scholarly journals Intriguing aspects of F-region plasma irregularities revealed by the Gadanki radar observations during the SAFAR campaign

2009 ◽  
Vol 27 (10) ◽  
pp. 3781-3790 ◽  
Author(s):  
A. K. Patra ◽  
D. V. Phanikumar
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Plasma Irregularities ◽  
F Region ◽  
Mst Radar ◽  
E Region ◽  
Summer Time ◽  
Interesting Event ◽  
Region Plasma ◽  
Activity Condition

Abstract. Intriguing new results of F-region irregularities observed using the Gadanki MST radar during the SAFAR campaigns, which were conducted during the equinox and summer of 2008 that corresponds to low solar activity condition, are presented. The summer observations are first of its kind from Gadanki. Observations revealed remarkably different morphology of the F-region irregularities in summer when compared to that in equinox. In summer, the F-region irregularities were observed as horizontally stratified structures, while in equinox they were observed as plume structures. Further, the irregularities in summer commenced during the post-midnight hours in contrast to their commencement in the post-sunset hours and occurrence extending to post-midnight hours in equinox. In addition, an intriguing observation of the summer time irregularities is that they occurred when the background electron density was remarkably low as characterized by the disappearance of the F layer trace in the ionograms. An interesting event of equinox that was observed for 10 h and extended beyond the sunrise time displayed multiple plume structures having periods similar to those of the E-region velocity variations. These observations are discussed with due focus on the genesis of post-midnight F-region irregularities and their possible linkage to the E-region dynamics.

scholarly journals On the relation between ionospheric parameters and sunspot number

2020 ◽  
Vol 1 ◽  
Author(s):  
Chris Hall ◽  
Magnar Gullikstad Johnsen
Keyword(s):  
Solar Activity ◽  
Change Point ◽  
Critical Frequency ◽  
Auroral Oval ◽  
Change Points ◽  
Observation Site ◽  
F Region ◽  
Critical Frequency Fof2 ◽  
E Region ◽  
The Relationship

AbstractIn a recent study, mid-latitude ionospheric parameters were compared with solar activity; it was suggested that the relationship between these, earlier assumed stable, might be changing with time (Lastovicka, 2019). Here, the information is extended to higher latitude (69.6°N, 19.2E) and further back in time. For the ionospheric F-region (viz. the critical frequency, FoF2) the same behaviour is seen with a change-point around 1996. For the ionospheric E-region (viz. the critical frequency, foE), change-points are less obvious than in the mid-latitude study, presumably owing to the observation site lying under the auroral oval.

scholarly journals Vertical and longitudinal electron density structures of equatorial E- and F-regions

2011 ◽  
Vol 29 (1) ◽  
pp. 81-89 ◽  
Author(s):  
P. S. Brahmanandam ◽  
Y.-H. Chu ◽  
K.-H. Wu ◽  
H.-P. Hsia ◽  
C.-L. Su ◽  
...  
Keyword(s):  
Electron Density ◽  
Phase Relation ◽  
F Region ◽  
Good Consistency ◽  
June Solstice ◽  
December Solstice ◽  
Different Seasons ◽  
E Region ◽  
First Time ◽  
Longitudinal Structures

Abstract. From global soundings of ionospheric electron density made with FORMOSAT 3/COSMIC satellites for September 2006–August 2009, day-night variations in vertical and longitudinal structures of the electron densities in equatorial E- and F-regions for different seasons are investigated for the first time. The results reveal that the wavenumber-3 and wavenumber-4 patterns dominated the nighttime (22:00–04:00 LT) F-region longitudinal structures in solstice and in equinox seasons, respectively. In daytime (08:00–18:00 LT) F-region, the wavenumber-4 patterns governed the longitudinal structures in the September equinox and December solstice, and wavenumber-3 in March equinox and June solstice respectively. A comparison of the daytime and nighttime longitudinal electron density structures indicates that they are approximately 180° out of phase with each other. It is believed that this out of phase relation is very likely the result of the opposite phase relation between daytime and nighttime nonmigrating diurnal tidal winds that modulate background E-region dynamo electric field at different places, leading to the day-night change in the locations of the equatorial plasma fountains that are responsible for the formation of the F-region longitudinal structures. Further, a good consistency between the locations of the density structures in the same seasons of the different years for both daytime and nighttime epochs has been noticed indicating that the source mechanism for these structures could be the same.

scholarly journals A comparison of velocity measurements from the CUTLASS Finland radar and the EISCAT UHF system

1999 ◽  
Vol 17 (7) ◽  
pp. 892-902 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester ◽  
S. E. Milan ◽  
T. K. Yeoman
Keyword(s):  
Total Duration ◽  
Field Of View ◽  
Simultaneous Occurrence ◽  
Plasma Convection ◽  
Contributing Factors ◽  
Plasma Irregularities ◽  
Incoherent Scatter ◽  
F Region ◽  
Initial Comparison ◽  
E Region

Abstract. The CUTLASS Finland radar, which comprises an integral part of the SuperDARN system of HF coherent radars, provides near continuous observations of high-latitude plasma irregularities within a field-of-view which extends over some four million square kilometres. Within the Finland radar field-of-view lie both the EISCAT mainland and EISCAT Svalbard incoherent scatter radar facilities. Since the CUTLASS Finland radar commenced operation, in February 1995, the mainland EISCAT UHF radar has been run in common programme 1 and 2 modes for a total duration exceeding 1000 h. Simultaneous and spatially coincident returns from these two radars over this period provide the basis for a comparison of irregularity drift velocity and F-region ion velocity. Initial comparison is limited to velocities from four intervals of simultaneous radar returns; intervals are selected such that they exhibit a variety of velocity signatures including that characteristic of the convection reversal and a rapidly fluctuating velocity feature. Subsequent comparison is on a statistical basis. The velocities measured by the two systems demonstrate reasonable correspondence over the velocity regime encountered during the simultaneous occurrence of coherent and incoherent scatter; differences between the EISCAT UHF measurements of F-region ion drift and the irregularity drift velocities from the Finland radar are explained in terms of a number of contributing factors including contamination of the latter by E-region echoes, a factor which is investigated further, and the potentially deleterious effect of discrepant volume and time sampling intervals.Key words. Ionosphere (ionospheric irregularities; plasma convection)

Application of alternating codes for EISCAT observations during the ERRRIS campaign for E-region plasma irregularities

1990 ◽  
Vol 52 (6-8) ◽  
pp. 431-438 ◽  
Author(s):  
I Häggström ◽  
H Opgenoorth ◽  
P.J.S Williams ◽  
G.O.L Jones ◽  
K Schlegel
Keyword(s):  
Plasma Irregularities ◽  
E Region ◽  
Region Plasma

scholarly journals Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

2008 ◽  
Vol 26 (7) ◽  
pp. 1865-1876 ◽  
Author(s):  
D. V. Phanikumar ◽  
A. K. Patra ◽  
C. V. Devasia ◽  
G. Yellaiah
Keyword(s):  
Seasonal Variation ◽  
Seasonal Variations ◽  
Low Latitude ◽  
Plasma Irregularities ◽  
Daytime Activity ◽  
Significant Difference ◽  
E Region ◽  
Region Plasma ◽  
Present Understanding ◽  
Field Aligned Irregularities

Abstract. In this paper, we present seasonal variation of E region field-aligned irregularities (FAIs) observed using the Gadanki radar and compare them with the seasonal variation of Es observed from a nearby location SHAR. During daytime, FAIs occur maximum in summer and throughout the day, as compared to other seasons. During nighttime, FAIs occur equally in both summer and winter, and relatively less in equinoxes. Seasonal variations of Es (i.e. ftEs and fbEs) show that the daytime activity is maximum in summer and the nighttime activity is maximum in equinoxes. No relation is found between FAIs occurrence/SNR and ftEs/fbEs. FAIs occurrence, however, is found to be related well with (ftEs−fbEs). This aspect is discussed in the light of the present understanding of the mid-latitude Es-FAIs relationship. The seasonal variations of FAIs observed at Gadanki are compared in detail with those of Piura, which show a significant difference in the daytime observations. The observed difference has been discussed considering the factors governing the generation of FAIs.

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