scholarly journals Long-term ionospheric cooling: Dependency on local time, season, solar activity, and geomagnetic activity

2013 ◽  
Vol 118 (6) ◽  
pp. 3719-3730 ◽  
Author(s):  
Shun-Rong Zhang ◽  
John M. Holt
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Geomagnetic Activity

scholarly journals Climatology Characteristics of Ionospheric Irregularities Described with GNSS ROTI

2020 ◽  
Vol 12 (16) ◽  
pp. 2634 ◽  
Author(s):  
Kacper Kotulak ◽  
Irina Zakharenkova ◽  
Andrzej Krankowski ◽  
Iurii Cherniak ◽  
Ningbo Wang ◽  
...  
Keyword(s):  
Solar Activity ◽  
Geomagnetic Activity ◽  
Geomagnetic Storms ◽  
Auroral Oval ◽  
Ionospheric Irregularities ◽  
Moderate Intensity ◽  
Navigation Systems ◽  
Quiet Time ◽  
Magnetic Latitude

At equatorial and high latitudes, the intense ionospheric irregularities and plasma density gradients can seriously affect the performances of radio communication and satellite-based navigation systems; that represents a challenging topic for the scientific and engineering communities and operational use of communication and navigation services. The GNSS-based ROTI (rate of TEC index) is one of the most widely used indices to monitor the occurrence and intensity of ionospheric irregularities. In this paper, we examined the long-term performance of the ROTI in terms of finding the climatological characteristics of TEC fluctuations. We considered the different scale temporal signatures and checked the general sensitivity to the solar and geomagnetic activity. We retrieved and analyzed long-term time-series of ROTI values for two chains of GNSS stations located in European and North-American regions. This analysis covers three full years of the 24th solar cycle, which represent different levels of solar activity and include periods of intense geomagnetic storms. The ionospheric irregularities’ geographical distribution, as derived from ROTI, shows a reasonable consistency to be found within the poleward/equatorward boundaries of the auroral oval specified by empirical models. During magnetic midnight and quiet-time conditions, the equatorward boundary of the ROTI-derived ionospheric irregularity zone was observed at 65–70° of north magnetic latitude, while for local noon conditions this boundary was more poleward at 75–85 magnetic latitude. The ionospheric irregularities of low-to-moderate intensity were found to occur within the auroral oval at all levels of geomagnetic activity and seasons. At moderate and high levels of solar activity, the intensities of ionospheric irregularities are larger during local winter conditions than for the local summer and polar day conditions. We found that ROTI displays a selective latitudinal sensitivity to the auroral electrojet activity—the strongest dependence (correlation R > 0.6–0.8) was observed within a narrow latitudinal range of 55–70°N magnetic latitude, which corresponded to a band of the largest ROTI values within the auroral oval zone expanded equatorward during geomagnetic disturbances.

scholarly journals Ionospheric climatology and variability from long-term and multiple incoherent scatter radar observations: variability

2008 ◽  
Vol 26 (6) ◽  
pp. 1525-1537 ◽  
Author(s):  
S.-R. Zhang ◽  
J. M. Holt
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Geomagnetic Activity ◽  
Plasma Temperature ◽  
High Electron ◽  
High Electron Density ◽  
Incoherent Scatter Radar ◽  
Incoherent Scatter ◽  
Scatter Radar

Abstract. Long-term incoherent scatter radar (ISR) observations are used to study ionospheric variability for two midlatitude sites, Millstone Hill and St. Santin. This work is based on our prior efforts which resulted in an empirical model system, ISR Ionospheric Model (ISRIM), of climatology (and now variability) of the ionosphere. We assume that the variability can be expressed in three terms, the background, solar activity and geomagnetic activity components, each of which is a function of local time, season and height. So the background variability is ascribed mostly to the day-to-day variability arising from non solar and geomagnetic activity sources. (1) The background variability shows clear differences between the bottomside and the topside and changes with season. The Ne variability is low in the bottomside in summer, and high in the topside in winter and spring. The plasma temperature variability increases with height, and reaches a minimum in summer. Ti variability has a marked maximum in spring; at Millstone Hill it is twice as high as at St. Santin. (2) For enhanced solar activity conditions, the overall variability in Ne is reduced in the bottomside of the ionosphere and increases in the topside. For Te, the solar activity enhancement reduces the variability in seasons of high electron density (winter and equinox) at altitudes of high electron density (near the F2-peak). For Ti, however, while the variability tends to decrease at Millstone Hill (except for altitudes near 200 km), it increases at St. Santin for altitudes up to 350 km; the solar flux influence on the variability tends to be stronger at St. Santin than at Millstone Hill.

scholarly journals Long-term solar activity and its implications to the heliosphere, geomagnetic activity, and the Earth’s climate

2013 ◽  
Vol 3 ◽  
pp. A21 ◽  
Author(s):  
Kalevi Mursula ◽  
Periasamy Manoharan ◽  
Dibyendu Nandy ◽  
Eija Tanskanen ◽  
Pekka Verronen
Keyword(s):  
Solar Activity ◽  
Geomagnetic Activity ◽  
Earth’S Climate

scholarly journals Geomagnetic activity recurrences for predicting the amplitude and shape of solar cycle N. 25

2021 ◽  
Author(s):  
Piero Diego ◽  
Monica Laurenza
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
Climate Data ◽  
Activity Prediction ◽  
Successful Prediction ◽  
Physical Phenomena ◽  
Maximum Sunspot

The prediction of solar activity is one of the most challenging topics among the various Space    Weather and Space Climate issues. In the last decades, the constant enhancement of Space Climate    data allowed to improve the comprehension of the related physical phenomena and the statistical    bases for prediction algorithms. For this purpose, we used geomagnetic indices to provide a pow erful algorithm (see Diego et al 2010) for the solar activity prediction, based on the evaluation of    the recurrence rate in the geomagnetic activity. The aim of this paper is to present the validation    of our algorithm over solar cycle n. 24, for which a successful prediction was made, and upgrade    it to forecast the shape and time as well as the amplitude of the upcoming cycle n. 25. Contrary    to the consensus, we predict it to be quite high, with a maximum sunspot number of 205  ±  29,  that should be reached in the first half of 2023. This prediction is consistent with the scenario in    which the long-term Gleissberg cycle has reached its minimum in cycle n. 24 and the rising phase  is beginning.

scholarly journals Long-term trends in the ionospheric F2 region with different solar activity indices

2013 ◽  
Vol 31 (2) ◽  
pp. 291-303 ◽  
Author(s):  
J. Mielich ◽  
J. Bremer
Keyword(s):  
Solar Activity ◽  
Geomagnetic Activity ◽  
Data Series ◽  
Radio Flux ◽  
Model Calculations ◽  
Long Term Trends ◽  
Global Mean ◽  
Good Agreement ◽  
Activity Indices

Abstract. A new comprehensive data collection by Damboldt and Suessmann (2012a) with monthly foF2 and M(3000)F2 median values is an excellent basis for the derivation of long-term trends in the ionospheric F2 region. Ionospheric trends have been derived only for stations with data series of at least 22 years (124 stations with foF2 data and 113 stations with M(3000)F2 data) using a twofold regression analysis depending on solar and geomagnetic activity. Three main results have been derived: Firstly, it could be shown that the solar 10.7 cm radio flux F10.7 is a better index for the description of the solar activity than the relative solar sunspot number R as well as the solar EUV proxy E10.7. Secondly, the global mean foF2 and hmF2 trends derived for the interval between 1948 and 2006 are in surprisingly good agreement with model calculations of an increasing atmospheric greenhouse effect (Rishbeth and Roble, 1992). Thirdly, during the years 2007 until 2009, the hmF2 values and to a smaller amount the foF2 values strongly decrease. The reason for this effect is a reduction of the thermospheric density and ionization due to a markedly reduced solar EUV irradiation and extremely small geomagnetic activity during the solar cycle 23/24 minimum.

scholarly journals Long-term trends of <i>fo</i>F2 independent of geomagnetic activity

2003 ◽  
Vol 21 (5) ◽  
pp. 1167-1176 ◽  
Author(s):  
A. D. Danilov
Keyword(s):  
Detailed Analysis ◽  
Local Time ◽  
Geomagnetic Activity ◽  
Geomagnetic Latitude ◽  
Ionospheric Disturbances ◽  
Strong Argument ◽  
Long Term Changes ◽  
Long Term Trends ◽  
The Difference

Abstract. A detailed analysis of the foF2 data at a series of ionospheric stations is performed to reveal long-term trends independent of the long-term changes in geomagnetic activity during the recent decades (nongeomagnetic trends). The method developed by the author and published earlier is used. It is found that the results for 21 out of 23 stations considered agree well and give a relative nongeomagnetic trend of -0.0012 per year (or an absolute nongeomagnetic trend of about -0.012 MHz per year) for the period between 1958 and the mid-nineties. The trends derived show no dependence on geomagnetic latitude or local time, a fact confirming their independence of geomagnetic activity. The consideration of the earlier period (1948–1985) for a few stations for which the corresponding data are available provides significantly lower foF2 trends, the difference between the later and earlier periods being a factor of 1.6. This is a strong argument in favor of an anthropogenic nature of the trends derived.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances; mid-latitude ionosphere)

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