# Equinoctial Asymmetry in Solar Quiet Fields along the 120\({}^{\circ}\) E Meridian Chain
## 3 Results
Moreover, it is also noticed that the intensity of the asymmetry coefficients is very similar between both northern stations BMT and MZL; however, for the southern stations, it is obviously a smaller value in the equator station MUT than in the GZH station, probably related to the EEJ. When comparing with solar activity, equinoctial asymmetry is quite stable at each observatory. Asymmetry values are mostly negative at southern observatories and positive at northern observatories. Obviously, they do not appear to depend on solar cycle, as increases or decreases in the asymmetry coefficient seem to occur during any phase of the solar cycle (Figure 6). For example, large asymmetry coefficient values are found during high solar activity years--negative in 1969 at GZH and positive in 1980 at LZH--or during low solar activity years, such as 1964 at GZH. Similarly, large values are found during both the descending--in 1983 at GZH or in 2005 at BMT and LZH--and ascending--in 1998 at BMT--phases of the solar cycle. In addition, a few near-zero asymmetry coefficient values are recorded at each observatory. About ten percent of cases from all measurements show values of the asymmetry coefficient that are less than 0.05. This implies that in these years the SqH range is comparable in spring and in autumn. Figure 7 shows the variations (black dots) and SEM (red bars) of the equinoctial asymmetry \(AA\) and of the asymmetry coefficient--both averaged at each observatory over all available measurements--as a function of geographic latitude. The linear fit to the asymmetry coefficient is also shown (green line in the right panel), which has a median value of the errors of A and B (evaluated from the differences between the linear fit value and the measurement) of about \(-1.14\) and \(-7.54\), respectively. Equinoctial asymmetry is clearly visible along the meridian chain: the maximum value of the averaged AA is about \(-4\) nT at \"southern station\" (GZH) and \(5\) nT at \"northern station\" (BMT), and the minimum value is about \(1.5\) nT presented at \"central stations\" (WHN and LZH). Accordingly, the maximum averaged asymmetry coefficient is about \(\pm 30\%\), and the minimum value is about \(10\%\). Both quantities increase with geographic latitude and with increasing distance between the observatory and the Sq current focus, possibly suggesting that the distant observatories are more sensitive to the asymmetry mechanism than those close to the Sq current focus. Remarkably, a reversal of the equinoctial asymmetry sign is seen between the northern (positive) and southern (negative) observatories. Additionally, the latitude of the reversal is about \(28.1^{\circ}\), which is located near the focus of the focus of the average Sq current (as seen in Figure 1) because of the linear fitting between the asymmetry coefficient and the geographic latitude. Notably, this reverse latitude is only a statistical average result from all the data. The linear fitting results will generally change if the SEM and the confidence interval are considered. After doing some tests with different confidence intervals, we found little change in coefficient A, suggesting the stability of the latitudinal trend of the equinoctial asymmetry of the SqH. Moreover, there is obvious fluctuation in coefficient B, implying the variability of the reversal latitude under different levels of the equinoctial asymmetry of the SqH.