In India along the coast there are sometime booming sounds of unknown origin called the Barisol guns. A similar sound occurs in North Carolina, New Jersey, Delaware and Virginia called the
Seneca guns. Yesterday, in the afternoon and evening of 26 June 2010 both my wife and I heard the phenomenon in Accokeek, Maryland for many hours. It was not thunder due to lightning as no lightning was visible. The sky was totally clear, and of course, it was only a few days after the summer solstice. As it happens, it was also only shortly after a lunar eclipse.
I have long noticed various strange electrical phenomena a few days after the summer solstice. I attribute this to the solar wind dragging electrical charge into the North magnetosphere and out the South magnetosphere toward the outer reaches of the solar system. That the recently eclipsed moon would also have been directly away from the Earth from the Sun, also suggests that, in the case we heard yesterday, that the moon might have been the target of all that charge.
Although a humid atmosphere discharges local charge, it is a dry atmosphere that best for long distance charge transport. The reason for this is that water molecules adhere with electrons and consequently bind and slow them during transport. Consequently, it is a dry completely clear atmosphere that would best fast transport charge from the Earth's surface up to the magnetosphere, and, thence, to outer space.
It is fun to stay up at night after the summer solstice and and await the astronomical midnight. On most occasions there will be observed a phenomenon usually termed "heat lightning" in a completely clear sky. Astronomical midnight is when your local longitude is exactly away from the sun. Therefore in computing astronomical midnight you must both take into account both daylight savings time and your exact longitude within the longitudinal time zone. Here in Accokeek I seem to recall it occurs around 1:20 am daylight savings time. A more exact calculation is possible, but an exact calculation isn't necessary to observe the phenomenon since it occurs at a wide range around astronomical midnight. I attribute the midnight heat lightning to the same cause as the Seneca or Barisol guns. Notably, heat lighting shows no visible lighting stroke anywhere, the sky just flashes.
