I recently broke out my new electromagnetic field meter, and noticed the device kept showing an electric field value of 200 N/C towards the ground, without being near any obvious charge sources. I even took a long walk to check if the reading was somehow localized to my house, but I got the same result. How might you explain the reading (assuming the device is working properly)? What amount of charge would produce that field strength? And how many charges would that correspond to?