694 research outputs found
Improving the NeQuick topside representation by means of Swarm satellites data
No full textThe ionospheric topside representation made by the NeQuick model is improved by correcting the H0 parameter used by the model to calculate the topside plasma scale height. The task is accomplished by fitting the NeQuick topside analytical function through two anchor points: the F2-layer absolute electron density maximum; the electron density value as measured by Swarm satellites from December 2013 to September 2018. Specifically, two-dimensional grids of H0 as a function of foF2 and hmF2 are obtained, one by employing data from Swarm A and Swarm C, both flying at about 460 km of altitude, and the other one by employing data from Swarm B, flying at about 520 km of altitude. These two grids are used to calculate corrected values of H0, which allows a more reliable description of the topside region. The new NeQuick formulation is statistically validated by comparing corresponding modeled vertical total electron content (vTEC) values to those derived from COSMIC/FORMOSAT-3 measured Radio Occultation profiles, and those measured by Swarm satellites. The results show that the proposed formulation significantly improves the topside description made by the NeQuick model at mid latitudes, for both high and low solar activities. Its inclusion in the International Reference Ionosphere (IRI) model is recommended
Modeling the topside ionosphere by means of electron density values as recorded by the Swarm satellites constellation
No full textAn empirical method to model the ionospheric topside vertical electron density profile over the European region is proposed. The method is based on electron density values recorded by Langmuir Probes on board Swarm satellites, and on foF2 and hmF2 values provided by IRI UP (International Reference Ionosphere UPdate), which is a method developed to update the IRI (International Reference Ionosphere) model relying on the assimilation of ionospheric data routinely recorded by a network of European ionosonde stations. Topside effective scale heights are calculated by fitting some definite analytical functions (α-Chapman, β-Chapman, Epstein and Exponential) through the values recorded by Swarm and the ones outputted by IRI UP, with the assumption that the effective scale height is constant in the altitude range considered. Calculated effective scale heights are then modeled as a function of the F2-layer peak characteristics, foF2 and hmF2. A statistical comparison with COSMIC/FORMOSAT-3 collected Radio Occultation profiles is carried out to assess the validity of the proposed method, and to investigate which of the considered topside profilers is the best one
Modeling the topside ionosphere by means of electron density values as recorded by the Swarm constellation
No full textThe topside part of the ionosphere lies above the ionospheric F2 layer peak and extends up to the plasmasphere. Since it contains a considerable part of the ionospheric plasma, its modeling is important for telecommunication’s purposes. In this work, electron density values recorded by Langmuir Probes on board the Swarm constellation are used as top anchor points by definite analytical functions (α-Chapman, β-Chapman, Epstein and Exponential) to investigate the variability of the topside plasma scale height H, a parameter which is crucial to perform a reliable modeling of the topside ionosphere. Bottom anchor points are provided by the IRIUP (International Reference Ionosphere UPdate) method, which is a method developed to update the IRI model relying on the assimilation of foF2 and M(3000)F2 data routinely recorded by a network of ionosonde stations. The IRIUP method calculates updated effective indices IG12eff and R12eff at each station of the network and, applying a universal Kriging method, generates maps of these indices which are then used to update the IRI output in terms of foF2 and hmF2. The height and electron density values of both top and bottom anchor points are used to obtain the H value, by means of a minimization procedure, making use of each of the aforementioned four topside analytical functions. The reliability of this approach is based on the hypothesis that H at heights around the F2 layer peak and for the first hundreds kilometers above is nearly constant, being this region dominated by O+ ions and with a temperature nearly constant. H values are statistically evaluated to look for any relevant relation with foF2 and hmF2. Moreover, a statistical comparison with COSMIC radio occulation profiles is carried out to asses which analytical profile function is the best one to represent the topside ionospheric profile, making use of the modelled H values
Detecting Post-Midnight Plasma Depletions Through Plasma Density and Electric Field Measurements in the Low-Latitude Ionosphere
No full textPlasma depletions in the low-latitude ionosphere are irregularities of special interest in space weather research, as they are highly detrimental to the operation of satellite-based communication and navigation systems. In this frame, we present the results of a systematic study of the low-latitude topside ionosphere, based on in situ measurements of both electron density (Ne) and electric field provided by the Langmuir Probe (LP) and the Electric Field Detector (EFD) onboard the first China Seismo-Electromagnetic Satellite (CSES-01). Specifically, by exploiting in situ measurements from 1 January 2019 to 31 May 2024, we devised two different techniques for the automatic detection of post-midnight plasma depletions at about 500 km of altitude: one using only Ne observations, the other using only electric field measurements. We validated these new techniques against each other and performed a statistical investigation of the main characteristics of the observed plasma irregularities, such as their latitudinal extension, longitudinal distribution, and monthly and seasonal occurrence. To test the robustness and reliability of our algorithms, we also applied them to well-established Swarm B satellite observations. In particular, we first investigated both the monthly and the seasonal occurrences of post-sunset plasma depletions detected between 18:00 and 04:00 local time (LT), by LP onboard the Swarm B satellite at about 500 km of altitude. In addition, we compared ionospheric irregularities detected by Swarm B with those detected by CSES-01. For the comparison, we considered Swarm B LP data collected for the same period as the CSES-01 dataset and under the same conditions by selecting Swarm B observations in the range 01:00 ≤LT 03:00. Our results prove the robustness and reliability of both LP and EFD algorithms in detecting plasma depletions, and their good agreement suggests their complementarity in detecting such kinds of plasma irregularities. Results also confirm consistency between CSES-01 and Swarm B observations (once the same LT orbits have been considered) and with the relevant literature on the topic
Effective solar indices for ionospheric modeling: a proposal for a real time IRI
No full textThe knowledge of accurate solar indices is essential to reliably forecast the conditions of the near-Earth space environment. The International
Reference Ionosphere (IRI) model, based on R12 and IG12 solar indices, provides a climatological depiction of the ionospheric plasma that can be
different from the real one, especially at solar terminator and for disturbed conditions. Assimilating data from a grid of ionosondes is possible to
obtain effective values of R12 and IG12 that can significantly improve the electron density representation made by the IRI model. Universal Kriging
interpolation method is employed for spatial mapping these indices
Effective solar indices for ionospheric modeling: a proposal for a real time regional IRI
No full textTITIPy: A Python tool for the calculation and mapping of topside ionosphere turbulence indices
No full textTITIPy (Topside Ionosphere Turbulence Indices with Python) is a stand-alone Python tool developed for the calculation and mapping of RODI, ROTI, and ROTEI indices, for the characterization of the turbulent state of the topside ionosphere. Data gathered by Langmuir Probes and Precise Orbit Determination antennas on-board ESA Swarm satellites constellation are used to calculate topside ionosphere indices with a high time rate and a global coverage. From the study of these topside indices, information on physical mechanisms involved in the formation of small-scale irregularities (both spatial and temporal) can be drawn, particularly at high and low latitudes. TITIPy provides outputs as time series of calculated indices in text files, and figures as maps in geographic and magnetic coordinates. TITIPy is particularly suited for the investigation of the topside ionosphere irregularities, and for the identification of peculiar spatial and temporal patterns. The paper describes the TITIPy design and code workflow along with a detailed explanation of RODI, ROTI, and ROTEI indices calculation. Furthermore, an example of application based on data collected during the St. Patrick 2015 geomagnetic storm is also shown. TITIPy is open-source and freely downloadable at https://github.com/pignalberi/TITIPy.Published1046752A. Fisica dell'alta atmosferaJCR Journa
On the solar cycle dependence of the amplitude modulation characterizing the mid-latitude sporadic E layer diurnal periodicity
No full textSpectral analyses are employed to investigate how the diurnal periodicity of the critical frequency of the sporadic E (Es) layer varies with solar activity. The study is based on ionograms recorded at the ionospheric station of Rome (41.8°N, 12.5°E), Italy, from 1976 to 2009, a period of time covering three solar cycles. It was confirmed that the diurnal periodicity is always affected by an amplitude modulation with periods of several days, which is the proof that Es layers are affected indirectly by planetary waves through their nonlinear interaction with atmospheric tides at lower altitudes. The most striking features coming out from this study is however that this amplitude modulation is greater for high-solar activity than for low-solar activity
On the influence of solar activity on the mid-latitude sporadic E layer
No full textTo investigate the influence of solar cycle variability on the sporadic E layer (Es), hourly measurements of the critical frequency of the Es ordinary mode of propagation, foEs, and of the blanketing frequency of the Es layer, fbEs, recorded from January 1976 to December 2009 at the Rome (Italy) ionospheric station (41.8° N, 12.5° E), were examined. The results are: (1) a high positive correlation between the F10.7 solar index and foEs as well as between F10.7 and fbEs, both for the whole data set and for each solar cycle separately, the correlation between F10.7 and fbEs being much higher than the one between F10.7 and foEs; (2) a decreasing long-term trend of the F10.7, foEs and fbEs time series, with foEs decreasing more rapidly than F10.7 and fbEs; (3) clear and statistically significant peaks at 11 years in the foEs and fbEs time series, inferred from Lomb-Scargle periodograms
The relation between GPS loss of locks and the Interplanetary Magnetic Field orientation: Swarm observations
No full textSwarm enabled researchers to investigate the disturbing phenomena that have affected spacecraft transiting in the F-region ionosphere over the last ten years, in addition to the mission's primary scientific goals. Indeed, plasma density irregularities in the ionospheric region traversed by Swarm satellites can affect both the phase and amplitude of electromagnetic waves propagating through it. As a result, the accuracy and reliability of the Global Navigation Satellite System's (GNSS) performance may be compromised. In the worst-case scenario, a GNSS signal interruption could occur while a Loss of Lock (LoL) event is taking place. This type of events appears to be important in the space weather framework, as it is favored by increased solar activity and disturbed geomagnetic conditions. The high-latitude ionospheric region is particularly impacted by these GNSS signal interruptions.
Here, we look into how the orientation of the interplanetary magnetic field affects the growth of the plasma irregularities that give rise to GPS LoL events. We use LoL events recorded between July 15, 2014, and December 31, 2021, onboard two of the three Swarm satellites, and examine how the orientations of the interplanetary magnetic fields affect the GPS LoL events distribution in magnetic local time and magnetic latitude, in both hemispheres. The results show that there is a clear dependence on the IMF orientation in the y-z plane. The effect of the IMF x component on the LoL distribution is found to be linked to the IMF y component, mainly due to the IMF spiral structure. The results are discussed considering the ionospheric convection patterns as reconstructed by SuperDARN radar observations. The capacity provided by Swarm to track these events and study their dependence on solar, interplanetary, and geophysical parameters may pave the way for a further development of LoL hazard maps at high-latitudes, and thus significantly contribute to space weather effect mitigation
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