scholarly journals The solar activity dependence of nonmigrating tides in electron density at low and middle latitudes observed by CHAMP and GRACE

2016 ◽  
Vol 34 (4) ◽  
pp. 463-472 ◽  
Author(s):  
Yun-Liang Zhou ◽  
Li Wang ◽  
Chao Xiong ◽  
Hermann Lühr ◽  
Shu-Ying Ma
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Solar Maximum ◽  
Middle Latitudes ◽  
F Region ◽  
Low Latitudes ◽  
The Absolute ◽  
Nonmigrating Tides ◽  
Activity Dependence

Abstract. In this paper we use more than a decade of in situ electron density observations from CHAMP and GRACE satellites to investigate the solar activity dependence of nonmigrating tides at both low and middle latitudes. The results indicate that the longitudinal patterns of F region electron density vary with season and latitude, which are exhibiting a wavenumber 4 (WN4) pattern around September equinox at low latitudes and WN1/WN2 patterns during local summer at the southern/northern middle latitudes. These wave patterns in the F region ionosphere can clearly be seen during both solar maximum and minimum years. At low latitudes the absolute amplitudes of DE3 (contributing to the WN4 pattern) are found to be highly related to the solar activity, showing larger amplitudes during solar maximum years. Similarly a solar activity dependence can also be found for the absolute amplitudes of D0, DW2 and DE1 (contributing to the WN1 and WN2 pattern) at middle latitudes. The relative amplitudes (normalized by the zonal mean) of these nonmigrating tides at both low and middle altitudes show little dependence on solar activity. We further found a clear modulation by the quasi-biennial oscillation (QBO) of the relative DE3 amplitudes in both satellite observations, which is consistent with the QBO dependence as reported for the E region temperatures and zonal wind. It also supports the strong coupling of the low-latitude nonmigrating tidal activity between the E and F regions. However, the QBO dependence cannot be found for the relative amplitudes of the nonmigrating tides at middle latitudes, which implies that these tides are generated in situ at F region altitudes.

Strong equatorial plasma bubble associated with prominent TEC enhancement observed at mid-latitude ionosphere under the quiescent condition

2021 ◽  
Author(s):  
Fuqing Huang ◽  
Jiuhou Lei ◽  
Chao Xiong
Keyword(s):  
Electron Density ◽  
Electron Content ◽  
Radio Waves ◽  
Plasma Bubble ◽  
Total Electron ◽  
Middle Latitudes ◽  
Multiple Observations ◽  
Equatorial Plasma Bubbles ◽  
Low Latitudes

<p>Equatorial plasma bubbles (EPBs) are typically ionospheric irregularities that frequently occur at the low latitudes and equatorial regions, which can significantly affect the propagation of radio waves. In this study, we reported a unique strong EPB that happened at middle latitudes over the Asian sector during the quiescent period. The multiple observations including total electron content (TEC) from Beidou geostationary satellites and GPS, ionosondes, in-situ electron density from SWARM and meteor radar are used to explore the characteristic and mechanism of the observed EPB. The unique strong EPB was associated with great nighttime TEC/electron density enhancement at the middle latitudes, which moves toward eastward. The potential physical processes of the observed EPB are also discussed.</p>

scholarly journals Equinoctial asymmetry in solar activity variations of <I>Nm</I>F2 and TEC

2012 ◽  
Vol 30 (3) ◽  
pp. 613-622 ◽  
Author(s):  
Y. Chen ◽  
L. Liu ◽  
W. Wan ◽  
Z. Ren
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
High Solar Activity ◽  
Solar Cycles ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Increase Rate ◽  
Dip Equator ◽  
The Difference

Abstract. The ionosonde NmF2 data (covering several solar cycles) and the JPL TEC maps (from 1998 through 2009) were collected to investigate the equinoctial asymmetries in ionospheric electron density and its variation with solar activity. With solar activity increasing, the equinoctial asymmetry of noontime NmF2 increases at middle latitudes but decreases or changes little at low latitudes, while the equinoctial asymmetry of TEC increases at all latitudes. The latitudinal feature of the equinoctial asymmetry at high solar activity is different from that at low solar activity. The increases of NmF2 and TEC with the solar proxy P = (F10.7+F10.7A)/2 also show equinoctial asymmetries that depend on latitudes. The increase rate of NmF2 with P at March equinox (ME) is higher than that at September equinox (SE) at middle latitudes, but the latter is higher than the former at the EIA crest latitudes, and the difference between them is small at the EIA trough latitudes. The phenomenon of higher increase rate at SE than at ME does not appear in TEC. The increase rate of noontime TEC with P at ME is higher than that at SE at all latitudes, and the difference between them peaks at both sides of dip equator. It is mentionable that the equinoctial asymmetries of NmF2 and TEC increase rates present some longitudinal dependence at low latitude. The influences of equinoctial differences in the thermosphere and ionospheric dynamics processes on the equinoctial asymmetry of the electron density were briefly discussed.

scholarly journals Alfvénic fluctuations in "newborn"' polar solar wind

2005 ◽  
Vol 23 (4) ◽  
pp. 1513-1520 ◽  
Author(s):  
B. Bavassano ◽  
E. Pietropaolo ◽  
R. Bruno
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Solar Maximum ◽  
Activity Cycle ◽  
Residual Energy ◽  
Mhd Waves ◽  
Polar Wind ◽  
Interplanetary Physics ◽  
Low Latitudes ◽  
Comparative Statistical Analysis

Abstract. The 3-D structure of the solar wind is strongly dependent upon the Sun's activity cycle. At low solar activity a bimodal structure is dominant, with a fast and uniform flow at the high latitudes, and slow and variable flows at low latitudes. Around solar maximum, in sharp contrast, variable flows are observed at all latitudes. This last kind of pattern, however, is a relatively short-lived feature, and quite soon after solar maximum the polar wind tends to regain its role. The plasma parameter distributions for these newborn polar flows appear very similar to those typically observed in polar wind at low solar activity. The point addressed here is about polar wind fluctuations. As is well known, the low-solar-activity polar wind is characterized by a strong flow of Alfvénic fluctuations. Does this hold for the new polar flows too? An answer to this question is given here through a comparative statistical analysis on parameters such as total energy, cross helicity, and residual energy, that are of general use to describe the Alfvénic character of fluctuations. Our results indicate that the main features of the Alfvénic fluctuations observed in low-solar-activity polar wind have been quickly recovered in the new polar flows developed shortly after solar maximum. Keywords. Interplanetary physics (MHD waves and turbulence; Sources of the solar wind) – Space plasma physics (Turbulence)

scholarly journals Comparative study of electron density from incoherent scatter measurements at Arecibo with the IRI-95 model during solar maximum

2000 ◽  
Vol 18 (12) ◽  
pp. 1630-1634 ◽  
Author(s):  
N. K. Sethi ◽  
V. K. Pandey
Keyword(s):  
Electron Density ◽  
Solar Maximum ◽  
Iri Model ◽  
Bottom Part ◽  
Density Profiles ◽  
Incoherent Scatter ◽  
F Region ◽  
Electron Density Profiles ◽  
Thickness Parameter ◽  
Modelling And Forecasting

Abstract. Arecibo (18.4 N, 66.7 W) incoherent scatter (IS) observations of electron density N(h) are compared with the International Reference Ionosphere (IRI-95) during midday (10–14 h), for summer, winter and equinox, at solar maximum (1981). The N(h) profiles below the F2 peak, are normalized to the peak density NmF2 of the F region and are then compared with the IRI-95 model using both the standard B0 (old option) and the Gulyaeva-B0 thickness (new option). The thickness parameter B0 is obtained from the observed electron density profiles and compared with those obtained from the IRI-95 using both the options. Our studies indicate that during summer and equinox, in general, the values of electron densities at all the heights given by the IRI model (new option), are generally larger than those obtained from IS measurements. However, during winter, the agreement between the IRI and the observed values is reasonably good in the bottom part of the F2 layer but IRI underestimates electron density at F1 layer heights. The IRI profiles obtained with the old option gives much better results than those generated with the new option. Compared to the observations, the IRI profiles are found to be much thicker using Gulyaeva-B0 option than using standard B0.Key words: Ionosphere (modelling and forecasting)

Modeling study of nighttime enhancements in F region electron density at low latitudes

2014 ◽  
Vol 119 (8) ◽  
pp. 6648-6656 ◽  
Author(s):  
Huijun Le ◽  
Libo Liu ◽  
Yiding Chen ◽  
Hui Zhang ◽  
Weixing Wan
Keyword(s):  
Electron Density ◽  
F Region ◽  
Low Latitudes ◽  
Modeling Study

scholarly journals F-Region electron density irregularities during the development of equatorial plasma bubbles

2000 ◽  
Vol 39 (1) ◽  
pp. 117-125
Author(s):  
P. Muralikrishna
Keyword(s):  
Electron Density ◽  
Plasma Bubbles ◽  
Black Brant ◽  
F Region ◽  
Equatorial Plasma Bubbles ◽  
Electron Density Irregularities

Algunos resultados nuevos que se obtuvieron de mediciones in situ de la variación de la densidad electrónica hechas con sondas instaladas en cohetes para medir la densidad electrónica durante dos campañas que se llevaron a cabo en Alcántara (2.31° Sur 32.5° Oeste) se presentan aquí. Durante la primera campaña que se llevó a cabo en colaboración con la NASA (campaña de Iguará donde se lanzó el cohete Black Brant X el 14 de octubre de 1994) para investigar el fenómeno de los eventos de dispersión F que ocurren en altas altitudes en zonas ecuatoriales. Adicionalmente a algunos instrumentos de diagnóstico de plasma que fueron provistos por otros institutos participantes, la División de Acronomía del Instituto de Pesquisas Espaciales en Brasil, proporcionó una sonda de capacitancia de alta frecuencia que midió el perfil de alturas de la densidad electrónica. Durante la segunda campaña el cohete sonda 3 hecho en Brasil fue lanzado el 18 de diciembre de 1995. El cohete llevaba instrumentos para medir la densidad electrónica que determinaron el perfil de densidades electrónicas en la ionosfera. Algunos equipos fueron operados desde tierra para asegurarnos que los cohetes fueran lanzados en condiciones favorables para la generación de burbujas de plasma en la región F; los cohetes en ambas ocasiones atravesaron algunas burbujas de plasma en desarrollo. El espectro K de las irregularidades de plasma se obtuvo por análisis espectral de las fluctuaciones de la densidad electrónica. Las irregularidades en la densidad electrónica asociadas con las burbujas de plasma tienen líneas muy agudas en sus espectros K; estas líneas se extienden sobre un amplio rango de alturas. Lo que podría esperarse de las teorías existentes en la generación de irregularidades de pequeña escala por el proceso de cascada es un espectro K plano. Los resultados actuales podrían indicarnos la presencia de modos de onda preferidos en burbujas de plasma en desarrollo.

scholarly journals Tidal signatures of the thermospheric mass density and zonal wind at midlatitude: CHAMP and GRACE observations

2015 ◽  
Vol 33 (2) ◽  
pp. 185-196 ◽  
Author(s):  
C. Xiong ◽  
Y.-L. Zhou ◽  
H. Lühr ◽  
S.-Y. Ma
Keyword(s):  
Electron Density ◽  
Zonal Wind ◽  
Mass Density ◽  
Phase Variation ◽  
Atmospheric Models ◽  
F Region ◽  
Main Driver ◽  
Grace Satellites ◽  
Thermospheric Dynamics

Abstract. By using the accelerometer measurements from CHAMP and GRACE satellites, the tidal signatures of the thermospheric mass density and zonal wind at midlatitudes have been analyzed in this study. The results show that the mass density and zonal wind at southern midlatitudes are dominated by a longitudinal wave-1 pattern. The most prominent tidal components in mass density and zonal wind are the diurnal tides D0 and DW2 and the semidiurnal tides SW1 and SW3. This is consistent with the tidal signatures in the F region electron density at midlatitudes as reported by Xiong and Lühr (2014). These same tidal components are observed both in the thermospheric and ionospheric quantities, supporting a mechanism that the non-migrating tides in the upper atmosphere are excited in situ by ion–neutral interactions at midlatitudes, consistent with the modeling results of Jones Jr. et al. (2013). We regard the thermospheric dynamics as the main driver for the electron density tidal structures. An example is the in-phase variation of D0 between electron density and mass density in both hemispheres. Further research including coupled atmospheric models is probably needed for explaining the similarities and differences between thermospheric and ionospheric tidal signals at midlatitudes.

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