scholarly journals Joint Ionosonde Studies of F2 Layer Critical Frequency Variations in the Ionosphere Over Kharkiv and Tromsø During Fall Equinox in Quiet and Disturbed Conditions

2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Taras Zhivolup ◽  
Sergii Panasenko ◽  
Olexander Koloskov ◽  
Volodymyr Lisachenko
Keyword(s):  
Critical Frequency ◽  
Local Maximum ◽  
Temporal Variations ◽  
Time Interval ◽  
High Latitudes ◽  
Lower Amplitude ◽  
Low Latitudes ◽  
Frequency Variations ◽  
Quiet Day ◽  
Magnetic Disturbances

According to the results of joint ionosonde studies of variations in the ionospheric F2 layer critical frequency over Kharkiv and Tromsø during low solar activity for fall equinox on September 22 – 24, 2020, the features of foF2 variations in middle and low latitudes were investigated for magnetically quiet and magnetically disturbed conditions. On the magnetically quiet day of September 22, 2020, the foF2 values over Kharkiv were found to exceed the foF2 values over Tromsø for the entire time interval of joint observations 02:45 - 16:45 UT. Both over Tromsø and over Kharkiv, a rapid increase in foF2 to its local maximum value was observed after the sunrise. Quasi-periodic variations in foF2 were revealed at high latitudes, which had lower amplitude compared to variations in foF2 over Kharkiv. Over both measuring sites, a pre-sunset local maximum in foF2 was observed. During magnetically disturbed conditions over Tromsø and Kharkiv, quasi-periodic fluctuations in foF2 were observed after the sunrise. Oscillations over Tromsø had lower amplitude than over Kharkiv, and were almost completely suppressed after the onset of a strong magnetic disturbance at high latitudes on September 23, 2020. The foF2 values over Tromsø exceeded its values over Kharkiv in a time interval of 10:45 – 12:15 UT. Comparison of the time variation of foF2 over Tromso on a magnetically quiet day, September 22, 2020, and on a magnetically disturbed day, September 23, 2020, showed that the foF2 value for September 23, 2020 from 10:15 to 15:00 UT exceeded the foF2 values for the same period on September 22, 2020. Comparison of the temporal variations in foF2 over Kharkiv on a magnetically quiet day, September 22, 2020, and on a magnetically disturbed day, September 24, 2020, showed that the foF2 value for September 24, 2020 exceeded its value for September 22, 2020 from 03:00 to 04:45 UT and from 07:00 to 13:00 UT. Magnetic disturbances were found to cause a rapid increase in foF2 values both over Kharkiv and Tromsø, which exceeded foF2 values under magnetically quiet conditions, and also led to a significant increase in the relative amplitudes of traveling ionospheric disturbances over Kharkiv.

scholarly journals MODELING CRITICAL FREQUENCY OF IONOSPHERE D-LAYER AT MINIMUM AND MAXIMUM OF THE SOLAR CYCLE 22WITH IRI-2016

2021 ◽  
Vol 9 (08) ◽  
pp. 960-965
Author(s):  
Nakolemda Roger ◽  
◽  
Nanema Emmanuel ◽  
Sawadogo Gedeon ◽  
◽  
...  
Keyword(s):  
Solar Cycle ◽  
Temporal Variability ◽  
Critical Frequency ◽  
Temporal Variations ◽  
Minimum Phase ◽  
Radio Waves ◽  
Iri Model ◽  
Geographical Position ◽  
Quiet Day

One of the interests of the study of the ionosphere lies in its importance for the transmission of radio waves in telecommunications. The ionospherebehaves as an obstacle to the passage of waves. Thus, the signals of short wavelengths are reflected by the F layer or the upper part of the sublayer E, while theD-layeris the seat of the reflection of low-frequencywaves. The presentstudyinvestigates the temporal variability of the criticalfrequency of the D-layer (for) using the 2016 version of the International Reference Ionosphere (IRI) model under quiet day conditions during at maximum and minimum phase of solar cycle 22. The workisconductedat the Ouagadougou station, located in West Africa. The methodology of the workadopted for the determination of the parameter foDisbased on the calculation of the monthlyhourlyaverages of this variable obtainedwith the help of the model during the monthsthatcharacterize the seasons. The resultsobtained for the parameter for as a function of time during the minimum and maximum of the solar cycle 22 have been presented. The seasonal and temporal variations of the criticalfrequency of the ionosphereD-layer show that the foD values are lower during a minimum of the solar cycle and present maximum values at the Zenith (1200 TL) at a minimum and maximum. Theseresultsalsorevealthatthisparameter varies with time, season, and geographical position. The results of thisstudy show a criticalfrequencybelow 1 MHz during both phases of the solar cycle.

scholarly journals The Planetary Wave Activity in Temperatures of the Stratosphere, Mesosphere and in Critical Frequencies of Ionospheric F2 Layer

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
N. M. Polekh ◽  
G. V. Vergasova ◽  
E. S. Kazimirovsky ◽  
N. P. Perevalova ◽  
V. I. Kurkin ◽  
...  
Keyword(s):  
Planetary Wave ◽  
Critical Frequency ◽  
Periodic Structures ◽  
Large Body ◽  
Time Interval ◽  
Temperature Variations ◽  
Mesospheric Temperature ◽  
Close Relationship ◽  
Frequency Variations ◽  
Ionospheric Sounding

A large body of experimental evidence lends credit to the existence of a close relationship between ionospheric parameters and the underlying atmosphere. Vertical-incidence ionospheric sounding data and temperature measurements at stratospheric (30 km) and mesospheric (80 km) heights have been used in investigating the interrelation between the occurrence of fluctuations with periods of planetary waves in temperature variations at different heights and inF2layer critical frequency variations (foF2) under low solar activity conditions for the time interval 2006-2007. The distinctive characteristics of the manifestation of common periodicities of the wave structures under consideration are discussed. The statistically significant periods of stratospheric and mesospheric temperature fluctuations vary from 11 to 49 days, whereas foF2 periodograms show higher-frequency fluctuations with periods of 5, 8, 9, and 10 days. The study revealed a similarity between periodic structures for the variations in the parameters involved.

scholarly journals The impact of CMEs on the critical frequency of F2-layer ionosphere (foF2)

2019 ◽  
Vol 15 (S356) ◽  
pp. 400-402
Author(s):  
Alene Seyoum ◽  
Nat Gopalswamy ◽  
Melessew Nigussie ◽  
Nigusse Mezgebe
Keyword(s):  
Critical Frequency ◽  
Angular Width ◽  
High Latitudes ◽  
Solar Cycles ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Critical Frequency Fof2 ◽  
The Impact ◽  
Very High

AbstractThe ionospheric critical frequency (foF2) from ionosonde measurements at geographic high, middle, and low latitudes are analyzed with the occurrence of coronal mass ejections (CMEs) in long term variability of the solar cycles. We observed trends of monthly maximum foF2 values and monthly averaged values of CME parameters such as speed, angular width, mass, and kinetic energy with respect to time. The impact of CMEs on foF2 is very high at high latitudes and low at low latitudes. The time series for monthly maximum foF2 and monthly-averaged CME speed are moderately correlated at high and middle latitudes.

The paleomagnetism of Huronian red beds and Nipissing diabase; Post-Huronian Igneous Events and apparent polar path for the interval −2300 to −1500 Ma for Laurentia

1976 ◽  
Vol 13 (6) ◽  
pp. 749-773 ◽  
Author(s):  
J. L. Roy ◽  
P. L. Lapointe
Keyword(s):  
High Stability ◽  
Vertical Axis ◽  
Time Range ◽  
High Latitudes ◽  
Red Beds ◽  
Two Stage ◽  
Low Latitudes ◽  
The Many ◽  
Age Determinations ◽  
Good Agreement

Thermal, chemical, and alternating field (and two-stage) cleaning treatments of Huronian sediments and Nipissing diabase (which intrudes the sediments) from the Cobalt area yield five directions of magnetizations (A–E) of high stability; A, B, C, and E are found in the sediments, and C, D, and E in the diabase. It is suggested that magnetization B (337°, +52°; α95 = 8°; pole 158 °E, 67 °N) was acquired shortly after deposition of the Firstbrook beds [Formula: see text]; magnetization C (259°, +82°; α95 = 5°; pole 258 °E, 42 °N), found in both the diabase and sediments in contact with the diabase, was acquired during cooling following emplacement of the diabase [Formula: see text]; and magnetizations D and E, yielding poles at 264 °E, 15 °S and 000°, 09 °N respectively, were produced during the Hudsonian orogeny (−1850 to −1700 Ma). This interpretation resolves the previous inconsistencies between poles and age determinations. Good agreement between results from the Nipissing diabase and other igneous bodies indicate that widespread igneous events occurred in the time range approximately −2200 to −2100 Ma, immediately following deposition of Huronian sediments. This is referred to as 'Post-Huronian Igneous Events'. A proposed apparent polar path relative to Laurentia shows two distinct motions; for the 2300–1850 Ma interval, a latitudinal change (roughly along longitude 250° E) from high [Formula: see text] to low [Formula: see text] latitudes and, for the 1850–1500 Ma interval, a displacement along the present-day equator with first an eastward motion to about 000° longitude followed by a westward motion to 240° E longitude; the apex of the eastward excursion is given a date of [Formula: see text]. It is possible that this reflects a rotation of Laurentia about a vertical axis at the time of and following the Hudsonian orogeny. Subsequent uplift and cooling would explain the many overprinted stable magnetizations yielding poles distributed along the equator (track 4). Latitude maps indicate that Laurentia was in high latitudes from 2200–2000 Ma and in intermediate to low latitudes from 1900–1500 Ma.

scholarly journals The Influence of Ocean Thermocline Temperatures on the Earth’s Surface Climate

2005 ◽  
Vol 18 (13) ◽  
pp. 2222-2246 ◽  
Author(s):  
Robert J. Oglesby ◽  
Monica Y. Stephens ◽  
Barry Saltzman
Keyword(s):  
Carbon Dioxide ◽  
Mixed Layer ◽  
General Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Deep Ocean ◽  
High Latitudes ◽  
Surface Climate ◽  
Low Latitudes ◽  
Atmospheric Carbon ◽  
The Impact

Abstract A coupled mixed layer–atmospheric general circulation model has been used to evaluate the impact of ocean thermocline temperatures (and by proxy those of the deep ocean) on the surface climate of the earth. Particular attention has been devoted to temperature regimes both warmer and cooler than at present. The mixed layer ocean model (MLOM) simulates vertical dynamics and thermodynamics in the upper ocean, including wind mixing and buoyancy effects, and has been coupled to the NCAR Community Climate Model (CCM3). Simulations were made with globally uniform thermocline warmings of +2°, +5°, and +10°C, as well as a globally uniform cooling of −5°C. A simulation was made with latitudinally varying changes in thermocline temperature such that the warming at mid- and high latitudes is much larger than at low latitudes. In all simulations, the response of surface temperature over both land and ocean was larger than that expected just as a result of the imposed thermocline temperature change, largely because of water vapor feedbacks. In this respect, the simulations were similar to those in which only changes in atmospheric carbon dioxide were imposed. In fact, when carbon dioxide was explicitly changed along with thermocline temperatures, the results were not much different than if only the thermocline temperatures were altered. Land versus ocean differences are explained largely by latent heat flux differences: the ocean is an infinite evaporative source, while land can be quite dry. The latitudinally varying case has a much larger response at mid- to high latitudes than at low latitudes; the high latitudes actually appear to effectively warm the low latitudes. Simulations exploring scenarios of glacial inception suggest that the deep ocean alone is not likely to be a key trigger but must operate in conjunction with other forcings, such as reduced carbon dioxide. Moist upland regions at mid- and high latitudes, and land regions adjacent to perennial sea ice, are the preferred locations for glacial inception in these runs. Finally, the model combination equilibrates very rapidly, meaning that a large number of simulations can be made for a fairly modest computational cost. A drawback to this is greatly reduced sensitivity to parameters such as atmospheric carbon dioxide, which requires a full response of the ocean. Thus, this approach can be considered intermediate between fixing, or prescribing, sea surface temperatures and a fully coupled modeling approach.

scholarly journals Interannual variability of precipitable water

1996 ◽  
Vol 14 (4) ◽  
pp. 464-467 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Precipitable Water ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Zonal Winds ◽  
Low Latitudes ◽  
Linear Trends

Abstract. The 12-month running means of the surface-to-500 mb precipitable water obtained from analysis of radiosonde data at seven selected locations showed three types of variability viz: (1) quasi-biennial oscillations; these were different in nature at different latitudes and also different from the QBO of the stratospheric tropical zonal winds; (2) decadal effects; these were prominent at middle and high latitudes and (3) linear trends; these were prominent at low latitudes, up trends in the Northern Hemisphere and downtrends in the Southern Hemisphere.

Strong earthquake activity influenced by solar flare intensity

2021 ◽  
Author(s):  
Gerald Duma
Keyword(s):  
Solar Flares ◽  
Strong Earthquake ◽  
Temporal Variations ◽  
Seasonal Effect ◽  
Earthquake Activity ◽  
Strong Earthquakes ◽  
International Service ◽  
Earthquake Frequency ◽  
Magnetic Index ◽  
Magnetic Disturbances

<p>Based on the comprehensive earthquake catalogue USGS ( HYPERLINK<span>  </span>https://earthquake.usgs.gov) the paper demonstrates that strong earthquake activity, seismic events with M≥6, exhibits a seasonal trend. This feature is the result of<span>  </span>analyses of earthquake data for the N- and S- Earth Hemisphere in period 2010-2019. It can be shown also for single earthquake prone regions as well, like Japan, Eurasia, S-America.</p><p>Any seasonal effect suggests an external influence. In that regard, one can think also of a solar-terrestrial effect, that is suggested already in several studies (e.g<span>  </span>M.Tavares, A.Azevedo, 2011; D.A.E. Vares, M.A.Persinger,2014; G.Duma, 2019). This assumption leads to the question: Which dynamic process can cause a trigger effect for strong earthquakes in the Earth's lithosphere.</p><p>In this study the intensity of solar flares and the resulting radiation, the solar wind, towards the Earth was taken into account. An appropriate parameter which has been regularity measured and reported for many decades and which reflects the intensity of solar radiation is the magnetic index Kp. It is measured at numerous geomagnetic observatories and describes the magnetic disturbances in nT within 3 hour intervals, respectively. Averages of all the measured 3-hour values are then published as Kp, therefore considered a planetary parameter (International Service of Geomagnetic Indices ISGI,France).</p><p>The temporal variations of strong earthquake activity over 10 years and their energy release was compared with the above mentioned index Kp. Actually, a distinct correlation between the two quantities, Kp and earthquake frequency, resulted in cases of different regions as well as globally. Another essential result of the study is that maxima of Kp preceed those of earthquake activity by about 60 to 80 days in most cases. The mechanism has not yet been modeled satisfactorily.</p>

scholarly journals Simultaneous high- and low-latitude reconnection: ESR and DMSP observations

2002 ◽  
Vol 20 (9) ◽  
pp. 1311-1320 ◽  
Author(s):  
F. Pitout ◽  
P. T. Newell ◽  
S. C. Buchert
Keyword(s):  
High Latitude ◽  
Time Interval ◽  
High Latitudes ◽  
Polar Ionosphere ◽  
Plasma Convection ◽  
Low Latitude ◽  
Svalbard Archipelago ◽  
Cusp Region ◽  
Ionosphere Plasma ◽  
Particle Measurement

Abstract. We present EISCAT Svalbard Radar and DMSP observations of a double cusp during an interval of predominantly northward IMF on 26 November 2000. In the cusp region, the ESR dish, pointing northward, recorded sun-ward ionospheric flow at high latitudes (above 82° GL), indicating reconnection occuring in the magnetospheric lobe. Meanwhile, the same dish also recorded bursts of poleward flow, indicative of bursty reconnection at the subsolar magnetopause. Within this time interval, the DMSP F13 satellite passed in the close vicinity of the Svalbard archipelago. The particle measurement on board exhibited a double cusp structure in which two oppositely oriented ion dispersions are recorded. We interpret this set of data in terms of simultaneous merging at low- and high-latitude magnetopause. We discuss the conditions for which such simultaneous high-latitude and low-latitude reconnection can be anticipated. We also discuss the consequences of the presence of two X-lines in the dayside polar ionosphere.Key words. Magnetospheric physics (solar wind-magnetosphere interactions) – Ionosphere (polar ionosphere; plasma convection)

scholarly journals Retrieval of tropospheric column densities of NO<sub>2</sub> from combined SCIAMACHY nadir/limb measurements

2010 ◽  
Vol 3 (1) ◽  
pp. 283-299 ◽  
Author(s):  
S. Beirle ◽  
S. Kühl ◽  
J. Puķīte ◽  
T. Wagner
Keyword(s):  
Spatial Patterns ◽  
Unique Feature ◽  
Trace Gases ◽  
Systematic Errors ◽  
High Latitudes ◽  
Correction Scheme ◽  
Low Latitudes ◽  
Tropospheric No2 ◽  
Estimation Scheme ◽  
Sector Method

Abstract. The SCIAMACHY instrument onboard the ESA satellite ENVISAT allows measurements of various atmospheric trace gases, such as NO2. A unique feature of SCIAMACHY is that measurements are made alternately in limb and nadir mode. The limb measurements provide an opportunity for directly determining stratospheric column densities (CDs), which are needed to extract tropospheric CDs from the total CD measurements performed in (quasi simultaneous) nadir geometry. Here we discuss the potential and limitations of SCIAMACHY limb measurements for estimating stratospheric CDs of NO2 in comparison to a simple reference sector method, and the consequences for the resulting tropospheric CDs. A direct, absolute limb correction scheme is presented that improves spatial patterns of tropospheric NO2 column densities at high latitudes, but results in artificial zonal stripes at low latitudes. Subsequently, a relative limb correction scheme is introduced that successfully reduces stratospheric artefacts in the tropospheric data product without introducing new ones. This relative limb correction scheme is rather simple, robust, and, in essence, based on measurements alone. The effects of the different stratospheric estimation schemes on tropospheric CDs are discussed with respect to zonal and temporal dependencies. In addition, we define error quantities from the nadir/limb measurements that indicate remaining systematic errors as a function of latitude and day. Our new suggested stratospheric estimation scheme, the relative limb correction, improves mean tropospheric slant CDs significantly, e.g. from −1×1015 molec/cm2 (using a reference sector method) to ≈0 in the Atlantic ocean, and from +1×1015 molec/cm2 to ≈0 over Siberia, at 50° N in January 2003–2008.

4. The Effect of Moisture on the Electric Discharge

1882 ◽  
Vol 11 ◽  
pp. 801-804
Author(s):  
A. Macfarlane ◽  
D. Rintoul
Keyword(s):  
Electric Discharge ◽  
Solar Physics ◽  
High Latitudes ◽  
Moist Air ◽  
Effect Of Moisture ◽  
Magnetic Disturbances

In his recent lectures on Solar Physics, Professor Stokes, while expounding his theory of the connection of magnetic disturbances, auroræ, and earth currents, says:—“We might not have tension enough to produce such a discharge (that is, a flash of lightning), the resistance to the passage of electricity from one portion of the air to another, which at any rate would be comparatively dry compared with what we have in warm latitudes, would prevent it by itself alone.” Professor Stokes subsequently remarked in a letter to Nature: —“These words, without actually asserting, seem to imply that the resistance to such a discharge through moist air would be less than through dry. My attention has been called by a friend to the fact that it has been found by experiment that moist air insulates as well as dry. I have not met with experiments tending to show whether the resistance to a disruptive discharge is the same or not in the two. Be that as it may, it does not affect what follows; for we know, as a fact, that thunderstorms are absent in high latitudes.”

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