scholarly journals Climatology of Spread F over Tucumán from Massive Statistical Analysis of Autoscaled Data

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1351
Author(s):  
Carlo Scotto ◽  
Dario Sabbagh
Keyword(s):  
Solar Activity ◽  
Retrospective Studies ◽  
Temporal Evolution ◽  
Radio Signal ◽  
Low Latitude ◽  
Ionospheric Station ◽  
Spread F ◽  
Signal Path ◽  
Maximum Occurrence ◽  
Different Levels

Automatic ionogram interpretation methods developed for real-time ionospheric monitoring can be applied in retrospective studies to analyze large quantities of data. The Autoscala software, implemented for such a purpose, includes a routine for automatic detection of diffused echoes known as spread F, which appear in ionograms due to the presence of ionospheric irregularities along the radio signal path. The main objective of this routine is to reject bad quality ionograms. This new capability was used in a climatological study including a large number of ionograms recorded at the low-latitude ionospheric station of Tucumán (26.9° S, 294.6° E, magnetic latitude 15.5° S, Argentina). The study took into account different levels of geomagnetic and solar activity from 2012 to 2020. The results demonstrate the capability of Autoscala to capture the main signature characteristics of spread F and the temporal evolution of the ionosphere peak heigh hmF2, capturing the post-sunset plasma surge that precedes development of spread F. Maximum occurrence of spread F is observed in local summer, with a tendency to shift before midnight with increasing solar activity. Other new climatological details that emerged from the study are illustrated and briefly discussed, dealing with connection with geomagnetic activity, and morning hmF2 behavior after extremely marked nighttime spread F occurrence.

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 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)

scholarly journals Postmidnight equatorial plasma irregularities on the June solstice during low solar activity – a case study

2019 ◽  
Vol 37 (4) ◽  
pp. 657-672
Author(s):  
Claudia M. N. Candido ◽  
Jiankui Shi ◽  
Inez S. Batista ◽  
Fabio Becker-Guedes ◽  
Emília Correia ◽  
...  
Keyword(s):  
Solar Activity ◽  
Low Latitude ◽  
Plasma Irregularities ◽  
Fabry Perot ◽  
June Solstice ◽  
Spread F ◽  
Plasma Depletions ◽  
Dip Angle ◽  
Layer Peak

Abstract. We present a case study of unusual spread-F structures observed by ionosondes at two equatorial and low-latitude Brazilian stations – São Luís (SL: 44.2∘ W, 2.33∘ S; dip angle: −6.9∘) and Fortaleza (FZ: 38.45∘ W, 3.9∘ S; dip angle: −16∘). The irregularity structures observed from midnight to postmidnight hours of moderate solar activity (F10.7 < 97 sfu, where 1 sfu = 10−22 W m−2 s−1) have characteristics different from typical post-sunset equatorial spread F. The spread-F traces first appeared at or above the F-layer peak and gradually became well-formed mixed spread F. They also appeared as plasma depletions in the 630.0 nm airglow emissions made by a wide-angle imager located at the nearby low-latitude station Cajazeiras (CZ: 38.56∘ W, 6.87∘ S; dip angle: −21.4∘). The irregularities appeared first over FZ and later over SL, giving evidence of an unusual westward propagation or a horizontal plasma advection. The drift-mode operation available in one of the ionosondes (a digital portable sounder, DPS-4) has enabled us to analyze the horizontal drift velocities and directions of the irregularity movement. We also analyzed the neutral wind velocity measured by a Fabry–Pérot interferometer (FPI) installed at CZ and discuss its possible role in the development of the irregularities.

scholarly journals Characteristics of VHF radiowave scintillations over a solar cycle (1983−1993) at a low-latitude station: Waltair (17.7°N, 83.3°E)

1997 ◽  
Vol 15 (6) ◽  
pp. 729-733 ◽  
Author(s):  
P. V. S. Rama Rao ◽  
P. T. Jayachandran ◽  
P. Sri Ram ◽  
B. V. Ramana Rao ◽  
D. S. V. V. D. Prasad ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
High Solar Activity ◽  
Night Time ◽  
Low Latitude ◽  
Latitude Station ◽  
Maximum Occurrence

Abstract. The characteristics of VHF radiowave scintillations at 244 MHz (FLEETSAT) during a complete solar cycle (1983–93) at a low-latitude station, Waltair (17.7°N, 83.3°E), are presented. The occurrence of night-time scintillations shows equinoctial maxima and summer minima in all the epochs of solar activity, and follows the solar activity. The daytime scintillation occurrence is negatively correlated with the solar activity and shows maximum occurrence during the summer months in a period of low solar activity. The occurrence of night-time scintillations is inhibited during disturbed days of high solar activity and enhanced during low solar activity.

scholarly journals Statistical analysis of low-latitude spread F observed over Puer, China, during 2015–2016

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Ting Lan ◽  
Chunhua Jiang ◽  
Guobin Yang ◽  
Yuannong Zhang ◽  
Jing Liu ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Magnetic Activity ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Equatorial Ionization Anomaly ◽  
Spread F ◽  
Latitude Region ◽  
Range Spread ◽  
Activity Dependence ◽  
Maximum Occurrence

AbstractStatistical analysis of spread F (SF), recorded at Puer (PUR, 22.7° N, 101.05° E, Dip Latitude 12.9° N) during 2015–2016, was carried out to reveal its characteristics at the northern equatorial ionization anomaly. In our study, SF was categorized into four types, frequency spread F (FSF), range spread F (RSF), mix spread F (MSF) and strong range spread F (SSF). The statistical results presented that FSF and MSF were dominant over Puer. Most types of SF appeared mostly in summer months, except the maximum occurrence of SSF in equinox months. Moreover, observations of SF events also showed that the solar activity and magnetic activity dependence of SF varied with seasons. Compared with observations at other region, the present results suggest that medium-scale traveling ionospheric disturbances (MSTIDs) may play a key role in generation of SF in low-latitude region.

scholarly journals Postmidnight equatorial plasma irregularities on June solstice during low solar activity – a case study

2018 ◽  
Author(s):  
Claudia M. N. Candido ◽  
Jiankui Shi ◽  
Inez S. Batista ◽  
Fabio Becker-Guedes ◽  
Emília Correia ◽  
...  
Keyword(s):  
Solar Activity ◽  
Low Latitude ◽  
Plasma Irregularities ◽  
June Solstice ◽  
Spread F ◽  
Dip Angle

Abstract. We present a case study of unusual spread-F structures observed by ionosondes at two equatorial and low latitude Brazilian stations – Sao Luis (SL: 44.2° W, 2.33° S, dip angle: −6.9°) and Fortaleza (FZ: 38.45° W, 3.9° S, dip angle: −16°). The irregularity structures observed from midnight to post-midnight hours of moderate solar activity (F10.7 

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 Low-latitude equinoctial spread-F occurrence at different longitude sectors under low solar activity

2013 ◽  
Vol 31 (2) ◽  
pp. 153-162 ◽  
Author(s):  
M. Pezzopane ◽  
E. Zuccheretti ◽  
P. Abadi ◽  
A. J. de Abreu ◽  
R. de Jesus ◽  
...  
Keyword(s):  
Solar Activity ◽  
Comparative Study ◽  
Continuous Wave ◽  
Physical Processes ◽  
Low Latitude ◽  
Frequency Spread ◽  
Equatorial Ionization Anomaly ◽  
Spread F ◽  
Range Spread

Abstract. We present the results of a comparative study of spread-F signatures over five low-latitude sites: Chiangmai (CGM; 18.8° N, 98.9° E, mag. Lat. 8.8° N), Thailand; Tanjungsari (TNJ; 6.9° S, 107.6° E, mag. Lat. 16.9° S), Indonesia; Palmas (PAL; 10.2° S, 311.8° E, mag. Lat. 0.9° S) and São José Dos Campos (SJC; 23.2° S, 314.1° E, mag. Lat. 14.0° S), Brazil; and Tucumán (TUC; 26.9° S, 294.6° E, mag. Lat. 16.8° S), Argentina. The investigation was based on simultaneous ionograms recorded by an FMCW (frequency-modulated continuous-wave) at CGM, an IPS-71 (digital ionosonde from KEL aerospace) at TNJ, a CADI (Canadian Advanced Digital Ionosonde) at PAL and SJC, and an AIS-INGV (Advanced Ionospheric Sounder – Istituto Nazionale di Geofisica e Vulcanologia) at TUC, during the equinoctial periods March–April (R12 = 2.0 and R12 = 2.2) and September–October (R12 = 6.1 and R12 = 7.0) 2009, for very low solar activity. Spread-F signatures were categorized into two types: the range spread-F (RSF) and the frequency spread-F (FSF). The study confirms that the dynamics and the physical processes responsible for these phenomena are actually complicated. In fact, the features that arise from the investigation are different, depending on both the longitude sector and on the hemisphere. For instance, TUC, under the southern crest of the ionospheric equatorial ionization anomaly (EIA), shows a predominance of RSF signatures, while both SJC, under the southern crest of EIA but in a different longitude sector, and CGM, under the northern crest of EIA, show a predominance of FSF signatures. Moreover, the spread-F occurrence over the longitude sector that includes CGM and TNJ is significantly lower than the spread-F occurrence over the longitude sector of PAL, SJC, and TUC.

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.

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