due to the slow response of the thermosphere arising from the eects of the global thermospheric circulation. The observations also show that the relationship between the electron density and electron temperature is dierent for daytime and nighttime. During daytime the yearly variation of the electron temperature has negative correlation with the electron density, except at magnetic latitudes lower than 10°. At night, the correlation is positive.

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Section: Data Analysis and Resultsmentioning

confidence: 99%

Yearly variations in the low-latitude topside ionosphere

Bailey

Oyama

2000

Ann. Geophys.

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“…This implies that the enhancements are highly localized. Oya et al (1986) and Watanabe and Oya (1986) have reported localized regions of plasma density enhancements cooccurring with the plasma density depletions in the nighttime equatorial F region. The plasma density was found to be higher by a factor of about two in these enhancements.…”

Section: Discussionmentioning

confidence: 99%

“…They further found that the plasma blobs occur preferentially during solstices and periods of low magnetic disturbances and lower solar radiation. Although no mechanism was given, Oya et al (1986) and Watanabe and Oya (1986) suggested that the generation mechanisms for the plasma depletions and the enhancements were different. The ion density data given by Kil and Heelis (1998) also reveals a number of ion density enhancements along with the depletions in the ion density.…”

Section: Discussionmentioning

confidence: 99%

Observations in equatorial anomaly region of total electron content enhancements and depletions

Dashora¹,

Pandey²

2005

Ann. Geophys.

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Abstract.A GSV 4004A GPS receiver has been operational near the crest of the equatorial anomaly at Udaipur, India for some time now. The receiver provides the line-of-sight total electron content (TEC), the phase and amplitude scintillation index, σ φ and S 4 , respectively. This paper presents the first results on the nighttime TEC depletions associated with the equatorial spread F in the Indian zone. The TEC depletions are found to be very well correlated with the increased S 4 index. A new feature of low-latitude TEC is also reported, concerning the observation of isolated and localized TEC enhancements in the nighttime low-latitude ionosphere. The TEC enhancements are not correlated with the S 4 index. The TEC enhancements have also been observed along with the TEC depletions. The TEC enhancements have been interpreted as the manifestation of the plasma density enhancements reported by Le et al. (2003).

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“…Anderson et al [2004] found that equatorial plasma bubbles and resulting ionospheric scintillation occur, in general, when the vertical plasma drift is greater than 20 m s À1 . Statistical studies show that the earliest local time for bubble occurrence is 19:00-19:30 LT [Watanabe and Oya, 1986;Kil and Heelis, 1998;Chapagain et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

Generation and characteristics of equatorial plasma bubbles detected by the C/NOFS satellite near the sunset terminator

et al. 2012

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We present the observations of equatorial plasma bubbles in the evening sector by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite during 2011. We illustrate with a few examples the overall properties of the equatorial ionosphere as the solar activity approached maximum. C/NOFS was often below the F peak and this allowed us to examine the early phases of irregularity formation. We show examples when C/NOFS detected a continuous generation of plasma bubbles near the sunset terminator over eight successive orbits (∼12 h). A clear prereversal enhancement of upward plasma drift occurred between 18:00 and 19:00 LT when plasma bubbles were detected by C/NOFS, and the peak value of the upward ion drift at or near the magnetic equator was 40–70 m s−1. In some cases, C/NOFS was well below the Fpeak and detected wide regions with very low plasma density over ∼3000 km in longitude in the evening sector, and plasma bubbles were generated within the low‐density region. C/NOFS also detected simultaneous existence of plasma bubbles between 19:00 and 03:00 LT, corresponding to a longitudinal coverage of ∼12,000 km. Significant differences in the characteristics of plasma bubbles between periods of low and high solar activity are identified. Large plasma bubbles occur in the midnight‐dawn sector at low solar activity but in the evening sector at high solar activity. The lifetime of plasma bubbles is long (7 h or longer) at low solar activity but is short (∼3 h) at high solar activity. Broad plasma depletions occur near dawn at low solar activity, but wide low‐density regions with multiple plasma bubbles occur in the evening sector at high solar activity.

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Occurrence characteristics of low latitude ionosphere irregularities observed by impedance probe on board the Hinotori satellite.

Cited by 105 publications

References 35 publications

Yearly variations in the low-latitude topside ionosphere

Yearly variations in the low-latitude topside ionosphere

Observations in equatorial anomaly region of total electron content enhancements and depletions

Generation and characteristics of equatorial plasma bubbles detected by the C/NOFS satellite near the sunset terminator

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