scholarly journals Equatorial enhancement of SSC amplitudes: Solar activity dependence and effect of electric field.

1976 ◽  
Vol 28 (5) ◽  
pp. 333-341
Author(s):  
A. R. JAIN ◽  
K. G. SRINIVASACHARYA
Keyword(s):  
Solar Activity ◽  
Electric Field ◽  
Activity Dependence

Effects of Solar Activity on Ionospheric Ion Upflow During Geomagnetic Quiet Periods: DMSP Observations

2020 ◽  
Vol 29 (1) ◽  
pp. 158-167
Author(s):  
Shuai Fu ◽  
Yong Jiang ◽  
Xiaoping Zhang
Keyword(s):  
Solar Activity ◽  
Electric Field ◽  
Geomagnetic Disturbance ◽  
High Solar Activity ◽  
Ion Density ◽  
Similar Work ◽  
Background Density ◽  
Upward Velocity ◽  
Activity Dependence ◽  
Background Ions

AbstractBased on the Defense Meteorological Satellite Program (DMSP) observations during Solar Cycle 23, this paper examines solar activity dependence of ionospheric bulk ion upflow events (IUEs) in the Southern Hemisphere (SH). Much previous similar work was conducted over the Northern Hemisphere (NH) with measurements from European Incoherent Scatter (EISCAT). To eliminate the influence of geomagnetic disturbance on IUEs, we pick out observations during geomagnetic quiet periods (with Kp ≤ 2+). Results show that, ion upward densities and fluxes are dramatically elevated at times of high solar activity (HSA) but ion upward drifts and occurrences are increased at times of low solar activity (LSA) in the SH, which is consistent with the situation in the NH. The ratios between HSA and LSA for these four parameters (IUEs’ density, flux, upward drift and occurrence) are ~2.71, ~1.98, ~0.76 and ~0.57, respectively. Furthermore, lower flux event takes place frequently at LSA as the background ion density is low but the upward drift is large, while higher flux event happens commonly at times of HSA accompanied by high ion density but low upward velocity. Quantitatively, an increase in unit of solar activity (characterized by P index) causes a 4.2×108 m−3 increase in ion density and a 1.2×1011 m−2·s−1 enhancement in upward flux, together with a 0.6 m·s−1 and 0.02 % decrease in ion upward velocity and uprate, respectively. The acceleration from the ambipolar electric field is thought to be a possible mechanism affecting the dependence of IUEs on solar variations. For HSA, the acceleration from the ambipolar electric field weakens, but a large number of background ions provide abundant seeds for acceleration and upflow, which maintains a high IUE flux. It is inferred that upflow events and upward drifts are inhibited by the enhanced ionospheric background density.

On the solar activity dependence of midnight equatorial plasma bubbles during June solstice periods

2021 ◽  
Vol 5 (4) ◽  
pp. 1-9
Author(s):  
K. K. Ajith ◽  
◽  
S. Tulasi Ram ◽  
GuoZhu Li ◽  
M. Yamamoto ◽  
...  
Keyword(s):  
Solar Activity ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
June Solstice ◽  
Activity Dependence

scholarly journals Seasonal features of geomagnetic activity: a study on the solar activity dependence

2021 ◽  
Vol 39 (5) ◽  
pp. 929-943
Author(s):  
Adriane Marques de Souza Franco ◽  
Rajkumar Hajra ◽  
Ezequiel Echer ◽  
Mauricio José Alves Bolzan
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Geomagnetic Activity ◽  
Annual Variation ◽  
Geomagnetic Storms ◽  
Solar Wind Speed ◽  
Solar Cycles ◽  
Annual Variations ◽  
Long Duration ◽  
Activity Dependence

Abstract. Seasonal features of geomagnetic activity and their solar-wind–interplanetary drivers are studied using more than five solar cycles of geomagnetic activity and solar wind observations. This study involves a total of 1296 geomagnetic storms of varying intensity identified using the Dst index from January 1963 to December 2019, a total of 75 863 substorms identified from the SuperMAG AL/SML index from January 1976 to December 2019 and a total of 145 high-intensity long-duration continuous auroral electrojet (AE) activity (HILDCAA) events identified using the AE index from January 1975 to December 2017. The occurrence rates of the substorms and geomagnetic storms, including moderate (-50nT≥Dst>-100nT) and intense (-100nT≥Dst>-250nT) storms, exhibit a significant semi-annual variation (periodicity ∼6 months), while the super storms (Dst≤-250 nT) and HILDCAAs do not exhibit any clear seasonal feature. The geomagnetic activity indices Dst and ap exhibit a semi-annual variation, while AE exhibits an annual variation (periodicity ∼1 year). The annual and semi-annual variations are attributed to the annual variation of the solar wind speed Vsw and the semi-annual variation of the coupling function VBs (where V = Vsw, and Bs is the southward component of the interplanetary magnetic field), respectively. We present a detailed analysis of the annual and semi-annual variations and their dependencies on the solar activity cycles separated as the odd, even, weak and strong solar cycles.

scholarly journals Winter anomaly in NmF2 and TEC: when and where it can occur

2018 ◽  
Vol 8 ◽  
pp. A45 ◽  
Author(s):  
Yury V. Yasyukevich ◽  
Anna S. Yasyukevich ◽  
Konstantin G. Ratovsky ◽  
Maxim V. Klimenko ◽  
Vladimir V. Klimenko ◽  
...  
Keyword(s):  
Solar Activity ◽  
Meridional Wind ◽  
Global Scale ◽  
Activity Level ◽  
Electron Content ◽  
Intensity Increase ◽  
Total Electron ◽  
Solar Activity Level ◽  
Winter Anomaly ◽  
Activity Dependence

For the first time, by using a regression procedure, we analyzed the solar activity dependence of the winter anomaly intensity in the ionospheric F2-layer peak electron density (Nm F2) and in the Total Electron Content (TEC) on a global scale. We used the data from global ionospheric maps for 1998–2015, from GPS radio occultation observations with COSMIC, CHAMP, and GRACE satellites for 2001–2015, and ground-based ionosonde data. The fundamental features of the winter anomaly in Nm F2 and in TEC (spatial distribution and solar activity dependence) are similar for these parameters. We determined the regions, where the winter anomaly may be observed in principle, and the solar activity level, at which the winter anomaly may be recorded in different sectors. A growth in geomagnetic disturbance or in the solar activity level is shown to facilitate the winter anomaly intensity increase. Longitudinal variations in the winter anomaly intensity do not conform partly to the generally accepted Rishbeth theory. We consider the obtained results in the context of spatial and solar cycle variations in O/N2 ratio and thermospheric meridional wind. Additionally, we briefly discuss different definitions of the winter anomaly.

scholarly journals Stability of solar correction for calculating ionospheric trends

2016 ◽  
Vol 34 (12) ◽  
pp. 1191-1196 ◽  
Author(s):  
Jan Laštovička ◽  
Dalia Burešová ◽  
Daniel Kouba ◽  
Peter Križan
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Global Climate ◽  
Standard Technique ◽  
Model Data ◽  
Data Set ◽  
Long Term Trends ◽  
Cycle 24 ◽  
Activity Dependence

Abstract. Global climate change affects the whole atmosphere, including the thermosphere and ionosphere. Calculations of long-term trends in the ionosphere are critically dependent on solar activity (solar cycle) correction of ionospheric input data. The standard technique is to establish an experimental model via calculating the dependence of ionospheric parameter on solar activity from the whole analysed data set, subtract these model data from observed data and analyse the trend of residuals. However, if the solar activity dependence changes with time, the solar correction calculated from the whole data set may result in miscalculating the ionospheric trends. To test this, data from two European ionospheric stations – Juliusruh and Slough/Chilton – which provide long-term reliable data, have been used for the period 1975–2014. The main result of this study is the finding that the solar activity correction used in calculating ionospheric long-term trends need not be stable, as was assumed in all previous investigations of ionospheric trends. During the previous solar cycle 23 and the current solar cycle 24, the solar activity correction appears to be different from that for the previous period and the Sun seems to behave in a different way than throughout the whole previous era of ionospheric measurements. In future ionospheric trend investigations the non-stability of solar activity correction has to be very seriously taken into account, because it can substantially affect calculated long-term trends of ionospheric parameters.

scholarly journals Invariability of relationship between the polar cap magnetic activity and geoeffective interplanetary electric field

2011 ◽  
Vol 29 (8) ◽  
pp. 1479-1489 ◽  
Author(s):  
O. A. Troshichev ◽  
N. A. Podorozhkina ◽  
A. S. Janzhura
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Electric Field ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Magnetic Activity ◽  
Polar Cap ◽  
Polar Caps ◽  
The Relationship ◽  
Wind Energy Input

Abstract. The PC (polar cap) index characterizing the solar wind energy input into the magnetosphere is calculated with use of parameters α, β, and φ, determining the relationship between the interplanetary electric field (EKL) and the value of magnetic activity δF in the polar caps. These parameters were noted as valid for large and small EKL values, and as a result the suggestion was made (Troshichev et al., 2006) that the parameters should remain invariant irrespective of solar activity. To verify this suggestion, the independent sets of calibration parameters α, β, and φ were derived separately for the solar maximum (1998–2001) and solar minimum (1997, 2007–2009) epochs, with a proper choice of a quiet daily variation (QDC) as a level of reference for the polar cap magnetic activity value. The results presented in this paper demonstrate that parameters α, β, and φ, derived under conditions of solar maximum and solar minimum, are indeed in general conformity and provide consistent (within 10 % uncertainty) estimations of the PC index. It means that relationship between the geoeffective solar wind variations and the polar cap magnetic activity responding to these variations remains invariant irrespective of solar activity. The conclusion is made that parameters α, β, and φ derived in AARI#3 version for complete cycle of solar activity (1995–2005) can be regarded as forever valid.

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