scholarly journals The semiannual variation of transpolar arc incidence and its relationship to the Russell–McPherron effect

2020 ◽  
Vol 4 (6) ◽  
pp. 1-8
Author(s):  
Tao Tang ◽  
◽  
Jun Yang ◽  
QuanQi Shi ◽  
AnMin Tian ◽  
...  
Keyword(s):  
Semiannual Variation

scholarly journals On the Semiannual Variation of the Upper Atmosphere

1969 ◽  
Vol 26 (2) ◽  
pp. 233-240 ◽  
Author(s):  
Isadore Harris ◽  
Wolfgang Priester
Keyword(s):  
Upper Atmosphere ◽  
Semiannual Variation

A simulation study on the semiannual variation of the ionosphericF2layer zonal electric fields at the magnetic equator

2006 ◽  
Vol 111 (A9) ◽  
Author(s):  
Tao Yu ◽  
Weixing Wan ◽  
Libo Liu ◽  
Xiaoyin Li ◽  
XiaoLi Luan ◽  
...  
Keyword(s):  
Electric Fields ◽  
Simulation Study ◽  
Magnetic Equator ◽  
Semiannual Variation

scholarly journals Model results for the ionospheric lower transition height over mid-latitude

2004 ◽  
Vol 22 (6) ◽  
pp. 2037-2045 ◽  
Author(s):  
J. Lei ◽  
L. Liu ◽  
W. Wan ◽  
S.-R. Zhang
Keyword(s):  
Solar Activity ◽  
Theoretical Calculations ◽  
Magnetic Activity ◽  
Composition Analysis ◽  
Time Asymmetry ◽  
Quantitative Studies ◽  
Semiannual Variation ◽  
Lower Transition ◽  
Ap Index ◽  
Opposite Tendency

Abstract. Theoretical calculations of the ionospheric lower transition height (LTH), a level of equal O+ and molecular ion densities, were performed and compared with empirical models by Zhang et al. (1996). This paper represents a substantial extension of the prior work by including the AE-C data of ion composition analysis and by detailed quantitative studies of the LTH simulation, and by creating a new LTH empirical model based on our simulations. Results show that: (1) the calculated LTH, in general, is lowest near 11-13LT and reaches the diurnal maximum after midnight (about 01~02LT). The local time asymmetry becomes more evident in summer, when the time of minimum shifts to 16LT. (2) The simulated LTH presents a dominant, semiannual variation during nighttime, and a pronounced annual variation during daytime. (3) The simulated LTH increases with solar activity at night and decreases by day, while the standard IRI option has an opposite tendency at night in summer and equinox. Therefore, the day-night difference of simulated LTH significantly increases with solar activity. (4) Both daytime and nighttime LTHs, tend to increase with the increasing geomagnetic activity Ap index, with a mean slope about 0.1455km per Ap unit. (5) The diurnal variation of LTH is found to be more than 20 km, which is much larger than the seasonal variation under F107=100 and Ap=10. Thus, the diurnal and solar activity variations of LTH are more pronounced than its seasonal and magnetic activity variations.

scholarly journals Semiannual variation in the heterosphere: A reappraisal

1971 ◽  
Vol 76 (19) ◽  
pp. 4602-4607 ◽  
Author(s):  
L. G. Jacchia
Keyword(s):  
Semiannual Variation

scholarly journals Semiannual and annual variations in the height of the ionospheric F2-peak

2000 ◽  
Vol 18 (3) ◽  
pp. 285-299 ◽  
Author(s):  
H. Rishbeth ◽  
K. J. F. Sedgemore-Schulthess ◽  
T. Ulich
Keyword(s):  
Solar Activity ◽  
Computational Models ◽  
Annual Variation ◽  
Late Summer ◽  
Early Summer ◽  
Atmospheric Composition ◽  
Annual Variations ◽  
Composition And Structure ◽  
Semiannual Variation ◽  
Quiet Day

Abstract. Ionosonde data from sixteen stations are used to study the semiannual and annual variations in the height of the ionospheric F2-peak, hmF2. The semiannual variation, which peaks shortly after equinox, has an amplitude of about 8 km at an average level of solar activity (10.7 cm flux = 140 units), both at noon and midnight. The annual variation has an amplitude of about 11 km at northern midlatitudes, peaking in early summer; and is larger at southern stations, where it peaks in late summer. Both annual and semiannual amplitudes increase with increasing solar activity by day, but not at night. The semiannual variation in hmF2 is unrelated to the semiannual variation of the peak electron density NmF2, and is not reproduced by the CTIP and TIME-GCM computational models of the quiet-day thermosphere and ionosphere. The semiannual variation in hmF2 is approximately "isobaric", in that its amplitude corresponds quite well to the semiannual variation in the height of fixed pressure-levels in the thermosphere, as represented by the MSIS empirical model. The annual variation is not "isobaric". The annual mean of hmF2 increases with solar 10.7 cm flux, both by night and by day, on average by about 0.45 km/flux unit, rather smaller than the corresponding increase of height of constant pressure-levels in the MSIS model. The discrepancy may be due to solar-cycle variations of thermospheric winds. Although geomagnetic activity, which affects thermospheric density and temperature and therefore hmF2 also, is greatest at the equinoxes, this seems to account for less than half the semiannual variation of hmF2. The rest may be due to a semiannual variation of tidal and wave energy transmitted to the thermosphere from lower levels in the atmosphere.Key words: Atmospheric composition and structure (thermosphere - composition and chemistry) - Ionosphere (mid-latitude ionosphere)

LONG-TERM BALLOON COSMIC RAY EXPERIMENT: RESULTS OF ANALYSIS OF ENERGETIC ELECTRON PRECIPITATION EVENTS

2005 ◽  
Vol 20 (29) ◽  
pp. 6843-6845 ◽  
Author(s):  
V. S. MAKHMUTOV ◽  
G. A. BAZILEVSKAYA ◽  
Y. I. STOZHKOV ◽  
A. K. SVIRZHEVSKAYA ◽  
N. S. SVIRZHEVSKY
Keyword(s):  
Energetic Electron ◽  
Cosmic Ray ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Electron Precipitation ◽  
Occurrence Rate ◽  
Balloon Experiment ◽  
Semiannual Variation ◽  
Precipitation Events

More than 500 energetic Electron Precipitation Events were observed in the Earth's Northern and Southern polar atmosphere during a long-term cosmic ray balloon experiment. The results of analysis of these events allow to show (1) distribution of occurrence rate of EPEs within solar activity cycle, (2) semiannual variation in the EPE occurrence, (3) interplanetary and geomagnetic conditions related to the EPEs in the atmosphere.

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