Secondly, most of the objective magnetic fluctuations are different from the magnetic fluctuation accompanying the equatorial plasma bubble (EPB) because our objective variations exist almost all the time and globally and appreciable variation is not seen in the parallel component.
In addition, the characteristics of the occurrence frequency on the nightside of our objective magnetic fluctuations have the same characteristics with the mid-latitude magnetic fluctuations (MMFs) on the nightside reported by Park et al. (2009b), and they may be a part of our objective magnetic fluctuations.
To compare the MMF with our objective magnetic fluctuations, the occurrence frequency is calculated.
Therefore, most of our objective magnetic fluctuations in middle and low latitudes also cannot be attributed to magnetospheric disturbance effects.Thirdly, the seasonal dependence is described.
For investigating the lower atmospheric origin in detail, the correlation between the amplitude of our objective magnetic fluctuations and meteorological conditions should be examined for each pass of the CHAMP satellite, which is not done in this paper.
Red circles, a red dotted line, upper triangle and cross mark indicate objective magnetic fluctuations above the volcano and its conjugate point, the dip equator at an altitude of SW-B orbit, the location of the Calbuco volcano and its geomagnetic conjugate point, respectively.
Therefore, the strongest amplitude of the objective magnetic fluctuation is located at about 8° in latitude from the dip equator.
Secondly, the objective magnetic fluctuation has the three observational characteristics, i.e., the geomagnetic conjugacy, no altitude dependence, which implies that they do not have atmospheric density dependence, and the smaller amplitude on the dip equator.
First, our objective magnetic fluctuation exists globally and near all the time as shown in Figures 2 and 5. Second, the magnetic fluctuation on the nightside has the same characteristics with those on other local times except for the difference of the amplitude, described in the previous sections.
Moreover, from the Fig. 3, compared to other methods, the ASHLO method also gets the slightest fluctuation of objective function, which implies that the ASHLO method has good convergent property and robustness.
