scholarly journals Occurrence of Equatorial Plasma Bubbles during Intense Magnetic Storms

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Chao-Song Huang
Keyword(s):  
Electric Field ◽  
Magnetic Storms ◽  
Ion Density ◽  
Plasma Bubbles ◽  
Defense Meteorological Satellite Program ◽  
Equatorial Plasma Bubbles ◽  
Evening Sector ◽  
Plasma Depletions ◽  
Meteorological Satellite ◽  
The Imf

An important issue in low-latitude ionospheric space weather is how magnetic storms affect the generation of equatorial plasma bubbles. In this study, we present the measurements of the ion density and velocity in the evening equatorial ionosphere by the Defense Meteorological Satellite Program (DMSP) satellites during 22 intense magnetic storms. The DMSP measurements show that deep ion density depletions (plasma bubbles) are generated after the interplanetary magnetic field (IMF) turns southward. The time delay between the IMF southward turning and the first DMSP detection of plasma depletions decreases with the minimum value of the IMFBz, the maximum value of the interplanetary electric field (IEF)Ey, and the magnitude of the Dst index. The results of this study provide strong evidence that penetration electric field associated with southward IMF during the main phase of magnetic storms increases the generation of equatorial plasma bubbles in the evening sector.

scholarly journals Seasonal-longitudinal variability of equatorial plasma bubbles

2004 ◽  
Vol 22 (9) ◽  
pp. 3089-3098 ◽  
Author(s):  
W. J. Burke ◽  
C. Y. Huang ◽  
L. C. Gentile ◽  
L. Bauer
Keyword(s):  
Solar Cycle ◽  
Phase Shifts ◽  
Linear Growth Rate ◽  
Cycle Phase ◽  
Loss Cone ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Evening Sector ◽  
Radiation Belt Electrons ◽  
Longitudinal Variability

Abstract. We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs) observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γRT, of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, Beq, and the angle, α, it makes with the dusk terminator line. The independence of α and Beq from the solar cycle phase justifies our comparisons. We have sorted data acquired during more than 75000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP) satellites into 24 longitude and 12 one-month bins, each containing ~250 samples. We show that: (1) in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0°; (2) unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0°; (3) While EPB occurrence rates vary inversely with Beq, the relationships are very different in regions where Beq is increasing and decreasing with longitude. Results (2) and (3) indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0°. Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γRT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈-27°, to illustrate how electric-field penetration from high latitudes can overwhelm the damping effects of weak gradients in Pedersen conductance near dusk.

scholarly journals Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx)

2009 ◽  
Vol 27 (6) ◽  
pp. 2371-2381 ◽  
Author(s):  
P.-D. Pautet ◽  
M. J. Taylor ◽  
N. P. Chapagain ◽  
H. Takahashi ◽  
A. F. Medeiros ◽  
...  
Keyword(s):  
Gravity Wave ◽  
State University ◽  
Large Area ◽  
Plasma Bubbles ◽  
F Region ◽  
Equatorial Plasma Bubbles ◽  
Star Program ◽  
Spread F ◽  
Plasma Depletions ◽  
Bubble Characteristics

Abstract. From September to November 2005, the NASA Living with a Star program supported the Spread-F Experiment campaign (SpreadFEx) in Brazil to study the effects of convectively generated gravity waves on the ionosphere and their role in seeding Rayleigh-Taylor instabilities, and associated equatorial plasma bubbles. Several US and Brazilian institutes deployed a broad range of instruments (all-sky imagers, digisondes, photometers, meteor/VHF radars, GPS receivers) covering a large area of Brazil. The campaign was divided in two observational phases centered on the September and October new moon periods. During these periods, an Utah State University (USU) all-sky CCD imager operated at São João d'Aliança (14.8° S, 47.6° W), near Brasilia, and a Brazilian all-sky CCD imager located at Cariri (7.4° S, 36° W), observed simultaneously the evolution of the ionospheric bubbles in the OI (630 nm) emission and the mesospheric gravity wave field. The two sites had approximately the same magnetic latitude (9–10° S) but were separated in longitude by ~1500 km. Plasma bubbles were observed on every clear night (17 from Brasilia and 19 from Cariri, with 8 coincident nights). These joint datasets provided important information for characterizing the ionospheric depletions during the campaign and to perform a novel longitudinal investigation of their variability. Measurements of the drift velocities at both sites are in good agreement with previous studies, however, the overlapping fields of view revealed significant differences in the occurrence and structure of the plasma bubbles, providing new evidence for localized generation. This paper summarizes the observed bubble characteristics important for related investigations of their seeding mechanisms associated with gravity wave activity.

scholarly journals Stormtime dynamics of the global thermosphere and equatorial ionosphere

2009 ◽  
Vol 27 (5) ◽  
pp. 2035-2044 ◽  
Author(s):  
W. J. Burke ◽  
C. Y. Huang ◽  
R. D. Sharma
Keyword(s):  
Equatorial Ionosphere ◽  
Magnetic Storms ◽  
Main Phase ◽  
New Method ◽  
Sufficient Time ◽  
Quiet Time ◽  
Early Recovery ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Phase Activity

Abstract. During magnetic storms the development of equatorial plasma bubbles (EPBs) and distributions of thermospheric densities are strongly influenced by the histories of imposed magnetospheric electric (εM) fields. Periods of intense EPB activity driven by penetration εM fields in the main phase are followed by their worldwide absence during recovery. A new method is applied to estimate global thermospheric energy (Eth) budgets from orbit-averaged densities measured by accelerometers on polar-orbiting satellites. During the main phase of storms Eth increases as long as the stormtime εM operates, then exponentially decays toward quiet-time values during early recovery. Some fraction of the energy deposited at high magnetic latitudes during the main phase propagates into the subauroral ionosphere-thermosphere where it affects chemical and azimuthal-wind dynamics well into recovery. We suggest a scenario wherein fossils of main phase activity inhibit full restoration of quiet-time dayside dynamos and pre-reversal enhancements of upward plasma drifts near dusk denying bottomside irregularities sufficient time to grow into EPBs.

scholarly journals Dynamics Ionospheric Plasma Bubbles Measured by Optical Imaging System

2015 ◽  
Vol 20 (1) ◽  
pp. 20-27
Author(s):  
Narayan P. Chapagain
Keyword(s):  
Imaging System ◽  
Equatorial Ionosphere ◽  
Navigation Systems ◽  
Plasma Bubble ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Plasma Bubbles ◽  
Christmas Island ◽  
Equatorial Plasma Bubbles ◽  
Plasma Depletions

Deep plasma depletions during the nighttime period in the equatorial ionosphere (referred to as equatorial plasma bubbles –EPBs) can significantly affect communications and navigation systems. In this study, we present the image measurements of plasma bubble from Christmas Island (2.1°N, 157.4°W, dip latitude 2.8°N) in the central Pacific Ocean. These observations were made during September-October 1995 using a Utah State University (USU) CCD imaging system measured at ~280 km altitude. Well-defined magnetic field-aligned plasma depletions were observed for 18 nights, including strong post-midnight fossilized structures, enabling detailed measurements of their morphology and dynamics. We also estimate zonal velocity of the plasma bubbles from available images. The zonal drift velocity of the EPBs is a very important parameter for the understanding and modeling of the electrodynamics of the equatorial ionosphere and for the predictions of ionospheric irregularities. The eastward zonal drift velocities were around 90-100 m/s prior to local midnight, and decreases during the post-midnight period that persisted until dawn.Journal of Institute of Science and Technology, 2015, 20(1): 20-27

scholarly journals The characteristics of field-aligned currents associated with equatorial plasma bubbles as observed by the CHAMP satellite

2009 ◽  
Vol 27 (7) ◽  
pp. 2685-2697 ◽  
Author(s):  
J. Park ◽  
H. Lühr ◽  
C. Stolle ◽  
M. Rother ◽  
K. W. Min ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Field Measurements ◽  
Current Strength ◽  
Meridional Plane ◽  
Champ Satellite ◽  
Poynting Flux ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Earth Magnetic Field

Abstract. Field-aligned currents (FACs) generate magnetic deflections perpendicular to the ambient Earth magnetic field. We investigate the characteristics of FACs associated with equatorial plasma bubbles (EPBs) as deduced from magnetic field measurements by the CHAMP satellite. Meridional magnetic deflections inside EPBs show a clear hemispheric anti-symmetry for events observed before 21:00 LT: inward in the Northern Hemisphere and outward in the Southern Hemisphere. When an eastward electric field is assumed the magnetic signature signifies a Poynting flux directed downward along the magnetic field lines. This means that FACs are driven by a high-altitude equatorial source. Such a scheme cannot be drawn as strictly from our observations after 22:00 LT, possibly because of a westward turning of the electric field inside EPBs and/or a decay of EPBs later at night. The perpendicular magnetic deflection is tilted by 40° from the magnetic meridional plane in westward direction, which implies that the depleted volume of EPBs, as well as the FAC structure, is tilted westward by 40° above the magnetic equator. The peak-to-peak amplitude of the FAC density is found to range typically between 0.1–0.5 μA/m2. The field-aligned sheet current density and the diamagnetic current strength show no correlation.

scholarly journals Airglow observations over the equatorial ionization anomaly zone in Taiwan

2011 ◽  
Vol 29 (5) ◽  
pp. 749-757 ◽  
Author(s):  
J. Y. Liu ◽  
P. K. Rajesh ◽  
I. T. Lee ◽  
T. C. Chow
Keyword(s):  
Global Positioning System ◽  
Ionospheric Disturbances ◽  
Iri Model ◽  
Plasma Bubbles ◽  
Equatorial Ionization Anomaly ◽  
Equatorial Plasma Bubbles ◽  
Global Positioning ◽  
Plasma Depletions ◽  
First Time ◽  
Eastern Wall

Abstract. Airglow imaging at mid-latitude stations often show intensity modulations associated with medium scale travelling ionospheric disturbances (MSTID), while those carried out near the equatorial regions reveal depletions caused by equatorial plasma bubbles (EPB). Two all sky cameras are used to observe plasma depletions in the 630.0 nm emission over the equatorial ionization anomaly (EIA) region, Taiwan (23° N, 121° E; 13.5° N Magnetic) during 1998–2002 and 2006–2007. The results show EPB and MSTID depletions in different solar activity conditions. Several new features of the EPB depletions such as bifurcation, secondary structure on the walls, westward tilt, etc., are discussed in this paper. Evidence of tilted depletions with secondary structures developing on the eastern wall that later evolve to appear as bifurcations, are presented for the first time. Moreover, detail investigations are carried out using International Reference Ionosphere (IRI) model as well as the electron density from Ionosonde and Global Positioning System (GPS) Occultation Experiment (GOX) onboard FORMOSAT-3/COSMIC satellite, to understand the conditions that favor the propagation of MSTID to the latitude of Taiwan.

scholarly journals Interhemispheric conjugate effect in longitude variations of mid-latitude ion density

2020 ◽  
Author(s):  
Yiding Chen ◽  
Libo Liu ◽  
Huijun Le ◽  
Hui Zhang
Keyword(s):  
Solar Minimum ◽  
Neutral Wind ◽  
Ion Density ◽  
Flux Tubes ◽  
The Earth ◽  
Defense Meteorological Satellite Program ◽  
June Solstice ◽  
Magnetic Flux Tubes ◽  
First Time ◽  
Meteorological Satellite

<p>Interhemispheric coupling between the northern and southern mid-lattitude ionosphere through the plasmasphere is difficult to confirm directly from observations. A possible result induced by this coupling is interhemispheric conjugacy of the mid-latitude ionosphere. In this paper, interhemispheric conjugate effect in longitude variations of mid-latitude total ion density (N<sub>i</sub>) is presented, for the first time, using the Defense Meteorological Satellite Program (DMSP) measurements; northern and southern N<sub>i</sub> longitude variations at 21:30 LT are similar between magnetically conjugate mid-latitudes around solar minimum June Solstice of 1996. The conjugate effect after sunset also occurs around the June Solstice in other solar minimum years but disappears when solar activity increases. We suggested that mid-latitude interhemispheric coupling is responsible for the conjugate effect. Neutral wind induced ionospheric transport causes topside longitude variations via upward diffusion at summer mid-latitudes; this further induces similar longitude variations of topside N<sub>i</sub> at winter mid-latitudes via the summer to winter interhemispheric coupling. The conjugate effect occurs only inside the plasmapause where magnetic flux tubes are closed and the plasma in these tubes can stably corotate with the Earth. The conjugate effect not only proves mid-latitude interhemispheric coupling through the plasmasphere, but also implies that neutral wind induced transport can affect ionospheric coupling to the plasmasphere at mid-latitudes.</p>

scholarly journals Zonal velocity of the equatorial plasma bubbles over Kolhapur, India

2013 ◽  
Vol 31 (11) ◽  
pp. 2077-2084 ◽  
Author(s):  
D. P. Nade ◽  
A. K. Sharma ◽  
S. S. Nikte ◽  
P. T. Patil ◽  
R. N. Ghodpage ◽  
...  
Keyword(s):  
Ionospheric Plasma ◽  
Universal Time ◽  
Low Latitude ◽  
Plasma Bubbles ◽  
Standard Time ◽  
Latitude Station ◽  
Equatorial Plasma Bubbles ◽  
Evening Sector ◽  
Zonal Velocity ◽  
Good Agreement

Abstract. This paper presents the observations of zonal drift velocities of equatorial ionospheric plasma bubbles and their comparison with model values. These velocities are determined by nightglow OI 630.0 nm images. The nightglow observations have been carried out from the low latitude station Kolhapur (16.8° N, 74.2° E; 10.6° N dip lat.) during clear moonless nights. Herein we have presented the drift velocities of equatorial plasma bubbles for the period of February–April 2011. Out of 80 nights, 39 showed the occurrence of equatorial plasma bubbles (49%). These 39 nights correspond to magnetically quiet days (ΣKp < 26). The average eastward zonal velocities (112 ± 10 m s−1) of equatorial plasma bubbles increased from evening sector to 21:00 IST (Indian Standard Time = Universal Time + 05:30:00 h), reach maximum about 165 ± 30 m s−1 and then decreases with time. The calculated velocities are in good agreement with that of recently reported values obtained with models with occasional differences; possible mechanisms of which are discussed.

scholarly journals Interhemispheric conjugate effect in longitude variations of mid-latitude ion density

2019 ◽  
Vol 9 ◽  
pp. A40
Author(s):  
Yiding Chen ◽  
Libo Liu ◽  
Huijun Le ◽  
Hui Zhang
Keyword(s):  
Solar Minimum ◽  
Neutral Wind ◽  
Ion Density ◽  
Flux Tubes ◽  
Defense Meteorological Satellite Program ◽  
June Solstice ◽  
Radar Measurements ◽  
Magnetic Flux Tubes ◽  
First Time ◽  
Meteorological Satellite

Earlier incoherent scatter radar measurements revealed upward topside ion fluxes in the summer and downward fluxes in the winter at mid-latitudes at night; a summer to winter interhemispheric coupling was accordingly inferred. However, this interhemispheric coupling through the plasmasphere is difficult to confirm directly from observations. A possible result induced by this coupling is interhemispheric conjugacy of the mid-latitude ionosphere. In this paper, interhemispheric conjugate effect in longitude variations of mid-latitude total ion density (Ni) is presented, for the first time, using the Defense Meteorological Satellite Program (DMSP) measurements; northern and southern Ni longitude variations at 21:30 LT are similar between magnetically conjugate mid-latitudes around solar minimum June Solstice of 1996. The conjugate effect after sunset also occurs around the June Solstice in other solar minimum years but disappears when solar activity increases. We suggested that mid-latitude interhemispheric coupling is responsible for the conjugate effect. Neutral wind induced ionospheric transport causes topside longitude variations via upward diffusion at summer mid-latitudes; this further induces similar longitude variations of topside Ni at winter mid-latitudes via the summer to winter interhemispheric coupling. The conjugate effect occurs only inside the plasmapause where magnetic flux tubes are closed and the plasma in these tubes can stably corotate with the Earth. The conjugate effect not only proves mid-latitude interhemispheric coupling through the plasmasphere, but also implies that neutral wind induced transport can affect ionospheric coupling to the plasmasphere at mid-latitudes.

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