scholarly journals Behaviour of the F1-region, and Esand spread-F phenomena at European middle latitudes, particularly under geomagnetic storm conditions

2009 ◽  
Vol 47 (2-3 Sup.) ◽  
Author(s):  
P. Bencze ◽  
D. Buresová ◽  
J. Lastovicka ◽  
F. Märcz
Keyword(s):  
Geomagnetic Storm ◽  
Middle Latitudes ◽  
Spread F

scholarly journals Ionosonde Observations of Spread F and Spread Es at Low and Middle Latitudes during the Recovery Phase of the 7–9 September 2017 Geomagnetic Storm

2021 ◽  
Vol 13 (5) ◽  
pp. 1010
Author(s):  
Lehui Wei ◽  
Chunhua Jiang ◽  
Yaogai Hu ◽  
Ercha Aa ◽  
Wengeng Huang ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Large Scale ◽  
Satellite System ◽  
Recovery Phase ◽  
Ionospheric Irregularities ◽  
Middle Latitudes ◽  
Multiple Observations ◽  
Swarm Satellites ◽  
Spread F ◽  
Global Navigation Satellite

This study presents observations of nighttime spread F/ionospheric irregularities and spread Es at low and middle latitudes in the South East Asia longitude of China sectors during the recovery phase of the 7–9 September 2017 geomagnetic storm. In this study, multiple observations, including a chain of three ionosondes located about the longitude of 100°E, Swarm satellites, and Global Navigation Satellite System (GNSS) ROTI maps, were used to study the development process and evolution characteristics of the nighttime spread F/ionospheric irregularities at low and middle latitudes. Interestingly, spread F and intense spread Es were simultaneously observed by three ionosondes during the recovery phase. Moreover, associated ionospheric irregularities could be observed by Swarm satellites and ground-based GNSS ionospheric TEC. Nighttime spread F and spread Es at low and middle latitudes might be due to multiple off-vertical reflection echoes from the large-scale tilts in the bottom ionosphere. In addition, we found that the periods of the disturbance ionosphere are ~1 h at ZHY station, ~1.5 h at LSH station and ~1 h at PUR station, respectively. It suggested that the large-scale tilts in the bottom ionosphere might be produced by LSTIDs (Large scale Traveling Ionospheric Disturbances), which might be induced by the high-latitude energy inputs during the recovery phase of this storm. Furthermore, the associated ionospheric irregularities observed by satellites and ground-based GNSS receivers might be caused by the local electric field induced by LSTIDs.

Ionosonde observations of daytime spread F at middle latitudes during a geomagnetic storm

2018 ◽  
Vol 179 ◽  
pp. 174-180 ◽  
Author(s):  
Guobin Yang ◽  
Chunhua Jiang ◽  
Ting Lan ◽  
Wengeng Huang ◽  
Zhengyu Zhao
Keyword(s):  
Geomagnetic Storm ◽  
Middle Latitudes ◽  
Spread F

scholarly journals Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21–22 January 2005

2011 ◽  
Vol 29 (5) ◽  
pp. 919-929 ◽  
Author(s):  
Y. Sahai ◽  
P. R. Fagundes ◽  
R. de Jesus ◽  
A. J. de Abreu ◽  
G. Crowley ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Latin American ◽  
Geomagnetic Disturbance ◽  
Equatorial Station ◽  
Phase Fluctuations ◽  
Interplanetary Magnetic Fields ◽  
F Region ◽  
Storm Sudden Commencement ◽  
Reversal Time ◽  
Spread F

Abstract. In the present investigation, we have studied the response of the ionospheric F-region in the Latin American sector during the intense geomagnetic storm of 21–22 January 2005. This geomagnetic storm has been considered "anomalous" (minimum Dst reached −105 nT at 07:00 UT on 22 January) because the main storm phase occurred during the northward excursion of the Bz component of interplanetary magnetic fields (IMFs). The monthly mean F10.7 solar flux for the month of January 2005 was 99.0 sfu. The F-region parameters observed by ionosondes at Ramey (RAM; 18.5° N, 67.1° W), Puerto Rico, Jicamarca (JIC; 12.0° S, 76.8° W), Peru, Manaus (MAN; 2.9° S, 60.0° W), and São José dos Campos (SJC; 23.2° S, 45.9° W), Brazil, during 21–22 January (geomagnetically disturbed) and 25 January (geomagnetically quiet) have been analyzed. Both JIC and MAN, the equatorial stations, show unusually rapid uplifting of the F-region peak heights (hpF2/hmF2) and a decrease in the NmF2 coincident with the time of storm sudden commencement (SSC). The observed variations in the F-region ionospheric parameters are compared with the TIMEGCM model run for 21–22 January and the model results show both similarities and differences from the observed results. Average GPS-TEC (21, 22 and 25 January) and phase fluctuations (21, 22, 25, 26 January) observed at Belem (BELE; 1.5° S, 48.5° W), Brasilia (BRAZ; 15.9° S, 47.9° W), Presidente Prudente (UEPP; 22.3° S, 51.4° W), and Porto Alegre (POAL; 30.1° S, 51.1° W), Brazil, are also presented. These GPS stations belong to the RBMC/IBGE network of Brazil. A few hours after the onset of the storm, large enhancements in the VTEC and NmF2 between about 20:00 and 24:00 UT on 21 January were observed at all the stations. However, the increase in VTEC was greatest at the near equatorial station (BELE) and enhancements in VTEC decreased with latitude. It should be pointed out that no phase fluctuations or spread-F were observed in the Latin American sector during the post-sunset pre-reversal time in the geomagnetic disturbance (21 January). The disturbance dynamo electric field possibly resulted in downward drift of the F-region plasma and inhibited the formation of spread-F.

RADIO STAR SCINTILLATIONS AND IONOSPHERIC DISTURBANCES

1959 ◽  
Vol 37 (10) ◽  
pp. 1137-1152 ◽  
Author(s):  
T. R. Hartz
Keyword(s):  
Geographical Location ◽  
Generation Mechanism ◽  
Upper Atmosphere ◽  
Ionospheric Disturbances ◽  
High Latitudes ◽  
General Belief ◽  
Auroral Activity ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Spread F

The generation mechanism for the ionization irregularities in the upper atmosphere which are responsible for radio star scintillations is considered. The general belief that scintillations are related to the spread-F phenomenon observed on ionosonde recordings is found to be an inadequate explanation for the scintillations at 53 Mc/s recorded at Ottawa. An examination of the Ottawa recordings shows that there is a definite association, both in time of occurrence and geographical location, with those ionospheric disturbances that are usually considered to be due to incoming solar particles. Since other workers at more southerly geomagnetic latitudes have associated their scintillation observations with the spread-F phenomenon which they consider to be independent of auroral activity, it would appear that two mechanisms, at least, are responsible for the radio star fluctuations: namely, the precipitation of solar corpuscles and a mechanism linked with the spread-F phenomenon. The former seems to predominate at high latitudes, the latter is probably predominant at low latitudes, while both mechanisms probably are operative in middle latitudes.

scholarly journals Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

2004 ◽  
Vol 22 (9) ◽  
pp. 3241-3250 ◽  
Author(s):  
D. Pallamraju ◽  
S. Chakrabarti ◽  
C. E. Valladares
Keyword(s):  
Gravity Wave ◽  
Magnetic Storm ◽  
Geomagnetic Storm ◽  
Local Time ◽  
Direct Effect ◽  
Spatial Structures ◽  
Low Latitude ◽  
Equatorial Ionization Anomaly ◽  
Low Latitudes ◽  
Spread F

Abstract. We describe the effect of the 6 November 2001 magnetic storm on the low latitude thermospheric composition. Daytime red line (OI 630.0nm) emissions from Carmen Alto, Chile showed anomalous 2-3 times larger emissions in the morning (05:30-08:30 Local Time; LT) on the disturbed day compared to the quiet days. We interpret these emission enhancements to be caused due to the increase in neutral densities over low latitudes, as a direct effect of the geomagnetic storm. As an aftereffect of the geomagnetic storm, the dayglow emissions on the following day show gravity wave features that gradually increase in periodicities from around 30min in the morning to around 100min by the evening. The integrated dayglow emissions on quiet days show day-to-day variabilities in spatial structures in terms of their movement away from the magnetic equator in response to the Equatorial Ionization Anomaly (EIA) development in the daytime. The EIA signatures in the daytime OI 630.0nm column-integrated dayglow emission brightness show different behavior on days with and without the post-sunset Equatorial Spread F (ESF) occurrence.

scholarly journals A Qualitative Study of the Ionospheric Weak Response to Super Geomagnetic Storms

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 635
Author(s):  
Haimeng Li ◽  
Zhou Chen ◽  
Lianqi Xie ◽  
Fan Li
Keyword(s):  
Geomagnetic Storm ◽  
Geomagnetic Storms ◽  
Processing Method ◽  
Statistical Characteristics ◽  
High Solar Activity ◽  
Storm Event ◽  
Time Interval ◽  
Weak Response ◽  
Ionospheric Response ◽  
Middle Latitudes

The ionospheric response to a geomagnetic storm is a geophysical process. Although strong geomagnetic storms input more energy into the Earth’s upper atmosphere, the ionospheric response often does not reflect the same level of variation as the geomagnetic storm, and the response may be weak during a very strong storm. However, the estimated ionospheric response to geomagnetic activity also varies with extraction method. Here, two different methods—the spectral whitening method (SWM) and the monthly median method (MMM)—are used to verify whether the apparent weak ionospheric response is an artifact of the processing method. The weak ionospheric response is found with both methods, which suggests it is a real ionospheric phenomenon. The statistical characteristics of the regional and global ionospheric weak response to a super geomagnetic storm (SGS) and to an SGS with a preceding storm event (SGS-PRE) are investigated and compared. The results show that the regional ionospheric weak response to an SGS is more prevalent at middle latitudes than those at low and high latitudes. The global ionospheric weak response occurs more frequently under high solar activity and has a strong correlation with SGS-PRE, which suggests that the effect of a storm on the ionosphere can be influenced by its preconditioning, especially when there is an earlier storm and the time interval between the two storms is short. In fact, an ionospheric long-lasting disturbance may be an important reason for the ionospheric weak response caused by the SGS-PRE.

scholarly journals Geomagnetic storm and equatorial spread-F

2004 ◽  
Vol 22 (9) ◽  
pp. 3231-3239 ◽  
Author(s):  
F. Becker-Guedes ◽  
Y. Sahai ◽  
P. R. Fagundes ◽  
W. L. C. Lima ◽  
V. G. Pillat ◽  
...  
Keyword(s):  
Case Studies ◽  
Geomagnetic Storm ◽  
Geomagnetic Storms ◽  
Equatorial Spread F ◽  
University Center ◽  
Different Seasons ◽  
Spread F ◽  
Salient Features ◽  
The University ◽  
Ionospheric Sounding

Abstract. In August 2000, a new ionospheric sounding station was established at Sao Jose dos Campos (23.2° S, 45.9° W; dip latitude 17.6° S), Brazil, by the University of Vale do Paraiba (UNIVAP). Another ionospheric sounding station was established at Palmas (10.2° S, 48.2° W; dip latitude 5.5° S), Brazil, in April 2002, by UNIVAP in collaboration with the Lutheran University Center of Palmas (CEULP), Lutheran University of Brazil (ULBRA). Both the stations are equipped with digital ionosonde of the type known as Canadian Advanced Digital Ionosonde (CADI). In order to study the effects of geomagnetic storms on equatorial spread-F, we present and discuss three case studies, two from the ionospheric sounding observations at Sao Jose dos Campos (September and November 2000) and one from the simultaneous ionospheric sounding observations at Sao Jose dos Campos and Palmas (July 2003). Salient features from these ionospheric observations are presented and discussed in this paper. It has been observed that sometimes (e.g. 4-5 November 2000) the geomagnetic storm acts as an inhibitor (high strong spread-F season), whereas at other times (e.g. 11-12 July 2003) they act as an initiator (low strong spread-F season), possibly due to corresponding changes in the quiet and disturbed drift patterns during different seasons.

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