Burbujas de plasma ionosférico ecuatorial (EPBs)

Las burbujas de plasma ionosférico ecuatorial (EPBs, del inglés: “Equatorial Plasma Bubbles”) son regiones en las que la densidad del plasma es menor que la del medio que las rodea, pudiendo disminuir hasta en tres órdenes de magnitud. El concepto de burbuja está estrechamente ligado con el de Equatorial Spread F (ESF), descubierto por Booker y Wells en 1938 a partir de ecos difusos en ionogramas. Posteriormente se descubrió su influencia en el radar (Woodman y La Hoz, 1976) y en la aparición de centelleo (Basu y Kelly, 1977). El fenómeno del ESF consiste en el intercambio turbulento de tubos de flujo magnético de alta densidad con otros más ligeros situados a alturas mayores. Este intercambio crea perturbaciones locales de densidad en un amplio espectro de tamaños (desde unos pocos metros hasta centenares de km), que se propagan rápidamente siguiendo las líneas del campo magnético terrestre y penetrando en el límite superior de la región F de la ionosfera. Estas irregularidades influyen negativamente sobre los sistemas de observación de manera distinta según su tamaño. Las que tienen dimensiones cercanas al metro pueden dar lugar a estructuras en forma de pluma en los registros de radar, mientras que cuando las estructuras tienen tamaños próximos al Dm es posible detectar el spread F en los ionogramas. Las de tamaños comprendidos entre Hm y km provocan el efecto de centelleo (scintillation), que consiste en el debilitamiento de la intensidad de la señal electromagnética recibida. Todas estas irregularidades en el plasma ionosférico coexisten, al menos, durante la fase inicial de desarrollo.

http://www.ucm.es/info/Geofis/Estudios_Ionosfericos/LintrabajoWEBf.htm

Plasma bubbles form at night because the thermosphere and ionosphere have a mix of plasma and electrically neutral gas which becomes unstable after sunset. During the daytime, radiation from the sun creates plasma by tearing electrons from atoms and molecules in the thermosphere and ionosphere. The solar radiation maintains relatively constant levels of plasma in these regions, so they are quite smooth and well behaved. But during the nighttime, there is no solar radiation to prevent the charged particles from recombining back into electrically neutral atoms or molecules again.

The recombination happens faster at lower altitudes, because there are more heavy charged particles (molecular ions) there, and they recombine more quickly than charged particles made from single atoms. More rapid recombination makes the plasma less dense at lower altitudes. The region then becomes unstable because the less dense plasma below, which is trapped in the neutral gas, wants to rise above the higher density plasma above it.

This nighttime instability actually happens at all latitudes, but the equatorial regions become especially turbulent because the plasma bubbles are suspended on Earth's magnetic field, which is horizontal over the equator.

http://www.nasa.gov/mission_pages/cindi/cindi_feature.html

como se ven (radar de las burbujas y estructura): http://cedarweb.hao.ucar.edu/workshop/archive/2007/presentations/comberiate_pd07.pdf

que son, más en profundidad:

Equatorial Plasma Bubbles at Altitudes of the Topside Ionosphere
L. N. Sidorova
Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation, Russian Academy of Sciences,
Troitsk, Moscow oblast, 142190 Russia
Received May 30, 2006; in final form, April 23, 2007
Abstract—A consistent patter, indicating that subtroughs in the He+ density and plasma bubbles can be con

sidered as phenomena of the same origin, has been obtained within the scope of the existent model of equa

torial plasma bubbles. The study has been performed based on the measurements of the ISS
b satellite, which
flew during the period of high solar activity. The conclusion has been made based on a comparative analysis
of the characteristics of subtroughs with the parameters of the known equatorial phenomena. (1) The simi

larity of the LT variations in the latitude of the minimums of subtroughs in the He+ density has been revealed.
(2) It has been displayed that the variations in the averaged depth of subtroughs change from season to season
similarly to the LT variations in the average velocity of the equatorial vertical plasma drift. (3) Good correla

tion (R = 0.67) between the occurrence probability of subtroughs and equatorial spread F statistics, con

structed as the functions of LT and month, has been obtained. (4) The obtained velocity of the possible rise
of plasma irregularities (observed as regions depleted in He+) is in good agreement with the ionosonde, sat

ellite, and radar measurements of the equatorial plasma bubble velocities of the same period. (5) It has been
indicated that plasma irregularities, reaching the altitudes of the topside ionosphere in the low
latitude and
midlatitude regions during high solar activity, are most observable as depleted regions (subtroughs) of He+
density.
PACS numbers: 94.20.Wf, 94.20.Vv, 94.20.dl
DOI: 10.1134/S0016793208010076

http://www.springerlink.com/content/t850507r23g7k291/fulltext.pdf

seguiremos informando, causas, consecuencias, ciclos,....

Annales Geophysicae (2004) 22: 3089–3098
SRef-ID: 1432-0576/ag/2004-22-3089
© European Geosciences Union 2004
Annales
Geophysicae
Seasonal-longitudinal variability of equatorial plasma bubbles
W. J. Burke1, C. Y. Huang2, L. C. Gentile2, and L. Bauer3
1Space Vehicles Directorate, Air Force Research Laboratory, Hanscom AFB, MA, USA
2Institute for Scientific Research, Boston College, Chestnut Hill, MA, USA
3Department of Physics, Air Force Academy, Colorado Springs, CO, USA
Received: 25 September 2003 – Revised: 7 April 2004 – Accepted: 20 April 2004 – Published: 23 September 2004
Part of Special Issue “Equatorial and low latitude aeronomy”

Seasonal-longitudinal variability of equatorial plasma bubbles (pdf)

Relación con el ciclo solar,

Annales Geophysicae, 24, 163–172, 2006
SRef-ID: 1432-0576/ag/2006-24-163
© European Geosciences Union 2006
Annales
Geophysicae
A global climatology for equatorial plasma bubbles in the topside
ionosphere
L. C. Gentile1, W. J. Burke2, and F. J. Rich2
1Institute for Scientific Research, Boston College, Chestnut Hill, MA, USA
2Space Vehicles Directorate, Air Force Research Laboratory, Hanscom AFB, MA, USA
Received: 8 April 2006 – Revised: 18 November 2005 – Accepted: 21 December 2005 – Published: 7 March 2006

A global climatology for equatorial plasma bubbles in the topside
ionosphere

(ejemplo de distribución: Plasma Instabilities in the Equatorial F-Region)

What is plasma bubble?
How is plasma bubble observed?
When does plasma bubble occur?

MichiNishioka - Department of Geophysics - Kyoto University

Plasma bubble in the ionosphere

Conclusions
We have studied geomagnetically-conjugate plasma bubbles
observed with ground-based all-sky imagers and simultaneous
global-scale (∼10,000 km in longitude) ionospheric
structures imaged by the IMAGE satellite. We confirm
that plasma bubbles observed at Darwin and Shigaraki
reach a maximum altitude of ∼1800 km over the geomagnetic
equator and have longitudinal scale lengths less than
100 km with spacings of 200–250 km. Eastward phase velocity
of the bubbles is ∼200 ms−1 near sunset and ∼100
ms−1 at later hours. The global-scale plasma structures
consist of an array of small- to medium-scale wavy structures
(a few hundreds to 1000 km in longitude) that are also
geomagnetically conjugate. New findings are as follows:
1) Bubbles observed with all-sky imagers and IMAGE
are embedded within the small- to medium-scale structures.
Some bubbles are surely located near the crest of an enhanced
electron density region associated with the wavy
structure, consistent with the results from previous radar
observations. Bubbles were also observed in a low electron
density region (faint 135.6-nm airglow region). In this case,
we speculate that the electron density at around the F-layer
peak was low and that the 630.0-nm bubbles existed below
the F-layer peak.
2) Both the small- to medium-scale structures and bubbles
that are generated near sunset show a slant to the west
with increasing latitude in both hemispheres. The tilts do
not change with longitude (i.e., local time).
The above findings suggest that the generation and evolution
of plasma bubbles with a longitudinal scale of 100 km
are closely related to those of plasma structures with scales
of a few hundreds to 1000 km. The bubbles are believed to
be generated through the Rayleigh-Taylor instability. We,
however, do not know how the longer-scale structures are
produced near sunset. This paper has presented one case
study. More simultaneous ground- and satellite-based observations
of airglow are required to clarify the spatial and
temporal relationship between plasma bubbles and longerscale
ionospheric structures.

Simultaneous ground- and satellite-based airglow observations of geomagnetic
conjugate plasma bubbles in the equatorial anomaly

más detecciones (hay un montón de métodos)
Coordinated Space-Based Observations of Equatorial Plasma Bubbles Using TIMED/GUVI and DMSP

de este estudio sobre la distribución de las EPB a lo largo de un ciclo solar, remarco un detalle "inesperado", (el resto también está bien, muy técnico)

Our final comments concern the relationship b etween EPB rates of occurrence and the
equatorial magnetic field strength (Huang et al., 2001). The concept is simple. The R -T
growth rate is directly proportional to V P. Whether imposed through the Sq (Eccles,
1998) or high -latitude (Nopper and Carovil lano, 1978) current systems, for the same
electric field strength the fastest/slowest growth should occur where the magnetic field is
weakest/strongest. DMSP measurements presented in Figure 4 show that this is true in
more than half of the globe. Betwee n longitudes of 180 o and 330o the correlation breaks
down. In fact both the % max and <%> traces in Figure 4D show local minima just to the
west of the weakest magnetic field. This surprising observation appears to be an effect of
energetic electrons in t he drift loss cone precipitating from the radiation belts to increase
E
P S along the western reaches of the SAA. As pointed out by Luhmann and Vampola
(1977), electrons trapped in the radiation belts are subject to pitch angle scattering as they
gradient-curvature drift to the west. Between -60o and 120o longitude the magnetic field
strength above the ionosphere increases and the atmospheric loss cone for energetic
electrons narrows. As electrons drift further to the west the loss cone again widens,
allowing some fraction of the population to be lost in and near the SAA. Equation (1)
suggests that consequently enhanced ionization increases E
P S and thus slows the R -T
growth rate.

http://sd-www.jhuapl.edu/UPOS/FLLIT/Annales_EPB.pdf

y una causalidad,

...
The basic hypothesis in our proposal is that the high and low latitudes are coupled by the Region 1 and Region 2 currents which are generated by the polar cap potential and ionospheric conductances. Under conditions of magnetic activity, the IEF can penetrate to all latitudes until Region 2 shielding currents are established. In the evening sector this penetration electric field contributes to formation of equatorial plasma bubbles.
...

http://sd-www.jhuapl.edu/UPOS/FLLIT/1st_year_report.pdf

Efectos de las EPB sobre la termosfera,

Equatorial plasma bubbles are common in the low-latitude ionosphere at night, particularly at solar maximum. The bubbles form on the bottomside of the F-layer as a result of the Rayleigh-Taylor instability and then drift upwards and to the east. As the bubbles evolve, the entire north-south extent of the plasma flux tubes in the bubbles becomes depleted, and the bubbles take the form of vertically elongated wedges of depleted plasma. The east-west width of a bubble domain can be several thousand kilometers and the plasma density depletion in the bubbles varies from a factor of 10 to 1000. Because equatorial plasma bubbles could have an appreciable effect on the upper atmosphere, a time-dependent, three-dimensional, high-resolution model of the global thermosphere was used to calculate the response of the neutral gas to “idealized” plasma bubble depletions. The model predicts that there are both neutral density and temperature depressions and enhancements in association with the plasma bubbles. The bubble regions can contain either neutral gas enhancements or depressions depending on the background conditions, which change throughout the night. However, the calculated neutral gas perturbations are small, with maximum neutral density perturbations of 6% and maximum temperature perturbations of about 35°K. Nevertheless, these results support the recent experimental evidence that plasma bubbles produce depletions in the neutral density.

Effect of equatorial plasma bubbles on the thermosphere


relación entre las ondas gravitacionales mesosféricas y las EPBs
Simultaneous observation of ionospheric plasma bubbles and mesospheric gravity waves during the SpreadFEx Campaign

Campo Magnético y EPBs,

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.

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

Buenas _0_, te lo iba a poner en el topic de la termosfera hace 15 días. Pero , Como la termosfera va por partes. También he visto una alusión a la ionosfera en el topic de actividad volcánica y clima

Aquí me parece mejor, en este topic, me parece interesantisimo:

Mapa de Contenido Total de Electrones  (TEC) en la ionosfera en tiempo real





Saludos