scholarly journals Influence of the semidiurnal lunar tide in the equatorial plasma bubble zonal drifts over Brazil

2021 ◽  
Vol 39 (6) ◽  
pp. 1005-1012
Author(s):  
Igo Paulino ◽  
Ana Roberta Paulino ◽  
Amauri F. Medeiros ◽  
Cristiano M. Wrasse ◽  
Ricardo Arlen Buriti ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Electron Concentration ◽  
Complex Dynamics ◽  
The Other ◽  
High Solar Activity ◽  
Lunar Tide ◽  
Plasma Bubble ◽  
E Region ◽  
Equatorial Plasma Bubble

Abstract. Using OI6300 airglow images collected over São João do Cariri (7.4∘ S, 36.5∘ W) from 2000 to 2007, the equatorial plasma bubble (EPB) zonal drifts were calculated. A strong day-to-day variability was observed in the EPB zonal drifts, which is directly associated with the very complex dynamics of the nighttime thermosphere–ionosphere system near the Equator. The present work investigated the contribution of the semidiurnal lunar tide M2 for the EPB zonal drifts. The M2 presented an amplitude of 3.1 m s−1 in the EPB zonal drifts, which corresponds to 5.6 % of the average drifts. The results showed that the M2 amplitudes in the EPB zonal drifts were solar cycle and seasonally dependent. The amplitude of the M2 was stronger during the high solar activity, reaching over 10 % of the EPB zonal drift average. Regarding the seasons, during the Southern Hemisphere summer, the M2 amplitude was twice as large (12 %) compared to the equinox ones. The seasonality agrees with other observations of the M2 in the ionospheric parameters such as vertical drifts and electron concentration, for instance. On the other hand, the very large M2 amplitudes found during the high solar activity agree with previous observations of the lunar tide in the ionospheric E region.

scholarly journals Influence of the semidiurnal lunar tide on the equatorial plasma bubble zonal drifts over Brazil

2021 ◽  
Author(s):  
Igo Paulino ◽  
Ana Roberta Paulino ◽  
Amauri F. Medeiros ◽  
Cristiano M. Wrasse ◽  
Ricardo A. Buriti ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Southern Hemisphere ◽  
Electron Concentration ◽  
The Other ◽  
High Solar Activity ◽  
Lunar Tide ◽  
Plasma Bubble ◽  
Other Hand ◽  
Equatorial Plasma Bubble

Abstract. Using OI6300 airglow images collected over São João do Cariri (7.4° S, 36.5° W) from 2000 to 2007, the equatorial plasma bubble (EPB) zonal drifts were calculated. A strong day-to-day variability was observed in the EPB zonal drifts due to the complexity in the dynamics of the nighttime thermosphere-ionosphere system near the equator. The present work investigated the contribution of the semidiurnal lunar tide M2 for the EPB zonal drifts. On average, the M2 contributes 5.6 % to the variability of the EPB zonal drifts, presenting an amplitude of 3.1 m/s. The results showed that the M2 amplitudes in the EPB zonal drifts were solar cycle and seasonal dependents. The amplitude of the M2 was stronger during the high solar activity reaching over 10 % of the EPB zonal drift average. Regarding the seasons, during the southern hemisphere summer, the M2 amplitude was twice larger (12 %) compared to the equinox ones. The seasonality agrees with other observations of the M2 in the ionospheric parameters such as vertical drifts and electron concentration, for instance. On the other hand, the very large M2 amplitudes found during the high solar activity must be further investigated.

M(3000)F2 and IRI-2012 model at an equatorial latitude in the African sector

2021 ◽  
Vol 16 (3) ◽  
pp. 49-54
Author(s):  
A.O. Olawepo ◽  
J.O. Adeniyi ◽  
A. Afolabi
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Correlation Coefficient ◽  
High Solar Activity ◽  
Equatorial Latitude ◽  
Magnetic Declination ◽  
Two Peaks

We have used ionosonde data from Ouagadougou (Geo. Lat.12.40 N, Long. 358.50, Magnetic declination -5.1320) to study the morphology of M(3000)F2 and to investigate the performance of IRI-12 during 1991 and 1995, years of high and low solar activities respectively. Results show that M(3000)F2 exhibits diurnal and solar cycle characteristics with no distinctive monthly/seasonal features. The two peaks which characterize the diurnal M(3000)F2 during high solar activity (HSA) are reduced to just one (the sunrise peak) during low solar activity (LSA). The study also shows that IRI-12 gives good representations of the observed values of M(3000)F2 with high correlation coefficient, R ranging between 0.9 and 0.95 during LSA and 0.94 and 0.99 during HSA. The model gives its best performance in the months of April irrespective of the solar activity. It either under-estimates or over-estimates the observed values of M(3000)F2 during other months.

scholarly journals Cosmic-ray propagation around the Sun: investigating the influence of the solar magnetic field on the cosmic-ray Sun shadow

2020 ◽  
Vol 633 ◽  
pp. A83
Author(s):  
J. Becker Tjus ◽  
P. Desiati ◽  
N. Döpper ◽  
H. Fichtner ◽  
J. Kleimann ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Solar Cycle ◽  
Cosmic Rays ◽  
Solar Magnetic Field ◽  
Cosmic Ray ◽  
High Energy ◽  
High Solar Activity ◽  
The Sun ◽  
Theoretical Understanding

The cosmic-ray Sun shadow, which is caused by high-energy charged cosmic rays being blocked and deflected by the Sun and its magnetic field, has been observed by various experiments, such as Argo-YBJ, Tibet, HAWC, and IceCube. Most notably, the shadow’s size and depth was recently shown to correlate with the 11-year solar cycle. The interpretation of such measurements, which help to bridge the gap between solar physics and high-energy particle astrophysics, requires a solid theoretical understanding of cosmic-ray propagation in the coronal magnetic field. It is the aim of this paper to establish theoretical predictions for the cosmic-ray Sun shadow in order to identify observables that can be used to study this link in more detail. To determine the cosmic-ray Sun shadow, we numerically compute trajectories of charged cosmic rays in the energy range of 5−316 TeV for five different mass numbers. We present and analyze the resulting shadow images for protons and iron, as well as for typically measured cosmic-ray compositions. We confirm the observationally established correlation between the magnitude of the shadowing effect and both the mean sunspot number and the polarity of the magnetic field during the solar cycle. We also show that during low solar activity, the Sun’s shadow behaves similarly to that of a dipole, for which we find a non-monotonous dependence on energy. In particular, the shadow can become significantly more pronounced than the geometrical disk expected for a totally unmagnetized Sun. For times of high solar activity, we instead predict the shadow to depend monotonously on energy and to be generally weaker than the geometrical shadow for all tested energies. These effects should become visible in energy-resolved measurements of the Sun shadow, and may in the future become an independent measure for the level of disorder in the solar magnetic field.

scholarly journals The statistical properties of spread F observed at Hainan station during the declining period of the 23rd solar cycle

2010 ◽  
Vol 28 (6) ◽  
pp. 1263-1271 ◽  
Author(s):  
G. J. Wang ◽  
J. K. Shi ◽  
X. Wang ◽  
S. P. Shang ◽  
G. Zherebtsov ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Temporal Variations ◽  
High Solar Activity ◽  
Positive Relation ◽  
Low Latitude ◽  
23Rd Solar Cycle ◽  
Reversal Time ◽  
Spread F ◽  
Maximum Occurrence

Abstract. The temporal variations of the low latitude nighttime spread F (SF) observed by DPS-4 digisonde at low latitude Hainan station (geog. 19.5° N, 109.1° E, dip lat. 9.5° N) during the declining solar cycle 23 from March 2002 to February 2008 are studied. The spread F measured by the digisonde were classified into four types, i.e., frequency SF (FSF), range SF (RSF), mixed SF (MSF), and strong range SF (SSF). The statistical results show that MSF and SSF are the outstanding irregularities in Hainan, MSF mainly occurs during summer and low solar activity years, whereas SSF mainly occurs during equinoxes and high solar activity years. The SSF has a diurnal peak before midnight and usually appears during 20:00–02:00 LT, whereas MSF peaks nearly or after midnight and occurs during 22:00–06:00 LT. The time of maximum occurrence of SSF is later in summer than in equinoxes and this time delay can be caused by the later reversal time of the E×B drift in summer. The SunSpot Number (SSN) dependence of each type SF is different during different season. The FSF is independent of SSN during each season; RSF with SSN is positive relation during equinoxes and summer and is no relationship during the winter; MSF is significant dependence on SSN during the summer and winter, and does not relate to SSN during the equinoxes; SSF is clearly increasing with SSN during equinoxes and summer, while it is independent of SSN during the winter. The occurrence numbers of each type SF and total SF have the same trend, i.e., increasing as Kp increases from 0 to 1, and then decreasing as increasing Kp. The correlation with Kp is negative for RSF, MSF, SSF and total SF, but is vague for the FSF.

scholarly journals THE STRUCTURE OF THE SOLAR WIND IN THE HELIOSPHERE DEPENDING ON THE PHASE OF THE SOLAR CYCLE: LARGE-SCALE DYNAMICS OF THE HELIOSPHERIC CURRENT SHEET

2019 ◽  
Vol 47 (1) ◽  
pp. 85-87
Author(s):  
E.V. Maiewski ◽  
R.A. Kislov ◽  
H.V. Malova ◽  
O.V. Khabarova ◽  
V.Yu. Popov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Activity ◽  
Solar Cycle ◽  
Current Sheet ◽  
Heliospheric Current Sheet ◽  
High Solar Activity ◽  
The Sun ◽  
High Latitudes ◽  
The Magnetic Field

A stationary axisymmetric MHD model of the solar wind has been constructed, which allows us to study the spatial distribution of the magnetic field and plasma characteristics at radial distances from 20 to 400 radii of the Sun at almost all heliolatitudes. The model takes into account the changes in the magnetic field of the Sun during a quarter of the solar cycle, when the dominant dipole magnetic field is replaced by a quadrupole. Selfconsistent solutions for the magnetic and velocity fields, plasma concentration and current density of the solar wind depending on the phase of the solar cycle are obtained. It is shown that during the domination of the dipole magnetic component in the solar wind heliospheric current sheet (HCS) is located in the equatorial plane, which is a part of the system of radial and transverse currents, symmetrical in the northern and southern hemispheres. As the relative contribution of the quadrupole component to the total magnetic field increases, the shape of the HCS becomes conical; the angle of the cone gradually decreases, so that the current sheet moves entirely to one of the hemispheres. At the same time, at high latitudes of the opposite hemisphere, a second conical HCS arises, the angle of which increases. When the quadrupole field becomes dominant (at maximum solar activity), both HCS lie on conical surfaces inclined at an angle of 35 degrees to the equator. The model describes the transition from the fast solar wind at high latitudes to the slow solar wind at low latitudes: a relatively gentle transition in the period of low solar activity gives way to more drastic when high solar activity. The model also predicts an increase in the steepness of the profiles of the main characteristics of the solar wind with an increase in the radial distance from the Sun. Comparison of the obtained dependences with the available observational data is discussed.

scholarly journals Effect of solar cycle on topside ion temperature measured by SROSS C2 and ROCSAT 1 over the Indian equatorial and low latitudes

2012 ◽  
Vol 30 (12) ◽  
pp. 1645-1654 ◽  
Author(s):  
A. Borgohain ◽  
P. K. Bhuyan
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Significant Negative Correlation ◽  
Solar Flux ◽  
High Solar Activity ◽  
Topside Ionosphere ◽  
Ion Temperature ◽  
Ion Density ◽  
Positive Correlation ◽  
June Solstice

Abstract. The effect of solar activity on the diurnal, seasonal and latitudinal variations of ion temperature Ti and its relationship with corresponding ion density Ni over the Indian low and equatorial topside ionosphere within 17.5° S to 22.5° N magnetic latitudes are being investigated, combining the data from SROSS C2 and ROCSAT 1 for the 9-year period from 1995 to 2003 during solar cycle 23. Ti varies between 800 K and 1100 K during nighttime and rises to peak values of ~1800 K in the post sunrise hours. Daytime Ti varies from 1000 K to 1500 K. The time of occurrence, magnitude and duration of the morning enhancement show distinct seasonal bias. For example, in the June solstice, Ti increases to ~1650 K at ~06:00 h and exhibits a daytime plateau till 17:00 LT. In the equinoxes, enhanced ion temperature is observed for a longer duration in the morning. There is also a latitudinal asymmetry in the ion temperature distribution. In the equinoxes, the daytime Ti is higher at off equatorial latitudes and lower over the Equator, while in the solstices, Ti exhibits a north–south gradient during daytime. Nighttime Ti is found to be higher over the Equator. Daytime ion temperature exhibits insignificant positive correlation with F10.7 cm solar flux, while nighttime ion temperature decreases with increase in solar flux. Daytime ion temperature and ion density are negatively correlated during solar minimum, while nighttime Ti does not exhibit any correlation. However, during high solar activity, significant positive correlation of Ti with Ni has been observed over the Equator, while at 10° S and 10° N temperature and density exhibit significant negative correlation. The neutral temperature Tn derived from the MSISE 90 model is found to be higher than measured Ti during nighttime, while daytime Ti is higher than model Tn.

scholarly journals Characteristics of VHF radiowave scintillations over a solar cycle (1983−1993) at a low-latitude station: Waltair (17.7°N, 83.3°E)

1997 ◽  
Vol 15 (6) ◽  
pp. 729-733 ◽  
Author(s):  
P. V. S. Rama Rao ◽  
P. T. Jayachandran ◽  
P. Sri Ram ◽  
B. V. Ramana Rao ◽  
D. S. V. V. D. Prasad ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
High Solar Activity ◽  
Night Time ◽  
Low Latitude ◽  
Latitude Station ◽  
Maximum Occurrence

Abstract. The characteristics of VHF radiowave scintillations at 244 MHz (FLEETSAT) during a complete solar cycle (1983–93) at a low-latitude station, Waltair (17.7°N, 83.3°E), are presented. The occurrence of night-time scintillations shows equinoctial maxima and summer minima in all the epochs of solar activity, and follows the solar activity. The daytime scintillation occurrence is negatively correlated with the solar activity and shows maximum occurrence during the summer months in a period of low solar activity. The occurrence of night-time scintillations is inhibited during disturbed days of high solar activity and enhanced during low solar activity.

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.

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