Night-time sporadic E measurements on an oblique path along the mid-latitude trough at sunspot minimum and sunspot maximum

2009 ◽  
Author(s):  
A.J. Stocker ◽  
E.M. Warrington
Keyword(s):  
Night Time ◽  
Sunspot Maximum ◽  
Sunspot Minimum ◽  
Sporadic E

scholarly journals Evolutions of various solar indices around sunspot maximum and sunspot minimum years

2002 ◽  
Vol 20 (6) ◽  
pp. 741-755 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Magnetic Fields ◽  
Solar Physics ◽  
Total Solar Irradiance ◽  
Solar Magnetic Fields ◽  
Solar Cycles ◽  
Sunspot Maximum ◽  
Sunspot Minimum ◽  
Coronal Green Line ◽  
Two Indices ◽  
Two Peaks

Abstract. The smoothed monthly sunspot numbers showed that in many solar cycles, (a) during years around sunspot maxima, there was only one prominent maximum, but in some cycles there was a broad plateau. If the beginning and end of these are termed as first and second maxima (separated by several months), the first maximum was generally the higher one, and the valley in between was very shallow. Solar indices at or near the photosphere generally showed similar structures with maxima matching with sunspot maxima within a month or two. Indices originating in the chromosphere and above showed two peaks in roughly the same months as sunspots (with some exceptions, notably the Coronal green line, and the Total Solar Irradiance). Yet often, the second maximum was larger than the first maximum, and the valley between the two maxima was deeper, as compared to sunspot maxima, and (b) during years around sunspot minima, the smoothed sunspot minimum could be sharp and distinct, lasting for a month or two, or could spread over several months. Among the indices originating at or near the photosphere, the Ca K line intensity showed good matching with sunspots, but the Ca Plage area, the Sunspot Group Area, and the solar magnetic fields seemed to show minima earlier than the sunspots, indicating that these activities died out first. These also showed recoveries from the minima later than sunspots. Most of the other indices originating in the chromosphere and corona attained minima coincident with sunspot minima, but in some cases, minima earlier than sunspots were seen, while in some other cases minima occurred after the sunspot minima. Thus, the energy dissipation in the upper part of the solar atmosphere sometimes lagged or led the evolution of sunspots near sunspot minimum. In a few cases, after the minimum, the indices recovered faster than the sunspots. In general, the chromospheric indices seemed to evolve similar to sunspots, but the evolution of coronal indices was not always similar to sunspots, and may differ considerably between themselves.Key words. Solar physics, astrophysics and astronomy (Corona and transition region; Magnetic fields; Photosphere and chromosphere)

Large Scale TIDs climatology over Europe using HF Interferometry method

2020 ◽  
Author(s):  
Estefania Blanch ◽  
Antoni Segarra ◽  
David Altadill ◽  
Vadym Paznukhov ◽  
Jose Miguel Juan
Keyword(s):  
Solar Activity ◽  
Propagation Velocity ◽  
Large Scale ◽  
Large Data ◽  
Density Fluctuations ◽  
Night Time ◽  
Wide Range ◽  
Propagation Parameters ◽  
The Difference ◽  
Sporadic E

<p>Travelling Ionospheric Disturbances (TIDs) are ionospheric irregularities that occur as plasma density fluctuations that propagate as waves through the ionosphere over a wide range of velocities and frequencies. It has been demonstrated that Large Scale TIDs (LSTID) can be detected with several ionospheric sensors such as ionosondes and their main characteristics such as velocity, direction of propagation and amplitude can be inferred.</p><p>We have applied the recent developed HF Interferometry (HF-Int) method to detect the occurrence and main characteristics of LSTIDs over Europe for different solar activities (2014 – 2019) in order to perform a climatological analysis. HF-Int determines the dominant period of oscillation and the amplitude of the LSTIDs using spectral analysis, and estimates the propagation parameters of the LSTIDs from the measured time delays of the disturbance detected at different sensor sites.</p><p>The results show that larger diurnal and seasonal occurrence of LSTID happens near sunrise hours and night-time, especially during equinox. In the morning sector, prevailing velocity propagation is westward influenced by the solar terminator effect and it also depends on the season: during winter the dominant propagation velocity is north-westward and during summer is south-westward. In the evening and night sector, the prevailing propagation velocity is southward suggesting auroral origin of the disturbance. The higher activity at night-time might be the result that neutral winds favour equatorward propagation at night whereas at day might prevent to propagate to low latitudes.</p><p>Similar behaviour has been found for high and low solar activity with the difference that during summer at low solar activity, large occurrence of sporadic E layer happens during day time. Then, ionospheric data experience large data gaps at the F region because of screening of the Es (Es Blanketing effect). This results in a poor statistic under such a conditions for daytime summer low solar activity and the number of detected LSTID is lower.</p>

scholarly journals HF Doppler radar observations of sporadic E at an Indian low latitude station, Visakhapatnam

2009 ◽  
Vol 27 (2) ◽  
pp. 537-545 ◽  
Author(s):  
M. S. S. R. K. N Sarma ◽  
C. Raghava Reddy ◽  
K. Niranjan
Keyword(s):  
Doppler Radar ◽  
Doppler Velocity ◽  
Night Time ◽  
Low Latitude ◽  
Radar Observations ◽  
Latitude Station ◽  
Velocity Variations ◽  
Sporadic E ◽  
Gradient Drift ◽  
Drift Instability

Abstract. 5.5 MHz HF Doppler radar observations of Sporadic E over an Indian low latitude station, Visakhapatnam (17.7° N, 83.3° E and Dip 20°) with 10 s resolution showed quasi-periodic variations of the echo strength and Doppler velocity variations with periods of a few minutes to a few tens of minutes. The echo strength and Doppler velocity variations with time in different range bins of the ES echo showed variations which are some times similar and some times significantly different in successive range bins at intervals of 7.5 km. The ES echo occurs with the height of maximum echo strength in the range of 100 km to 120 km and some times at 130 km. The altitude variation of the average Doppler velocity is highly variable and the height of maximum echo strength is not the same as the height of maximum Doppler velocity. Observations of ES echoes at different times of the day are presented to bring out the differences between the day and night time ES echoes. The relationship between Radar and ES parameters derived from Ionograms is poorer than that of mid latitudes which is quite consistent with the expectations based on gradient drift instability.

scholarly journals Mid Latitude Sporadic E-layer Variability during Ascending Phase of Solar Cycle 24

2017 ◽  
Vol 9 (1) ◽  
pp. 27-41
Author(s):  
R. Atulkar ◽  
P. A. Khan ◽  
A. A. Mansoori ◽  
P. K. Purohit
Keyword(s):  
Solar Cycle ◽  
Summer Season ◽  
High Solar Activity ◽  
Night Time ◽  
Solar Cycle 24 ◽  
E Region ◽  
Sporadic E Layer ◽  
Sporadic E ◽  
Cycle 24 ◽  
Short Time

The paper presents a comparative study of the ionospheric sporadic E layer parameters (fbEs, foEs, and h’Es) retrieved from ground based ionosonde at mid latitude station Yamagawa, Japan (31.20 N, 130.370 E) during the ascending phase of 24th solar cycle i.e. during January 2012 to December 2014. The comparison between the E-region parameters has been carried out on a diurnal, seasonal, annual and day night basis. The diurnal maxima of foEs, fbEs, and h’Es are generally higher during high solar activity. From the present study it is found that the highest values of fbEs are observed during the summer while the lowest values are observed during autumn at mid latitude. Similarly, the highest values of foEs are observed during the summer season while the lowest values are recorded in autumn season. However, the highest values of h’Es are recorded during the spring and the lowest values are recorded in autumn. The variability of Es during the day and night time is also studied. The sporadic E can form and disappear in a short time during either the day or night. We have also studied the percentage occurrence of sporadic E. The occurrence of Es changes from year to year.

Biota

1997 ◽  
Author(s):  
Douglas V. Hoyt ◽  
Kenneth H. Shatten
Keyword(s):  
Solar Activity ◽  
Food Chain ◽  
Life Forms ◽  
Sunspot Maximum ◽  
Sunspot Minimum ◽  
Temperature And Precipitation ◽  
Biological Phenomena ◽  
Climate Indicators ◽  
Insect Populations ◽  
Agricultural Yields

We now consider insect populations, circumpolar mammal populations, seaweed density, agricultural yields, and similar topics. Good reasons exist to link such biological phenomena to solar activity. For one thing, if such meteorological parameters as temperature and precipitation vary with solar activity, life forms sensitive to small changes in these parameters may show dramatic responses. We will examine various claims from the 100 to 200 articles that either provide support for or criticize these types of ideas. The topics generally start at the lower levels of the food chain (i.e., insects) and proceed to the upper levels (i.e., predatory mammals), concluding with agricultural and economic studies. Insect populations are sensitive climate indicators. Paleontologists have used fossilized insects (see, for example, Coope, 1977) to show that very rapid changes in climate can occur in only a few years. Certain species of insects can tolerate only narrow ranges of temperature or precipitation. If meteorological variables alter that range, a new species of insect will replace the old. Insects occupy one of the lower rungs of the food chain, so fluctuations in their numbers may cause corresponding fluctuations in such predators as birds or spiders. Therefore, correlating insect populations with solar activity is a worthwhile venture. In his doctoral treatise, “Über die Beziehungen der Sonnenfleckenperiode zu meteorologischen Erscheinungen” published in 1877, F. G. Hahn argues that locusts will probably appear in temperate regions only during unusually hot and dry years. Hahn shows that European locusts appear preferentially between the years of sunspot minimums up to the next sunspot maximum, an average of about 4 years. For the 7 years from the sunspot maximum to the next sunspot minimum, locusts are scarcer. Since sunspot minimums produced relatively warm temperatures for the years 1800–1862, this suggests that the sun influences European locust populations. E. D. Archibald, who in his later years was a very ardent advocate of sun/climate relationships, extended Hahn’s findings. In a letter to Nature in 1878, Archibald showed that locusts appeared in Europe in 1613, 1690, and 1748–1749. According to Wolf, these dates occur 1 to 3 years after a sunspot minimum, which is consistent with Hahn’s findings.

A discussion on D and E region winds over Europe - Some studies of sporadic E-layer drifts

1972 ◽  
Vol 271 (1217) ◽  
pp. 613-622 ◽  
Keyword(s):  
Large Scale ◽  
Great Majority ◽  
Theoretical Work ◽  
Night Time ◽  
Drift Motion ◽  
The Past ◽  
E Region ◽  
Sporadic E Layer ◽  
Sporadic E ◽  
Ionospheric Drifts

In the past two decades, measurements of E-region drifts, using the conventional closely spaced receiver method with pulse signals incident normally on the ionosphere, have been made by many workers. The great majority of such measurements have been carried out at frequencies in the 2 to 3 MHz range and refer to drift movements in the lower part of the normal E region. Measurements of sporadic E drifts by the fading method have almost always been limited to night-time hours, when the normal E layer is absent, and the results have generally been used to extend daytime normal E measurements over the full 24 h. The objectives of the present work, in which the fading method has again been used, were to obtain some simultaneous measurements of drift in the normal E and the sporadic E regions, to obtain some qualitative data on height gradient of sporadic E-layer drifts, and to compare the horizontal drifts of small- and large-scale sporadic E irregularities. (A survey of current experimental and theoretical work on sporadic E, and of outstanding problems, has recently been published by Whitehead (1970).) The closely spaced receiver technique measures changes in a diffraction pattern at the ground and the interpretation of these changes in terms of ‘ionospheric drift motion’ is, of course, open to question. Certain basic ambiguities in the interpretation of experimental data obtained in the fading method cannot readily be resolved and are likely to remain until some direct comparisons can be made with actual movements at ionospheric levels of both the ionized and neutral constituents. In continuing the practice of referring to the processed data as ‘ionospheric drifts’ we recognize that the more appropriate term would be ‘apparent ionospheric drifts’, and that the ‘drifts’ refer only to possible motion of, or within the ionization.

Sign in / Sign up

Export Citation Format

Share Document