Solar cycle related range type spread-F occurrence characteristics over equatorial and low latitude stations in Brazil

1985 ◽  
Vol 47 (8-10) ◽  
pp. 901-905 ◽  
Author(s):  
M.A Abdu ◽  
J.H.A Sobral ◽  
O.R Nelson ◽  
I.S Batista
Keyword(s):  
Solar Cycle ◽  
Low Latitude ◽  
Range Type ◽  
Spread F ◽  
Occurrence Characteristics

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

2010 ◽  
Vol 28 (6) ◽  
pp. 1263-1271 ◽  
Author(s):  
G. J. Wang ◽  
J. K. Shi ◽  
X. Wang ◽  
S. P. Shang ◽  
G. Zherebtsov ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Temporal Variations ◽  
High Solar Activity ◽  
Positive Relation ◽  
Low Latitude ◽  
23Rd Solar Cycle ◽  
Reversal Time ◽  
Spread F ◽  
Maximum Occurrence

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.

scholarly journals Observation of seasonal asymmetry in the range spread F occurrence at different longitudes during low and moderate solar activity

2019 ◽  
Vol 37 (4) ◽  
pp. 733-745
Author(s):  
Abimbola O. Afolayan ◽  
Mandeep Jit Singh ◽  
Mardina Abdullah ◽  
Suhaila M. Buhari ◽  
Tatsuhiro Yokoyama ◽  
...  
Keyword(s):  
Solar Activity ◽  
Onset Time ◽  
Longitudinal Distribution ◽  
Low Latitude ◽  
Range Type ◽  
Seeding Effect ◽  
Spread F ◽  
Range Spread ◽  
Major Factors ◽  
Ionospheric Condition

Abstract. A comparative study of the equatorial spread F occurrence was conducted at different longitudes during 2010 and 2013 representing the low (LSA) and moderate (MSA) solar activity periods respectively. The ionogram data were recorded at low-latitude stations including Jicamarca (JIC;75.76∘ W, 8.17∘ S), Fortaleza (FZA; 38.52∘ W, 3.73∘ S), Ilorin (ILR; 7.55∘ E, 9.93∘ N), Chumphon (CPN; 88.46∘ E, 11∘ N) and Kwajalein (KWA; 167.73∘ E, 8.72∘ N). The range type spread F (RSF) occurrence was manually recorded at an hourly interval between 18:00 and 06:00 LT, and a monthly average of the RSF occurrence was estimated for each season. The longitudinal distribution of the RSF occurrence features included the observed difference in the onset time, the duration and the seasonal occurrence peak. The seasonal asymmetry in the RSF occurrence distribution was analysed in relation to the zonal drift reversal’s effect on the plasma irregularity initiation. We believe that the inconsistent equinoctial asymmetry pattern in the RSF occurrence is modulated by the seasonal/longitudinal variation of the zonal drift reversal delay during both solar epochs. Likewise, the seeding effect and the background ionospheric condition were also considered as major factors influencing the frequency of irregularity generation in these regions.

scholarly journals Investigation of Low Latitude Spread-F Triggered by Nighttime Medium-Scale Traveling Ionospheric Disturbance

2021 ◽  
Vol 13 (5) ◽  
pp. 945
Author(s):  
Zhongxin Deng ◽  
Rui Wang ◽  
Yi Liu ◽  
Tong Xu ◽  
Zhuangkai Wang ◽  
...  
Keyword(s):  
Ionospheric Disturbance ◽  
Phase Speed ◽  
Morphological Processing ◽  
Wave Number ◽  
Occurrence Rate ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Spread F

In the current study, we investigated the mechanism of medium-scale traveling ionospheric disturbance (MSTID) triggering spread-F in the low latitude ionosphere using ionosonde observation and Global Navigation Satellite System-Total Electron Content (GNSS-TEC) measurement. We use a series of morphological processing techniques applied to ionograms to retrieve the O-wave traces automatically. The maximum entropy method (MEM) was also utilized to obtain the propagation parameters of MSTID. Although it is widely acknowledged that MSTID is normally accompanied by polarization electric fields which can trigger Rayleigh–Taylor (RT) instability and consequently excite spread-F, our statistical analysis of 13 months of MSTID and spread-F occurrence showed that there is an inverse seasonal occurrence rate between MSTID and spread-F. Thus, we assert that only MSTID with certain properties can trigger spread-F occurrence. We also note that the MSTID at night has a high possibility to trigger spread-F. We assume that this tendency is consistent with the fact that the polarization electric field caused by MSTID is generally the main source of post-midnight F-layer instability. Moreover, after thorough investigation over the azimuth, phase speed, main frequency, and wave number over the South America region, we found that the spread-F has a tendency to be triggered by nighttime MSTID, which is generally characterized by larger ΔTEC amplitudes.

scholarly journals HF Doppler radar observations of low-latitude spread F

Radio Science ◽  
2009 ◽  
Vol 44 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. R. Reddi ◽  
M. S. S. R. K. N. Sarma ◽  
K. Niranjan
Keyword(s):  
Doppler Radar ◽  
Low Latitude ◽  
Radar Observations ◽  
Spread F

Seasonal behavior of H component during solar cycle 24

2021 ◽  
Author(s):  
Yasmina Bouderba ◽  
Ener Aganou ◽  
Abdenaceur Lemgharbi
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Horizontal Component ◽  
Low Latitude ◽  
Seasonal Behavior ◽  
The Earth ◽  
Earth Magnetic Field ◽  
Solar Cycle 24 ◽  
Minimum Solar Activity ◽  
Cycle 24

<p>In this work we will show the behavior of the horizontal component H of the Earth Magnetic Field (EMF) along the seasons during the period of solar cycle 24 lasting from 2009 to 2019. By means of  continuous measurements of geomagnetic components (X, Y) of the EMF, we compute the horizontal component H at the Earth’s surface. The data are recorded with a time resolution of one minute at Tamanrasset observatory in Algeria at the geographical coordinates of 22.79° North and 5.53° East. These data are available from the INTERMAGNET network. We find that the variation in amplitude of the hourly average of H component at low latitude changes from a season to another and it is greater at the maximum solar activity than at the minimum solar activity.</p><p><strong>Keywords:</strong> Solar cycle 24, Season, Horizontal component H. </p>

scholarly journals Post midnight spread-F occurrence over Waltair (17.7° N, 83.3° E) during low and ascending phases of solar activity

2003 ◽  
Vol 21 (3) ◽  
pp. 745-750 ◽  
Author(s):  
K. Niranjan ◽  
P. S. Brahmanandam ◽  
P. Ramakrishna Rao ◽  
G. Uma ◽  
D. S. V. V. D. Prasad ◽  
...  
Keyword(s):  
Solar Activity ◽  
Atmospheric Composition ◽  
Activity Period ◽  
Sunspot Activity ◽  
Low Latitude ◽  
F Region ◽  
Composition And Structure ◽  
Spread F ◽  
Solar Activity Period ◽  
Night Airglow

Abstract. A study carried out on the occurrence of post midnight spread-F events at a low-latitude station, Waltair (17.7° N, 83.3° E), India revealed that its occurrence is maximum in the summer solstice months of the low solar activity period and decreases with an increase in the sunspot activity. The F-region virtual height variations show that 80% of these spread-F cases are associated with an increase in the F-region altitude. It is suggested with the support of the night airglow 6300 A zenith intensity data obtained with co-located ground-based night airglow photometer and electron temperature data from the Indian SROSS C2 satellite that the seasonal variation of the occurrence and probable onset times of the post midnight spread-F depend on the characteristics of the highly variable semipermanent equatorial Midnight Temperature Maximum (MTM).Key words. Ionosphere (ionospheric irregularities; ionosphere atmosphere interactions) Atmospheric composition and structure (airglow and Aurora)

Low-latitude ionospheric response from GPS, IRI and TIE-GCM TEC to Solar Cycle 24

2019 ◽  
Vol 364 (12) ◽  
Author(s):  
S. S. Rao ◽  
Monti Chakraborty ◽  
Sanjay Kumar ◽  
A. K. Singh
Keyword(s):  
Solar Cycle ◽  
Low Latitude ◽  
Ionospheric Response ◽  
Solar Cycle 24 ◽  
Cycle 24
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