Seasonal and solar cycle variations of spread F at the equatorial anomaly crest zone.

Huang, Yinn‐Nien; Cheng, Kang; Huang, Wen-Ter

doi:10.5636/jgg.39.639

Cited by 25 publications

(25 citation statements)

References 49 publications

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“…He presented that, during high solar activity, the RSF occur most frequently at equinoxes, and the FSF occurrence has a maximum in summer and a minimum in winter. These results are similar to those found by Huang et al (1987), which examined the ionosonde data observed at Chung-Li and Taipei (25.0 • N, 121.5 • E) stations during 1960-1982. As mentioned above, the spread F near the equatorial ionization anomaly (EIA) crest and low latitude in different longitudes have been investigated by many workers. However, the study on spread F using ionosonde at low latitude, especially over the south of EIA crest in East Asian region, is seldom achieved.…”

Section: Introductionsupporting

confidence: 80%

The statistical properties of spread F observed at Hainan station during the declining period of the 23rd solar cycle

et al. 2010

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Abstract. The temporal variations of the low latitude nighttime spread F (SF) observed by DPS-4 digisonde at low latitude Hainan station (geog. 19.5 • N, 109.1 • E, dip lat. 9.5 • N) during the declining solar cycle 23 from March 2002 to February 2008 are studied. The spread F measured by the digisonde were classified into four types, i.e., frequency SF (FSF), range SF (RSF), mixed SF (MSF), and strong range SF (SSF). The statistical results show that MSF and SSF are the outstanding irregularities in Hainan, MSF mainly occurs during summer and low solar activity years, whereas SSF mainly occurs during equinoxes and high solar activity years. The SSF has a diurnal peak before midnight and usually appears during 20:00-02:00 LT, whereas MSF peaks nearly or after midnight and occurs during 22:00-06:00 LT. The time of maximum occurrence of SSF is later in summer than in equinoxes and this time delay can be caused by the later reversal time of the E ×B drift in summer. The SunSpot Number (SSN) dependence of each type SF is different during different season. The FSF is independent of SSN during each season; RSF with SSN is positive relation during equinoxes and summer and is no relationship during the winter; MSF is significant dependence on SSN during the summer and winter, and does not relate to SSN during the equinoxes; SSF is clearly increasing with SSN during equinoxes and summer, while it is independent of SSN during the winter. The occurrence numbers of each type SF and total SF have the same trend, i.e., increasing as Kp increases from 0 to 1, and then decreasing as increasing Kp. The correlation with Kp is negative for RSF, MSF, SSF and total SF, but is vague for the FSF.

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Section: Introductionsupporting

confidence: 80%

The statistical properties of spread F observed at Hainan station during the declining period of the 23rd solar cycle

et al. 2010

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“…Huang [] and Huang et al . [] analyzed the data of spread F observed by the Chungli ionosonde, and they reported the seasonal and nighttime variations of range spread F (RSF) and frequency spread F (FSF) during high and low solar activities. Furthermore, C .‐ M .…”

Section: Introductionmentioning

confidence: 99%

Observation of F region irregularities near a northern equatorial anomaly crest during solar minimum using ionosonde, GPS receiver, and satellites

2013

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[1] For solar minimum, the spread F, GPS phase fluctuations, and plasma bubbles near the crest of equatorial ionization anomaly (EIA) are simultaneously analyzed to investigate F region irregularities for the first time. The data were observed using the Chungli ionosonde, YMSM GPS receiver, and DMSP satellites during 1996. It is found that in the observed ionograms, the frequency spread F (FSF) usually comes after the range spread F (RSF) in a series of nighttime spread F events. This results in that the maximum occurrence of RSF appears before that of FSF in the nighttime variations in occurrence probabilities. Moreover, the seasonal variation for RSF is close to that for FSF. Both have a board maximum in the J-months and a secondary maximum in December. These indicate that RSF and FSF should be regarded as one type of spread F, which is the all spread F (ASF) in this study. Because the equatorial plasma bubbles occur infrequently during solar minimum, the F region irregularities forming ASF are not related to the equatorial spread F. On the other hand, the similarity in seasonal occurrence between ASF and medium-scale traveling ionospheric disturbances (MSTIDs) demonstrates that the F region irregularities near the EIA crest are mainly generated by the gradient drift instability driven by MSTIDs. The irregularities, generated by MSTIDs, mostly occur in the bottom side of the F region. Consequently, the events of significant GPS phase fluctuations and plasma bubble near the EIA crest are rare during 1996.

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“…Both computer simulation [ Ossakow et al , 1979] and data analysis [ Niranjan et al , 2003; Bowman , 1984] showed that the spread F occurrence is closely correlated with the peak height of the F region. What is particularly interesting is that in different regions of the world the spread F often shows different occurrence levels in relation to solar activity and seasons [ Earle et al , 2006; Chandra et al , 2003; Abdu et al , 1998; Saksena , 1996; Huang et al , 1987; Bhaneja et al , 2009].…”

Section: Introductionmentioning

confidence: 99%

Case study of apparent longitudinal differences of spread F occurrence for two midlatitude stations

Huang

Xiao

et al. 2011

Radio Science

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[1] Spread F is a widely studied subject, and the occurrence of spread F is affected by many factors. One of these factors is acoustic gravity waves (AGWs) which are very important in seeding spread F. Since most of the AGWs in the ionosphere originate from the lower atmosphere, there should be some regional features of spread F due to the different meteorological or ground conditions immediately beneath the local ionosphere. In this paper, a data set with a time coverage of one solar cycle from two Chinese stations located at exactly the same latitude and a 38 degrees separation in longitude, and having sharp contrasts of ground meteorological conditions, are used to make comparisons of spread F occurrence rates. The results showed that the total number of occurrence or occurrence percentage at Changchun station (very near the coast) is always much higher than that at Urumqi station (in the very center of the Europe-Asia continent). The annual maxima of spread F occurrence are in summer and winter. Other features of spread F occurrence at these two stations are in agreement with known properties of spread F. However, the great difference of occurrence frequency between the two stations is striking and worth further studying.

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Seasonal and solar cycle variations of spread F at the equatorial anomaly crest zone.

Cited by 25 publications

References 49 publications

The statistical properties of spread F observed at Hainan station during the declining period of the 23rd solar cycle

The statistical properties of spread F observed at Hainan station during the declining period of the 23rd solar cycle

Observation of F region irregularities near a northern equatorial anomaly crest during solar minimum using ionosonde, GPS receiver, and satellites

Case study of apparent longitudinal differences of spread F occurrence for two midlatitude stations

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