What did create the question?
I was analyzing a data set where the researchers have used objective data. They have calculated earth's magnetic field through sensors and that research was conducted in Bangladesh. I have read some articles (1, 2, 3) regarding earth's magnetic field and everywhere, I found that it ranges from 25 to 65 μT. However, in their data set, the different components (x, y, z axis) value of the magnetic field ranges from -85μT to +70.46μT. Even, there are many values which are less than 10μT.
Therefore, my question
Can different components (x, y, z axis) values of earth's magnetic field be as less as -85μT and as much as +70.46μT?
So far, what I have found?
Here, I have found that
The strength of the field at the Earth's surface ranges from less than 30 microteslas (0.3 gauss) in an area including most of South America and South Africa to over 60 microteslas (0.6 gauss) around the magnetic poles in northern Canada and south of Australia, and in part of Siberia.
Moreover, here I find
It shows clearly that the field has weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia.
Furthermore, here in question a, I found that
The earth's magnetic field varies from point to point in space.
Then, what do I think?
As the data set, I am working is regarding Bangladesh which is in south Asia, earth's magnetic field may vary from -85 to +70.46 μT. However, I am really confused as I do not find any literature or any reference where they have discussed that this value may vary so much. Moreover, I do not know, how and why this value of earth's magnetic field can deviate so much from the widely known 25μT to 65μT?
Here is a little description of the data set:
The earth magnetic field's data is presented in three different axis, that is, magnetic field value in x axis, y axis, z axis. They have retrieved these data for 30 minutes, on an interval of 1 sec. Therefore, there are many instances.
What about the magnetic field of the city where the study was conducted?
Setting the value of latitude, longitude (23.8103° N, 90.4125° E) and elevation 4m, I calculated the components (x, y, z) of the magnetic field using this site. I find that Y component value of magnetic field is negative and it is -0.2756μT which is near to 0. And these values seems to be similar of the data set, I am working.