Time filter

Source Type

Magdaleno S.,Atmospheric Sounding Station El Arenosillo | Magdaleno S.,GMV Inc | Cueto M.,GMV Inc | Herraiz M.,Complutense University of Madrid | And 3 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics

Plasma depletions (or bubbles) are strong reductions in the ionospheric F-region plasma density due to the appearance of a Rayleigh-Taylor instability in the post-sunset, producing severe radio signal disruptions when crossing them. Most of the plasma depletions are confined on the Appleton Anomaly region, which also shows the presence of strong scintillations activity. Therefore, stations located in the vicinity of the geomagnetic equator are expected to be frequently affected by the presence of plasma depletions. This paper provides a comparison between the plasma depletion detection results achieved using two algorithms: one developed by the National Institute for Aerospace Technology and the University Complutense of Madrid and one developed by GMV. Six equatorial stations distributed all over the world and different solar activity and seasonal conditions have been selected to analyze the algorithms' response to different plasma depletions characteristics. A regional behavior analysis of the plasma depletion occurrence and characteristics is also provided. © 2013 Elsevier Ltd. Source

Altadill D.,Ramon Llull University | Magdaleno S.,Atmospheric Sounding Station El Arenosillo | Torta J.M.,Ramon Llull University | Blanch E.,Ramon Llull University
Advances in Space Research

Monthly average electron density profiles have been calculated from hourly electron density N(h) recorded in 26 digisonde stations distributed worldwide encompassing the time interval 1998-2006. The ionospheric electron density peak height of the F2 region, hmF2, and the effective scale height at the hmF2, Hm, deduced from average profiles have been analyzed to obtain the quiet-time behavior and have been analytically modeled by the spherical harmonic analysis (SH) technique using the modip latitude as the coordinate of the reference system. The coefficients of the SH models of hmF2 and Hm are bounded to the solar activity, and the temporal and seasonal variations are considered by Fourier expansion of the coefficients. The SH models provide a tool to predict hmF2 and Hm located anywhere in the range of latitudes between of 70 N and 70 S and at any time. The SH analytical model for hmF2 improves the fit to the observations by 10% in average compared to the IRI prediction, and it might improve the IRI prediction of hmF2 by more than 30% at high and low latitudes. The analytical model for Hm predicts the quiet behavior of the effective scale height with accuracy better than 15% in average which enables to obtain a good estimation of vertical profiles. These results could be useful to estimate information for the topside profile formulation. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

Magdaleno S.,Atmospheric Sounding Station El Arenosillo | Altadill D.,Ramon Llull University | Herraiz M.,Complutense University of Madrid | Blanch E.,Ramon Llull University | de la Morena B.,Atmospheric Sounding Station El Arenosillo
Journal of Atmospheric and Solar-Terrestrial Physics

The quiet behavior of the ionospheric electron density peak height of the F2 region, hmF2, at different latitudes has been evaluated for different seasons and solar activity levels and compared with the prediction of the International Reference Ionosphere model (IRI). The results show clear disagreements of the IRI prediction compared to the experimental behavior. Though IRI prediction agrees reasonably well with the experimental values of the hmF2 for mid-latitudes, this model may underestimate the equatorial values as low as -40% of the experimental ones and it may overestimate the hmF2 by 30% at high latitudes. Preliminary models based on Fourier analysis performed better than IRI for high and low latitudes and they may reduce the deviations by a 23% and 40%, respectively, compared to the deviations of the IRI prediction. © 2011 Elsevier Ltd. Source

Magdaleno S.,Atmospheric Sounding Station El Arenosillo | Herraiz M.,Complutense University of Madrid | de la Morena B.A.,Atmospheric Sounding Station El Arenosillo
Journal of Atmospheric and Solar-Terrestrial Physics

The equatorial plasma bubbles (EPBs) have been studied using slant total electron content (sTEC) derived from GPS data. The sTEC has been calculated from data measured at 15 International GNSS Service (IGS) stations located from 90°W to 30°W, covering the ionospheric equatorial anomaly at the American sector, for the years 2000, 2001, 2004, 2005 and 2008. The Ionospheric Bubbles Seeker (IBS) application has been used to detect and characterize the sTEC depletions associated to the EPBs. This technique bases its analysis on the time-variation of the sTEC and the population variance of this time-variation. The default configuration has been used and an EPB has been considered when a sTEC depletion was greater than 5 TEC units (TECu). The hourly occurrence shows the well-known maximum number of depletions after the post-sunset. The monthly occurrence of the EPBs is also analyzed and compared with previous studies. The International Reference Ionosphere model (IRI) has been used to calculate the equatorial vertical drift (EVD) and the peak densities of the E- and F-layers (NmE and NmF2, respectively). The EVD variation has been compared with the seasonal variation of the EPB. A discussion between the yearly mean occurrence EPBs rate and the solar activity is included. The variation of the yearly mean depth and duration of the sTEC depletions with the solar activity conditions and its relation with the ionospheric characteristics given by the IRI model has been also studied. © 2011 Elsevier Ltd. Source

Gomez-Moreno F.J.,CIEMAT | Alonso E.,CIEMAT | Artinano B.,CIEMAT | Juncal-Bello V.,University of La Coruna | And 19 more authors.
Aerosol Science and Technology

Red Española de DMAs Ambientales (REDMAAS), the Spanish network of environmental differential mobility analyzers (DMAs), currently comprises six research groups involved in the measurement of atmospheric aerosol size distributions by means of DMAs. The aim of this network is to guarantee the good quality and comparability of the routine measurements carried out at each location and in diverse environments across Spain. In order to achieve this objective, one of its main activities is the annual intercomparison of mobility size spectrometers used within the network (five units of scanning mobility particle sizers[SMPS] and one ultrafine particle monitor [UFPM]). Here we report the 2main results obtained during the 2010-2012 campaigns, including a study on particle deposition in dryers used in ambient air sampling systems. In general, all instruments showed good performance with deviations in accepted tolerance. The intercomparisons have been proved to be a useful exercise to detect instrument problems, such as incorrect calibrations. DMA calibration checks were performed with polystyrene latex reference particles. Deviations of less than 1% were observed during the first year, which increased 4.7% during the last campaign. Some differences among the responses of different condensation particle counter (CPC) models were encountered, being mainly connected to the intrinsic characteristics of each counter. The comparison of UFPM with CPCs has given good results. The SMPS intercomparisons, especially for particles above 20 nm, have been within +/-15% tolerance. Regarding particle deposition in dryers used in sampling systems, particle penetration was lower than predicted by the recommended model. This result was probably due to the fact that not all the possible mechanisms were considered in the model. Copyright © American Association for Aerosol Research. Source

Discover hidden collaborations