Characteristics of global plasmaspheric TEC in comparison with the ionosphere simultaneously observed by Jason‐1 satellite

Abstract

[1] We compared the global plasmaspheric total electron content (pTEC) with the ionospheric TEC (iTEC) simultaneously measured by Jason-1 satellite during the declining phase of solar cycle 23 (2002-2009) to investigate the global morphology of the plasmaspheric density in relation to the ionosphere. Our study showed that the plasmaspheric density structures fundamentally follow the ionosphere, but there are also significant differences between them. Although the diurnal variations are very similar to each region, the plasmasphere shows much weaker variations, only approximately 1 TECU day-night difference. By analyzing the day-night differences in the plasmasphere, we found that the plasmaspheric contribution to the nighttime ionosphere does not increase with solar activity and the largest contribution occurs during June solstice. The plasmasphere shows similar seasonal variations to the ionosphere, except for the semiannual variation, which is essentially absent in the plasmasphere. There is also an important difference in the annual variation: although the annual variation in the ionosphere exists regardless of longitude, it occurs only at American sector in the plasmasphere. As solar activity increases to moderate level, the pTEC substantially enhances from approximately 2 to 4 TECU at the initial increase of solar activity below F10.7p = 100 and then quickly slows down while the iTEC almost linearly enhances. Although it is well known that magnetic storms are the major source of plasmaspheric density depletion, pTEC does not show this aspect of the plasmasphere probably due to the relatively small K p values for high magnetic activity

Plasmaspheric Electron Content Inferred from Residuals between GNSS-Derived and TOPEX/JASON Vertical TEC Data

“…Therefore, we believe that small difference in the CODE GIM and JPL GIM will not significantly affect the final PEC extraction. Moreover, the PEC distributions and magnitudes (left and right column of Figures 6 and 7) do not differ significantly, and the results agree with previous studies using other methods and data [2,11,16,39]. This indicates that potential errors from CODE GIM and JPL GIM in our study will have a negligible impact on final PEC extraction.…”

“…After subtracting the background systematic bias, we obtain Figure 6. As expected, the values are all positive, and the PEC distribution is in good agreement with the general plasmaspheric distribution investigated by other measurements and methods [2,11,12,16]. Hence, our proposed method for extracting PEC is suitable and reliable, and the systematic bias correction is reasonable.…”

“…The PEC variation in the plasmasphere (higher during the day than at night) is not as large as that in the ionosphere, and the PEC pattern is mainly driven by coupling to the ionosphere via plasmaspheric flux along magnetic field lines [3,11,39]: During the day, the PEC in the plasmasphere is enhanced, and upward plasma flow from the underlying ionosphere fills plasmaspheric flux tubes when the ionospheric density and temperature are high enough to produce a negative O+ pressure gradient with altitude. This negative pressure gradient competes with the downward gravitational force and results in upward plasma flow to achieve a diffusive equilibrium.…”

“…We propose a method here to remove the systematic bias, namely, the zero assumption method [3,9,11], whereby observed vTEC (or PEC) above the LEO satellite orbital altitude can be very small (even close to zero) at high latitudes or during nighttime.…”

“…Specifically, PEC can be estimated using dual frequency signals transmitted by GPS satellites and recorded by GPS receivers on LEO satellites. Then, the contribution to GPS TEC can be calculated from ground-based GPS TEC and onboard LEO satellites PEC [9][10][11][12]. For example, Yizengaw et al [9] discussed the PEC contribution based on JASON1 onboard and ground-based GPS measurements.…”