Variations of daytime and nighttime electron temperature and heat flux in the upper ionosphere, topside ionosphere and lower plasmasphere for low and high solar activity

Abstract. In this paper, the ten-year (1996–2005) total ion density Ni measurements from the Defense Meteorological Satellite Program (DMSP) spacecraft in the morning and evening (09:30 and 21:30 LT) sectors have been analyzed to explore the dependence of plasma densities in the topside ionosphere at middle and low latitudes on the solar activity level. Results indicate that there is a strong solar activity dependence of DMSP Ni at 848 km altitude, which has latitudinal and seasonal features. The plasma density in the topside ionosphere has an approximately linear dependence on daily F107 and a strongly nonlinear dependence on SEM/SOHO EUV, such that the change rate of Ni becomes greater with increasing solar EUV. This is quite different from the dependence of Ni near the F-Region peak (NmF2), at which the rate of change of NmF2 decreases with increasing solar EUV. The rate of change of Ni at the DMSP altitude is greatest in the latitude range where Ni is greatest during high solar activity. We suggest that this greater rate of change (or amplification effect) of Ni at the DMSP altitude is mainly a consequence of the solar activity variations of the topside scale height. The changes in the height of the F-Region peak (hmF2) and the density NmF2 play a secondary role.

Download Full-text

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

Annales Geophysicae ◽

10.5194/angeo-30-1645-2012 ◽

2012 ◽

Vol 30 (12) ◽

pp. 1645-1654 ◽

Cited By ~ 5

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.

Download Full-text

Global empirical model of electron temperature in the outer ionosphere for period of high solar activity based on data of three Intercosmos satellites

Advances in Space Research ◽

10.1016/s0273-1177(99)00914-x ◽

2000 ◽

Vol 25 (1) ◽

pp. 163-169 ◽

Cited By ~ 21

Author(s):

V. Truhlík ◽

L. Třísková ◽

J. Šmilauer ◽

V.V. Afonin

Keyword(s):

Solar Activity ◽

Electron Temperature ◽

Empirical Model ◽

High Solar Activity ◽

Outer Ionosphere

Download Full-text

Diurnal, seasonal, latitudinal and solar cycle variation of electron temperature in the topside F-region of the Indian zone ionosphere

Annales Geophysicae ◽

10.5194/angeo-25-1995-2007 ◽

2007 ◽

Vol 25 (9) ◽

pp. 1995-2006 ◽

Cited By ~ 1

Author(s):

M. Chamua ◽

P. K. Bhuyan ◽

P. Subrahmanyam ◽

S. C. Garg

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Electron Temperature ◽

Time Scale ◽

Time Lag ◽

Solar Flux ◽

Activity Period ◽

High Solar Activity ◽

Solar Cycle Variation ◽

Solar Cycle 23

Abstract. Electron temperature Te observed by the SROSS C2 satellite at equatorial and low latitudes during the low to high solar activity period of 1995–2001 at the height of ~500 km is investigated in terms of local time, season, latitude, solar sunspot number Rz and F10.7 cm solar flux. The satellite covered the latitude belt of 31° S–34° N and the longitude range of 40°–100° E. The average nighttime (20:00–04:00 LT) Te varies between 750–1200 K and then rises sharply in the sunrise period (04:00–06:00 LT) to the morning high from 07:00 to 10:00 LT and attains a daytime (10:00–14:00 LT) average of 1100–2300 K. The morning enhancement is more pronounced in the equinoxes. A secondary maximum in Te is also observed around 16:00–18:00 LT in the June solstice and in the equinoxes. Daytime electron temperature was found to be higher in autumn compared to that in spring in all latitudes. Between the solstices, the amplitude of the morning enhancement is higher in winter compared to that in summer. Both day and nighttime Te observed by the SROSS C2 satellite bears a positive correlation with solar activity when averaged on a shorter time scale, i.e. over the period of a month. But on a longer time scale, i.e. averaged over a year, the daytime electron temperature gradually decreases from 1995 till it reaches the minimum value in 1997, after which Te again continues to rise till 2001. The variations are distinctly seen in summer and in the equinoxes. The sunspot activity during solar cycle 23 was minimum in 1996 and maximum in 2000. Annual average electron temperature, therefore, appears to follow the variation of solar activity with a time lag of about one year, both at the bottom and top of solar cycle 23, indicating an inherent inertia of the ionosphere thermosphere regime to variations in solar flux.

Download Full-text

Topside electron temperature models for low and high solar activity

Advances in Space Research ◽

10.1016/j.asr.2003.07.011 ◽

2004 ◽

Vol 33 (6) ◽

pp. 959-962 ◽

Cited By ~ 2

Author(s):

V.K. Pandey ◽

N.K. Sethi ◽

K.K. Mahajan

Keyword(s):

Solar Activity ◽

Electron Temperature ◽

High Solar Activity

Download Full-text

Enhanced variability in the topside ionosphere

Annals of Geophysics ◽

10.4401/ag-4104 ◽

1995 ◽

Vol 38 (3-4) ◽

Author(s):

T. Gulyaeva ◽

P. Spalla

Keyword(s):

Solar Activity ◽

Faraday Rotation ◽

Solar Minimum ◽

High Solar Activity ◽

Dynamic Processes ◽

Topside Ionosphere ◽

Electron Content ◽

Total Electron ◽

F Region ◽

Rotation Method

Variability of total electron content (TEC) observed by the Faraday rotation method at Florence has been stud- ied with the same technique applied independently to the ionospheric parameters foF2 and M(3000)F2 of the ground-based vertical-incidence sounding database (VID). Results of daily and monthly TEC disturbance indices at sub-ionospheric point are compared with variability of the ionosphere at Rome and Gibilmanna (de- duced from VID) for a period of 1976 to 1991. During moderate and high solar activity the variability of TEC is greater than the variability of VID, whereas during solar minimum the situation is opposite. In this context joint TEC and VID observations distinguish either the F region peak or the topside ionosphere heights where the dynamic processes dominate at different times.

Download Full-text