scholarly journals Observation of polar cap patches and calculation of gradient drift instability growth times: A Swarm case study

2015 ◽  
Vol 42 (2) ◽  
pp. 201-206 ◽  
Author(s):  
A. Spicher ◽  
T. Cameron ◽  
E. M. Grono ◽  
K. N. Yakymenko ◽  
S. C. Buchert ◽  
...  
Keyword(s):  
Polar Cap ◽  
Instability Growth ◽  
Gradient Drift ◽  
Drift Instability

scholarly journals Gradient drift instability growth rates from global-scale modeling of the polar ionosphere

Radio Science ◽  
1998 ◽  
Vol 33 (6) ◽  
pp. 1915-1928 ◽  
Author(s):  
J. J. Sojka ◽  
M. V. Subramanium ◽  
L. Zhu ◽  
R. W. Schunk
Keyword(s):  
Growth Rates ◽  
Global Scale ◽  
Polar Ionosphere ◽  
Scale Modeling ◽  
Instability Growth ◽  
Gradient Drift ◽  
Drift Instability

scholarly journals Global Positioning System (GPS) Scintillation Associated with a Polar Cap Patch

2021 ◽  
Vol 13 (10) ◽  
pp. 1915
Author(s):  
Jayachandran P. Thayyil ◽  
Anthony M. McCaffrey ◽  
Yong Wang ◽  
David R. Themens ◽  
Christopher Watson ◽  
...  
Keyword(s):  
Global Positioning System ◽  
Leading Edge ◽  
Signal Amplitude ◽  
Positioning System ◽  
Polar Cap ◽  
Linear Evolution ◽  
Gps Scintillation ◽  
Global Positioning ◽  
Gradient Drift ◽  
Drift Instability

A Global Positioning System (GPS) network in the polar cap, along with ionosonde and SuperDARN radar measurements, are used to study GPS signal amplitude and phase scintillation associated with a polar cap patch. The patch was formed due to a north-to-south transition of the interplanetary magnetic field (IMF Bz). The patch moved antisunward with an average speed of ~600 m/s and lasted for ~2 h. Significant scintillation occurred on the leading edge of the patch, with smaller bursts of scintillation inside and on the trailing edge. As the patch moved, it maintained the integrity of the scintillation, producing irregularities (Fresnel scale) on the leading edge. There were no convection shears or changes in the direction of convection during scintillation events. Observations suggest that scintillation-producing Fresnel scale structures are generated through the non-linear evolution of the gradient drift instability mechanism.

scholarly journals Aurora and open magnetic flux during isolated substorms, sawteeth, and SMC events

2007 ◽  
Vol 25 (8) ◽  
pp. 1865-1876 ◽  
Author(s):  
A. D. DeJong ◽  
X. Cai ◽  
R. C. Clauer ◽  
J. F. Spann
Keyword(s):  
Magnetic Flux ◽  
Temporal Variations ◽  
Auroral Oval ◽  
Polar Cap ◽  
Expansion Phase ◽  
Magnetospheric Convection ◽  
Open Magnetic Flux ◽  
Open Flux ◽  
The Individual

Abstract. Using Polar UVI LBHl and IMAGE FUV WIC data, we have compared the auroral signatures and polar cap open flux for isolated substorms, sawteeth oscillations, and steady magnetospheric convection (SMC) events. First, a case study of each event type is performed, comparing auroral signatures and open magnetic fluxes to one another. The latitude location of the auroral oval is similar during isolated substorms and SMC events. The auroral intensity during SMC events is similar to that observed during the expansion phase of an isolated substorm. Examination of an individual sawtooth shows that the auroral intensity is much greater than the SMC or isolated substorm events and the auroral oval is displaced equatorward making a larger polar cap. The temporal variations observed during the individual sawtooth are similar to that observed during the isolated substorm, and while the change in polar cap flux measured during the sawtooth is larger, the percent change in flux is similar to that measured during the isolated substorm. These results are confirmed by a statistical analysis of events within these three classes. The results show that the auroral oval measured during individual sawteeth contains a polar cap with, on average, 150% more magnetic flux than the oval measured during isolated substorms or during SMC events. However, both isolated substorms and sawteeth show a 30% decrease in polar cap magnetic flux during the dipolarization (expansion) phase.

scholarly journals E-Region Field-Aligned Irregularities in the Middle of a Solar Eclipse Observed by a Bistatic Radar

2022 ◽  
Vol 14 (2) ◽  
pp. 392
Author(s):  
Lei Qiao ◽  
Gang Chen ◽  
Wanlin Gong ◽  
Xuesi Cai ◽  
Erxiao Liu ◽  
...  
Keyword(s):  
Solar Eclipse ◽  
Recovery Phase ◽  
Bistatic Radar ◽  
Doppler Shifts ◽  
Propagation Parameters ◽  
E Region ◽  
Gradient Drift ◽  
Drift Instability ◽  
Wave Induced ◽  
Field Aligned Irregularities

The Wuhan Ionospheric Oblique Backscatter Sounding System (WIOBSS) was applied as a bistatic radar to record the ionospheric E-region responses to a solar eclipse on 22 July 2009. The transmitter was located in Wuhan and the receiver was located in Huaian. The receiver observed anomalous echoes with larger Doppler shifts at the farther ranges compared with the echoes reflected by Es. According to the simulated ray propagation paths of the reflected and scattered waves, we considered that the anomalous echoes were scattered by E-region field-aligned irregularities (FAIs). The locations of the FAIs recorded by the WIOBSS were estimated with the International Geomagnetic Reference Field (IGRF) and the observed propagation parameters. These irregularities occurred at around the eclipse maximum and lasted for ~20–40 min. The steep plasma density gradient induced by the fast drop photo ionization under the lunar shadow was beneficial to the occurrence of gradient drift instability to generate the FAIs. They were different from the gravity wave-induced irregularities occurring in the recovery phase of the solar eclipse.

scholarly journals Simultaneous VHF radar backscatter and ionosonde observations of low-latitude E region

2005 ◽  
Vol 23 (3) ◽  
pp. 773-779 ◽  
Author(s):  
A. K. Patra ◽  
S. Sripathi ◽  
P. B. Rao ◽  
K. S. V. Subbarao
Keyword(s):  
Low Latitude ◽  
Vhf Radar ◽  
Radar Echoes ◽  
First Results ◽  
E Region ◽  
Gradient Drift ◽  
Drift Instability ◽  
Relationship Of ◽  
The Relationship ◽  
Field Aligned Irregularities

Abstract. The first results of simultaneous observations made on the low-latitude field-aligned irregularities (FAI) using the MST radar located at Gadanki (13.5° N, 79.2° E, dip 12.5°) and the Es parameters using an ionosonde at a nearby station Sriharikota (13.7° N, 80.1° E, dip 12.6°) are presented. The observations show that while the height of the most intense radar echoes is below the virtual height of Es (h'Es) during daytime, it is found to be either below or above during nighttime. The strength of the FAI is better correlated with the top penetration frequency (ftEs) and the blanketing frequency (fbEs) during the night (r=0.4 in both cases) as compared to the day (r=0.35 and -0.04, respectively). Furthermore, the signal strength of FAI is reasonably correlated with (ftEs-fbEs) during daytime (r=0.59) while very poorly correlated during nighttime (r=0.18). While the radar observations in general appear to have characteristics close to that of mid-latitudes, the relationship of these with the Es parameters are poorer than that of mid-latitudes. The observations reported here, nevertheless, are quite consistent with the expectations based on the gradient drift instability mechanism.

Likelihood of gradient drift instability development during the August 21, 2017 solar eclipse

2020 ◽  
Vol 175 (1-2) ◽  
pp. 136-140
Author(s):  
Chirag Rathod ◽  
Lee Kordella ◽  
Wayne Scales ◽  
Greg Earle ◽  
Bhuvana Srinivasan
Keyword(s):  
Solar Eclipse ◽  
Instability Development ◽  
Gradient Drift ◽  
Drift Instability
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